welcome to anatomy and physiology chapter 2. the information is credited to this book Wikipedia and many other sources chapter 2 covers cells and tissues a quick reminder that the organization level of the body is from Adam to cells to tissues to organs then to systems and finally organism cell the cell is amazingly complex it has a control center internal transportation system power plants a factory making needed materials and packaging plants despite their complexity most cells are so small that they can be observed only under a microscope light microscope uses visible light as the source of Illumination and the electron microscope enables researchers to study the fine detail Ultra structure of cells in their parts the photograph taken with a light microscope is referred to as a light micrograph LM whereas one taken with an electron microscope is an electron micrograph em cell all cells are similar in that they contain a gelatinous substance composed of water protein sugar fats and various minerals the cell is a fundamental unit of all living things major parts of the cell include cell membrane nucleus chromosomes Gene DNA karyotype cytoplasm mitochondria endoplasmic reticulum and Golgi apparatus let's first discuss the cell membrane cell membrane surrounds by a thin plasma membrane that protects and regulates what passes into the out of the cell the plasma membrane consists of a double layer by layer of lipids phospholipids in which a variety of proteins are embedded nucleus is the control center of the cell it's typically a large rounded organelle surrounded by a double membrane called the nuclear envelope nucleus pores in the nucleus envelope allow the passage of material between the nucleus and cytoplasm chromosomes the nucleus contain Loosely coiled material called chromatin when a cell prepares to divide the chromatin coils tightly and condense to form rod-like structures within the nucleus all human body cells except for the sex cells the egg and the sperm short for spermatozo on contains 23 pairs of chromosomes each sperm in each egg cell have only 23 of her chromosomes after an egg in a sperm cell United to form the embryo each cell of the embryo then has 46 chromosomes 23 pairs Gene chromosomes regions called genes thousands each gene contains a chemical called DNA deoxyribonucleic acid DNA regulates the activities of the cell according to its sequence's Arrangement into genes on each chromosome DNA sequence resembles a series of recipes in code this code then passed out to the nucleus to the rest of the cell directs the activities of the cell such as cell division and synthesis of proteins we can think of the chromosomes as a chemical cookbook for the cell the genes are recipes for making specific proteins the complete set of genes that make up the human genetic Mater is the human genome the Human Genome Project completed in 2003 mapped their 30 000 or so genes that made up the human genome here is a connection why this matters the knowledge and experience scientists gained from their work on the Human Genome Project research has been applied to developing technology for prevention and treatment of many disorders including cancer and diabetes karyotype is a photograph of an individual's chromosomes arranged by size shape and number karyotyping can determine whether chromosomes are normal this is an abnormal karyotype of down syndrome trisomy 21 it has three chromosomes at number 21. the nucleolus is a granular region within the nucleus the nucleus assembles ribosomes organelles that help manufacture proteins the endoplasmic reticulum is a network reticulum of canals within the cell these canals are cellular tunnel systems that manufacture proteins for the cell there are two types of er R rough and smooth the rough ER has a granular appearance that results from organelles called ribosomes along its outwalls ribosome function as factories where proteins are manufactured smooth ER is specialized to synthesize steroids phospholipids and fatty acids in the liver cells smooth ER has enzymes that break down many drugs including alcohol and amphetamines Golgi complex is composed of layers of plate-like membranes this organelle functions as a protein processing and packaging plant it also produces lysosomes lysosomes are little sacs that contain about 40 different digestive enzymes that destroy bacterial and other foreign matter under some conditions lysosomes break down organelles the components of these organelles can then be recycled or used as an energy source mitochondria are the power plant these organelles carry on cellular respiration the process of breaking down fuel molecules and releasing their energy some of the energy is temporarily stored in ATP adenosine triphosphate a chemical compound that can be used to power a variety of chemical reactions in the cell mitochondria can affect health and aging by leaking electrons that form free radicals and highly toxic and reactive compounds interfere with normal cell functions mitochondria also play an important role in program cell death referred to as apoptosis a normal part of development and maintenance vesicles is a small membrane enclosed structure that holds or transports some type of cargo within the cell vesicles are covered by a vacuole a larger membrane enclosed Sac found in the cytoplasm evacule a larger membrane enclosed Sac found in the cytoplasm vacuoles form when a cell ingested a large particle such as a bacterium cytoskeleton is a dense network of tiny protein filaments provide structural support and is