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StatPearls . Treasure Island (FL): StatPearls Publishing; 2021 Jan-.


Anatomy, Thorax, Diaphragm

Kanwal Naveen S. Bains; Sarang Kashyap; sarah L. Lappin.

Author Information


The diaphragm in the thorax is dubbed the thoracic diaphragm and also serves as an important anatomical landmark the separates the thorax, or chest, native the abdomen. The functions during breathing as soon as it contract to enlarge the thoracic cavity and reduce the intrathoracic press so that lungs might expand and fill your alveoli through air. It is a dome-shaped muscle and tendon that functions as the key muscle of respiration and is essential to the breathing process. It is a fibromuscular sheet that has actually a convex upper surface that develops the floor the the thoracic cavity and also a concave under surface ar to type the roof of the ab cavity. The esophagus, phrenic, and also vagus nerves, diminish aorta, and also inferior vena cava pass through the diaphragm between the thoracic and abdominal muscle cavities. The diaphragm is asymmetric through the left side slightly much more inferior 보다 the right, chiefly due to the fact that of the presence of the liver located on the right. The left next may likewise be partially inferiorly located because of the push by the heart.<1>,<2>

Structure and Function

Functions the the Diaphragm

Muscle that Inspiration

The diaphragm pulls its central tendon down throughout contraction and then increases the upright diameter that the thorax. This rises the negative pressure inside the thoracic cavity, i m sorry draws in air. Thus, the diaphragm is the most vital muscle offered in inspiration. During inhalation, the diaphragm contracts and is propelled inferiorly into the abdominal muscle cavity wherein it appears flat. At the same time the external intercostal muscles located in between the ribs raise the anterior chest wall like the handle of a bucket. This results in the chest cavity coming to be larger and also wider, which enables air in indigenous the outside. Throughout exhalation, the rib cage and chest wall start to sag and also revert to the original position. In ~ the exact same time, over there is relaxation and elevation of the diaphragm. This motion forces the air within the lung to press out the the body.<2>,<3>

Muscle of abdominal muscle Straining

The contraction of the diaphragm will assist in the convulsion of the muscle of the anterior abdominal wall in increasing the intra-abdominal pressure will normal processes choose micturition, defecation, and also parturition.

Weightlifting Muscle

When a person takes and also holds a deep breath, the diaphragm will assist the muscles of the anterior abdominal wall to raise the intra-abdominal pressure. This practice is likewise called as Valsalva maneuver and also is provided to augment love murmurs and also classify them whether they are clinically right-sided or left-sided.

Thoracoabdominal Pump

When human being breathe in, the diaphragm descends, which decreases the intrathoracic pressure and improves the intra-abdominal pressure. This compresses the blood in the worse vena cava (IVC) and also forces it upward right into the right atrium and also helps to to fill the heart. When abdominal muscle lymph vessels are additionally compressed, the passage increase within the thoracic duct is aided through the an unfavorable intrathoracic pressure. Furthermore, valves in the thoracic duct avoid the backflow that the lymph in the thoracic duct.


The diaphragm inserts into a main tendon. The top surface the the tendon is partially connected to the reduced surface of the fibrous pericardium. Muscle fibers arising from the ideal crus traverse up on the left side and also encircle the orifice of the stomach in a sling-like loop. These fibers act as a sphincter and also likely assist in staying clear of the regurgitation that the stomach materials into the thoracic component of the esophagus.<4>

Origin of Diaphragm


The sternal component originates as 2 fleshy slips native the earlier of the xiphoid process.


The costal component originates native inner surfaces of the cartilages, surrounding parts the the reduced sixth ribs on every side. It interdigitates through transversus abdominis.


The medial lumbocostal arch is a tendinous arch in fascia spanning psoas major. Medially, that attaches to the side of the human body of vertebra L1. Laterally, it connects to the prior of the transverse procedure of vertebra L1.

The lateral lumbocostal arch is a tendinous arch in fascia spanning the upper part of quadratus lumborum. Medially, connect to the prior of the transverse process of vertebra L1. Laterally, it connects to the lower border of the 12th rib.

The appropriate crus occurs from the anterolateral surface of the body of the upper 3 lumbar vertebrae and also the intervening intervertebral disc

The left crus arises indigenous the corresponding parts that the top 2 lumbar vertebrae.

Medial margin of 2 crura creates a tendinous arc throughout the front of the aorta called the median arcuate ligament.


Motor Nerve Supply

Right and left phrenic nerves (C3 v C5)

Sensory Nerve Supply

The phrenic nerve innervates the parietal pleura and also peritoneum spanning the central surfaces of the diaphragm. The reduced 6 intercostal nerves supply the periphery of the diaphragm.

