Diaphragm (anatomy)

Respiratory system
subject #117 404
ArteryPericardiacophrenic artery, Musculophrenic artery, Inferior phrenic arteries
VeinSuperior phrenic vein, Inferior phrenic vein
Nervephrenic and lower intercostal nerves
Precursorseptum transversum, pleuroperitoneal folds, body wall [1]
MeSH Diaphragm
Dorlands/Elsevier d_15/12293509
For other types of diaphragm, see Diaphragm.

In the anatomy of mammals, the diaphragm is a sheet of muscle extending across the bottom of the ribcage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration.

In order to avoid confusion with other types of diaphragm, it is sometimes referred to as the thoracic diaphragm. Any reference to the diaphragm is understood to refer to this structure.


It is crucial in respiration: in order to draw air into the lungs, the diaphragm contracts, thus enlarging the thoracic cavity and reducing intra-thoracic pressure (the external intercostal muscles also participate in this enlargement). When the diaphragm relaxes, air is exhaled by elastic recoil of the lung and the tissues lining the thoracic cavity in conjunction with the abdominal muscle which act as the antagonist pair to diaphragm's contraction Antagonist (muscle). The diaphragm is also found in other vertebrates such as reptiles.

It is not responsible for all the breathing related to voice, a common misconception espoused by many teachers but few great singers. One has more control over the abdominals and intercostals than the actual diaphragm, which lacks proprioceptive nerve endings. By training proper posture and balance in the rest of the body, the diaphragm naturally strenghtens and works in concert with surrounding structures rather than in isolation.

The diaphragm also helps to expel vomit, feces, and urine from the body by increasing intra-abdominal pressure.


A hiatal hernia can result from a tear or weakness in the diaphragm near the gastroesophageal junction.

If the diaphragm is struck, or otherwise spasms, breathing will become difficult. This is called "having the wind knocked out of you."

A hiccup occurs when the diaphragm contracts periodically without voluntary control.

Diaphragmatic injuries result from either blunt or penetrating trauma.


The Diaphragm is a dome-shaped musculofibrous septum which separates the thoracic from the abdominal cavity, its convex upper surface forming the floor of the former, and its concave under surface the roof of the latter. Its peripheral part consists of muscular fibers which take origin from the circumference of the thoracic outlet and converge to be inserted into a central tendon.

The muscular fibers may be grouped according to their origins into three parts:

sternaltwo fleshy slips from the back of the xiphoid process.
costalthe inner surfaces of the cartilages and adjacent portions of the lower six ribs on either side, interdigitating with the Transversus abdominis.
lumbaraponeurotic arches, named the lumbocostal arches, and from the lumbar vertebrae by two pillars or crura.

There are two lumbocostal arches, a medial and a lateral, on either side.


The diaphragm is innervated by the phrenic nerve.

Crura and central tendon

At their origins the crura are tendinous in structure, and blend with the anterior longitudinal ligament of the vertebral column.

The central tendon of the diaphragm is a thin but strong aponeurosis situated near the center of the vault formed by the muscle, but somewhat closer to the front than to the back of the thorax, so that the posterior muscular fibers are the longer.

Openings in the Diaphragm

The diaphragm is pierced by a series of apertures to permit of the passage of structures between the thorax and abdomen. Three large openings—the aortic, the esophageal, and the vena cava—and a series of smaller ones are described.

caval openingT8inferior vena cava, and some branches of the right phrenic nerve
esophageal hiatusT10esophagus, the vagus nerves, and some small esophageal arteries
aortic hiatusT12the aorta, the azygos vein, and the thoracic duct
two lesser aperture of right crusgreater and lesser right splanchnic nerves
three lesser aperture of left crusgreater and lesser left splanchnic nerves and the hemiazygos vein
behind the diaphragm, under the medial lumbocostal archesgangliated trunks of the sympathetic
areolar tissue between the sternal and costal parts (see also foramina of Morgagni)the superior epigastric branch of the internal mammary artery and some lymphatics from the abdominal wall and convex surface of the liver
areolar tissue between the fibers springing from the medial and lateral lumbocostal archesThis interval is less constant; when this interval exists, the upper and back part of the kidney is separated from the pleura by areolar tissue only.


The sternal portion of the muscle is sometimes wanting and more rarely defects occur in the lateral part of the central tendon or adjoining muscle fibers.

Additional images

Inferior view of the human diaphragm

The phrenic nerve and its relations with the vagus nerve.

Plan of right sympathetic cord and splanchnic nerves.

Thoracic portion of the sympathetic trunk.

The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind.

Front view of the thoracic and abdominal viscera.

The duodenum and pancreas.

Topography of thoracic and abdominal viscera.

Organs of abdomen

Peritoneopericardial diaphragmatic hernia in a cat.

Probably the first dictionary definition of "diaphragm"

See also


External links

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
Official status
Official language of: Vatican City
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Arteries are muscular blood vessels that carry blood away from the heart.[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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The pericardiacophrenic artery is a long slender branch of the internal thoracic artery. It accompanies the phrenic nerve, between the pleura and pericardium, to the diaphragm, to which it is distributed; it anastomoses with the musculophrenic and inferior phrenic arteries.
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The Musculophrenic Artery arises from the internal thoracic artery, directed obliquely downward and lateralward, behind the cartilages of the false ribs; it perforates the diaphragm at the eighth or ninth costal cartilage, and ends, considerably reduced in size, opposite the last
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The inferior phrenic arteries are two small vessels, which supply the diaphragm but present much variety in their origin.

They may arise separately from the front of the aorta, immediately above the celiac artery, or by a common trunk, which may spring either from the aorta
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vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.
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The superior phrenic vein, i.e., the vein accompanying the pericardiacophrenic artery, usually opens into the internal mammary vein.

This article was originally based on an entry from a public domain edition of Gray's Anatomy.
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The Inferior Phrenic Veins follow the course of the inferior phrenic arteries;
  • the right ends in the inferior vena cava;
  • the left is often represented by two branches,

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A nerve is an enclosed, cable-like bundle of axons (the long, slender projection of a neuron). Neurons are sometimes called nerve cells, though this term is technically imprecise since many neurons do not form nerves, and nerves also include the glial cells that
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The phrenic nerve arises from the third, fourth, and fifth cervical spinal nerves (C3-C5) in humans. It arises from the fifth, sixth and seventh cervical spinal nerves (C5-7) in most domestic animals.
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The intercostal nerves are the anterior divisions (rami anteriores; ventral divisions) of the thoracic spinal nerves from T1 to T11.

Each nerve is connected with the adjoining ganglion of the sympathetic trunk by a gray and a white ramus communicans.
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Embryology is the study of the development of an embryo. An embryo is defined as any vertebrate in a stage before birth or hatching. Embryology refers to the development of the egg cell (zygote) after fertilization and the differentiation of cells into tissues and organs.
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The septum transversum is a thick mass of cranial mesenchyme that gives rise to parts of the thoracic diaphragm and the ventral mesentery of the foregut in the developed human being.
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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Diaphragm may refer to:


  • Thoracic diaphragm, a sheet of muscle separating the thorax and abdomen of mammals
  • Urogenital diaphragm, a layer of the pelvis separating deep perineal sac from the upper pelvis

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Anatomy (from the Greek ἀνατομία anatomia, from ἀνατέμνειν
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Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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RIB can mean:
  • