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What is a Hemithorax?

By Marisa O'Connor
Updated Mar 03, 2024
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A hemithorax is one side of the chest. The thorax is the medical term for the chest area, and hemithorax indicates only one half of the chest. The plural for this medical term is hemithoraxes or hemithoraces. The hemithoraces are made up of the ribs, sternum, and thoracic vertebrae. It holds and provides protection to vital organs in the chest, such as the lungs and heart.

The thorax is the chest area of the body, positioned between the neck and abdomen. The boundaries of this region are drawn by the ribs, sternum, and the thoracic vertebrae, also known as the dorsal vertebrae. The thoracic vertebrae are the 12 segments between the cervical vertebrae, which are the first seven vertebrae in the neck and the lumbar vertebrae, which include five vertebrae in the curved portion of the lower back.

Each hemithorax serves as a home and protection for the organs in the chest. These organs include the lungs, heart, and part of the aorta, which are key aspects of the circulatory and respiratory systems. The lungs facilitate breathing and provide oxygen to the blood. The heart pumps and filters blood to the rest of the body, and the aorta is the largest artery in the body, providing a path by which blood reaches other vital organs.

The left hemithorax contains both the heart and the left lung. The left lung is smaller than the right lung because it has to make room for the heart. The right lung is basically alone in the right hemithorax and so can take up more space. In some rare cases, other organs are displaced in the thorax.

When there is no separation between the hemithoraxes, it is called a buffalo chest. The term buffalo chest first gained popularity in a 2003 report in The New England Journal of Medicine. This condition is often caused by tension pneumothorax, which is a collapsed lung due to air under pressure. The term buffalo chest is in reference to North American buffalo, which were often taken down by a single Indian arrow to the chest, collapsing the lungs of the beast.

Another common problem affecting the hemithoraxes is hemothorax. Hemothorax occurs when blood collects between the lung and the chest wall. It is most often caused by blunt trauma to the chest, but may also be caused by blood clotting, cancer, or tuberculosis. Symptoms of hemothorax include anxiety, chest pain, and rapid heart rate.

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Discussion Comments
By hanley79 — On Jul 25, 2011

@TheGraham - That's because "thorax" is the name for the section of a person or animal running between their head and their abdomen.

I wanted to comment on here and say that separating the hemithoraces by calling each side of the chest different things may seem a bit odd, but it's extremely helpful in medical treatments. With conditions such as pneumonia, doctors can quickly communicate where the problem is by mentioning the left or right hemithorax.

Pneumonia causes something called hemithorax opacification. This is the name for any condition that causes one hemithorax to show up dark on a radiology chart of the chest. Opaque hemithoraces can indicate pleural effusion (fluid filling the lungs), too. If you had pneumonia, he first way that the doctor would likely be able to tell is that you would have an opacified left or right hemithorax.

You don't see any charts with both hemithoraces opacified because then the lungs would both be unable to function, and so the patient would die from lack of oxygen. Radiology scans on a drowning victim would probably demonstrate this dramatically.

By TheGraham — On Jul 25, 2011

The words "hemithorax" and "hemothorax" are very close, but one means blood gathering between the lung and the chest wall and the other means half of your chest. I think I'd get confused fast if I worked in a medical field, if any other terms were just as similar.

A hemothorax sounds like an uncomfortable condition to have -- yikes. Oh, and then of course there is the tension pneumothorax mentioned in the article, too. That term I've actually heard before -- from the scene in the movie "Just Like Heaven" where the protagonist has to treat a tension pneumothorax in an emergency.

I guess most problems that have to do with the chest have the word "thorax" in them, huh?

By Hawthorne — On Jul 25, 2011

@SkittisH - Maybe the smaller volume of the left lung is more of a front to back kind of size difference? Most pictures of lungs I've ever seen are from the front, so perhaps the size difference just isn't visible.

Hemithoraces are an interesting concept. Not all of the body is divided on one half of the other; I mean, since the article lists that the vertebrae are inside the hemithoraces, that means half of your spine is in the left hemithorax and half of it is in the right hemithorax, right?

Buffalo Chest is an interesting term, as well. Listening to somebody in the medical field talk about these and other conditions/body part names would probably require a definition list and/or dictionary for me to keep up!

And on that note, the hemithoraces contain a lot of vital organs. I hope nothing ever happens to either of mine.

By SkittisH — On Jul 24, 2011

Very interesting article... I learned several new things today, including just what a hemithorax is. I had no idea that one lung is smaller than the other. It makes sense to make room for the heart, but all medical pictures of them always show them so symmetrical.

Why, I wonder? It's a pretty well known fact that the human body is not perfectly symmetrical, inside or out. Everyone has one foot and one hand slightly larger than the other, and of course some organs are only on one side or the other (and in one hemithorax or the other).

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