Diaphragm: Definition, Anatomy, Function, Muscles, Actions and Associated Conditions

It is the primary muscle that the body uses when breathing.

The diaphragm, also known as the thoracic diaphragm, is a large structure located in the lower part of the chest cavity.


The chest cavity is the area of ​​your chest where your heart and lungs are supported. The diaphragm also serves as a divider between the thoracic and abdominal cavities.

The abdominal cavity is below the thoracic cavity. The diaphragm is located in the lower part of the thoracic cavity; it is the floor of the thoracic cavity.

The diaphragm is a musculotendinous structure, which means that it is made of muscles and tendons. The diaphragm is made up of the peripheral muscle and the central tendon. In the relaxed position, it is shaped like two domes.

There is a left dome under the left lung and a right dome under the right lung.

The domes are convex, which means that they slope upwards. When the diaphragm is contracted, it looks like a flat sheet.


Muscles have origin points where they begin and insertion points where they end, called attachments.

The diaphragm comes from several places. According to its origin, the peripheral muscle has three regions: sternal, costal, and lumbar regions.

The sternal region is composed of two small muscle segments attached to the sternum in the xiphoid process on the posterior aspect.

The coastal region comprises several broad muscle segments whose origins are located in the internal area of ​​the lower ribs and the costal cartilages.

The lumbar region, for its part, originates from the lumbar vertebra, in the lower part of the spine.

Specifically, the diaphragm is attached to the spine by processes that protrude laterally from the vertebrae, called the crura, and their coincident ligaments.

The spinal insert is in the upper lumbar section. The insertion point of the diaphragm is called the central tendon.

It is shaped like a clover with three leaflets called the right, middle and left leaflets. The central tendon is described as aponeurotic.

The aponeurosis is a flat tendon that forms the origin or insertion point of a flat muscle.

The central tendon causes the diaphragm to contract or collapse, causing inspiration.

The diaphragm has some openings, or holes, to facilitate the passage of the main arteries, veins, and nerves.

The esophagus, aorta, and cava are the most significant openings.

The aortic opening carries the aorta (the main artery), the thoracic duct (a lymphatic vessel), and the azygos vein (a central vein that connects the superior and inferior venous systems).

The esophagus passes through the esophageal opening, the vagus nerves, and other blood and lymphatic vessels.

Opening the cava allows the inferior vena cava to pass through the right side of the phrenic nerve.

The inferior vena cava is the central vein in the lower half of the body.

The phrenic nerve is the main nerve that drives the breathing process.

There are other small openings, for example, the opening for the lesser splanchnic nerve.


The diaphragm is the primary muscle of respiration.

Depending on the amount of effort we exert, the act of breathing can be accomplished with the help of many muscles.

The primary muscle of respiration is a muscle called the diaphragm. A diaphragm is something that separates two structures.

The diaphragm muscle separates the heart and lungs from the abdominal organs, with a double domed shape inside the chest like a parachute.

The diaphragm is also involved in non-respiratory functions, such as going to the bathroom and vomiting.

The diaphragm is one of many diaphragms in the body but the only one labeled as such.

It is often called the thoracic diaphragm, located at the base of the rib cage and the thoracic spine.

There are several primary muscles for breathing.

While the diaphragm should do about 75% of the work, the abdominal muscles and the intercostal muscles between the ribs also play a role.

The secondary muscles of respiration, designed to function when the body works harder, are:

  • The pectoral muscles (the chest).
  • The trapezius.
  • The sternocleidomastoid.
  • The scalenes (all connect to the head).

Due to poor posture, these secondary muscles often do the work of the primary forces, especially the diaphragm.

Inhalation occurs when the diaphragm drops or the rib cage expands and carries the lungs.

The resulting suction draws air from the mouth into the windpipe and the lungs.

Exhalation occurs when the connective tissue in the lungs pulls upward on the diaphragm.

Muscle doesn’t retract on itself, so the lungs have a protein called surfactant that essentially gums them up to shrink after expansion.

This helps create the action of the bellows, which is the function of holding air and then expelling it.

Breathing is considered diaphragmatic when the diaphragm can descend when inhaling.

This is an efficient type of breathing as it is likely to draw air into the lower part of the lungs where blood resides.

When in an upright position, very efficient breathing is needed to get oxygen to all the lungs.

Chest breathing occurs when the rib cage expands more than the diaphragm descends.

This requires more work for the same gas, blood, and oxygen mixture.

More oxygen is needed to accommodate the increased effort, which means more work for the heart.

The diaphragm can also be used to increase pressure within the abdomen.

This is an essential function when performing tasks that increase the load on the lower back.

Any time the lower back or sacroiliac joints are damaged, nearby muscles, such as the diaphragm, can be affected.

Sacroiliac joint pain can increase when the stomach and diaphragm muscles stop working together.

Some people find that their pain is controlled by learning to coordinate these muscles while doing activities.

Physical therapists design specific exercise programs to treat these types of symptoms.

Muscles and actions of the diaphragm

The diaphragm is a large, flat muscle that rests under the lungs and runs through the chest cavity.

