Comprehensive Biology Review Summary

What is going on? It's Medicosus Perfectionatus where medicine makes perfect sense. This is the ultimate biology review video. First of all, let me be clear. Trying to review all of biology in less than 90 minutes is an insane task. I'm going to go over the most important points in this video. And we'll do this in the following order. We will start by talking about the cell and what's in it. Of course, there is the nucleus with DNA and the cytoplasm with the organelles. Then we'll talk about reproduction, mitosis, and meiosis. After this, embryogenesis and the fetal circulation, followed by the nervous system, somatic and autonomic, central nervous system versus peripheral nervous system. After that, the endocrine system. Then the respiratory system, followed by the cardiovascular system. Next, the immune system, digestive system, homeostasis, which includes kidney and skin. musculoskeletal system, bone and muscle, and last will be genetics and evolution. So let's go! This video will be a very quick review. If you want the detailed explanation, go to my biology playlist. First, cell theory. Prokaryotes versus eukaryotes. Karyote is the nucleus. So which one has the true nucleus, the true nut? Eukaryotes. It's a true nucleus bound by a membrane. And it's not just the nucleus. Even the organelles are bound by membranes. Eukaryotes have mitochondria. They can make their own energy. Their DNA is protein-bound, but the prokaryotes have naked DNA. In eukaryotes, the DNA is linear, anti-parallel. In prokaryotes, it is circular. Give me one example of prokaryotes, bacteria. How about eukaryotes? We have many, including mammals, which will include humans. What are the fundamental tenets of the cell theory? Number one, all living things are composed of cells. No kidding. the cell is the basic functional unit of life cells arise only from pre-existing cells this is the story of reproduction cells carry genetic information in the form of dna here's your cell it has a nucleus it has cytoplasm if you lump them together this is called the protoplasm the cell is bound and surrounded by a plasma membrane or a cell membrane or a lipid bilayer what kind of lipid phospholipid in this lovely cell membrane the head is hydrophilic. It loves water. So we put it on the outside. How about the tail? Well, the tail is on the inside because it hates water. It loves lipid, but it hates water. Hydrophobic lipophilic. And since there is water outside the cell and water inside the cell, we will put the water loving hydrophilic heads towards water, i.e. on the outside and the inside. And we will hide this hydrophobic tail away from water. just bury it in the center. What's the genetic material? DNA, which is organized in chromosomes. You find chromosomes inside the nucleus. How about the organelles like the mitochondria? You'll find it in the cytoplasm. The mitochondria will give you energy in form of ATP. Since the sperm needs lots and lots of energy, it has lots and lots of mitochondria. If you want to secrete a lot like the pancreas, you will need lots of Golgi and endoplasmic reticulate. Don't you ever forget that red blood cells do not have organelles? They do not have mitochondria. Therefore, there is no TCA cycle or electron transport chain inside the red blood cell. Let's talk about these organelles. The mitochondria is the powerhouse. Ligosome is the soldier. It destroys foreign invaders. How about endosome? The delivery guy. The endoplasmic reticulum comes in two shapes, rough and smooth. The rough is the translator. We translate proteins for secretion. We need rough endoplasmic and Golgi to work together. How about the smooth? This is the donut for fat synthesis. Look how smooth this fat belly is. Golgi is the sorter. It modifies cellular products and directs them for delivery. And it works in conjunction with the rough endoplasmic reticulum. Peroxisome from peroxide is the gym trainer, destroys fat. Is there a difference between cytosol and cytoplasm? Yes. Cytosol is just fluid with no organelles. If you want to add the fluid, cytosol, to the organelles, now you have cytoplasm. If you want to add the cytoplasm to nucleus, you get protoplasm. Here is your cell and your cell membrane. Inside we have protoplasm, which is nucleus and cytoplasm. The cytoplasm is organelles plus cytosol. Next, the nucleus. This is the control room of your body. Why? Because it has the DNA. DNA carries your genes. And don't forget the story of the nuclear pores inside the nuclear membrane. These pores allow entry and exit from and to the nucleus. The outer membrane of the nucleus is continuous with the rough endoplasmic reticulum. This is how you make and then secrete proteins. Here's your DNA double helix. Wrap it around histones, wrap it around, wrap it around, wrap... But before you know it, we have your chromosomes. How many of these do you have in each somatic cell? 46 chromosomes. Do you remember the nuclear pore? Yeah, this is when mRNA... tries to leave. why does it want to leave? because it will get translated later in the cytoplasm. if you want to make another copy of dna this is called the replication. if you want to convert dna into rna this is called transcription. if you want to translate the rna into meaningful proteins this is called translation. by the way you can download these notes and all of the notes in the entire biology series at medicosisperfectionellist.com Inside the nucleus, we have the nucleolus. For assembly of ribosome, ribosome. This is the sentence of ribosomal RNA, the rRNA. Your average cell has only one nucleus. Red blood cells have none. Osteoclasts of bones have many. Sometimes the nucleus is lobated or segmented, such as your neutrophils, which are white blood cells or leukocytes. Next, the powerhouse. The mighty mitochondria provides you with energy. This is on a good day, but on a bad day, it will kill your cell. Why is this? Because this cell is old, malfunctioning, starting to become harmful, so it's gotta go. Who's gonna let her go? Mitochondria. What do you call it when the cell plans its own death? Apoptosis. Here's the structure of the mitochondria. Please pause and review. When you keep pumping protons, pumping protons, pumping protons, this is called electron transport chain. Where does it happen? In the mitochondria. When you keep pumping protons, you are pumping them from the inside to the outside. The cristae will increase the surface area for the electron transport chain. The inner membrane contains all of the molecules and enzymes necessary for the electron transport chain. But how about the inside matrix? It has the enzymes for the Krebs cycle or the tricarboxylic acid cycle or citric acid cycle. Do not forget that your mitochondria has its own mitochondrial DNA. You got your mitochondrial DNA from your mother only, not from your father, because your daddy's sperm left his tail outside. He left the mitochondria outside. Red blood cells, again, no mitochondria, but liver cell, gazillion mitochondria. Next, the destroyer. Let's destroy foreign invaders and let's destroy our own stuff. that is senescent and no longer of value. The lysosome is a destroyer because it contains hydrolytic enzymes that work in an acidic medium. How come the lysosome is not killing me at all times? Because these hydrolytic digestive enzymes are protected and kept inside the lysosome thanks to the lysosomal membrane. If you're a foreign invader, the lysosome will destroy you by endocytosis first and then destruction. If you are coming from within i.e. old senescent harmful particle then will destroy you by autophagy. In the former process, the lysosome needs help from the endosome for endocytosis, but in the latter process, it needs help from the phagosome for phagocytosis. Here's the lysosome with the hydraulic enzymes engulf and do destroy. There is a protein here that helps this vesicle separate from the membrane. The name is called clathrin. They love to ask about clathrin on the exam. Next, the endoplasmic reticulum is rough and smooth. Don't forget that it's continuous with the nuclear membrane. The rough is the translator to translate proteins which were coded for in the DNA of the nucleus and then secrete them to the outside. That's why its membrane is continuous with the nuclear membrane. The smooth endoplasmic reticulum is the donut. The rough has ribosomes. Rough, ribosomes. But the smooth, no ribosomes. function of the rough er translation i.e protein synthesis i.e to convert the rna into proteins how about the function of the smooth reticulum fat synthesis and detoxification don't forget that the sarcoplasmic reticulum in your muscle is a modified smooth endoplasmic reticulum here's the rough versus smooth endoplasmic reticulum Rough is to make proteins, smooth is to make fat and to detoxify. Don't forget that your steroid hormones are made of fat, and these include the sex hormones, such as estrogen, progesterone, and androgens. Next is the sorter. Sort them and direct them for delivery. The Golgi works with the endoplasmic reticulum. The nucleus has the code and it makes RNA in a process known as transcription. Then, this mRNA will leave the nucleus through the nuclear pore and will go to the cytoplasm, where it will get translated in the rough endoplasmic reticulum, i.e. protein synthesis. Then we put those proteins in vesicles, we give them to the sota, Golgi, and Golgi can secrete them to the outside world. Here's your nucleus. mRNA will leave or continues with the rough endoplasmic reticulum, translate that mRNA into proteins. Then give me those lovely vesicles and pew, exocytosis. From the intracellular fluid to the extracellular fluid. So the Golgi can work in harmony with the rough endoplasmic reticulum. Moreover, Golgi can work with endosome and lysosome. We can do the exact opposite thing if this is a foreign invader. Get it in by endocytosis and then lysosome and then pew, we will destroy you. Paroxysome. the gym trainer that destroys fat. It drives me crazy when students make a mistake on the exam when it comes to peroxisome. How can you forget that the name has the answer? Peroxisome, from peroxide. Here is hydrogen peroxide. Why do you need this peroxide for beta oxidation of fat, lipid catabolism? Why do you need this hydrogen peroxide, Mr. Peroxisome? Because it can help me kill foreign invaders. This is the story of the reactive oxygen species or free radicals. And this is a lovely peroxide for you. Some diseases in medicine are paroxysmal diseases, such as adrenoleukodystrophy. On your biology exam, assume that all X-linked diseases are X-linked recessive, unless they tell you otherwise. If it's X-linked recessive, it's gonna be more common in boys. Next, the cytoskeleton. What's the most abundant thing in every cell in your body? It's water. What's the second most abundant? Proteins. We have two types of proteins in the cell. Structural, for the cytoskeleton, and functional, for enzymes, pores, channels, pumps, etc. Your cytoskeleton is a protein network. Who made it? Well, ribosome again, because it's a protein. It helps the entire cell move, cytokinesis. It helps the cell divide. during cell division, mitosis or meiosis. And it provides railroad tracks so that you can move your packages on the railroad. The cytoskeleton has jazillion other functions. Pause and review. There are three types of cytoskeleton. Microfilament, microtubules, and intermediate filaments. Microfilaments, actin. How about microtubules? Alpha-tubulin or beta-tubulin. And you find microtubules in cilia or flagella. First, microfilaments. Remember my actin? You start with monomers, then they become polymers of G-actin, and then before you know it, you have your actin filaments. Actin filaments have many functions including cell division. These are your cleavage furrows that you studied in mitosis or meiosis for that matter. Next, microtubules which have tubulin. You have alpha tubulin and beta tubulin. Microtubules can provide the backbone for many structures. If you want to make a centriole, easy. I'll give you nine triplets of microtubules and you will have a centriole. But if you want a cilium or a flagellum... I'll give you 9 doublets of microtubules plus 2 additional ones. Don't forget the story of kinesin and dynein. Dynein defect is seen in a disease known as cortagener's syndrome or immotile cilia syndrome. Here is the cilia as you know, 9 doublets of microtubules plus 2 extra ones. Cilia could be motile such as the one in your respiratory tract, to get all the gunk out of your airways or they could be immotile such as the special ones in the rods of the eye if i have cartaginar syndrome or immutile cilia syndrome then the cilia in my fallopian tube will not work and i can get ectopic pregnancy because i was unable to push the ovum from the fallopian tube to the uterine cavity because i did not have cilia there are many genetic diseases that will give me respiratory problems, including Cartesiner syndrome, where the problem is in the dynian arm of cilia, and cystic fibrosis, which is a CFTR mutation. The first disease is having no motile cilia. The other disease is having very thick mucus because of a defect in the chloride channel. Flagella, structurally speaking, very similar to cilia. Nine doublets of microtubules plus two single central ones. The sperm has a flagellum and H. pylori bacteria has a flagellum too. This is the nasty bacteria that lives in the stomach. Here is the structure of cilia or flagella. We have nine doublets on the periphery and two single microtubules centrally. What if I want to make a centriole, not cilia or flagella? Then you go with triplets, nine triplets of microtubules. Remember that your cytoskeleton head microfilaments, actin, microtubules, tubulin, and intermediate filaments. These intermediate filaments are different types depending on your tissue. Different tissues have different types. If you're talking about your mesenchymal cells, your intermediate filament will be vimentin. If you're talking about your epithelial cells, keratin. Your neural cells, neurofilaments, nuclear envelope, lamine, muscles, desmin, neuroglial cells, GFAP. Next, we'll talk about types of tissue, including your epithelial tissue and your connective tissue. As you know, what's the building unit of your body? The cell. Group of cells together, tissue. Group of tissues together, organ. Group of organs together, make a system, and the system will carry your body functions. Speaking of tissues, you have four types of tissues. Epithelium, connective, muscle, nerve. Epithelium, I cover your surfaces, I line your cavities. Doesn't that sound filthy? I stand upon a basement membrane. I am the parenchyma of your cells. Suppose we're talking about any gland in your body. The gland will have a parenchyma, the actual functioning cells, such as the neurons in your brain, the alveoli in your lungs, and basically this will be mostly epithelial cells. And the stroma, which is just for support, inner support, outer support, etc. And the stroma will be the connective tissue. Here are examples of epithelium in your body. Please pause and review. And here are different types of epithelium based on the number of layers or based upon the shape of the epithelium. Next, bringing people together. The connective tissue. When you talk about ligaments, bones, blood, tendons, fat, lymph, these are basically mostly connective tissue. The actual function is undertaken by the parenchyma, i.e. epithelium. But for the support, you'll need your connective tissue. Connective tissue, you speak about yourself. I provide support, I give a framework, I make your stroma that supports you. Without me, epithelium is nothing, left with no support. Moreover, I also make some collagen and elastin, so I'm not that useless. Epithelium is here, connective tissue is here. If I flip you upside down, metaphorically speaking, Will your organs fall out of place? The answer is no. Why not? Connective tissue, baby. Here are some examples of connective tissue. We're talking bones, cartilages, fat cells, or adipose. cells, tendons, muscles, some textbook even include blood and lymph as types of connective tissue. Next, the cell cycle. When you