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The diaphragm is an important organ of our body. In our today’s article on diaphragm structure and function, we will do what we told – describe its structure and mentions its functions. 

The diaphragm, just like larynx, pharynx, etc. is mostly taken for granted. Did you know that diaphragm plays a pivotal role in respiration? 

Now that you understood how important it is, let us jump into the structure and function of the diaphragm without wasting time any further. Let us begin.

Diaphragm Structure and Function: Structure

The diaphragm is a dome-like skeletal muscle that is present in the torso. 

The diaphragm is shaped like two halves (but it is not divided). Each half is called the suprapleural membrane or Sibson’s fascia. 

The diaphragm structure is asymmetric meaning the right half is slightly higher than the left half because of the positioning of the liver towards the right side of the diaphragm. 

There is a depression present between the two halves that is caused by the pericardium.

It has three different muscular parts – sternal, costal, and lumbar parts. 

The diaphragm structure consists of two major parts – the first part is the peripheral muscle and a central tendon. 

The peripheral muscle is the radial muscles originating from the spine (lumbar part), the sternum (sternal part), and the ribs (the costal part). 

These muscles converge on the central tendon (which is a sheet of white fibrous tissue that replaces actual tendon in flat muscles).

When a person inhales, the central tendon moves into the abdominal cavity pushing the muscles up thereby helping in the upward movement of the diaphragm during inspiration. 

It is triangular in shape. Its tip is attached to the seventh cervical vertebra and its base is attached to the first rib’s inner border. 

It is attached to a lot of bony structures. It is attached laterally to 11th and 12th ribs, anteriorly to the costal margin and xiphoid process, and posteriorly to lumbar vertebrae (first, second, and third lumbar vertebrae). 

The diaphragm attaches to the lumbar vertebrae in the form of tendon bands called crura. 

It has two surfaces – thoracic and abdominal surfaces. The thoracic surface of the diaphragm is in contact with lungs and pericardium.

The abdominal surface of the diaphragm is in contact with the stomach, liver, and spleen. 

The nerves that pass through the diaphragm are phrenic nerve and cervical nerves.

The diaphragm has several openings such as esophageal hiatus, vena cava foramen or caval opening, and aortic hiatus, etc. 

The structures that pass through these openings are inferior vena cava, vagus nerves, esophagus, descending aorta, azygos vein, thoracic duct,  etc. 

OpeningsStructures that pass
Vena cava foramen/caval openingInferior vena cava, right phrenic nerve’s branches
Aortic hiatusAzygos vein, thoracic duct, descending aorta
Esophageal hiatusEsophagus, vagus nerves

The arteries that supply blood to the diaphragm are 5 pairs of intercostal arteries, inferior phrenic arteries, superior phrenic arteries, and subcostal arteries. 

The arteries which supply the majority of the blood to the diaphragm are inferior phrenic arteries. 

The diaphragm starts developing in the fetus from the third week of conception. 

Diaphragm Structure and Function: Functions

As mentioned earlier, the diaphragm is extremely important for respiration. 

Before a person starts inhaling, the muscles contract including the diaphragm. When the diaphragm contracts, it flattens. 

When it is flattened, the volume of the thoracic cavity increases vertically. 

When the volume increases, the pressure decreases. To maintain pressure, the air is inhaled. 

When the muscles relax (including the diaphragm), the diaphragm gets back to its original shape. 

This leads to a decrease in the volume and as the volume decreases, the pressure increases. 

The air flows out of the lungs to maintain the pressure.

Don’t think that this is the only function of the diaphragm. When the diaphragm contracts, it raises the muscles of the anterior abdominal wall. 

This builds pressure in the abdomen and in turn, helps in processes like urination (micturition), parturition (the process of delivering the baby), expelling vomit, and defecation. 

It also indirectly helps in weight lifting by keeping the air pressure intact. 

Did you know that diaphragm has a role to play in strengthening the posture of the core? It also helps in strengthening the lumbar spine. 

Both the above points require a person taking deeper breaths than usual. 

It also aids in preventing acid reflux by putting pressure on the esophagus. 

Diaphragm Structure and Function: Medical Issues

It may be a bit unbelievable but the diaphragm may be paralyzed if there is any interruption to the supply of nerves.

The interruption to the nervous supply maybe because to various reasons such as damage to any of the nerves that pass through the diaphragm, damage to nerves during surgery, development of tumor in the chest cavity, etc. 

If one half of the diaphragm is paralyzed then it is asymptomatic. However, if both halves are paralyzed then the person may experience fatigue, poor tolerance to exercise, etc. 

Then there is something called diaphragmatic hernia. It is a birth defect. 

The child develops a hole in the diaphragm (not the openings that it usually has) through which organs of the abdomen can move upwards in the chest. 

When any organ pushes through that hole, it is called a hernia. A hernia doesn’t allow the lungs to develop properly and causes breathing difficulties. 

According to researches, 1 in 3,600 babies develops diaphragmatic hernia. 

What is more disturbing is the fact that half of the babies who have this hernia also have birth defects in the intestine, heart, or brain

In adults, hiatus hernia can be seen where parts of the stomach or esophagus can enter the chest cavity through the opening of the diaphragm. 

Hiccups are also a disorder of the diaphragm. Don’t be worried or shocked, every human on this planet experiences hiccups. 

Hiccups are caused when the diaphragm contracts involuntarily and at intervals. 

The main reason for hiccups is many. Some of the reasons include the consumption of large amounts of food (solid or liquid) in a short duration, consuming carbonated drinks, acid indigestion, even dealing with a bad day!

Usually, hiccups are short-lived but if the hiccups stay for days then it may be due to irritated nerves, and consulting a doctor would be a wise idea. 

However, it is interesting to note that animals like cows don’t really require or need the diaphragm like the way humans need it. 

The diaphragm structure and function article pretty much sum up almost everything you need to learn. If you want an in-depth article on any of the organs like the diaphragm structure and function, you can simply comment or mail to us and we will happily oblige. 


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