this lecture covers module 1.4 organization of the human body so we're going to start with body cavities what is a body cavity any fluid filled space within the axial region of the body so the axial region of the body basically goes from the head down to the pubic region it excludes arms and legs the appendages so cavities protect internal organs and allow them to move and expand as necessary to perform their functions major cavities include the dorsal and ventral cavities and their subdivisions all right so here's a picture of the dorsal and ventral body cavities and their subdivisions the dorsal body cavity is actually quite easy the dorsal body cavity contains the cranial cavity remember the cranium that part of the head that contains the brain and then the vertebral spinal cavity now this is the posterior side of the body but remember the other word for posterior is dorsal so how are you going to remember that dorsal means posterior side also remember the dorsal fin on a shark it's on the back side of the shark so dorsal body cavity contains the brain and spinal cord ventral body cavity ventral is belly side so the ventral body cavity has two main cavities the thoracic cavity which we have covered the thoracic region is here basically that region underneath the rib cage the dividing line between the thoracic and the abdominal pelvic cavity is the diaphragm so everything above the diaphragm is the thoracic cavity everything below the diaphragm is the abdominal pelvic and the abdominal pelvic has the abdominal portion and the pelvic portion you can imagine the belly button is right about here so a little bit below the belly button that's where your pelvic is from a little below the belly button up to the diaphragm is your abdominal region now let's look at the subdivisions of the thoracic cavity first of all on the outside the two cavities which contain the lungs are called the pleural cavities in the middle we have the mediastinum at the bottom of the mediastinum is the cavity which contains the heart called the pericardial cavity so parry around cardial heart okay so pericardial pleural mediastinum and all of those are contained within the thoracic cavity all right abdominal pelvic cavity can be divided up into quadrants now why would we want to do this because the chief complaint for people coming into the emergency room is pain in the abdominal pelvic cavity so there are certain organs and structures which reside inside each of these cavities and it can sometimes help speed up the diagnosis by being able to describe where the patient's pain is located so the four quadrants of the abdominal pelvic cavity are right upper quadrant right lower quadrant left upper quadrant and left lower quadrant and you'll most likely see them written like this so get used to those abbreviations so here's our image with the four quadrants so here's our imaginary line going through the umbilicus dividing it up into your right upper left upper right lower and left lower quadrants now here's your clue what organs can be found in each of these quadrants because if your patient arrives complaining of pain you want to start thinking about what organs are in each of these quadrants that could create the sensation of pain so let's start here in our right upper quadrant what kind of organs are present here well we could create pain from the liver from the gallbladder and then here we have a portion of our transverse colon what organs are in the left upper quadrant we're going to have most of our stomach and you can't see it but on the bottom back side of the stomach is the pancreas we've got our spleen and the rest of our transverse colon left lower quadrant we have our descending colon and some small intestines and for a female you're going to have an ovary in here in our right lower quadrant where intestines our ascending colon our appendix and for a female a right ovary so those would be the most common organs which go haywire now the information on this slide reinforces the previous slide that we just covered so abdominal pain is a common complaint of individuals seeking health care the cause of the pain can be difficult to diagnose due to the number of structures in the abdominal pelvic cavity knowing the organs in the specific quadrants can narrow down potential diagnoses it's a very helpful first step so here's that list of organs that we just went through so what organs would you find in the right lower quadrant your appendix right ovary for females and the first section of the large intestine last part of the small intestine what organs are in the left upper quadrant stomach spleen pancreas parts of the large intestine and what do you find in the right upper quadrant liver gallbladder and parts of the large intestine now an organ that they did not talk about here are the kidneys because getting kidney stones and the the pain from kidney stones is very common so how come it's not included here kidneys are considered retroperitoneal in other words they're outside of the abdominal pelvic cavity so kidney pain when you're passing kidney stones is typically described as waves of pain radiating in your back so that's why it's not included here the next structures i want to teach you about are serous membranes what is a serous membrane it is a double walled membrane and in between these two membranes there's a fluid being secreted called serous fluid the serous fluid is a type of lubricant so the job of the serous membranes they help to lubricate organs and reduce friction so that they don't damage each other and they also help to hold organs in place we have the peritoneum that's one that you need to know surrounds much of the abdominal pelvic cavity then the pleura membrane surrounds each of the lungs and the pericardium surrounds the heart once again parry around cardium heart the inner membrane of a serous membrane is