are resting your G0 and then you grow, growth phase 1, and then you make DNA, synthesis, and then you grow again, growth 2, and then mitosis or meiosis, M phase. Somatic cells versus germ cells. Pause and review. If I want to make another copy of my DNA, this is called DNA replication, which happens during the S phase of the cell cycle. Taking the DNA into RNA is transcription. Taking the RNA to proteins is translation. With medicosis, everything is a piece of cake. Where's the actual division happening in the M phase, mitosis or meiosis? That's why anything else is an interphase. G0 is for rest. G1 is for growth. because we're preparing for the S. In the S phase, you'll synthesize another copy of DNA. Hashtag replication. Then in the G2, you grow again. And then in the M phase, you have mitosis or meiosis. Pro, meta, ana, telophase. Pro, meta, ana, telophase. Pro phase, meta phase, ana phase, telophase. Pause and review. If the question asks you, when does karyokinesis and cytokinesis take place? The answer is M phase. And here are some pearls for you. Pause and review. Cell types. You have permanent cells or stable or labile cells. Labile cells are always dividing. Permanent cells do not divide. Stable cells do not divide under normal circumstances. But under crazy circumstances, they can divide, such as your liver. Permanent do not divide, such as your neurons. Labile, always dividing, such as sperm cells. GI cells, your hair, etc. Staple cells are only under certain conditions like the liver. If my cells are dividing like crazy with no check, this is cancer. How does chemotherapy work? They stop or arrest cell division. What's the good news? We're killing cancer cells. What's the bad news? We're also killing some of your cells, especially those who divide very rapidly. That's why with chemotherapy you get hair loss. and diarrhea. Cell cycle checkpoint to recognize the mutation or the error early on so that we can stop cell division. Otherwise, we can get cancer. We have three main checkpoints in the cell cycle. The first one is at the G1, or to be more precise, it's between G1 and S. So that if you discover an error, you do not go to S. Recall that the p53 and the RB genes are tumor suppressor. genes. The second checkpoint is here, between the G2 and the M, so that you do not progress to the M phase with an error. And the third checkpoint is in the M phase. It's called the metaphase checkpoint. And remember, during the metaphase, everything is aligned in the midline, and we thank our mitotic spindle. Defects in any area of the cell cycle checkpoints can lead to diseases, and here are some examples. Please pause and review. More examples, pause and review. And some more. If you have trouble with these, please check the original video called Cell Cycle Checkpoint in my Biology playlist. P53 is a tumor suppressor gene. What if my tumor suppressor gene is malfunctioning? Then you get what? Tumors! Which could be benign or could be malignant. Mitosis and meiosis. Here is a comparison between the two. Please pause and review. In mitosis, you start with 2N and you give me two identical cells. Each one is exactly identical to the parent cell, also 2N. But in meiosis, well, it's called a reduction division. Because you start with 2N and you give me four cells, each one is N. Each one is not identical to the parent cell. In fact, each new offspring is half the parent. What are the phases? Pro, meta, enatello, pro... before we're preparing meta everything is in the midline anna separate me and then what's your telos and purpose in life that's the last part during prophase there was condensation separation formation dissolution condensation of chromatin into chromosomes separation of the centriole pairs formation of the mitotic spindle we're getting ready and dissolution of the nuclear membrane next metaphase everything is m we are in the midline thanks to the mitotic spindle which is basically microtubule and you can draw the line in the sand here and you get a mirror image also an m we are lined in the midline. Anaphase separates me up, split the centromere and separate the sister chromatids. The kinetochore is doing the pulling. In telophase, the mitotic spindle disappears, we reform the nuclear membrane, we form these cleavage furrows, thank you microfilaments, and then you separate the cell into two cells, this is called cytokinesis. Myosis, there is myosis 1, and there is meiosis 2. Here is another comparison between mitosis and meiosis. Please pause and review. You know the saying that meiosis 2 is almost identical to mitosis. However, there are some tiny differences. Next, reproduction. This is the anatomy of the female reproductive tract. And here's the one for the male. Gonads in female, we're talking about the ovary. The gonad in males, the testicle. How about the gametes? Remember, this is meiotic division. In females, the gamete is the ovum. In males, the gamete is the sperm. Here is spermatogenesis. And this is oogenesis. Unlike spermatogenesis, oogenesis gives you one ovum and three polar bodies. Contrary to popular belief, fertilization is not when the sperm meets the ovum. Let's get technical. It's when the sperm meets the secondary oocyte, which is arrested in metaphase 2. Fertilization is when the sperm... meets the secondary oocyte which is arrested in meta phase 2. Remember that oogenesis has two famous arrests. Pro phase 1 and meta phase 2. Pro phase 1 and meta phase 2. Pro phase 1 were the primary one with one. Oocyte is arrested waiting for the female to reach puberty. How about the second arrest? Second arrest, secondary oocyte, meta phase 2. Everything here is 2. Waiting for what? for the sperm to go deep inside the ovum. X, X, female. X, Y, male. If you remember, this is my hypothalamus. Here's my anterior pituitary, which makes LH and FSH to influence the gonads. And then the gonads will give you the male hormones or the female hormones. This is the effect in the male. G, N, R, H from the hypothalamus will tell the anterior pituitary to make LH and FSH. FSH influences that Sertoli cell to feed the sperm. and to help with aromatization. But the LH is for lytic cell, which is to make testosterone. So what's the purpose of FSH in male? From to, I mean aromatization, from the female hormone to the male hormone. And then LH in males, lytic cell, to make testosterone and the even more powerful dihydrotestosterone. But what's the effect of FSH in females? It's called the follicle stimulating hormone. It stimulates the growth of the ovarian. follicle. How about LH in females? It's called luteinizing hormone. It helps make the luteal body, which will secrete progesterone until the placenta takes over. Here's the structure of the sperm. Remember that the nucleus is in the head, the mitochondria is in the middle piece. Here's the process of spermatogenesis. Thank you, Sertoli cells. We start with spermatogonia, then primary spermatocyte, secondary spermatocyte, and then sperms. Let's make an ovum. Follicle-stimulating hormone is going to stimulate the follicle growth. And then what? And then the LH is going to surge around day 14 and pew! Rupture the follicle, release the ovum. The ovum will go to the uterus. The rest of the follicle will become luteal body, which secretes progesterone. If fertilization happens, progesterone and estrogen will remain high. But if it did not happen, progesterone will drop, estrogen will drop. and the uterine lining will drop. Hashtag menses or menstrual bleeding. Pause and review. These are the phases of the menstrual cycle. We have proliferation phase. Thank you, estrogen. Secretory phase. Thank you, progesterone and some estrogen. Menstruation phase. Everything is dropping like a rock. Here's the function of FSH, follicle, LH, the surge and the rupture. Hashtag ovulation. And then the estrogen, female sex characteristics. and then progesterone, female secondary sex characteristics, and it sustains the endometrium of the uterus, and it raises the core body temperature in the second half of the cycle, because progesterone is more abundant in the second half of the cycle. The structure of the ovum, please pause and review. The steps of fertilization are 5. Capacitation, acrosomal reaction, polyspermy block, completion of meiosis 2, where the secondary oocyte was arrested in metaphase 2. and then you make a zygote. Capacitation is to increase the capacity. Thank you so much, calcium. Next is the acrosomer reaction. Recognition happens, release of hydrolytic enzymes so that the sperm can pierce through the zona pellucida. Next, to avoid double and triple and quadruple fertilization, there is polyspermy block to avoid polyploidy. After this, you complete meiosis 2, where the secondary oocyte was arrested in metaphase 2. Now the secondary oocyte is ready to become an ovum. After this, zygote formation. Congratulations. A zygote is one complete cell with 46 chromosomes. And then it will grow and grow embryo. And then grow and grow fetus. After birth, you are a neonate. Then an infant. After fertilization, there is cleavage, mitotic division. And then blastulation to make a blastocyst. Here's the blastocyst. We have an inner cell mass which will become the embryo itself. and an outer cell mass, trophoblast, which will become the placenta. Fertilization, then cleavage, then blastulation. After this, implantation in the uterine wall. Then you have the bilaminar embryo, epiblast and hypoblast, and the trilaminar embryo, endoderm, mesoderm, ectoderm. When you try to generate different layers, this is called gastrulation. Please pause and review. Here is the bilaminar embryo. and the trilaminar embryo. You need to memorize everything on this slide. If you want to learn about neurlation, check out my video called Neuralation in this biology series. But please remember that the nervous system comes from the ectoderm. The central nervous system, i.e. brain and spinal cord, come from the neural tube. The peripheral nervous system comes from the neural crest cells. This is your spinal cord, for example. The spinal cord itself is central nervous system, therefore neural tube. But the spinal nerves are peripheral nervous system, therefore neural crest cells. This is your neural tube early on. The anterior neuropore, this will become your brain, but the posterior neuropore will become your spinal cord. Stem cells. Totipotent, pluripotent, multipotent, unipotent. Think of it like a tree. branching and differentiating. these are pluripotent stem cells in the bone marrow, which gives you the blood cells. do you remember the bilaminar embryo? yeah, the inner cell mass is an example of totipotent stem cell, because it can give you any part of the embryo. how about the mesoderm alone, such as mesodermal cell in the mesenchyme of your bone marrow? they are pluripotent. for example, the bone marrow can only give you blood cells. not every single imaginable cell. Do adults have stem cells? Yes, they do. In fact, this is how you regenerate. The stem cells of your skin are the basal layer or the stratum basalis. In the alveoli, they are type 2 pneumocytes. Please remember that type 2 pneumocytes have two functions. Function number one, they are the stem cells of your lungs. Function number two is to release surfactant, which is anti-surface tension. The stem cell of your bone marrow is the hematopoietic stem cell, which is pluripotent. And the cell that regenerates sperms is spermatogonia. Apoptosis versus necrosis, please pause and review. We have two types of cell regeneration. There is complete and incomplete. Each time you undergo cell division and you pass through the cell cycle once, you're getting older. Your telomeres are shortened. Do this many times. and you are senescent, old. When your telomeres are shortening, it means that you are aging. But what if my telomeres do not shorten, like ever? Is this a good thing? Shut up, it's a horrible thing, it increases your risk of cancer. This slide is historic, that's why I keep repeating it. Pause and review. Next, let's talk about the fetal circulation. What's the purpose of the placenta? Give oxygen and nutrients from mommy to baby. and give CO2 and waste from baby to mommy. This is the difference between the adult circulation and the embryological circulation. Here is how the placenta looks. This is the maternal surface and this is the fetal surface. Fetal hemoglobin or hemoglobin F will shift the oxygen dissociation curve to the left and with left shift the tissue is left behind because oxygen will remain on the hemoglobin and will not go to tissue. Do you remember the story of the shifters of the oxygen-hemoglobin dissociation curve? With left shift, the tissue is left behind. Whose tissue? Mommy's tissue is left behind. You know why? Because this oxygen is gonna go to the hemoglobin F, because hemoglobin F loves the oxygen so much, i.e. more binding. but less dissociation and this is how the baby takes all the oxygen that it can from mommy smoking alcohol folate deficiency phenytoin warfarin thalidomide all of these are teratogens which can increase risk of congenital anomalies and mutations especially during the first trimester of pregnancy because during the first trimester the cells are dividing very rapidly that's why they are the most vulnerable this is the adult circulation we go from left ventricle and then all over your body back to right atrium right ventricle then give me to the lungs and then gas exchange back to the left atrium pause and review but the fetal circulation is different you are going to get the oxygenated blood from the mother thank you umbilical vein and then you bypass the liver thank you doctor's venosis we are in the inferior vena cava you go to the right atrium and thanks to the patent for raymond ovale you go to the left side Oxygenated blood will go all over your body. The deoxygenated blood comes back through the superior inferior vena cava. This deoxygenated blood was trying to go to the lung, but because the lungs are closed with very high resistance, the pulmonary artery said, you know what, screw it, I'm not going to the lungs. I'm gonna bypass the lung. Thank you, ductus arteriosus, and I will dish my blood onto the aorta. What's the fate of this embryological structure after birth? Ductus venosus will become ligamentum venosum. Foramen ovale will close and become the fossa ovalis. Ductus arteriosus will become ligamentum arteriosum. The nervous system. Central and peripheral. Central, brain and spinal cord. Peripheral, cranial nerves, spinal nerves. In your spinal cord, the gray matter is on the inside. White matter is on the outside. But in the brain, it's the opposite. Remember that myelin appears white. Therefore, if I am unmyelinated, I appear gray. Pause and review. Somatic is something that you can control, voluntary. Autonomic is something that you cannot, involuntary. The autonomic nervous system could be sympathetic or parasympathetic or enteric nervous system in your gut. A collection of cell bodies in the CNS is a nucleus. A collection of cell bodies in the PNS is a ganglion. A collection of axons in the CNS is a tract. In the PNS, it's called a nerve. What's the structural unit of the nervous system? Neuron. How about the functional unit? Reflex arc. Who makes myelin? Well, in the CNS, it's the oligodendrocytes, but in the PNS, it is Schwann cell. Myelin increased conduction via saltatory movement. Type A and B nerve fibers are myelinated, but type C fibers are unmyelinated. All your neurons have a neural embol sheath regardless. Why do we need action potential? Because the action potential is life. The nerve impulse in your body is unidirectional. It always goes in the direction from the soma towards the axon terminalis. The beginning part of the axon is the axon heloc. And this is the structure of the neuron. Please pause and review. This is the structure of your nerve. Endoneurium on the inside, then perineurium, and everything is covered with epineurium. Neurotropins are not the nerve impulse. Nerve impulse is unidirectional. It goes down there. But neurotropins can go by retrograde. Nestle bodies are a very important exam question. This is rough endoplasmic reticulum, and they are found in the neurons, but