Organization of the Body: Thoracic Cavity - Online Tutor, Practice Problems & Exam Prep

The thoracic cavity, located above the diaphragm and within the rib cage, contains the pleural cavities surrounding the lungs and the pericardial cavity encasing the heart. The mediastinum, a space between the pleural cavities, houses vital structures like the esophagus and trachea. Understanding these anatomical relationships is crucial for grasping the organization of the cardiovascular and respiratory systems, emphasizing the importance of serous membranes and their roles in protecting organs.

Organization of the Thoracic Cavity

We've been talking about the different cavities of the body and the different membranes, but now we want to take all that information and put it together, figuring out where everything is located relative to each other. So we're going to start with the thoracic cavity, and we're going to say that the thoracic cavity, remember, is the space superior to the diaphragm, the space within your rib cage. There are a few different spaces in there. We're going to talk about the ones that you already know first. So first up, we have the pleural cavities, and remember, those are serous membrane-bound. Remember a serous cavity is the space between that double layer membrane where the serous fluid is located. The pleural cavities are made up by the membrane the pleurae. And these surround the lungs. So if we look over at our anatomical model, we can see a frontal view of the thoracic cavity that's color-coded and in blue on each side you see a shape of the lungs and that's where the pleural cavities or the pleurae and the lungs are all going to be located.

Next, I'm going to jump down to the bottom of our list because that's the other one that we've already learned. We have the pericardial cavity. The pericardial cavity also serous membrane-bound, made up by the membrane the pericardium. And this is going to surround the heart because remember that cardiac means heart. So again, if we look at our frontal view here, we see the shape of the heart here right in the middle of the thoracic cavity. We also, though, have this shape that's in orange that I'll outline here, and this is the space between the two lungs and you'll notice that the heart and the pericardium are actually in that space. This space is called the mediastinum. And the mediastinum is just the space between the pleural cavities. This is going to contain a lot of different things. For example, we just said the heart and the pericardial cavity, the esophagus, the trachea, the thymus. Anything that's between the lungs or between the pleurae is going to be in the mediastinum. Now importantly, this is not technically a cavity. It's just a space in the thoracic cavity where some stuff is located. So if we want to really say everywhere that the heart is, we could start with the heart. Right? The heart is going to be surrounded by the pericardium. And within the pericardium is the pericardial cavity, which also surrounds the heart. The heart and the pericardium are located in the mediastinum because the mediastinum is the region between the lungs, and the heart is between the lungs. The mediastinum is located within the thoracic cavity. The thoracic cavity is part of the anterior body cavity. Okay. That's a lot of different layers, but we're going to practice it some more going forward, and then we'll talk about the abdominal pelvic cavity. I'll see you there.

Organization of the Body: Thoracic Cavity Example 1

This problem tells me that the esophagus is in the superior section of the digestive tract running from the pharynx, the back of the mouth, to the stomach. It runs through the middle of the thoracic cavity behind the trachea and the heart, and through the diaphragm where it meets the stomach and the abdominal cavity. Based on that information, fill in the table below. Well, in the table, our first column says location, and the locations it gives are the thoracic cavity, the pericardial cavity, the pleural cavity, and the mediastinum. And then it asks, is the esophagus found inside each? And if no, give a directional term indicating its relative location.

So let's start with the thoracic cavity. Is the esophagus in the thoracic cavity? Well, it says right here. It's in the middle of the thoracic cavity. So I'm going to say yes to that because it's inside. I don't need to give a directional term.

Next, we have the pericardial cavity. Is the esophagus in the pericardial cavity? Well, the pericardial cavity is the cavity made up by the pericardium, the membrane that surrounds the heart. Remember, the cavity is the space between those two layers of membrane. The esophagus is not in there, so I'm going to say no. Where is it relative to the heart in the pericardium? Well, it says right here that it is behind the heart. So we have a term for behind in the body, and that is posterior. Just also note you could write deep. Right? It's deeper into the body than the heart, so the esophagus is deep to the heart.

Next, we have the pleural cavity. Is the esophagus in the pleural cavity? Well, the pleural cavity made up by the pleura, a membrane that surrounds the lung. No, it is not in there, so I'll write no. But where is it relative to that cavity? Well, here it just says pleural cavity. It just lists one. It doesn't say the pleural cavities. Doesn't tell me left or right, but regardless either one the esophagus is going to be medial, towards the middle of the body compared to a pleural cavity. Now if it said pleural cavities or the pleurae, then I could say that it is also intermediate. Remember intermediate means between two things on that medial-lateral scale.

Finally, we have the mediastinum. Is the esophagus in the mediastinum? Well, the mediastinum is this orange region here. This orange region is the space between the lungs. The esophagus is running down the middle of the thoracic cavity, so it's absolutely in the mediastinum. Because it's in, I don't need to give a directional term.

With that, I'll see you in the next video.

Which term describes a structure that is directly superficial to the heart?

• A. Thoracic
• B. Pericardium
• C. Mediastinum
• D. Pleural cavity

How does the structure of the pleurae aid in their function?

• A. Serous fluid reduces friction.
• B. Rigid shape gives structure to the flexible lungs.
• C. Large surface area helps gas diffuse.
• D. A & C are correct.

Here’s what students ask on this topic:

What structures are contained within the thoracic cavity?

The thoracic cavity, located above the diaphragm and within the rib cage, contains several vital structures. It houses the pleural cavities, which surround the lungs, and the pericardial cavity, which encases the heart. Additionally, the mediastinum, a space between the pleural cavities, contains the esophagus, trachea, thymus, and other important structures. Understanding these anatomical relationships is crucial for grasping the organization of the cardiovascular and respiratory systems.

What is the function of the pleural cavities in the thoracic cavity?

The pleural cavities in the thoracic cavity serve to encase and protect the lungs. These cavities are lined by a serous membrane called the pleura, which produces serous fluid. This fluid reduces friction between the lungs and the chest wall during breathing, allowing for smooth respiratory movements. The pleural cavities are essential for maintaining the integrity and function of the lungs within the thoracic cavity.

How is the pericardial cavity related to the heart?

The pericardial cavity is a serous membrane-bound space that surrounds the heart. It is formed by the pericardium, a double-layered membrane that produces serous fluid to reduce friction as the heart beats. The pericardial cavity provides a protective environment for the heart, ensuring it can function efficiently within the thoracic cavity. This cavity is located within the mediastinum, the central compartment of the thoracic cavity.

What is the mediastinum and what does it contain?

The mediastinum is a central space within the thoracic cavity, situated between the pleural cavities that house the lungs. It is not technically a cavity but a region that contains several vital structures, including the heart (within the pericardial cavity), esophagus, trachea, thymus, and major blood vessels. The mediastinum plays a crucial role in separating the lungs and providing a passageway for structures that connect the head, neck, and abdomen.

How do the serous membranes function in the thoracic cavity?

Serous membranes in the thoracic cavity, such as the pleura and pericardium, play a critical role in protecting and facilitating the function of the lungs and heart. These membranes produce serous fluid, which fills the space between their double layers. This fluid acts as a lubricant, reducing friction between organs and surrounding structures during movements like breathing and heartbeats. By minimizing friction, serous membranes ensure smooth and efficient organ function within the thoracic cavity.