When the diaphragm contracts, the large-sized myelinated phrenic afferents fire. ~ above the other hand, the smaller sized diameter nerves proceed to discharge throughout the respiratory cycle. It is now well developed that activation that both non-myelinated and myelinated phrenic sensory nerves modulate respiratory output during each breath cycle. However, the activation the the phrenic afferents go increase substantially as the diaphragm proceeds to work and develops fatigue. Once the phrenic afferents room activated, they additionally modulate the sympathetic engine outflow. Furthermore, the phrenic afferents also contribute come somatosensation that the diaphragm and make one aware of the sensation of breath while awake. The precise influence of the spinal and also supraspinal nerves and synapses between the non-myelinated and also myelinated phrenic nerves is not known.

The use of deep muscle training added to a far-reaching change in the place of the body in the sagittal plane and the boost in the amplitude that breathing.<5>


One have the right to find the beginnings of the diaphragm along the lumbar vertebrae the the spine and also the worse border of the ribs and also sternum.

The exceptional diaphragm beginning is continuous from the xiphoid process anteriorly to reduced 6 costal cartilages the the thorax laterally and first 2 lumbar vertebrae posteriorly. The musculoskeletal fibers radiate native all angle to the facility of the body and also converge into a main tendon i beg your pardon is the inferior attachment or muscular skeleton point.

The diaphragm has a dome-like framework with the peripheral segment attached come the chest wall and abdominal muscle cavity. The muscle yarn from this attachments converge in a main tendon, which develops the crest of the dome. The perimeter of the diaphragm is do of solid muscular yarn that have their beginning from the surroundings of the worse thoracic aperture. These muscle fibers 보다 converge and insert into the main tendon.

Surgical Considerations

Diaphragmatic Hernia

A diaphragmatic hernia is a congenital special needs that occurs once one or much more of a person"s abdominal organs (stomach, spleen, liver, intestines) move upward into the chest through a defect in the diaphragm. The is normally congenital however can be acquired. Congenital hernias are thought about a clinical emergency and also require note surgery.<6>

Congenital Diaphragmatic Hernia (CDH)

A CDH is an abnormal breakthrough of the diaphragm throughout fetal life. The herniation leader to the i of one or other ab organ in the chest bring about the pulmonary hypoplasia which is normally unilateral. The most usual subtype the congenital diaphragmatic hernias is Bochdalek Hernia. Other species include Morgagni a hernia, diaphragm eventration, and main tendon defects that the diaphragm.

Acquired Diaphragmatic Hernia (ADH)

An ADH happens because of penetrating or blunt injury. Falls and motor vehicle crashes are significant causes of blunt injury when stabs and gunshot wounds bring about penetrating injuries. Penetrating injuries space the much more common cause than the blunt injuries as a reason of the diaphragmatic rupture. Further, there have the right to be accidental damages to the diaphragm native the operation causes. Infrequently, a diaphragmatic hernia may result without any kind of identifiable cause and also remain undiagnosed for an undetermined amount of time, until the herniation of ab organs in the chest start to cause symptoms.<7>


Both acquired, and also congenital diaphragmatic hernias generally require prompt surgery. Surgery calls for the return of the abdominal muscle organs native the chest cavity earlier into their original location in the ab cavity. The diaphragm need to be repaired through staples or permanent sutures with or without a prosthetic patch.

The vena caval trunk lies in ~ the level that the T8 vertebra in the main tendon. It allows passage of worse vena cava and some branches the the ideal phrenic nerve.
The esophageal hiatus lies in ~ the level the the T10 vertebra in a sling the muscle fibers derived from the best crus at the left the the median plane. It enables passage the esophagus, the right and also left vagus trunks, the esophageal branches the the left gastric vessels, and also the lymph vessels. 
The aortic hiatus lies anterior to the body of the T12 vertebra in between the crura. It permits passage the aorta, thoracic duct, and azygos vein.
The lesser aperture the left crus (permits hemiazygous vein; and lesser and also greater splanchnic nerves)                   
The sorry trunk operation posteriorly below the medial lumbocostal arches.                                    
Foramen the Morgagni is discovered in the areolar tissue between the sternal and also costal component of diaphragm contains the exceptional epigastric branch of the inner thoracic artery and the lymphatics of the abdominal wall.
The medial and also lateral lumbocostal arches can save on computer areolar organization that, as soon as present, the end the superior and posterior surface of a kidney indigenous the pleura.

The figure listed below shows the openings in the diaphragm: A=vena cava, B=esophagus, C=aorta. The muscular diaphragm surrounds the main tendon in the periphery.

Other Issues

The diaphragm has numerous other roles besides respiration. It acts as a obstacle between the thoracic and abdominal muscle cavity and prevents herniation of abdominal muscle organs right into the chest cavity.

Both penetrating and also blunt trauma have the right to injure the diaphragm. A tear or rupture the the diaphragm is frequently a challenging diagnosis. Choices for diagnosis include laparoscopy, thoracoscopy or a CT scan. Regardless of whether of the size of the tear, the muscle need to be repaired as shortly as possible to stop herniation of abdominal organs.

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The diaphragm is also involved in hiccups. Once the muscle is irritated, the can an outcome in suddenly contractions which have the right to be uncomfortable. Many hiccups are short-lived, however in rare cases, hiccups may last because that a day. If the hiccups persist, they deserve to interfere v breathing.