You have two big jobs:

  1. The diaphragm moves down to allow more air into the lungs when you breathe deeply.
  2. As you exhale, the diaphragm returns to its resting position.

Primary actions of the diaphragm


During inspiration or air intake, the diaphragm contracts and moves downward.

The chamber widens, and air enters the lungs.

  • External intercostals.
  • Serratus superior.
  • Internal intercostals.
  • Thoracic transverse.
  • Internal oblique.
  • External oblique.
  • Abdominal rect.

Forced inspiration

With forced inspiration, the thoracic cavity volume is increased to a greater degree than with relaxed inspiration.

This is carried out when you cough, inflate a balloon or play the trumpet, among others.

  • Pectoral minor.
  • Pectoral major.
  • External intercostals.
  • Scalenes
  • Tightened.
  • Upper posterior.
  • Internal intercostals.
  • Thoracic transverse.
  • Internal oblique.
  • External oblique.
  • Abdominal rect.

The diaphragm moves downward so that the lungs fill with air during inhalation.

It then moves upward during an exhalation, causing the lungs to empty.

Exhalation or expiration is a process opposite to inspiration; during this phenomenon, the air is expelled from the lungs.

This is a passive phase of the respiratory process.

The thorax is retracted, and the volume of the thoracic cavity decreases, regaining its original shape.

There is no muscular contraction in it, the muscles that were activated during inspiration relax again in this phase.

The ribs and diaphragm return to their initial position.

Causes of diaphragm pains

People can sometimes feel pain or discomfort in the diaphragm, although in some cases, the pain may be coming from a different and nearby part of the body.

Diaphragm pain can have multiple causes, some benign and some potentially serious. Here are some of them.

The exercise

The diaphragm can spasm when you breathe hard during strenuous exercise, such as running, which can cause pain in the sides.

Pain in the diaphragm can be extreme and restricts breathing, and does not allow a full breath to be exhaled without discomfort.

If you experience pain like this during exercise, take a short break to regulate your breathing and relieve spasms.

This situation worsens if proper stretching and warming up before exercising are neglected, so be sure to warm up before you step on the treadmill.

The pregnancy

Diaphragm discomfort and shortness of breath are normal during pregnancy.

These are not symptoms that a person with diaphragm pain should worry about.

During pregnancy, as the baby grows, the uterus expands and pushes the diaphragm up about an inch and a half, decreasing overall lung capacity.

This can cause shortness of breath in the mother but is considered a normal phenomenon and is not a cause for concern.

When you experience prolonged or severe pain or a persistent cough, you should see a doctor.

And trauma

Trauma to the diaphragm from injury, a car accident, or surgery can cause intermittent pain (comes and goes) or long-lasting.

Diaphragmatic rupture occurs due to a tear in the diaphragm caused by blunt trauma.

Although severe, a ruptured diaphragm can go unnoticed in the long run.

Your doctor can diagnose diaphragmatic rupture using a CT scan or thoracoscopy.

This condition requires surgery, as it does not heal on its own.

Musculoskeletal problems

A muscular tension of the rib muscles, which can occur due to trauma, coughing, or twisting movements, can cause pain that can be mistaken for diaphragm pain.

Rib fractures can also cause this type of pain.

Gallbladder problems

One of the most acute symptoms associated with gallbladder problems is a pain in the upper middle abdomen on the right, which could easily be mistaken for diaphragm pain.

Some gallbladder conditions that can cause the above symptoms to include infection, abscess, gallbladder disease, gallstones, bile duct obstruction, inflammation, and cancer.

Una hernia Hiatal

A hiatal hernia is experienced when the upper part of the stomach pushes up through an opening in the lower part of the esophagus called the hiatus.

It is characterized by the contents of the abdominal cavity, such as the stomach or intestines, that protrude up into the thoracic cavity through the esophageal opening in the diaphragm called the esophageal hiatus.

Hiatal hernias commonly occur in the older population (over 60), but can be seen in younger patients who smoke, perform frequent heavy lifting, or are obese.

Symptoms often include chest pain, difficulty swallowing, and frequent bouts of hiccups.

Spinal cord disorders

These include spinal trauma, amyotrophic lateral sclerosis, and motor neuron disease.

Myasthenia gravis

It is an autoimmune disorder characterized by weakness in the skeletal muscles, especially in the forces responsible for breathing that affect respiratory capacity.

A stroke

A stroke can cause one side of the diaphragm muscle to paralyze, with the unaffected side having to work harder, ultimately leading to the development of diaphragmatic pain.

Phrenic nerve neuropathy

The phrenic nerve directly innervates the diaphragm.

Injury to the phrenic nerve through surgical injury can lead to severe diaphragmatic pain.

Other possible causes of diaphragm pain include:

  • Bronchitis.
  • Heart surgery.
  • Lupus or other connective tissue disorders.
  • Pleuresía.
  • Pneumonia.
  • Radiation treatments.
  • Rheumatoid arthritis.
  • Poliomyelitis.
  • Thyroid disorders.
  • Malnutrition.
  • Infection.
  • Inefficient breathing pattern.
  • Chiropractic manipulation.