important in transporting materials within the cell the cytoskeleton helps determine the shape of a cell and its ability to move it is also important in cell division microtubules one of the components of the cytoskeleton are tiny hollow tubes that provide support microtubules are components of cilia and flagella organelles important in movement cilia are tiny hair-like organelles that project from the surface of some types of cells used to to move materials outside the cell sperm cell is equipped with a flagellum a whip-like tail that propels it toward the ovum egg materials move through the plasma membrane plasma membrane is selective permeable this means that it allows certain substances to enter or leave the cell while preventing the passage of other substance materials move through the cell membranes passively by physical processes including diffusions osmosis and filtration these processes do not require the cell to expend metabolic energy diffusion is the net movement of molecules or ions from a region of higher concentration to a region of lower concentration bought about by the energy of the molecules diffusion depends on the random movement of individual molecules in the above illustration when a cube of sugar is dropped in the water its molecules dissolve then the modules begin to diffuse through the water and eventually the sugar molecules are evenly distributed throughout the water gases and nutrients move in and out of cells by diffusion osmosis is the diffusion of water molecules through a selectively permeable membrane from a region where water molecules are more concentrated to a region where they are less concentrated the dissolved ions and molecules solute in the more concentrated solution pull the water molecules across the membrane by the force called the osmotic pressure when living cells are placed in a solution that has a solute concentration that is isotonic equal to that of the cells the water molecule concentration is also equal and therefore water molecules move in out of the cells at the same rate when cells are placed in a solution with a solute consultation that is hypertonic greater compared with that of the cell water leaves the cells causing them to dehydrate shrink and perhaps die when cells are placed in a hypotonic solution ion of lesser concentration compared with that of the cell the cell exerts an osmotic pressure on the solution water moves into the cells causing them to swell and perhaps burst filtration is the passage of materials through membranes by mechanical pressure for example blood pressure forces some of the liquid parts of the blood plasma through the capillary wall by filtration this is how tissue fluid is produced the cell must actively move some materials from a region of lower concentration to a region of higher concentration that is against a concentration gradient working a pill against a concentration gradient requires the cell to expend energy in active transport the cell must use some of its stored energy ATP to drive the active transport an example of active transport is the sodium potassium pumps found in the plasma membrane of virtually all cells each pump consists of a group of specific proteins in the plasma membrane ATP provides energy to pump sodium ions out of the cell at the same time potassium ions are moved into the cell phagocytosis means cell eating it is a form of active transport in phagocytosis cells in just large solid particles such as cellular debris of bacteria pinocytosis sometimes called cell drinking is another example of active transport folds of the plasma membrane track drops of fluid containing dissolved particles the folds are pinched off into the cytoplasm as small vesicles the vesicles become smaller as their contents are slowly transferred into the cytoplasm cells of the body must communicate with one another to carry out essential processes for example cells must recognize one another to form tissues cells also signal information about the condition of the body and then sends signals to initiate or terminate processes that restore homeostasis many types of cells must communicate to protect the body against invading disease organisms cells communicate by signaling one another a sequence of events takes place in cell signaling step one a cell must send a signal usually a chemical compound such as a hormone Step 2 reception receptors specific proteins on target cells cells that can respond to a specific signal bind with the signal step 3 signal transduction a process by which a receptor converts a signal outside the cell into a signal inside the cell that affects some cellular process and step 4 response by the cell some cell activity is altered cell division certain cell types in the body are divided almost continuously for example stem cells in the red bone narrow produce more than 2 million red blood cells every second however the mature blood cells do not divide before a cell divides to form two cells the chromosomes are precisely duplicated and the cell undergoes mitosis mitosis has four stages prophase metaphase anaphase and telophase life cycle stages of a cell include interphase the period of growth and activity between mitosis a cell reproduces Itself by undergoing mitosis and then dividing to form two new cells note that there are 46 chromosomes in this phase during prophase the first stage of mitosis the chromatin coils making the chromosomes visible the nuclear membrane dissolves centrioles migrate toward opposite ends of the cell and a spindle made of microtubules forms during metaphase