not in the axon. Please pause and review. And this is why myelin is awesome. What is the pilot of the nervous system? The neuron. How about the co-pilot? The co-neurons, i.e. neuroglial cells. The first two will make myelin. Astrocyte is for the blood-brain barrier. Microglia is the macrophage of your nervous system. Ependymal cells make the CSF. Do you remember my intermediate filaments? Yeah. In the neurons, they are the neurofilaments, but in the glial cells, they are the GFAP. Pause and review. If I lose my myelin in the CNS, this is multiple sclerosis. If I lose the myelin in the PNS, this is Guillain-Barré. More about the action potential. During resting state, potassium is leaving. And when the positive leaves, the inside becomes more negative. That's why it's resting, which means inactive. But when sodium decides to enter, sodium is positive. When positive comes in, the inside becomes more positive. Hashtag activation. Hashtag depolarization. During rest, resting membrane potent. Upon stimulation, action potent. Here's the action potent. During rest, potassium is leaving. That's why the inside is negative. And then upon depolarization, sodium enters. The inside becomes more positive and we are very active. Then we go back to being inactive. This is called repolarization. And if you take it too far, hyperpolarization, because potassium is leaving and the inside is becoming more negative again. Who's responsible for the resting membrane state? selective permeability, i.e. more potassium leaves than sodium entering. When the positive leaves, the inside becomes more negative. The second thing responsible for the resting membrane potential is the sodium potassium 80 base pump. Here's the action potential. Please pause and review. Depolarization is sodium entry. Repolarization is potassium efflux. And let's put everything together. When your neuron is sick and tired of being sick and tired, it's called the refractory period, which means I cannot get excited again. There is the absolute refractory period with very high standards. I am not going to be excited again no matter what. But relative refractory period is like, forgive me, is a two dollar hooker. I'm not gonna react, I'm not gonna be excited, but if you give me super threshold, too much money, I might give you an action potential. These are the types of fibers that we have, cholinergic versus adrenergic, and the receptor on each. Pause and review. How do I get the target to get excited? First, sodium entry, this is depolarization, and then action potential propagates in the presynaptic neuron. Calcium entry, calcium ruptures the vesicle, and then pew, exocytosis. Acetylcholine is going to bind to the acetylcholine receptor, assuming that this is a cholinergic fiber. And then look at the receptor here. if this is a skeletal muscle, nicotinic sub-M, and then the muscle will have its own action potential. How does the muscle contract? Well, well, well, the end plate potential will propagate through the T-tubules of the muscle, and then calcium will be released. Calcium with a C binds troponin C, and then myosin binds actin G contraction. The comparison between somatic and autonomic is very important. So please pause and review. If this is a ganglion, the fiber before it is preganglionic, the fiber after it is postganglionic. Before it, it's type B fiber, that's why preganglionic are myelinated. But in the postganglionic, we're talking C fibers, unmyelinated. Only autonomic fibers have ganglia. The somatic system does not. This is the sympathetic nervous system, thoracolumbar. And this is the parasympathetic system, which is craniosacral. What do you mean by cranio? I mean 1973. Cranial nerve 3, cranial nerve 7, 9, and 10 are the only cranial nerves that are parasympathetic. This is what happens when you are in fight-flight mode. Pause and review. And this is parasympathetic. Rest and digest, read, eat, and take a dump. Urination defecation. Sympathetic nervous system, when you're running from a tiger, you need to see far ahead, so far vision, because my lens is flat. However, if you are parasympathetic lens, you want to read a book, rest and digest, eat, read and take a dump. When you are reading, you need your lens to be spherical, accommodation. The sympathetic nervous system is gonna dilate the pupil, thank you alpha 1, but the parasympathetic will constrict the pupil, thank you M3 receptor. Here is the effect of sympathetic and parasympathetic on the male capillary organ. Parasympathetic will point. Sympathetic will shoot and shrink. On the urinary bladder, sympathetic will relax the wall, constrict the sphincter. But parasympathetic will contract the wall, relax the sphincter. Which sphincter? The internal. because it's involuntary, hashtag autonomic. Contrast that with the external, which is voluntary, hashtag somatic. Compare and contrast between sympathetic and parasympathetic. The parasympathetic is always cholinergic. However, the sympathetic starts cholinergic in the preganglionic, but the postganglionic is adrenergic. The endocrine system, hypothalamus, is interpituitary. Three glands that listen, three glands that do not care. The three that listen are thyroid, adrenal cortex, gonads. The thyroid listens to the pituitary's TSH. Adrenal cortex will obey the pituitary's ACTH. The gonads will listen to FSH and LH. All of these hormones are made and secreted by the anterior pituitary. However, ADH and oxytocin are made by the hypothalamus and then released by the posterior pituitary. the effect of different hormones on the female breast. estrogen increases the size and makes some ducts. progesterone makes the alveoli or the acini. prolactin is gonna fill them with milk. oxytocin is gonna push the milk out. if this was oxytocin how about adh then? this is for reabsorption of free water in the collecting ducts of your kidney. adh is called vasopressin with a v therefore the name of the receptor is v2 And the channel is called Aquaporin2 channel, free to choose. Choose what? Water only, without sodium. Here is the pituitary again, anterior pituitary versus posterior pituitary. Pause and review. Insulin versus everybody else. Insulin is anabolic on everything. All the other hormones are catabolic on everything. But growth hormone is kind of in the middle. From insulin, it borrowed the first thing. which is protein anabolic. But from the other hormones, it borrowed number 2 and 3. It is glycogen catabolic and fat catabolic. Here are the actions of growth hormone. Please pause and review. Thyroid land. Let's make thyroid hormone. Don't forget that we need iodine. What's the key enzyme? Thyroperoxidase. Who's gonna bind tyrosine? Thyroglobulin. Here are the actions of thyroid hormone. Remember, it's the stove of your body. It increases and boosts metabolism. That's why if you have too much thyroid hormone, everything is working really fast. But if you have hypothyroidism, I am so lazy. Behind the thyroid gland, we have two pairs of glands known as parathyroid glands to make the parathyroid hormone. The parathyroid hormone is pro-calcium. It increases calcium in the blood. However, it's also a phosphate-trashing hormone. It decreases serum phosphate. Calcitonin hates everybody, so lowers your calcium and phosphate. Vitamin D3 has a brain. I can increase serum calcium just like PTH. However, I noticed that both of them are trashing phosphate, which is dangerous because you need adenosine triphosphate, which is ATP. So I'm going to raise serum phosphate. Adrenal cortex versus adrenal medulla. The cortex will make aldosterone. cortisol, adrenal androgens. The medulla will make catecholamines including dopamine, norepinephrine, and epinephrine. What's the function of aldosterone made by the zonaglomerulosa? It reabsorbs two things and dumps two things into the urine. Glucocorticoids want to boost glucose via gluconeogenesis. Adrenal androgens are androgens. Don't you ever forget the renin and gluten in aldosterone system. The kidney makes renin, which converts angiotensin O-gen to angiotensin 1. Then ACE from the lung, the angiotensin-converting enzyme, is going to convert angiotensin 1 to angiotensin 2, which has two functions. Function 1, constrict vessels. Function 2, make aldosterone from the zonaglomerulosa of the adrenal gland, which will reabsorb two things back to the blood and dump two things down the toilet. Here is the adrenal medulla and the catecholamines, remember the song, phenylalanine tyrosine, dopedupamine, norepinephrine epinephrine. The adrenal cortex came from the mesoderm, but the medulla belongs to the ectoderm, because it's part of the peripheral nervous system. We treat her like a ganglion. Adrenal cortex vs medulla, pause and review. Pancreas time! Exocrine vs endocrine. Exocrine is to make the enzymes endocrinase to make the hormones what kind of hormones insulin from the beta cells and glucagon from the alpha cells insulin is anabolic it builds up protein from amino acid it builds up glycogen from glucose. It builds up triglycerides from free fatty acid. But glucagon is a destroyer. That's why it goes in the opposite direction. That's why when you're feeding, it's time to build up. You need insulin. But when you're fasting, it's time to break down and get some energy. You need glucagon. Alpha cell for glucagon, beta cell for insulin, and delta cell is the doofus somatostatin because it inhibits everything. Do you remember reproduction? Pause and review. Do you remember this? Pause and review. More hints about endocrine. Pineal glands make melatonin important for circadian rhythm. The kidney makes EPO which goes to the bone marrow to boost red blood cell production. When the heart gets stretched out because I have volume overload or heart failure, I secrete ANP or BNP, natriuretic peptide. Natriuretic. You will lose the natrium sodium. and water in the urine. It's time to breathe! Here's the anatomy of the respiratory system. Please remember that you have a conducting zone and a respiratory zone. Here are the functions of each part of your respiratory tract. Here's a comparison between conducting zone and respiratory zone. Your pleura surrounds your lungs. It's filled with a thin layer of fluid. It has a visceral layer and a parietal layer. air pressure is higher in California than Arizona, then wind will blow from California to Arizona, from high pressure to low pressure. Review Boyle law, which means volume and pressure, hate each other. If one is going up, the other is going down, provided that temperature remains constant. When I'm trying to breathe in, I expand my chest, volume goes up, pressure goes down, I have a more negative pressure inside. Therefore, I'm gonna suck air in because negative pressures pull in stuff. The exact opposite happens during expiration. You breathe air in from the atmosphere, it goes to your lungs, then it goes to your arterial blood. In the beginning, free and dissolved. Then it jumps on the hemoglobin, the cell will use it, and then you get the CO2 back to the hemoglobin and the lung will breathe it out for you. Surface tension is dangerous. It wants your lungs to collapse and recoil. But thankfully, you have a surfactant made by type 2 pneumocytes. And this surfactant is anti-surface tension, so that you can breathe. Here are the pulmonary function tests. Please pause and review. Lung volumes are here. Lung capacities are here. What's an acid? Anything that gives you protons. The more protons you have, the... higher your hydrogen ion concentration and the lower your pH. In your body, metabolism secretes acids and carbon dioxide, which is technically an acid because it combines with water and give you carbonic acid. Who will get rid of this volatile acid? The lungs. Who's going to get rid of these non-volatile or fixed acids? The kidneys. If you metabolize more, you will end up with more acids. If you breathe more... hyperventilation will lower your carbon dioxide in the blood. Conversely, hypoventilation will raise the carbon dioxide in your blood. Please pause and review Louis Châtelier's principle. If your bicarbonate goes up and pH goes up, this is called metabolic alkalosis. If bicarbonate goes down and pH goes down, this is called metabolic acidosis. If carbon dioxide goes up, pH will go down. respiratory acidosis. If carbon dioxide goes down and pH goes up, this is respiratory alkalosis. Between the artery and the vein, which one is more acidic? Of course the vein is more acidic because carbon dioxide is dumped from the cell onto the vein. And carbon dioxide is a freaking acid. When you go up on top of a mountain, there is a lower pressure, therefore lower PaO2. But the air itself is still 21% oxygen, so FiO2 did not change. Then why do I have less oxygen in my alveoli? Because the pressure of the atmospheric air, which includes oxygen, went down. Anytime you have low oxygen, your body will respond. By making more red blood cells, thank your kidney for secreting erythropoietin, and it can also make new blood vessels. When you're exercising, or when you go on top of the mountain what's going to happen shift to the right how about the opposite shift to the left anytime i exercise my right arm the right arm will have more metabolism and therefore more carbon dioxide more acidity because carbon dioxide is an acid i'm raising the temperature of my right arm and increasing glycolysis and therefore 2-3 bpg when all of them go up I will shift to the right. With right shift, there is giving of the oxygen to the tissue, which means oxygen is leaving the hemoglobin and going to the tissue. The exact opposite happens with left shift. With left shift, the tissue is left behind because oxygen is remaining on the hemoglobin and away from the tissue. Here's the effect of high altitude on your body. Please pause and review. When I go on top of the mountain, I get hypoxia and my body will respond. I shifted my oxygen dissociation curve to the right and the tissue is happy with more oxygen. Since there is less oxygen pressure upstairs, I will breathe more. Therefore, carbon dioxide in my blood will decrease because of the hyperventilation and the pH will go up. We call this respiratory alkalosis. Cardio time. Here is the adult circulation. Here are the four valves in the heart. All of them are tricuspid, i.e. with three cusps, except the mitral which only has two cusps. Do veins have valves? Yes. How about arteries? No. Please remember that the cardiac muscles are striated, involuntary, uninucleated, and branching, with lots and lots of gap junction. The gap junction is very important for your heart because it allows the entire heart to contract as a one singular unit, a syncytium. Here's the SA node and the AV node. That's why your heart is automatic. Sympathetic and parasympathetic are not initiators. They are just regulators. What causes the first heart sound? The closure of the mitral and tricuspid valves together. How about the second heart sound? The closure of the aortic and pulmonic valves together. Between the first heart sound and the second heart sound, it's called systole because your ventricles are contracting. Between the second heart sound. And the following first heart sound is called diastole because your ventricles are relaxing. Cardiac output is heart rate times the stroke volume. The productivity of your heart is based on how fast times how strong your heart is beating. The pressure inside big vessels is 120 during systole and 80 during diastole. But in the left ventricle, it's 120 during systole. Same. But almost zero during diastole. Then how come the aorta was 80, not 0 during diastere? It's thanks to clamping down on that blood, and this is why you get the diacrotic notch. That's how the aorta prevented your pressure from dropping to zero during diastere, unlike the left ventricle. Let's talk about volume of blood in the left ventricle. When the ventricle is squeezing itself and pushing the blood out, less blood will be left in the ventricle. Zip, you go down like this. But when the ventricle is relaxing and receiving blood, the volume of blood in the left ventricle will go up. Put everything together in one shot and you get the lovely cardiac cycle. You need to understand everything here. Let's talk about