The Anatomy of the Diaphragm

The diaphragm is a large muscle that separates the chest, and the organs in it, from the abdomen and the body organs located there. This muscle, also called the thoracic diaphragm, plays an important role in breathing as its alternating movement helps you to inhale and exhale.

Other diaphragm functions include a role in urination and bowel movements, and assisting the lymphatic system in maintaining lymph flow through the body.All of these roles can be affected by injury or disease, such as a hiatal hernia with its common digestive symptoms of heartburn, nausea, and shortness of breath.

This article explains the diaphragm and its function, as well as related health conditions. It adds some information about how conditions affecting the diaphragm are diagnosed and treated, too.

Anatomy

The diaphragm is a parachute-shaped fibrous muscle that runs between the chest and abdomen, separating these two large cavities. It is asymmetric, as its right dome is larger than the left dome. The diaphragm has openings that allow certain structures to span the chest and abdominal cavities.

As it moves rhythmically, the diaphragm remains anchored to the ribs, sternum (breastbone), and the spine.

Structure

The diaphragm is primarily composed of muscle and fibrous tissue. The central tendon is a large part of the diaphragm that anchors the diaphragm to the ribs.

There are three large openings (holes) through the diaphragm. They are:

• The esophageal opening (esophageal hiatus), through which the esophagus, right and left vagus nerves, and left gastric artery and vein pass
• The aortic opening (aortic hiatus), through which the aorta, thoracic duct, and azygous vein pass
• The caval opening (cavus hiatus), through which the inferior vena cava and parts of the phrenic nerve travel

In addition to these openings, several smaller openings also allow smaller nerves and blood vessels to run through.

Location

Your diaphragm body part spans from the front to the back. It is the floor of the thoracic cavity and the ceiling of the abdominal cavity.

Many body organs are near the diaphragm. Your heart, lungs, and the upper part of your esophagus (food pipe) are in the thoracic cavity above the diaphragm. Your lower esophagus, stomach, intestines, liver, and kidneys are below the diaphragm, in your abdominal cavity.

The left and right phrenic nerves send signals to control the diaphragm, which receives its blood supply primarily from the inferior phrenic arteries.

Anatomical Variations

A healthy person can have some minor variations in the diaphragm's anatomy. For example, the left or right side may be slightly higher or lower without affecting physical functions.

During pregnancy, a woman's enlarged uterus can shift the abdominal space a bit, raising the diaphragm and causing shortness of breath.

Diaphragm Function

The diaphragm plays an integral role in respiration (breathing). Most of the time, the diaphragm moves involuntarily.

Your thoracic diaphragm also plays a role in helping the movement of muscles during childbirth, having a bowel movement, urinating, and lifting heavy objects. This muscle also helps maintain the flow of lymphatic fluid throughout the body.

Diaphragmatic Movement

When the diaphragm is activated by a nerve, it contracts and flattens. This action decreases pressure and increases the space in the thoracic cavity, allowing your lungs to expand as you inhale. When the diaphragm relaxes, your chest cavity becomes smaller and your lungs release air.

Your diaphragm contracts rhythmically and involuntarily (such as during sleep) due to signals from your brain. You can also voluntarily contract your diaphragm to hold your breath, to breathe more deeply or faster, or to exert your muscles.

Conditions Affecting the Diaphragm

There are several medical conditions that involve the thoracic diaphragm. Traumatic injuries or anatomical defects can interfere with the diaphragm muscle, and the movement of the diaphragm can also be impaired by issues like nerve disease or cancer.

Hiccups

When the diaphragm is irritated, such as when eating or drinking quickly, it can repeatedly contract involuntarily, resulting in hiccups. The sound of hiccups is produced when air is exhaled at the same time that the diaphragm contracts.

Generally, hiccups tend to resolve on their own, but there are treatments for persistent cases.

Hiatal Hernia

A hiatal hernia is a protrusion of the lower esophagus (and sometimes the stomach, too) into the chest cavity through an opening in the diaphragm. This defect can cause heartburn, indigestion, and nausea.

