hey everyone in this anatomy and physiology lecture I'm gonna cover the major body cavities and membranes which not only help protect the organs but they also help keep them compartmentalized much like a tool box will keep your tools separated protected and organized now the body contains two major cavities a larger cavity called the ventral cavity and a smaller cavity called the dorsal cavity if you think back to the video I made over the directional terms you'll know that ventral or anterior means toward the front of the body and dorsal or posterior means toward the back of the body and that's exactly where these two cavities are located the dorsal body cavity is located toward the back of the body and it houses our central nervous system remember that the dorsal fin is on the Dolphins back and that will help you remember that the dorsal cavity is the one toward the back now the dorsal cavity can be subdivided into two main parts the cranial cavity which houses the brain and the vertebral cavity which houses the spinal cord the ventral body cavity is the larger cavity that is located towards the front of the body and it contains our visceral organs or guts remember ventral contains the viscera and that will help you remember that now the ventral cavity can also be divided into two main parts the thoracic cavity and the abdominopelvic cavity which are separated by the diaphragm the thoracic cavity also called the chest cavity sits superior to the abdominal pelvic cavity and it contains organs such as the heart lungs trachea and esophagus and it can be subdivided into three main portions the left pleural cavity which houses the left lung then you have the middle part of the thoracic cavity which is called the mediastinum this comes from a Latin word meaning Midway and this houses organs such as the heart esophagus thymus gland and trachea now the heart itself is located in that mediastinum and it's surrounded by its own cavity called the pericardial cavity and this is easy to remember because parry means around and cartee means heart and then you have the right pleural cavity which houses the right lung now the abdominopelvic but it can be subdivided into two other cavities which are really easy to remember because the name abdominopelvic is the dead giveaway you have the abdominal cavity and the pelvic cavity the abdominal cavity is going to contain organs such as the liver stomach pancreas spleen gallbladder intestines and kidneys and the pelvic cavity is going to contain the bladder reproductive organs and the distal portions of the large intestine such as the sigmoid colon and rectum now if you think back to a couple of moments ago I was talking about how the thoracic cavity will have certain organs that are housed within their own cavity for example the heart is housed within the pericardial cavity well in that same way your abdominal pelvic region contains a serous membrane called the peritoneum and within this peritoneum membrane you have what's called a peritoneal cavity so that's all there is to the two major cavities located within the body now you do have a lot of minor cavities such as the oral cavity orbital cavity your nasal cavity and sinuses your middle ear cavities and even some synovial cavities which are in your joints but for the scope of this video we're just going to focus on the major body cavities now let's shift gears for a minute and talk about body membranes because those major body cavities I just covered are lined with thin sheets of tissue called membranes which cover and protect the various organs the dorsal body cavity is lined with three layers of protective membranes the dura mater arachnoid and Pia mater which are called the meninges and back in 2014 I can remember reading a new story about a young nursing student who began feeling very ill she had a fever that kept climbing she just felt absolutely horrible she actually logged on to Twitter and posted a tweet that read I think I'm dying and not long after that she was admitted to the hospital where she passed away from bacterial meningitis what is meningitis it's inflammation of the meninges and one of the main symptoms of that is that you can get very stiff feeling in your neck that can be very painful and so that can kind of help you remember that the meninges are going to be in this dorsal cavity now the ventral body cavity contains various serous membranes which are filled with a watery substance called serous fluid which allows for lubrication and movement of the organs first you have the pleura which is the membrane that lines the pleural cavity and covers each lung you have the pericardium the membrane that lines the pericardial cavity and it covers the heart then you have the peritoneum which is the membrane that lines the peritoneal cavity in the abdominal pelvic region now in a previous video I covered the directional terms of the body such as superior and inferior distal and proximal and so forth now when it comes to these serous membranes anatomist use additional directional terms to describe portions of the membranes lining for example the part of the serous membrane lining that actually touches the organ is going to be called the visceral layer and the easy way to remember that is that your organs are called your viscera and so the part that's going to touch the viscera is going to be the visceral layer now that outer lining of the membrane that's going to line the wall of the cavity is going to be called the parietal layer and the word parietal comes from a Latin word that means wall so it can help you keep those two straight visceral is going to touch the viscera and the parietal is gonna line the wall usually now whenever you're talking about a specific serous membrane for example the pleura which covers each lung then oftentimes they'll put that directional term in front of it so for example if you're talking about the part of the pleura that lines that actually touches the lung then it will be called the visceral pleura and if you're talking about the lining which actually touches the wall in the thoracic cavity then that's going to be the parietal pleura and many people will confuse the membrane lining with the actual cavity contained within that membrane so for example when we're talking about the lung you would have the pleura that's gonna be the lining itself of that membrane and inside that fluid filled part that's actually the pleural cavity and so you got to watch getting those mixed up same thing with the heart you have the pericardium that's going to be the lining of that membrane around the heart and then inside of that lining where you have that fluid filled part that's going to be the pericardial cavity and then your peritoneum your peritoneum again that's the lining portion in your abdominal pelvic cavity of that serous membrane and the fluid filled serous fluid inside of that is going to be called the peritoneal cavity now when we're talking about the peritoneum there are a couple other directional terms are used for that serous membrane because it doesn't include all the organs in this region now if the organism behind the peritoneal space it is considered retroperitoneal and that prefix retro just means back or backwards and if the organ is within the peritoneal space it is considered intraperitoneal that prefix intra just means within and then if it's below that peritoneal space it's just called sub peritoneal and again sub just means below or under alright that was a lot of information so let's do a quick recap just to hit the highlights and make sure you've got this down you have two major body cavities the dorsal which is toward the back and dimensional which is the bigger when toward the front now the dorsal body cavity is going to be broken into two main ones the cranial cavity which houses the brain and the vertebral cavity which houses the spinal cord it also has that membrane back there which is known as the meninges in your ventral body cavity you can break it up into two main sections first you got the thoracic cavity which can be divided into three parts you've got the part where the left and right lung and then you've got the part in the middle called the mediastinum now each lung is going to be housed in a serous membrane called the pleura and that again is referring to the lining around it and that fluid filled space of serous fluid within that pleura is going to be called up pleural cavity your heart is also going to be housed within a cavity called the pericardium that's the name of the lining of that serous membrane and then again that fluid filled material within it it's gonna be called a pericardial cavity and again the diaphragm muscle is gonna separate the thoracic cavity from the abdominal pelvic cavity the abdominopelvic cavity can be divided into two cavities the abdominal and the pelvic and within this cavity you're going to have your digestive organs reproductive organs and so on you're also going to have the peritoneum which is that serous membrane lining and within that serous membrane lining you're gonna have the serous fluid which creates the peritoneal cavity okay so that wraps up this on the body cavities and membranes and if you click the link in the description below you can take a free quiz to test your knowledge on this material in addition we have some other videos on anatomy and physiology so you might want to check those out thank you so much for watching and please subscribe