capillaries. There is arterial end and venous end. Each vessel is made of tunica intima, tunica media, tunica adventitia. Contrast and compare among arteries, veins, and capillaries, please. These are the different types of arteries. different types of veins and different types of capillaries in your body some pro tip if you vasodilate you'll increase the radius and the diameter of the vessel therefore the resistance goes down the afterload goes down the blood pressure goes down remember the meta arterio please and remember that we have pushing forces hydrostatic pressure thank you blood volume and we have pulling forces oncotic pressure thank you albumin which is a plasma protein. If I want to feed my cell, i.e. I want the blood to go this way, from the capillary to the cell, therefore the favoring forces should exceed the opposing forces. What are your favoring forces here? Hydrostatic pressure in the capillary and oncotic pressure in the interstitial fluid. What are your opposing forces? Oncotic pressure in the capillary, because it pulls this way, and hydrostatic pressure in the interstitium. And then you do it this way. Favoring forces minus opposing forces. If the end result is a positive number, it means that you are pushing fluid out of the capillary into the cell. Let's talk about blood cells and plasma. As you know, your blood is made of plasma and cells. These cells are red blood cells, white blood cells, and platelets. But the plasma is water and proteins. Could be albumin proteins or globulin proteins. Which one is responsible for the oncotic pressure? Albumin. Which one will give your coagulation factors and your antibodies? Globulin. These are your blood cells. Please pause and review. Red blood cells are circular, biconcave, non-nucleated. They do not have a mitochondrion. Therefore, Where there is no Krebs cycle, no electron transport chain in the red blood cell, the only source of energy for the red blood cell is glycolysis, basically. Next, white blood cells. Why do we have neutrophils? They fight bacteria, and they are the cells of acute inflammation. Why lymphocytes? They fight viruses and fungi, and they are the cells of chronic inflammation. How about monocytes? They become macrophages, which are phagocytic cells. They eat up stuff. Eosinophils fight parasites and allergy. Remember eosinophils? Ew! How about basophils? They release histamine. Platelets or the thrombocytes? They help you make a clot. to stop the bleeding. How do you stop the bleeding? First, you vasoconstrict, then the platelets will help you in primary hemostasis. Then the coagulation factors, i.e. beta globulins, will help you. This is secondary hemostasis. Here is primary hemostasis. Thank you, platelets. Here is secondary hemostasis. Thank you, coagulation factors. Next, on the surface of your red blood cell, we have the ABO antigen system, and we have the RH antigen system. You only have two antigens, by the way, A and B. Well, how about O then? O means zero. O, you have neither A nor B. That's why we call you O. Please pause and review. Don't forget the blood typing and blood matching, which we have discussed before. Next, immunity. You have innate immunity, you're born with it, and adaptive immunity, which you acquire. The innate immunity is non-specific at all. Cells of the innate immunity are many. don't forget the macrophages, the microphages, mast cells and basophils, dendritic cells, and the natural killer cells. But when it comes to the adaptive immunity, we have B lymphocytes, hemorrhoids, or T lymphocytes, cellular. Here are the B lymphocytes making plasma cells, which will secrete antibodies. You have IgM, IgA, IgG, IgE, and IgD. All of them are gamma globulins. Each of these antibodies has heavy chains and light chains. When something invades your body, you take a piece called an antigen. Then the antigen-presenting cell will present that antigen to the lymphocyte. The lymphocytes can destroy that microbe. If it's a B lymphocyte, it will grow and become plasma cells to make antibodies. And more importantly, it will develop memory so that the second exposure is faster and stronger. Here is a comparison between hemoral immunity. and cell-mediated immunity. Here are your lymph nodes. Remember, there is the police academy. For the B lymphocytes, it's the bone marrow. For the T lymphocytes, it's the thymus. Then we have police officers. These are the lymphocytes. Then we have police stations. These are the lymphatic organs. Here is the lymph node. It has a cortex. It has a medulla. And in between, it has a paracortex. The cortex is for the B lymphocytes. Paracortex is for the T lymphocytes. and then the medulla with the medullary sinus is for plasma cells and macrophages. Compare and contrast, and again, and one more time. Next, digestion. Digestion is to break down the macro into the micro, and then you are able to absorb the micro and send it to blood. The liver will metabolize it. If you could not digest it and absorb it, you will end up pooping it. Your gut has a wall and a lumen. The wall is made of mycosis, submucosa, musculosus, cirrhosis. Digestion could be mechanical by motility or chemical by secretions. Motility is by the myenteric plexus. Secretion is with the submucosal plexus. You have lots of glands in the GI. Part of them are just part of the elementary canal. Others are outside or accessory glands. Here's the anatomy of the digestive system. Now let's talk about the function from head to toe. In the mouth there is mechanical called mastication and chemical digestion called salivation. The enzyme is amylase. The function is carbohydrate digestion. Next send the food to the pharynx and then the esophagus and then the stomach. The stomach has mechanical which is motility and chemical which is secretion. You need to memorize every cell in the stomach and what it makes. GI hormones include gastrin which is made by the G cell. The only hormone that is pro-stomach. increases motility and secretion of the stomach. Secretin is secreted by the S cells in the upper part of small intestine. Secretin tells the pancreatic ducts to make lots of water and bicarb to neutralize the acidity. CCK, cholecystokinin pancreaszyme. It's called cholecystokinin because it squeezes the gallbladder. It's called pancreaszyme because it increases the release of pancreatic digestive enzymes. from the acinar cells. Somatostatin is the doofus from the delta cell. Why doofus? Because it inhibits everything. It even then inhibits its own secretion. In order for you to digest and absorb the fat and the fat-soluble vitamin, you need three organs to be healthy. Liver and biliary system, pancreas, and the gut. After you digest, what do you do? You absorb. What if you could not absorb? Then you excrete. If you happen to be water-soluble, you will go the blood route. But if you are fat-soluble, you will go through the lymph route. And this is true for vitamins. If you are water soluble vitamin, blood route. If you are lipid soluble vitamin, lymph route. Here is all of digestion in one slide. Here is how we digest carbohydrates. Here is how we digest proteins. And here is how we digest fat. Next, kidney. Please review your anatomy and the physiology of the kidney. After the renal artery branches and branches and branches even more, you get the afferent arteriole, which becomes the glomerular capillary tuft, and then you push fluid this way called filtration. If you cannot push it, it's going to end up in the efferent arteriole, which will become peritubular capillaries. Here is the afferent, here's the glomerular capillary tuft, here is the efferent. The efferent will become peritubular capillaries. Now let's talk about the nephron. Here's the Bowman's capsule, proximal tubule. loop of Henle distal tibial collecting ducts. When something leaves that filtration fluid in the nephron and goes to peritibular capillary, this is called reabsorption. The opposite is called secretion. Anything that's going to end up in the urine is called excretion. How do we move based on what? Starling forces, hydrostatic and oncotic. Hydrostatic pushes, oncotic pulls. Hydrostatic depends on the volume of fluid. but oncotic depends on albumin. If you want filtration from the glomerular capillary to the nephron, the favoring forces should exceed the opposing forces. But if you want reabsorption, it's going to be the opposite. If you want secretion, it's going to go from here to there. Next, the skin. It has many functions. The epidermis of your skin came from the ectoderm, but the dermis is derived from the mesoderm. Here are the different layers of the epidermis. Please remember that the stratum basale is the stem cell for regeneration. The dermis is the connective tissue underneath. The skin is important for thermoregulation. Please pause and review. Bones and muscles. You have three types of muscles, right? We have compared among them before, correct? When it comes to smooth muscles, just say no. Here's the structure of your muscles from the inside to the outside. endomysium, perimysium, epimysium. Just like the nerve, endoneurium, perineurium, epineurium. Each muscle is made of muscle fibers. Each fiber is made of myofibrils. Each fibril is made of myofilaments, which include the thin actin and the thick myosin. Please pause and review. Please review the difference between the A-band and the I-band. I-band has only actin. A-band has myosin and actin. The H zone has only myosin. Upon contraction, what happens? Your I band will shorten. Your H zone will shorten. But E band does not change. How about the length of the entire muscle? It decreases. Contraction is sliding of myosin and actin. Myosin is going to extend those cross bridges and pull actin towards the midline. Skeletal muscles have nicotinic receptors. Smooth muscles have... muscernic or adrenergic receptors. How about cardiac muscles? Similar to smooth muscles. This is the neuromuscular transmission again. Please pause and review. When the action potential reaches the muscle, it will traverse the muscle via T-tubule, and then calcium is released from the jail, which is the terminal cistern of the sarcoplasmic reticulum, and then calcium will bind troponin C, and then tropomyosin is removed. The active site is exposed, myosin will pull actin towards the midline, hashtag contraction, which require lots of ATP. Let's compare between type 1 muscle fibers and type 2 fibers. Muscle contraction requires lots of ATP, which is in the myosin head because it has ATPase activity. Metabolism of the muscle. First, you start by using the phosphagen system, creatinine phosphate. ADP will become ATP and you have some energy. Thank you, creatine kinase. After this, you need to rely on your glycolysis to give you the famous two ATP molecules. After this, you need your oxidative phosphorylation and electron transport chain, i.e. TCA cycle and ETC, which gives you a net of 38 ATP molecules. After exercise, the muscle... And the lung made a deal. Hey, hey, hey, I'm the muscle. I need 500 ml to complete that marathon. But I can only get 400 right now. Okay, here's a deal. You can give me the 400 right now, but then after I finish exercise, you owe me 100. Bet. That's the oxygen debt. And that's why you're hyperventilating even after you finish the marathon. Why are you doing this? The lung is paying back her debt. Why is this 100 ml of oxygen crucial? For reformation of ATP and creatinine phosphate, removal of lactic acid, and refilling the myoglobin with oxygen. Next, bone and cartilage. We have exoskeleton and endoskeleton. If you're a human being, you only have an endoskeleton. Your endoskeleton is either axial in the midline or appendicular in the extremities. Bone. We have the head, we have the shaft. We have epiphysis, we have diaphysis, and we have metaphysis in between. Your bone could be compact, especially on the outside, or spongy, especially in the middle, near the medulla, near the bone marrow. Osteoblasts will build up your bone, but osteoclasts will cut down bone. Your bone is basically matrix, thank you collagen, and minerals, thank you calcium and phosphate. What kind of collagen is in bones? Bones have type 1 collagen, but type 2 collagen is in cartilage. Please review your haversian system. And here is a distinction between bone and cartilage. Type 1 versus type 2, vascular versus avascular. When two bones are ready to meet each other, it's a joint. And you have some lovely fluid for lubrication. And there are three types of joints in your body. Coming up next, genetics. This is the big picture of genetics. Please review the difference between penetrance and expressivity, which could be variable or constant. Understand and memorize your definitions. Master dominant versus recessive. Homozygous versus heterozygous. And here are the laws of Gregor Mendel. The first law of segregation. Thank you, NFA's one. And the second law of independent assortment. Thanks, pro phase one. This is pro phase one. the tetrad and the crossing ova, which explains the second law of Mendel. All the alleles in a given population of people is called the gene pool. Can we have mutations? Of course! We can have mutations affecting the nucleotide or a mutation affecting the entire chromosome. Please pause and review. Do not forget that missense is sickle cell disease. Nonsense will give you a stop codon. Stop the nonsense! You need to draw tons of Punnett squares before your exam. This is the result when you have one autosomal dominant parent and another autosomal recessive parent and both are homozygous. This is the result. Let's take that first generation and marry them with another person from the first generation and what do you get right now? You get a different ratio as you see and this was called the mono hybrid cross because we're talking about just one characteristic which is their color. But what if we're talking about two things, their color and their height? Then it's gonna be the dihybrid cross with a different ratio. Please pause and review. This is the result of sex-linked crosses. We can map genes and chromosomes and get the recombination frequency, which is proportional to the distance between two genes on a freaking chromosome. Using this theta, or recombination frequency, you can deduce the order of genes on a chromosome, and we've talked about this before. Hardy-Weinberg equation. It's not hard, you just need to memorize two equations. More importantly, you need to understand what each letter refer to. For example, the p alone is the frequency of the dominant elite in a population, but the p squared is talking about an individual in that population. p alone is the tall allele. p squared is a tall individual. and here is an example that we did before. just by giving you the first number which is 70 percent you can deduce all of the rest. please pause and review and do it yourself. evolution basics. do not confuse natural selection with evolution. they are not identical. in fact natural selection is a mechanism for evolution. there is the old theory and the modified modern synthesis theory. We have different modes of natural selection, could be stabilizing, directional, or disruptive. When it comes to reproductive isolation, it could be pre-zygotic, which prevents the zygote from forming in the first place, or post-zygotic, which allows the zygote to be formed. However, it's going to be non-viable or sterile. An exam question will ask you about the mule. The mule is an example of... hybrid sterility, which is a post-zygotic isolation. Pattern of evolution are many. We have divergent, parallel, and convergent. We did it! You can download my notes at medicosisperfectionalist.com. They have extra points than we discussed in this video, and you can download my surgery high yields course if you are interested. I also have many other pharmacology courses. The biology playlist is complete, and I've started talking about biochemistry in a separate playlist called biochemistry for the mcat thank you for watching please subscribe hit the bell and click on the join button you can support me here or here go to my website to download my courses be safe stay happy study hard this is medicosis perfectionatus where medicine makes perfect sense