A number of conditions can cause a hiatal hernia, including:

• Increased pressure in the abdomen, from obesity or pregnancy
• Straining, such as with heavy lifting, coughing, or having a bowel movement
• Smoking, which increases the risk
• Genetic conditions such as Ehlers-Danlos syndrome

Hiatal hernias can be treated with lifestyle measures and medications alone. In some cases, surgery is recommended to reduce the risk of complications, such as volvulus (twisting) and strangulation (cutting off the blood supply) of tissues.

Surgery may be performed either through an open or laparoscopic procedure. With the latter technique, several small incisions are made in the abdomen and the repair is done through special camera-equipped instruments.

Diaphragmatic Hernias

Diaphragmatic hernias are structural defects that allow abdominal organs to enter the chest cavity. They may be present from birth, or, less commonly, can result from trauma.

• Congenital: The diaphragm doesn't develop as it should in roughly 1 in 2,000 births. As a result, some of the contents of the abdominal cavity can enter the chest cavity. This can result in incomplete development of the lungs (pulmonary hypoplasia). With surgery, an artificial diaphragm may be constructed.
• Acquired: Diaphragmatic hernias may also affect adults as a result of injuries, such as trauma due to motor vehicle accidents, gunshots, or stab wounds. These hernias can cause life-threatening issues, such as lung compression, and they generally need to be repaired surgically.

Paralysis

Conditions that affect the nerves that control the diaphragm can result in weakness or complete paralysis of the muscle.

These nerves can be damaged due to several mechanisms:

• Tumor compression
• Damage during surgery
• Traumatic injury
• Neurological conditions, such as diabetic neuropathy, Guillain-Barré syndrome, and muscular dystrophy. 
• Viral infections, such as polio
• Bacterial infections, such as Lyme disease

Nerve injury-induced diaphragmatic weakness can result in shortness of breath, especially when lying down. Management may require medication, surgery, rehabilitation, or support with mechanically assisted breathing.

Chronic Obstructive Pulmonary Disease (COPD)

Lung disease, especially COPD, can cause weakness of the diaphragm. This happens through a progressive process that involves a number of contributing factors.

COPD results in hyperinflated lungs that physically push on the diaphragm. The whole muscle becomes flattened and its mobility declines. Over time, the cells of the diaphragm are altered due to excessive strain, causing them to lose the ability to function with maximal strength. Chronic oxygen deprivation due to COPD also damages these cells.

The result of COPD-induced diaphragmatic weakness is worsening shortness of breath.

Cancer

Tumors can spread to the diaphragm or may take up space in the chest or abdominal cavity, placing physical pressure on the diaphragm and interfering with its ability to function.

Types of cancer that may affect the diaphragm include:

• Mesothelioma, a cancer of the pleura (outer lining of the lungs)
• Lung cancer
• Lymphoma
• Stomach cancer

The symptoms can be gradual or abrupt, and may include shortness of breath, pain with breathing, or loss of consciousness. Treatment generally involves surgical removal of the tumor, radiation treatment and/or chemotherapy, and in some cases, immunotherapy drugs and targeted therapies.

Evaluating the Diaphragm

Evaluation of the diaphragm can include a variety of tests tailored to the suspected medical problem. Imaging tests such as chest or abdominal computerized tomography (CT), magnetic resonance imaging (MRI), or ultrasound may identify anatomical variations or tumors.

A hiatal hernia diagnosis may include tests like an upper endoscopy or a barium swallow, which evaluate the structure of the gastrointestinal system. And COPD-associated diaphragmatic problems may be assessed with breathing tests like spirometry or pulmonary function tests.

A Word From Verywell

Your diaphragm plays a critical role in your ability to breathe, as well as other body functions. Contact your healthcare provider if you have diaphragm pain or other symptoms, such as those associated with hiatal hernia or COPD. Early diagnosis and treatment may improve the outlook.