the chromosomes position along the Equator of the cell think of metaphase like in the Middle with the letter m during anaphase sister chromatid separate and the two sets of chromosomes move toward opposite ends of the cell during telophase chromosomes begin to uncoil and the nuclear membrane forms around each set of chromosomes cell division occurs mitosis ensures that the chromosomes are duplicated and distributed to each new cell this is the summary of the stages of a cell's life cycle please learn this cycle well let's move on to tissues a tissue is a group of closely associated cells that work together to carry out a specific function or group of functions the major function of epithelial tissue is protection it covers the body and lines the body cavities some epithelial tissue is specialized for secretion and forms glands based on shape epithelial cells may be squamous cuboidal or columnar epithelial cells may be arranged to form simple stratified or pseudostratified epithelial tissue a gland consists of one or more epithelial cells specialized to produce and secrete a products such as mucus sweat saliva milk enzymes or hormones for example in image a goblet cells in the lining of the intestine secrete mucus a slippery protective substance there are two types of glands exocrine and endocrine exocrine glands have ducts tubes that also consist of epithelial cells through which the secretion is discharged to some body surfaces these are the exocrine glands endocrine glands do not have ducts they release their products called hormones into the surrounding tissue fluid the hormone molecules usually diffuse into the blood which transports them to their destination below are the endocrine glands in the human body connective tissue joins other body tissues supports the body and protects underlying organs some main types of connective tissue are loose connective tissue adipose tissue cartilage bone blood lymph and tissues producing blood cells three types of connective tissue fibers are collagen fibers reticular fibers and elastic fibers whereas epithelial cells fit closely together the cells of connective tissue are separated by intercellular substance which consists of thread-like fibers scattered through a thick gel called a matrix collagen fibers contain the protein collagen the most abundant protein in the body fibroblasts blue cells in the picture the fiber producing cells and macrophages the large scavenger cells are commonly found in connective tissues loose connective tissue also called a realer tissue joints body structures it is found as a thin filling between body parts and serves as a reservoir for water and salts adipose fat tissue stores fat and releases it when the body needs energy adipose tissue helps to shape and protect the body and provides insulation cartilage tissue found in some supporting structures such as in the discs that serve as cushions between the vertebra and at the ends of some bones cartilage cells called chondrocytes secret a tough rubbery Matrix as well as collagen fibers the cartilage cells are found in small cavities culpicuni in The Matrix like cartilage bone consists mainly of Matrix bone cells called osteocytes are located in lecune within the Matrix a typical bone has an outer layer of compact bone that surrounds an inner region of spongy bone compact bone is made up of single-shaped units called osteons muscle tissue which consists of elongated cells called muscle fibers is specialized to contract there are different types of muscle tissues skeletal cardiac and smooth skeletal muscle and cardiac muscle fibers are striated or striped skeletal muscle is attached to bones and is voluntary cardiac muscle has intercalated discs tight junctions between adjacent muscle fibers that allow rapid transmission of information smooth muscle and cardiac muscle are involuntary smooth muscle functions in the movement of internal organs once again both smooth muscle and cardiac muscle are involuntary for example at night when you sleep your heart still Beats nervous tissue is specialized to transmit information it consists of neurons and glial cells which support the neurons a neuron has a large cell body that contains the nucleus and from which extend dendrites specialize for receiving impulses and an axon that transmits information away from the cell body Sensory neurons receive information from sensory receptors structures that detect information about changes in the internal or external environment for example touch receptors in the skin and photoreceptors in the retina of the eye these neurons transmit information to the brain and spinal cord motor neurons transmit information from the brain and spinal cord to muscles and glands membranes cover or line body surfaces membranes are sheets of tissue that cover or line body surfaces epithelial membranes consist of epithelial tissue and a layer of underlying connective tissue a mucous membrane or mucosa lines body cavities that open to the outside of the body serous membrane or sarasa lines a body cavity that does not open to the outside of the body the portion of the membrane attached to the wall of the cavity is the parietal membrane whereas the part of the membrane that covers the organs inside the cavity is the visceral membrane the membranes that cover bone and cartilage are examples of connective tissue membranes the synovial membrane is a connective tissue membrane that lines the joint cavities done with chapter 2. keep re-watching this video thank you for watching please subscribe comment like and share