What is going on? It's Medicosus Perfectionatus where medicine makes perfect sense. This is the ultimate biology review video.

First of all, let me be clear. Trying to review all of biology in less than 90 minutes is an insane task. I'm going to go over the most important points in this video. And we'll do this in the following order. We will start by talking about the cell and what's in it.

Of course, there is the nucleus with DNA and the cytoplasm with the organelles. Then we'll talk about reproduction, mitosis, and meiosis. After this, embryogenesis and the fetal circulation, followed by the nervous system, somatic and autonomic, central nervous system versus peripheral nervous system.

After that, the endocrine system. Then the respiratory system, followed by the cardiovascular system. Next, the immune system, digestive system, homeostasis, which includes kidney and skin. musculoskeletal system, bone and muscle, and last will be genetics and evolution. So let's go!

This video will be a very quick review. If you want the detailed explanation, go to my biology playlist. First, cell theory. Prokaryotes versus eukaryotes.

Karyote is the nucleus. So which one has the true nucleus, the true nut? Eukaryotes.

It's a true nucleus bound by a membrane. And it's not just the nucleus. Even the organelles are bound by membranes.

Eukaryotes have mitochondria. They can make their own energy. Their DNA is protein-bound, but the prokaryotes have naked DNA.

In eukaryotes, the DNA is linear, anti-parallel. In prokaryotes, it is circular. Give me one example of prokaryotes, bacteria.

How about eukaryotes? We have many, including mammals, which will include humans. What are the fundamental tenets of the cell theory? Number one, all living things are composed of cells. No kidding.

the cell is the basic functional unit of life cells arise only from pre-existing cells this is the story of reproduction cells carry genetic information in the form of dna here's your cell it has a nucleus it has cytoplasm if you lump them together this is called the protoplasm the cell is bound and surrounded by a plasma membrane or a cell membrane or a lipid bilayer what kind of lipid phospholipid in this lovely cell membrane the head is hydrophilic. It loves water. So we put it on the outside.

How about the tail? Well, the tail is on the inside because it hates water. It loves lipid, but it hates water. Hydrophobic lipophilic.

And since there is water outside the cell and water inside the cell, we will put the water loving hydrophilic heads towards water, i.e. on the outside and the inside. And we will hide this hydrophobic tail away from water. just bury it in the center. What's the genetic material? DNA, which is organized in chromosomes.

You find chromosomes inside the nucleus. How about the organelles like the mitochondria? You'll find it in the cytoplasm.

The mitochondria will give you energy in form of ATP. Since the sperm needs lots and lots of energy, it has lots and lots of mitochondria. If you want to secrete a lot like the pancreas, you will need lots of Golgi and endoplasmic reticulate. Don't you ever forget that red blood cells do not have organelles?

They do not have mitochondria. Therefore, there is no TCA cycle or electron transport chain inside the red blood cell. Let's talk about these organelles.

The mitochondria is the powerhouse. Ligosome is the soldier. It destroys foreign invaders.

How about endosome? The delivery guy. The endoplasmic reticulum comes in two shapes, rough and smooth.

The rough is the translator. We translate proteins for secretion. We need rough endoplasmic and Golgi to work together.

How about the smooth? This is the donut for fat synthesis. Look how smooth this fat belly is. Golgi is the sorter. It modifies cellular products and directs them for delivery.

And it works in conjunction with the rough endoplasmic reticulum. Peroxisome from peroxide is the gym trainer, destroys fat. Is there a difference between cytosol and cytoplasm?

Yes. Cytosol is just fluid with no organelles. If you want to add the fluid, cytosol, to the organelles, now you have cytoplasm.

If you want to add the cytoplasm to nucleus, you get protoplasm. Here is your cell and your cell membrane. Inside we have protoplasm, which is nucleus and cytoplasm.

The cytoplasm is organelles plus cytosol. Next, the nucleus. This is the control room of your body.

Why? Because it has the DNA. DNA carries your genes. And don't forget the story of the nuclear pores inside the nuclear membrane. These pores allow entry and exit from and to the nucleus.

The outer membrane of the nucleus is continuous with the rough endoplasmic reticulum. This is how you make and then secrete proteins. Here's your DNA double helix. Wrap it around histones, wrap it around, wrap it around, wrap... But before you know it, we have your chromosomes.

How many of these do you have in each somatic cell? 46 chromosomes. Do you remember the nuclear pore? Yeah, this is when mRNA... tries to leave.

why does it want to leave? because it will get translated later in the cytoplasm. if you want to make another copy of dna this is called the replication.

if you want to convert dna into rna this is called transcription. if you want to translate the rna into meaningful proteins this is called translation. by the way you can download these notes and all of the notes in the entire biology series at medicosisperfectionellist.com Inside the nucleus, we have the nucleolus. For assembly of ribosome, ribosome.

This is the sentence of ribosomal RNA, the rRNA. Your average cell has only one nucleus. Red blood cells have none. Osteoclasts of bones have many.

Sometimes the nucleus is lobated or segmented, such as your neutrophils, which are white blood cells or leukocytes. Next, the powerhouse. The mighty mitochondria provides you with energy.

This is on a good day, but on a bad day, it will kill your cell. Why is this? Because this cell is old, malfunctioning, starting to become harmful, so it's gotta go.

Who's gonna let her go? Mitochondria. What do you call it when the cell plans its own death? Apoptosis.

Here's the structure of the mitochondria. Please pause and review. When you keep pumping protons, pumping protons, pumping protons, this is called electron transport chain.

Where does it happen? In the mitochondria. When you keep pumping protons, you are pumping them from the inside to the outside.

The cristae will increase the surface area for the electron transport chain. The inner membrane contains all of the molecules and enzymes necessary for the electron transport chain. But how about the inside matrix?

It has the enzymes for the Krebs cycle or the tricarboxylic acid cycle or citric acid cycle. Do not forget that your mitochondria has its own mitochondrial DNA. You got your mitochondrial DNA from your mother only, not from your father, because your daddy's sperm left his tail outside.

He left the mitochondria outside. Red blood cells, again, no mitochondria, but liver cell, gazillion mitochondria. Next, the destroyer. Let's destroy foreign invaders and let's destroy our own stuff. that is senescent and no longer of value.

The lysosome is a destroyer because it contains hydrolytic enzymes that work in an acidic medium. How come the lysosome is not killing me at all times? Because these hydrolytic digestive enzymes are protected and kept inside the lysosome thanks to the lysosomal membrane.

If you're a foreign invader, the lysosome will destroy you by endocytosis first and then destruction. If you are coming from within i.e. old senescent harmful particle then will destroy you by autophagy. In the former process, the lysosome needs help from the endosome for endocytosis, but in the latter process, it needs help from the phagosome for phagocytosis.

Here's the lysosome with the hydraulic enzymes engulf and do destroy. There is a protein here that helps this vesicle separate from the membrane. The name is called clathrin.

They love to ask about clathrin on the exam. Next, the endoplasmic reticulum is rough and smooth. Don't forget that it's continuous with the nuclear membrane. The rough is the translator to translate proteins which were coded for in the DNA of the nucleus and then secrete them to the outside.

That's why its membrane is continuous with the nuclear membrane. The smooth endoplasmic reticulum is the donut. The rough has ribosomes. Rough, ribosomes.

But the smooth, no ribosomes. function of the rough er translation i.e protein synthesis i.e to convert the rna into proteins how about the function of the smooth reticulum fat synthesis and detoxification don't forget that the sarcoplasmic reticulum in your muscle is a modified smooth endoplasmic reticulum here's the rough versus smooth endoplasmic reticulum Rough is to make proteins, smooth is to make fat and to detoxify. Don't forget that your steroid hormones are made of fat, and these include the sex hormones, such as estrogen, progesterone, and androgens.

Next is the sorter. Sort them and direct them for delivery. The Golgi works with the endoplasmic reticulum.

The nucleus has the code and it makes RNA in a process known as transcription. Then, this mRNA will leave the nucleus through the nuclear pore and will go to the cytoplasm, where it will get translated in the rough endoplasmic reticulum, i.e. protein synthesis. Then we put those proteins in vesicles, we give them to the sota, Golgi, and Golgi can secrete them to the outside world.

Here's your nucleus. mRNA will leave or continues with the rough endoplasmic reticulum, translate that mRNA into proteins. Then give me those lovely vesicles and pew, exocytosis.

From the intracellular fluid to the extracellular fluid. So the Golgi can work in harmony with the rough endoplasmic reticulum. Moreover, Golgi can work with endosome and lysosome.

We can do the exact opposite thing if this is a foreign invader. Get it in by endocytosis and then lysosome and then pew, we will destroy you. Paroxysome. the gym trainer that destroys fat.

It drives me crazy when students make a mistake on the exam when it comes to peroxisome. How can you forget that the name has the answer? Peroxisome, from peroxide.

Here is hydrogen peroxide. Why do you need this peroxide for beta oxidation of fat, lipid catabolism? Why do you need this hydrogen peroxide, Mr. Peroxisome?

Because it can help me kill foreign invaders. This is the story of the reactive oxygen species or free radicals. And this is a lovely peroxide for you.

Some diseases in medicine are paroxysmal diseases, such as adrenoleukodystrophy. On your biology exam, assume that all X-linked diseases are X-linked recessive, unless they tell you otherwise. If it's X-linked recessive, it's gonna be more common in boys.

Next, the cytoskeleton. What's the most abundant thing in every cell in your body? It's water. What's the second most abundant? Proteins.

We have two types of proteins in the cell. Structural, for the cytoskeleton, and functional, for enzymes, pores, channels, pumps, etc. Your cytoskeleton is a protein network.

Who made it? Well, ribosome again, because it's a protein. It helps the entire cell move, cytokinesis. It helps the cell divide.

during cell division, mitosis or meiosis. And it provides railroad tracks so that you can move your packages on the railroad. The cytoskeleton has jazillion other functions. Pause and review. There are three types of cytoskeleton.

Microfilament, microtubules, and intermediate filaments. Microfilaments, actin. How about microtubules? Alpha-tubulin or beta-tubulin.

And you find microtubules in cilia or flagella. First, microfilaments. Remember my actin? You start with monomers, then they become polymers of G-actin, and then before you know it, you have your actin filaments.

Actin filaments have many functions including cell division. These are your cleavage furrows that you studied in mitosis or meiosis for that matter. Next, microtubules which have tubulin. You have alpha tubulin and beta tubulin.

Microtubules can provide the backbone for many structures. If you want to make a centriole, easy. I'll give you nine triplets of microtubules and you will have a centriole. But if you want a cilium or a flagellum... I'll give you 9 doublets of microtubules plus 2 additional ones.

Don't forget the story of kinesin and dynein. Dynein defect is seen in a disease known as cortagener's syndrome or immotile cilia syndrome. Here is the cilia as you know, 9 doublets of microtubules plus 2 extra ones. Cilia could be motile such as the one in your respiratory tract, to get all the gunk out of your airways or they could be immotile such as the special ones in the rods of the eye if i have cartaginar syndrome or immutile cilia syndrome then the cilia in my fallopian tube will not work and i can get ectopic pregnancy because i was unable to push the ovum from the fallopian tube to the uterine cavity because i did not have cilia there are many genetic diseases that will give me respiratory problems, including Cartesiner syndrome, where the problem is in the dynian arm of cilia, and cystic fibrosis, which is a CFTR mutation.

The first disease is having no motile cilia. The other disease is having very thick mucus because of a defect in the chloride channel. Flagella, structurally speaking, very similar to cilia. Nine doublets of microtubules plus two single central ones.

The sperm has a flagellum and H. pylori bacteria has a flagellum too. This is the nasty bacteria that lives in the stomach. Here is the structure of cilia or flagella.

We have nine doublets on the periphery and two single microtubules centrally. What if I want to make a centriole, not cilia or flagella? Then you go with triplets, nine triplets of microtubules. Remember that your cytoskeleton head microfilaments, actin, microtubules, tubulin, and intermediate filaments. These intermediate filaments are different types depending on your tissue.

Different tissues have different types. If you're talking about your mesenchymal cells, your intermediate filament will be vimentin. If you're talking about your epithelial cells, keratin. Your neural cells, neurofilaments, nuclear envelope, lamine, muscles, desmin, neuroglial cells, GFAP.

Next, we'll talk about types of tissue, including your epithelial tissue and your connective tissue. As you know, what's the building unit of your body? The cell. Group of cells together, tissue.

Group of tissues together, organ. Group of organs together, make a system, and the system will carry your body functions. Speaking of tissues, you have four types of tissues.

Epithelium, connective, muscle, nerve. Epithelium, I cover your surfaces, I line your cavities. Doesn't that sound filthy?

I stand upon a basement membrane. I am the parenchyma of your cells. Suppose we're talking about any gland in your body.

The gland will have a parenchyma, the actual functioning cells, such as the neurons in your brain, the alveoli in your lungs, and basically this will be mostly epithelial cells. And the stroma, which is just for support, inner support, outer support, etc. And the stroma will be the connective tissue.

Here are examples of epithelium in your body. Please pause and review. And here are different types of epithelium based on the number of layers or based upon the shape of the epithelium.

Next, bringing people together. The connective tissue. When you talk about ligaments, bones, blood, tendons, fat, lymph, these are basically mostly connective tissue.

The actual function is undertaken by the parenchyma, i.e. epithelium. But for the support, you'll need your connective tissue. Connective tissue, you speak about yourself.

I provide support, I give a framework, I make your stroma that supports you. Without me, epithelium is nothing, left with no support. Moreover, I also make some collagen and elastin, so I'm not that useless. Epithelium is here, connective tissue is here. If I flip you upside down, metaphorically speaking, Will your organs fall out of place?

The answer is no. Why not? Connective tissue, baby. Here are some examples of connective tissue.

We're talking bones, cartilages, fat cells, or adipose. cells, tendons, muscles, some textbook even include blood and lymph as types of connective tissue. Next, the cell cycle. When you are resting your G0 and then you grow, growth phase 1, and then you make DNA, synthesis, and then you grow again, growth 2, and then mitosis or meiosis, M phase.

Somatic cells versus germ cells. Pause and review. If I want to make another copy of my DNA, this is called DNA replication, which happens during the S phase of the cell cycle.

