Thoracic diaphragm

A big muscle helps you breathe.

It sits inside your chest. It separates your chest from your belly. This muscle is very busy. It uses a lot of air to work.

When the muscle moves down, it makes room. This pulls air into your lungs. This is how you take a breath. It is a very important part of your body.

The diaphragm is a very important muscle. It helps you breathe.

This muscle is shaped like a dome. It sits at the bottom of your chest. It separates your chest from your belly.

When you breathe in, the muscle contracts. This means it tightens and moves down. This movement makes more room in your chest. It also lowers the pressure inside. This low pressure pulls air into your lungs.

When the muscle relaxes, it moves up. This helps you push air out.

In humans, the diaphragm is not the same on both sides. The right side is higher than the left. This is because a large organ called the liver sits under it.

The diaphragm has small holes in it. These holes let important parts pass through. One hole lets the esophagus pass. The esophagus is the tube for food. Another hole lets a large vein pass. This vein is called the inferior vena cava. It carries blood to your heart.

The thoracic diaphragm is a very important muscle in humans and other mammals. It is a sheet of internal skeletal muscle that sits at the bottom of the chest cavity. This muscle serves as a divider between two main areas. It separates the thoracic cavity, which holds the heart and lungs, from the abdominal cavity.

Because it works so hard, it uses a lot of oxygen. It has more mitochondria and capillaries than any other skeletal muscle in the body. This helps it stay strong for the constant work of breathing.

This muscle works like a pump to move air in and out. When you breathe in, the diaphragm contracts and moves downward. This movement makes the volume of the chest cavity larger. As the space grows, it creates a negative pressure inside. This low pressure acts like a vacuum to draw air into the lungs.

When the muscle relaxes, it moves upward again. This helps the lungs push air out through a process called elastic recoil. You can even do "belly breathing" by moving the central tendon downward.

The diaphragm has a very specific shape and structure. It is an upward curved, C-shaped structure made of muscle and fibrous tissue.

The muscle fibers start at the edges of the chest and ribs. They all meet at a strong, thin center called the central tendon. The muscle has two main regions that do different jobs. The costal part helps drive the work of breathing. The crural part acts like an anchor by attaching to the ribs and spine.

There are several important openings in the diaphragm for body parts to pass through. One large opening is at the level of T8, called the caval opening. This allows the inferior vena cava, a large vein, to pass through.

Another opening is at the T10 level, known as the esophageal hiatus. This lets the esophagus pass from the throat to the stomach. At the T12 level, there is the aortic hiatus. This opening allows the aorta, the body's main artery, to pass through. The diaphragm also contains smaller openings for nerves and vessels.

In humans, the diaphragm is not perfectly even on both sides. The right half sits higher up than the left half. This happens because the large liver rests right beneath the right side.

The muscle is controlled by the phrenic nerve. This nerve starts in the neck at the C3, C4, and C5 levels. As a baby grows, the nerve follows the muscle as it moves down. This explains why the nerve takes such a long, circuitous path. The diaphragm also helps with other jobs, like pushing out waste or helping in childbirth.

The thoracic diaphragm is a vital sheet of internal skeletal muscle found in humans and other mammals. It sits at the base of the thoracic cavity, which is the chest area containing the heart and lungs. This muscle acts as a physical divider, separating the thoracic cavity from the abdominal cavity below. Because breathing is a constant necessity, the diaphragm is the most important muscle for respiration. It requires a massive amount of oxygen to function continuously. To support this, it contains more mitochondria and capillaries than any other skeletal muscle in the body.

The diaphragm operates through a specific mechanical process to move air. During inhalation, the muscle contracts and moves in an inferior, or downward, direction. This contraction increases the volume of the thoracic cavity. As the space inside the chest grows, it creates negative pressure, which acts like a vacuum. This low pressure pulls air into the lungs to fill the void. During exhalation, the diaphragm relaxes and moves in a superior, or upward, direction. The lungs then push air out through a process called elastic recoil.

Structurally, the diaphragm is an upward-curved, C-shaped dome of muscle and fibrous tissue. The muscle fibers originate from the circumference of the inferior thoracic aperture. These fibers radiate outward and converge at a central tendon, which forms the crest of the dome. The diaphragm is composed of two distinct functional regions. The costal diaphragm serves as the primary driver for the work of breathing. The crural diaphragm acts as an anchor, attaching the muscle to the lower ribs and the lumbar vertebrae.

The anatomy of the diaphragm includes several complex parts and ligaments. The vertebral part arises from the crura and arcuate ligaments. The right crus arises from the L1 to L3 vertebral bodies and their intervertebral discs. The left crus is smaller and arises from the L1 and L2 vertebral bodies. There are three specific arcuate ligaments: the medial, lateral, and median. The medial arcuate ligament arises from the fascia of the L2 vertebrae. The lateral arcuate ligament arises from the L1 transverse process and attaches to the 12th rib. The median arcuate ligament is formed by the fibrous parts of the right and left crura.

Because several major structures must travel between the chest and the abdomen, the diaphragm contains several openings. At the T8 vertebral level, the caval opening allows the inferior vena cava to pass through. This opening is located at the junction of the right and middle leaflets of the central tendon. At the T10 level, the esophageal hiatus allows the esophagus to pass through. This opening is located slightly left of the central tendon and is surrounded by the right crus. Finally, at the T12 level, the aortic hiatus allows the aorta, the thoracic duct, and the azygos vein to pass. The aorta actually passes behind the diaphragm between the left and right crus rather than piercing it.

The diaphragm is controlled by the phrenic nerve, which is formed from the cervical nerves C3, C4, and C5. This nerve supply is unique because of how the diaphragm develops during embryogenesis. In the third week after fertilization, the septum transversum forms the primitive central tendon in the cervical region. As the embryo grows, the septum transversum moves to the ventral thoracic region. The phrenic nerve must follow this descending muscle, resulting in its long, circuitous route from the neck to the chest. While the phrenic nerve handles the central portion, the intercostal and subcostal nerves provide sensory input for the peripheral parts.

Beyond breathing, the diaphragm performs several other essential functions. By increasing intra-abdominal pressure, it helps the body expel vomit, feces, and urine. It also assists during the process of childbirth. Additionally, it helps prevent acid reflux by exerting pressure on the esophagus as it passes through the esophageal hiatus. However, diaphragm dysfunction can lead to serious medical complications. Problems such as respiratory failure or difficulties with mechanical ventilation are often linked to diaphragm issues. In some diseases, such as sepsis or COVID-19, a reduction in diaphragm thickness can serve as a prognostic marker for a patient's condition.