called the visceral membrane whereas the outer membrane is called the parietal membrane visceral you can remember that it's closer to the gut or the structure the organ whereas parietal is a reference to wall think of your outer wall of your body cavities so outside toward the wall inside toward the organ here's our picture showing the three different serous membranes so what is the name of the serous membrane which surrounds the heart it is the pericardial membrane what is the name of the serous membrane which surrounds each of the lungs that is the pleural membrane so parietal pleura what are they pointing out that's on the outside next to the ribcage or the wall and then the visceral pleura would be the inside layer and in between the two is the pleural cavity and that's what's filled with serous fluid to help reduce friction we come over here this is our peritoneum it wraps around a large portion of the abdominal pelvic region and not only do we have the peritoneum but there's little offshoots of the peritoneum called mesenteries you can see that these mesenteries help to hold organs such as the intestines in place so that's one of the jobs is to help compartmentalize and keep these intestines from moving all over these mesenteries also have another job this provides a safe route for blood vessels nerves and lymphatic vessels to get to some of our internal organs all right let's wrap up this module with a look at some of the most common types of medical imaging so what do we use medical imaging for used to look inside patients without surgery so the progress that we have made on medical imaging since i was a kid is phenomenal back in the day if you had abdominal pelvic pain and they couldn't figure out what it was we didn't have that good of medical imaging and they just have to do exploratory surgery then you end up with scar tissue and sometimes the exploratory surgery would create more problems than it was worth so medical imaging is a gift now what are the most common examples good old-fashioned x-rays x-rays use ionizing radiation and they are best to visualize hard bony structures such as teeth and bones so whenever you get an x-ray the dense tissue is going to show up as white that's what the bones look like and the soft tissue will be dark downside of x-rays it does use ionizing radiation which can lead to mutations and potential cancer issues now computed tomography scan or a ct scan also uses ionizing radiation it's a 3d image it's computer generated from the data so basically they put you in this tube and the machine takes slices x-ray slices of the body and then the computer puts these slices together to create the image what is a ct good for ct images are of internal organs bones soft tissue blood vessels they provide greater detail than what x-rays do so here's a colorized example of a ct scan upside greater detail than x-rays can be used for some of the soft tissues downside still uses ionizing radiation magnetic resonance imaging also known more commonly as mri your body is placed within a magnetic field and then the computer compiles data producing a 3d image what is an mri good for producing high contrast images of soft tissues so it's one of the favored methods of obtaining scans of the brain or of the spinal cord but it doesn't stop there mris can be used for getting details of soft tissues of the abdominal pelvic cavity i also know some people who have had mris taken of the knee looking for torn menisci or various tendons or ligaments positive side about this we don't have to worry about any kind of ionizing radiation because the magnetic field is not a problem it doesn't cause you any harm you just have to be up front and make sure that you tell the technician giving you the mri if you have any metals placed in your body because if you do you have to have them removed before you can have the mri and last type of imaging that i'm going to cover with you is sonography also known as ultrasound the benefits it does not use radiation so no harmful radiation but instead uses sound waves that then echo or bounce off body parts this prime this type of imaging is primarily used in obstetrics so we use this whenever we're keeping track of fetuses at as they're developing in utero but that's not the only thing that we can use ultrasound for we are now using ultrasound to help image blood flow in the carotid arteries to see how much plaque may be built up in your carotid we can use sonography to do imaging on the heart imaging on the spleen imaging on the liver and the gallbladder so it's not limited to just obstetrics and the longer time goes along the more clear the pictures become from ultrasound review questions for module 1.4 the heart is contained in which three cavities from least specific to most specific cavity so this is basically from the biggest to smallest so what's the biggest cavity that the heart's contained in that's the thoracic cavity next it's contained in the mediastinum and the cavity at the bottom of the mediastinum is the pericardial cavity so those are the three cavities thoracic mediastinum and pericardial number two if a patient were experiencing a gallbladder attack they would most likely be complaining of pain in which quadrant your gallbladder is located in your right upper quadrant right below the liver number three if your patient fell and may have broken a bone what type of imaging would you use to visualize the bony structures you would use plain old-fashioned x-rays and number four if your patient were pregnant and complaining of abdominal pelvic pain what type of imaging would be safest a ct or an mri an mri would be safer because it does not contain ionizing radiation now i didn't have any questions on here about your serous membranes but make sure that you go back and you know the difference between your pericardium your pleura membranes and your peritoneum