Taking the DNA into RNA is transcription. Taking the RNA to proteins is translation. With medicosis, everything is a piece of cake.

Where's the actual division happening in the M phase, mitosis or meiosis? That's why anything else is an interphase. G0 is for rest.

G1 is for growth. because we're preparing for the S. In the S phase, you'll synthesize another copy of DNA.

Hashtag replication. Then in the G2, you grow again. And then in the M phase, you have mitosis or meiosis. Pro, meta, ana, telophase. Pro, meta, ana, telophase.

Pro phase, meta phase, ana phase, telophase. Pause and review. If the question asks you, when does karyokinesis and cytokinesis take place?

The answer is M phase. And here are some pearls for you. Pause and review.

Cell types. You have permanent cells or stable or labile cells. Labile cells are always dividing.

Permanent cells do not divide. Stable cells do not divide under normal circumstances. But under crazy circumstances, they can divide, such as your liver.

Permanent do not divide, such as your neurons. Labile, always dividing, such as sperm cells. GI cells, your hair, etc. Staple cells are only under certain conditions like the liver. If my cells are dividing like crazy with no check, this is cancer.

How does chemotherapy work? They stop or arrest cell division. What's the good news?

We're killing cancer cells. What's the bad news? We're also killing some of your cells, especially those who divide very rapidly. That's why with chemotherapy you get hair loss. and diarrhea.

Cell cycle checkpoint to recognize the mutation or the error early on so that we can stop cell division. Otherwise, we can get cancer. We have three main checkpoints in the cell cycle.

The first one is at the G1, or to be more precise, it's between G1 and S. So that if you discover an error, you do not go to S. Recall that the p53 and the RB genes are tumor suppressor. genes. The second checkpoint is here, between the G2 and the M, so that you do not progress to the M phase with an error.

And the third checkpoint is in the M phase. It's called the metaphase checkpoint. And remember, during the metaphase, everything is aligned in the midline, and we thank our mitotic spindle. Defects in any area of the cell cycle checkpoints can lead to diseases, and here are some examples. Please pause and review.

More examples, pause and review. And some more. If you have trouble with these, please check the original video called Cell Cycle Checkpoint in my Biology playlist. P53 is a tumor suppressor gene.

What if my tumor suppressor gene is malfunctioning? Then you get what? Tumors!

Which could be benign or could be malignant. Mitosis and meiosis. Here is a comparison between the two.

Please pause and review. In mitosis, you start with 2N and you give me two identical cells. Each one is exactly identical to the parent cell, also 2N. But in meiosis, well, it's called a reduction division. Because you start with 2N and you give me four cells, each one is N.

Each one is not identical to the parent cell. In fact, each new offspring is half the parent. What are the phases?

Pro, meta, enatello, pro... before we're preparing meta everything is in the midline anna separate me and then what's your telos and purpose in life that's the last part during prophase there was condensation separation formation dissolution condensation of chromatin into chromosomes separation of the centriole pairs formation of the mitotic spindle we're getting ready and dissolution of the nuclear membrane next metaphase everything is m we are in the midline thanks to the mitotic spindle which is basically microtubule and you can draw the line in the sand here and you get a mirror image also an m we are lined in the midline. Anaphase separates me up, split the centromere and separate the sister chromatids.

The kinetochore is doing the pulling. In telophase, the mitotic spindle disappears, we reform the nuclear membrane, we form these cleavage furrows, thank you microfilaments, and then you separate the cell into two cells, this is called cytokinesis. Myosis, there is myosis 1, and there is meiosis 2. Here is another comparison between mitosis and meiosis. Please pause and review.

You know the saying that meiosis 2 is almost identical to mitosis. However, there are some tiny differences. Next, reproduction.

This is the anatomy of the female reproductive tract. And here's the one for the male. Gonads in female, we're talking about the ovary. The gonad in males, the testicle.

How about the gametes? Remember, this is meiotic division. In females, the gamete is the ovum. In males, the gamete is the sperm. Here is spermatogenesis.

And this is oogenesis. Unlike spermatogenesis, oogenesis gives you one ovum and three polar bodies. Contrary to popular belief, fertilization is not when the sperm meets the ovum.

Let's get technical. It's when the sperm meets the secondary oocyte, which is arrested in metaphase 2. Fertilization is when the sperm... meets the secondary oocyte which is arrested in meta phase 2. Remember that oogenesis has two famous arrests. Pro phase 1 and meta phase 2. Pro phase 1 and meta phase 2. Pro phase 1 were the primary one with one. Oocyte is arrested waiting for the female to reach puberty.

How about the second arrest? Second arrest, secondary oocyte, meta phase 2. Everything here is 2. Waiting for what? for the sperm to go deep inside the ovum. X, X, female.

X, Y, male. If you remember, this is my hypothalamus. Here's my anterior pituitary, which makes LH and FSH to influence the gonads.

And then the gonads will give you the male hormones or the female hormones. This is the effect in the male. G, N, R, H from the hypothalamus will tell the anterior pituitary to make LH and FSH.

FSH influences that Sertoli cell to feed the sperm. and to help with aromatization. But the LH is for lytic cell, which is to make testosterone. So what's the purpose of FSH in male? From to, I mean aromatization, from the female hormone to the male hormone.

And then LH in males, lytic cell, to make testosterone and the even more powerful dihydrotestosterone. But what's the effect of FSH in females? It's called the follicle stimulating hormone. It stimulates the growth of the ovarian.

follicle. How about LH in females? It's called luteinizing hormone. It helps make the luteal body, which will secrete progesterone until the placenta takes over. Here's the structure of the sperm.

Remember that the nucleus is in the head, the mitochondria is in the middle piece. Here's the process of spermatogenesis. Thank you, Sertoli cells.

We start with spermatogonia, then primary spermatocyte, secondary spermatocyte, and then sperms. Let's make an ovum. Follicle-stimulating hormone is going to stimulate the follicle growth. And then what?

And then the LH is going to surge around day 14 and pew! Rupture the follicle, release the ovum. The ovum will go to the uterus. The rest of the follicle will become luteal body, which secretes progesterone.

If fertilization happens, progesterone and estrogen will remain high. But if it did not happen, progesterone will drop, estrogen will drop. and the uterine lining will drop.

Hashtag menses or menstrual bleeding. Pause and review. These are the phases of the menstrual cycle. We have proliferation phase.

Thank you, estrogen. Secretory phase. Thank you, progesterone and some estrogen. Menstruation phase.

Everything is dropping like a rock. Here's the function of FSH, follicle, LH, the surge and the rupture. Hashtag ovulation.

And then the estrogen, female sex characteristics. and then progesterone, female secondary sex characteristics, and it sustains the endometrium of the uterus, and it raises the core body temperature in the second half of the cycle, because progesterone is more abundant in the second half of the cycle. The structure of the ovum, please pause and review.

The steps of fertilization are 5. Capacitation, acrosomal reaction, polyspermy block, completion of meiosis 2, where the secondary oocyte was arrested in metaphase 2. and then you make a zygote. Capacitation is to increase the capacity. Thank you so much, calcium. Next is the acrosomer reaction. Recognition happens, release of hydrolytic enzymes so that the sperm can pierce through the zona pellucida.

Next, to avoid double and triple and quadruple fertilization, there is polyspermy block to avoid polyploidy. After this, you complete meiosis 2, where the secondary oocyte was arrested in metaphase 2. Now the secondary oocyte is ready to become an ovum. After this, zygote formation.

Congratulations. A zygote is one complete cell with 46 chromosomes. And then it will grow and grow embryo. And then grow and grow fetus.

After birth, you are a neonate. Then an infant. After fertilization, there is cleavage, mitotic division. And then blastulation to make a blastocyst. Here's the blastocyst.

We have an inner cell mass which will become the embryo itself. and an outer cell mass, trophoblast, which will become the placenta. Fertilization, then cleavage, then blastulation. After this, implantation in the uterine wall.

Then you have the bilaminar embryo, epiblast and hypoblast, and the trilaminar embryo, endoderm, mesoderm, ectoderm. When you try to generate different layers, this is called gastrulation. Please pause and review.

Here is the bilaminar embryo. and the trilaminar embryo. You need to memorize everything on this slide.

If you want to learn about neurlation, check out my video called Neuralation in this biology series. But please remember that the nervous system comes from the ectoderm. The central nervous system, i.e. brain and spinal cord, come from the neural tube. The peripheral nervous system comes from the neural crest cells. This is your spinal cord, for example.

The spinal cord itself is central nervous system, therefore neural tube. But the spinal nerves are peripheral nervous system, therefore neural crest cells. This is your neural tube early on. The anterior neuropore, this will become your brain, but the posterior neuropore will become your spinal cord. Stem cells.

Totipotent, pluripotent, multipotent, unipotent. Think of it like a tree. branching and differentiating. these are pluripotent stem cells in the bone marrow, which gives you the blood cells.

do you remember the bilaminar embryo? yeah, the inner cell mass is an example of totipotent stem cell, because it can give you any part of the embryo. how about the mesoderm alone, such as mesodermal cell in the mesenchyme of your bone marrow?

they are pluripotent. for example, the bone marrow can only give you blood cells. not every single imaginable cell.

Do adults have stem cells? Yes, they do. In fact, this is how you regenerate.

The stem cells of your skin are the basal layer or the stratum basalis. In the alveoli, they are type 2 pneumocytes. Please remember that type 2 pneumocytes have two functions. Function number one, they are the stem cells of your lungs.

Function number two is to release surfactant, which is anti-surface tension. The stem cell of your bone marrow is the hematopoietic stem cell, which is pluripotent. And the cell that regenerates sperms is spermatogonia. Apoptosis versus necrosis, please pause and review.

We have two types of cell regeneration. There is complete and incomplete. Each time you undergo cell division and you pass through the cell cycle once, you're getting older. Your telomeres are shortened. Do this many times.

and you are senescent, old. When your telomeres are shortening, it means that you are aging. But what if my telomeres do not shorten, like ever? Is this a good thing? Shut up, it's a horrible thing, it increases your risk of cancer.

This slide is historic, that's why I keep repeating it. Pause and review. Next, let's talk about the fetal circulation. What's the purpose of the placenta? Give oxygen and nutrients from mommy to baby.

and give CO2 and waste from baby to mommy. This is the difference between the adult circulation and the embryological circulation. Here is how the placenta looks. This is the maternal surface and this is the fetal surface.

Fetal hemoglobin or hemoglobin F will shift the oxygen dissociation curve to the left and with left shift the tissue is left behind because oxygen will remain on the hemoglobin and will not go to tissue. Do you remember the story of the shifters of the oxygen-hemoglobin dissociation curve? With left shift, the tissue is left behind.

Whose tissue? Mommy's tissue is left behind. You know why?

Because this oxygen is gonna go to the hemoglobin F, because hemoglobin F loves the oxygen so much, i.e. more binding. but less dissociation and this is how the baby takes all the oxygen that it can from mommy smoking alcohol folate deficiency phenytoin warfarin thalidomide all of these are teratogens which can increase risk of congenital anomalies and mutations especially during the first trimester of pregnancy because during the first trimester the cells are dividing very rapidly that's why they are the most vulnerable this is the adult circulation we go from left ventricle and then all over your body back to right atrium right ventricle then give me to the lungs and then gas exchange back to the left atrium pause and review but the fetal circulation is different you are going to get the oxygenated blood from the mother thank you umbilical vein and then you bypass the liver thank you doctor's venosis we are in the inferior vena cava you go to the right atrium and thanks to the patent for raymond ovale you go to the left side Oxygenated blood will go all over your body. The deoxygenated blood comes back through the superior inferior vena cava.

This deoxygenated blood was trying to go to the lung, but because the lungs are closed with very high resistance, the pulmonary artery said, you know what, screw it, I'm not going to the lungs. I'm gonna bypass the lung. Thank you, ductus arteriosus, and I will dish my blood onto the aorta. What's the fate of this embryological structure after birth? Ductus venosus will become ligamentum venosum.

Foramen ovale will close and become the fossa ovalis. Ductus arteriosus will become ligamentum arteriosum. The nervous system.

Central and peripheral. Central, brain and spinal cord. Peripheral, cranial nerves, spinal nerves.

In your spinal cord, the gray matter is on the inside. White matter is on the outside. But in the brain, it's the opposite.

Remember that myelin appears white. Therefore, if I am unmyelinated, I appear gray. Pause and review. Somatic is something that you can control, voluntary. Autonomic is something that you cannot, involuntary.

The autonomic nervous system could be sympathetic or parasympathetic or enteric nervous system in your gut. A collection of cell bodies in the CNS is a nucleus. A collection of cell bodies in the PNS is a ganglion.

A collection of axons in the CNS is a tract. In the PNS, it's called a nerve. What's the structural unit of the nervous system?

Neuron. How about the functional unit? Reflex arc.

Who makes myelin? Well, in the CNS, it's the oligodendrocytes, but in the PNS, it is Schwann cell. Myelin increased conduction via saltatory movement. Type A and B nerve fibers are myelinated, but type C fibers are unmyelinated. All your neurons have a neural embol sheath regardless.

Why do we need action potential? Because the action potential is life. The nerve impulse in your body is unidirectional.

It always goes in the direction from the soma towards the axon terminalis. The beginning part of the axon is the axon heloc. And this is the structure of the neuron. Please pause and review. This is the structure of your nerve.

Endoneurium on the inside, then perineurium, and everything is covered with epineurium. Neurotropins are not the nerve impulse. Nerve impulse is unidirectional.

It goes down there. But neurotropins can go by retrograde. Nestle bodies are a very important exam question. This is rough endoplasmic reticulum, and they are found in the neurons, but not in the axon. Please pause and review.

And this is why myelin is awesome. What is the pilot of the nervous system? The neuron.

How about the co-pilot? The co-neurons, i.e. neuroglial cells. The first two will make myelin. Astrocyte is for the blood-brain barrier. Microglia is the macrophage of your nervous system.

Ependymal cells make the CSF. Do you remember my intermediate filaments? Yeah.

In the neurons, they are the neurofilaments, but in the glial cells, they are the GFAP. Pause and review. If I lose my myelin in the CNS, this is multiple sclerosis. If I lose the myelin in the PNS, this is Guillain-Barré.

More about the action potential. During resting state, potassium is leaving. And when the positive leaves, the inside becomes more negative.

That's why it's resting, which means inactive. But when sodium decides to enter, sodium is positive. When positive comes in, the inside becomes more positive.

Hashtag activation. Hashtag depolarization. During rest, resting membrane potent. Upon stimulation, action potent. Here's the action potent.

During rest, potassium is leaving. That's why the inside is negative. And then upon depolarization, sodium enters. The inside becomes more positive and we are very active.

Then we go back to being inactive. This is called repolarization. And if you take it too far, hyperpolarization, because potassium is leaving and the inside is becoming more negative again.

Who's responsible for the resting membrane state? selective permeability, i.e. more potassium leaves than sodium entering. When the positive leaves, the inside becomes more negative. The second thing responsible for the resting membrane potential is the sodium potassium 80 base pump.

Here's the action potential. Please pause and review. Depolarization is sodium entry. Repolarization is potassium efflux.

And let's put everything together. When your neuron is sick and tired of being sick and tired, it's called the refractory period, which means I cannot get excited again. There is the absolute refractory period with very high standards. I am not going to be excited again no matter what.

But relative refractory period is like, forgive me, is a two dollar hooker. I'm not gonna react, I'm not gonna be excited, but if you give me super threshold, too much money, I might give you an action potential. These are the types of fibers that we have, cholinergic versus adrenergic, and the receptor on each.

Pause and review. How do I get the target to get excited? First, sodium entry, this is depolarization, and then action potential propagates in the presynaptic neuron.

Calcium entry, calcium ruptures the vesicle, and then pew, exocytosis. Acetylcholine is going to bind to the acetylcholine receptor, assuming that this is a cholinergic fiber. And then look at the receptor here. if this is a skeletal muscle, nicotinic sub-M, and then the muscle will have its own action potential. How does the muscle contract?

Well, well, well, the end plate potential will propagate through the T-tubules of the muscle, and then calcium will be released. Calcium with a C binds troponin C, and then myosin binds actin G contraction. The comparison between somatic and autonomic is very important.

So please pause and review. If this is a ganglion, the fiber before it is preganglionic, the fiber after it is postganglionic. Before it, it's type B fiber, that's why preganglionic are myelinated.

But in the postganglionic, we're talking C fibers, unmyelinated. Only autonomic fibers have ganglia. The somatic system does not. This is the sympathetic nervous system, thoracolumbar. And this is the parasympathetic system, which is craniosacral.

What do you mean by cranio? I mean 1973. Cranial nerve 3, cranial nerve 7, 9, and 10 are the only cranial nerves that are parasympathetic. This is what happens when you are in fight-flight mode.

Pause and review. And this is parasympathetic. Rest and digest, read, eat, and take a dump.

Urination defecation. Sympathetic nervous system, when you're running from a tiger, you need to see far ahead, so far vision, because my lens is flat. However, if you are parasympathetic lens, you want to read a book, rest and digest, eat, read and take a dump. When you are reading, you need your lens to be spherical, accommodation.

The sympathetic nervous system is gonna dilate the pupil, thank you alpha 1, but the parasympathetic will constrict the pupil, thank you M3 receptor. Here is the effect of sympathetic and parasympathetic on the male capillary organ. Parasympathetic will point.

Sympathetic will shoot and shrink. On the urinary bladder, sympathetic will relax the wall, constrict the sphincter. But parasympathetic will contract the wall, relax the sphincter. Which sphincter? The internal.

because it's involuntary, hashtag autonomic. Contrast that with the external, which is voluntary, hashtag somatic. Compare and contrast between sympathetic and parasympathetic.

The parasympathetic is always cholinergic. However, the sympathetic starts cholinergic in the preganglionic, but the postganglionic is adrenergic. The endocrine system, hypothalamus, is interpituitary. Three glands that listen, three glands that do not care. The three that listen are thyroid, adrenal cortex, gonads.

The thyroid listens to the pituitary's TSH. Adrenal cortex will obey the pituitary's ACTH. The gonads will listen to FSH and LH. All of these hormones are made and secreted by the anterior pituitary. However, ADH and oxytocin are made by the hypothalamus and then released by the posterior pituitary.

the effect of different hormones on the female breast. estrogen increases the size and makes some ducts. progesterone makes the alveoli or the acini. prolactin is gonna fill them with milk. oxytocin is gonna push the milk out.

if this was oxytocin how about adh then? this is for reabsorption of free water in the collecting ducts of your kidney. adh is called vasopressin with a v therefore the name of the receptor is v2 And the channel is called Aquaporin2 channel, free to choose. Choose what?

Water only, without sodium. Here is the pituitary again, anterior pituitary versus posterior pituitary. Pause and review.

Insulin versus everybody else. Insulin is anabolic on everything. All the other hormones are catabolic on everything.

But growth hormone is kind of in the middle. From insulin, it borrowed the first thing. which is protein anabolic.

But from the other hormones, it borrowed number 2 and 3. It is glycogen catabolic and fat catabolic. Here are the actions of growth hormone. Please pause and review. Thyroid land.

Let's make thyroid hormone. Don't forget that we need iodine. What's the key enzyme?

Thyroperoxidase. Who's gonna bind tyrosine? Thyroglobulin.

Here are the actions of thyroid hormone. Remember, it's the stove of your body. It increases and boosts metabolism. That's why if you have too much thyroid hormone, everything is working really fast. But if you have hypothyroidism, I am so lazy.

Behind the thyroid gland, we have two pairs of glands known as parathyroid glands to make the parathyroid hormone. The parathyroid hormone is pro-calcium. It increases calcium in the blood. However, it's also a phosphate-trashing hormone. It decreases serum phosphate.

Calcitonin hates everybody, so lowers your calcium and phosphate. Vitamin D3 has a brain. I can increase serum calcium just like PTH. However, I noticed that both of them are trashing phosphate, which is dangerous because you need adenosine triphosphate, which is ATP. So I'm going to raise serum phosphate.

Adrenal cortex versus adrenal medulla. The cortex will make aldosterone. cortisol, adrenal androgens. The medulla will make catecholamines including dopamine, norepinephrine, and epinephrine. What's the function of aldosterone made by the zonaglomerulosa?

It reabsorbs two things and dumps two things into the urine. Glucocorticoids want to boost glucose via gluconeogenesis. Adrenal androgens are androgens. Don't you ever forget the renin and gluten in aldosterone system. The kidney makes renin, which converts angiotensin O-gen to angiotensin 1. Then ACE from the lung, the angiotensin-converting enzyme, is going to convert angiotensin 1 to angiotensin 2, which has two functions.

Function 1, constrict vessels. Function 2, make aldosterone from the zonaglomerulosa of the adrenal gland, which will reabsorb two things back to the blood and dump two things down the toilet. Here is the adrenal medulla and the catecholamines, remember the song, phenylalanine tyrosine, dopedupamine, norepinephrine epinephrine. The adrenal cortex came from the mesoderm, but the medulla belongs to the ectoderm, because it's part of the peripheral nervous system. We treat her like a ganglion.

Adrenal cortex vs medulla, pause and review. Pancreas time! Exocrine vs endocrine. Exocrine is to make the enzymes endocrinase to make the hormones what kind of hormones insulin from the beta cells and glucagon from the alpha cells insulin is anabolic it builds up protein from amino acid it builds up glycogen from glucose. It builds up triglycerides from free fatty acid.

But glucagon is a destroyer. That's why it goes in the opposite direction. That's why when you're feeding, it's time to build up. You need insulin. But when you're fasting, it's time to break down and get some energy.

You need glucagon. Alpha cell for glucagon, beta cell for insulin, and delta cell is the doofus somatostatin because it inhibits everything. Do you remember reproduction?

Pause and review. Do you remember this? Pause and review.

More hints about endocrine. Pineal glands make melatonin important for circadian rhythm. The kidney makes EPO which goes to the bone marrow to boost red blood cell production.

When the heart gets stretched out because I have volume overload or heart failure, I secrete ANP or BNP, natriuretic peptide. Natriuretic. You will lose the natrium sodium. and water in the urine. It's time to breathe!

Here's the anatomy of the respiratory system. Please remember that you have a conducting zone and a respiratory zone. Here are the functions of each part of your respiratory tract. Here's a comparison between conducting zone and respiratory zone.

Your pleura surrounds your lungs. It's filled with a thin layer of fluid. It has a visceral layer and a parietal layer. air pressure is higher in California than Arizona, then wind will blow from California to Arizona, from high pressure to low pressure.

Review Boyle law, which means volume and pressure, hate each other. If one is going up, the other is going down, provided that temperature remains constant. When I'm trying to breathe in, I expand my chest, volume goes up, pressure goes down, I have a more negative pressure inside.

Therefore, I'm gonna suck air in because negative pressures pull in stuff. The exact opposite happens during expiration. You breathe air in from the atmosphere, it goes to your lungs, then it goes to your arterial blood. In the beginning, free and dissolved. Then it jumps on the hemoglobin, the cell will use it, and then you get the CO2 back to the hemoglobin and the lung will breathe it out for you.

Surface tension is dangerous. It wants your lungs to collapse and recoil. But thankfully, you have a surfactant made by type 2 pneumocytes.

And this surfactant is anti-surface tension, so that you can breathe. Here are the pulmonary function tests. Please pause and review. Lung volumes are here.

Lung capacities are here. What's an acid? Anything that gives you protons. The more protons you have, the... higher your hydrogen ion concentration and the lower your pH. In your body, metabolism secretes acids and carbon dioxide, which is technically an acid because it combines with water and give you carbonic acid.

Who will get rid of this volatile acid? The lungs. Who's going to get rid of these non-volatile or fixed acids? The kidneys. If you metabolize more, you will end up with more acids.

If you breathe more... hyperventilation will lower your carbon dioxide in the blood. Conversely, hypoventilation will raise the carbon dioxide in your blood.

Please pause and review Louis Châtelier's principle. If your bicarbonate goes up and pH goes up, this is called metabolic alkalosis. If bicarbonate goes down and pH goes down, this is called metabolic acidosis. If carbon dioxide goes up, pH will go down. respiratory acidosis.

If carbon dioxide goes down and pH goes up, this is respiratory alkalosis. Between the artery and the vein, which one is more acidic? Of course the vein is more acidic because carbon dioxide is dumped from the cell onto the vein.

And carbon dioxide is a freaking acid. When you go up on top of a mountain, there is a lower pressure, therefore lower PaO2. But the air itself is still 21% oxygen, so FiO2 did not change. Then why do I have less oxygen in my alveoli?

Because the pressure of the atmospheric air, which includes oxygen, went down. Anytime you have low oxygen, your body will respond. By making more red blood cells, thank your kidney for secreting erythropoietin, and it can also make new blood vessels. When you're exercising, or when you go on top of the mountain what's going to happen shift to the right how about the opposite shift to the left anytime i exercise my right arm the right arm will have more metabolism and therefore more carbon dioxide more acidity because carbon dioxide is an acid i'm raising the temperature of my right arm and increasing glycolysis and therefore 2-3 bpg when all of them go up I will shift to the right.

With right shift, there is giving of the oxygen to the tissue, which means oxygen is leaving the hemoglobin and going to the tissue. The exact opposite happens with left shift. With left shift, the tissue is left behind because oxygen is remaining on the hemoglobin and away from the tissue.

Here's the effect of high altitude on your body. Please pause and review. When I go on top of the mountain, I get hypoxia and my body will respond. I shifted my oxygen dissociation curve to the right and the tissue is happy with more oxygen. Since there is less oxygen pressure upstairs, I will breathe more.

Therefore, carbon dioxide in my blood will decrease because of the hyperventilation and the pH will go up. We call this respiratory alkalosis. Cardio time.

Here is the adult circulation. Here are the four valves in the heart. All of them are tricuspid, i.e. with three cusps, except the mitral which only has two cusps.

Do veins have valves? Yes. How about arteries? No.

Please remember that the cardiac muscles are striated, involuntary, uninucleated, and branching, with lots and lots of gap junction. The gap junction is very important for your heart because it allows the entire heart to contract as a one singular unit, a syncytium. Here's the SA node and the AV node.

That's why your heart is automatic. Sympathetic and parasympathetic are not initiators. They are just regulators. What causes the first heart sound? The closure of the mitral and tricuspid valves together.

How about the second heart sound? The closure of the aortic and pulmonic valves together. Between the first heart sound and the second heart sound, it's called systole because your ventricles are contracting. Between the second heart sound.

And the following first heart sound is called diastole because your ventricles are relaxing. Cardiac output is heart rate times the stroke volume. The productivity of your heart is based on how fast times how strong your heart is beating.

The pressure inside big vessels is 120 during systole and 80 during diastole. But in the left ventricle, it's 120 during systole. Same. But almost zero during diastole. Then how come the aorta was 80, not 0 during diastere?

It's thanks to clamping down on that blood, and this is why you get the diacrotic notch. That's how the aorta prevented your pressure from dropping to zero during diastere, unlike the left ventricle. Let's talk about volume of blood in the left ventricle. When the ventricle is squeezing itself and pushing the blood out, less blood will be left in the ventricle. Zip, you go down like this.

But when the ventricle is relaxing and receiving blood, the volume of blood in the left ventricle will go up. Put everything together in one shot and you get the lovely cardiac cycle. You need to understand everything here. Let's talk about capillaries.

There is arterial end and venous end. Each vessel is made of tunica intima, tunica media, tunica adventitia. Contrast and compare among arteries, veins, and capillaries, please.

These are the different types of arteries. different types of veins and different types of capillaries in your body some pro tip if you vasodilate you'll increase the radius and the diameter of the vessel therefore the resistance goes down the afterload goes down the blood pressure goes down remember the meta arterio please and remember that we have pushing forces hydrostatic pressure thank you blood volume and we have pulling forces oncotic pressure thank you albumin which is a plasma protein. If I want to feed my cell, i.e.

I want the blood to go this way, from the capillary to the cell, therefore the favoring forces should exceed the opposing forces. What are your favoring forces here? Hydrostatic pressure in the capillary and oncotic pressure in the interstitial fluid. What are your opposing forces?

Oncotic pressure in the capillary, because it pulls this way, and hydrostatic pressure in the interstitium. And then you do it this way. Favoring forces minus opposing forces.

If the end result is a positive number, it means that you are pushing fluid out of the capillary into the cell. Let's talk about blood cells and plasma. As you know, your blood is made of plasma and cells.

These cells are red blood cells, white blood cells, and platelets. But the plasma is water and proteins. Could be albumin proteins or globulin proteins.

Which one is responsible for the oncotic pressure? Albumin. Which one will give your coagulation factors and your antibodies?

Globulin. These are your blood cells. Please pause and review.

Red blood cells are circular, biconcave, non-nucleated. They do not have a mitochondrion. Therefore, Where there is no Krebs cycle, no electron transport chain in the red blood cell, the only source of energy for the red blood cell is glycolysis, basically. Next, white blood cells. Why do we have neutrophils?

They fight bacteria, and they are the cells of acute inflammation. Why lymphocytes? They fight viruses and fungi, and they are the cells of chronic inflammation. How about monocytes? They become macrophages, which are phagocytic cells.

They eat up stuff. Eosinophils fight parasites and allergy. Remember eosinophils? Ew! How about basophils?

They release histamine. Platelets or the thrombocytes? They help you make a clot. to stop the bleeding. How do you stop the bleeding?

First, you vasoconstrict, then the platelets will help you in primary hemostasis. Then the coagulation factors, i.e. beta globulins, will help you. This is secondary hemostasis.

Here is primary hemostasis. Thank you, platelets. Here is secondary hemostasis. Thank you, coagulation factors.

Next, on the surface of your red blood cell, we have the ABO antigen system, and we have the RH antigen system. You only have two antigens, by the way, A and B. Well, how about O then? O means zero. O, you have neither A nor B.

That's why we call you O. Please pause and review. Don't forget the blood typing and blood matching, which we have discussed before.

Next, immunity. You have innate immunity, you're born with it, and adaptive immunity, which you acquire. The innate immunity is non-specific at all. Cells of the innate immunity are many.

don't forget the macrophages, the microphages, mast cells and basophils, dendritic cells, and the natural killer cells. But when it comes to the adaptive immunity, we have B lymphocytes, hemorrhoids, or T lymphocytes, cellular. Here are the B lymphocytes making plasma cells, which will secrete antibodies.

You have IgM, IgA, IgG, IgE, and IgD. All of them are gamma globulins. Each of these antibodies has heavy chains and light chains.

When something invades your body, you take a piece called an antigen. Then the antigen-presenting cell will present that antigen to the lymphocyte. The lymphocytes can destroy that microbe.

If it's a B lymphocyte, it will grow and become plasma cells to make antibodies. And more importantly, it will develop memory so that the second exposure is faster and stronger. Here is a comparison between hemoral immunity. and cell-mediated immunity.

Here are your lymph nodes. Remember, there is the police academy. For the B lymphocytes, it's the bone marrow.

For the T lymphocytes, it's the thymus. Then we have police officers. These are the lymphocytes.

Then we have police stations. These are the lymphatic organs. Here is the lymph node. It has a cortex.

It has a medulla. And in between, it has a paracortex. The cortex is for the B lymphocytes. Paracortex is for the T lymphocytes.

and then the medulla with the medullary sinus is for plasma cells and macrophages. Compare and contrast, and again, and one more time. Next, digestion.

Digestion is to break down the macro into the micro, and then you are able to absorb the micro and send it to blood. The liver will metabolize it. If you could not digest it and absorb it, you will end up pooping it.

Your gut has a wall and a lumen. The wall is made of mycosis, submucosa, musculosus, cirrhosis. Digestion could be mechanical by motility or chemical by secretions.

Motility is by the myenteric plexus. Secretion is with the submucosal plexus. You have lots of glands in the GI. Part of them are just part of the elementary canal.

Others are outside or accessory glands. Here's the anatomy of the digestive system. Now let's talk about the function from head to toe.

In the mouth there is mechanical called mastication and chemical digestion called salivation. The enzyme is amylase. The function is carbohydrate digestion.

Next send the food to the pharynx and then the esophagus and then the stomach. The stomach has mechanical which is motility and chemical which is secretion. You need to memorize every cell in the stomach and what it makes.

GI hormones include gastrin which is made by the G cell. The only hormone that is pro-stomach. increases motility and secretion of the stomach. Secretin is secreted by the S cells in the upper part of small intestine. Secretin tells the pancreatic ducts to make lots of water and bicarb to neutralize the acidity.

CCK, cholecystokinin pancreaszyme. It's called cholecystokinin because it squeezes the gallbladder. It's called pancreaszyme because it increases the release of pancreatic digestive enzymes.

from the acinar cells. Somatostatin is the doofus from the delta cell. Why doofus? Because it inhibits everything.

It even then inhibits its own secretion. In order for you to digest and absorb the fat and the fat-soluble vitamin, you need three organs to be healthy. Liver and biliary system, pancreas, and the gut.

After you digest, what do you do? You absorb. What if you could not absorb? Then you excrete. If you happen to be water-soluble, you will go the blood route.

But if you are fat-soluble, you will go through the lymph route. And this is true for vitamins. If you are water soluble vitamin, blood route. If you are lipid soluble vitamin, lymph route.

Here is all of digestion in one slide. Here is how we digest carbohydrates. Here is how we digest proteins.

And here is how we digest fat. Next, kidney. Please review your anatomy and the physiology of the kidney. After the renal artery branches and branches and branches even more, you get the afferent arteriole, which becomes the glomerular capillary tuft, and then you push fluid this way called filtration.

If you cannot push it, it's going to end up in the efferent arteriole, which will become peritubular capillaries. Here is the afferent, here's the glomerular capillary tuft, here is the efferent. The efferent will become peritubular capillaries.

Now let's talk about the nephron. Here's the Bowman's capsule, proximal tubule. loop of Henle distal tibial collecting ducts. When something leaves that filtration fluid in the nephron and goes to peritibular capillary, this is called reabsorption.

The opposite is called secretion. Anything that's going to end up in the urine is called excretion. How do we move based on what? Starling forces, hydrostatic and oncotic. Hydrostatic pushes, oncotic pulls.

Hydrostatic depends on the volume of fluid. but oncotic depends on albumin. If you want filtration from the glomerular capillary to the nephron, the favoring forces should exceed the opposing forces.

But if you want reabsorption, it's going to be the opposite. If you want secretion, it's going to go from here to there. Next, the skin.

It has many functions. The epidermis of your skin came from the ectoderm, but the dermis is derived from the mesoderm. Here are the different layers of the epidermis. Please remember that the stratum basale is the stem cell for regeneration.

The dermis is the connective tissue underneath. The skin is important for thermoregulation. Please pause and review.

Bones and muscles. You have three types of muscles, right? We have compared among them before, correct? When it comes to smooth muscles, just say no.

Here's the structure of your muscles from the inside to the outside. endomysium, perimysium, epimysium. Just like the nerve, endoneurium, perineurium, epineurium. Each muscle is made of muscle fibers. Each fiber is made of myofibrils.

Each fibril is made of myofilaments, which include the thin actin and the thick myosin. Please pause and review. Please review the difference between the A-band and the I-band.

I-band has only actin. A-band has myosin and actin. The H zone has only myosin.

Upon contraction, what happens? Your I band will shorten. Your H zone will shorten. But E band does not change. How about the length of the entire muscle?

It decreases. Contraction is sliding of myosin and actin. Myosin is going to extend those cross bridges and pull actin towards the midline. Skeletal muscles have nicotinic receptors. Smooth muscles have...

muscernic or adrenergic receptors. How about cardiac muscles? Similar to smooth muscles.

This is the neuromuscular transmission again. Please pause and review. When the action potential reaches the muscle, it will traverse the muscle via T-tubule, and then calcium is released from the jail, which is the terminal cistern of the sarcoplasmic reticulum, and then calcium will bind troponin C, and then tropomyosin is removed. The active site is exposed, myosin will pull actin towards the midline, hashtag contraction, which require lots of ATP.

Let's compare between type 1 muscle fibers and type 2 fibers. Muscle contraction requires lots of ATP, which is in the myosin head because it has ATPase activity. Metabolism of the muscle.

First, you start by using the phosphagen system, creatinine phosphate. ADP will become ATP and you have some energy. Thank you, creatine kinase.

After this, you need to rely on your glycolysis to give you the famous two ATP molecules. After this, you need your oxidative phosphorylation and electron transport chain, i.e. TCA cycle and ETC, which gives you a net of 38 ATP molecules. After exercise, the muscle...

And the lung made a deal. Hey, hey, hey, I'm the muscle. I need 500 ml to complete that marathon. But I can only get 400 right now.

Okay, here's a deal. You can give me the 400 right now, but then after I finish exercise, you owe me 100. Bet. That's the oxygen debt. And that's why you're hyperventilating even after you finish the marathon. Why are you doing this?

The lung is paying back her debt. Why is this 100 ml of oxygen crucial? For reformation of ATP and creatinine phosphate, removal of lactic acid, and refilling the myoglobin with oxygen.

Next, bone and cartilage. We have exoskeleton and endoskeleton. If you're a human being, you only have an endoskeleton.

Your endoskeleton is either axial in the midline or appendicular in the extremities. Bone. We have the head, we have the shaft.

We have epiphysis, we have diaphysis, and we have metaphysis in between. Your bone could be compact, especially on the outside, or spongy, especially in the middle, near the medulla, near the bone marrow. Osteoblasts will build up your bone, but osteoclasts will cut down bone. Your bone is basically matrix, thank you collagen, and minerals, thank you calcium and phosphate.

What kind of collagen is in bones? Bones have type 1 collagen, but type 2 collagen is in cartilage. Please review your haversian system. And here is a distinction between bone and cartilage.

Type 1 versus type 2, vascular versus avascular. When two bones are ready to meet each other, it's a joint. And you have some lovely fluid for lubrication.

And there are three types of joints in your body. Coming up next, genetics. This is the big picture of genetics. Please review the difference between penetrance and expressivity, which could be variable or constant.

Understand and memorize your definitions. Master dominant versus recessive. Homozygous versus heterozygous. And here are the laws of Gregor Mendel.

The first law of segregation. Thank you, NFA's one. And the second law of independent assortment. Thanks, pro phase one.

This is pro phase one. the tetrad and the crossing ova, which explains the second law of Mendel. All the alleles in a given population of people is called the gene pool. Can we have mutations?

Of course! We can have mutations affecting the nucleotide or a mutation affecting the entire chromosome. Please pause and review. Do not forget that missense is sickle cell disease. Nonsense will give you a stop codon.

Stop the nonsense! You need to draw tons of Punnett squares before your exam. This is the result when you have one autosomal dominant parent and another autosomal recessive parent and both are homozygous. This is the result.

Let's take that first generation and marry them with another person from the first generation and what do you get right now? You get a different ratio as you see and this was called the mono hybrid cross because we're talking about just one characteristic which is their color. But what if we're talking about two things, their color and their height?

Then it's gonna be the dihybrid cross with a different ratio. Please pause and review. This is the result of sex-linked crosses. We can map genes and chromosomes and get the recombination frequency, which is proportional to the distance between two genes on a freaking chromosome.

Using this theta, or recombination frequency, you can deduce the order of genes on a chromosome, and we've talked about this before. Hardy-Weinberg equation. It's not hard, you just need to memorize two equations. More importantly, you need to understand what each letter refer to.

For example, the p alone is the frequency of the dominant elite in a population, but the p squared is talking about an individual in that population. p alone is the tall allele. p squared is a tall individual. and here is an example that we did before. just by giving you the first number which is 70 percent you can deduce all of the rest.

please pause and review and do it yourself. evolution basics. do not confuse natural selection with evolution. they are not identical.

in fact natural selection is a mechanism for evolution. there is the old theory and the modified modern synthesis theory. We have different modes of natural selection, could be stabilizing, directional, or disruptive.

When it comes to reproductive isolation, it could be pre-zygotic, which prevents the zygote from forming in the first place, or post-zygotic, which allows the zygote to be formed. However, it's going to be non-viable or sterile. An exam question will ask you about the mule.

The mule is an example of... hybrid sterility, which is a post-zygotic isolation. Pattern of evolution are many.

We have divergent, parallel, and convergent. We did it! You can download my notes at medicosisperfectionalist.com. They have extra points than we discussed in this video, and you can download my surgery high yields course if you are interested.

I also have many other pharmacology courses. The biology playlist is complete, and I've started talking about biochemistry in a separate playlist called biochemistry for the mcat thank you for watching please subscribe hit the bell and click on the join button you can support me here or here go to my website to download my courses be safe stay happy study hard this is medicosis perfectionatus where medicine makes perfect sense

Transcript for:Comprehensive Biology Review Summary

Transcript for:
Comprehensive Biology Review Summary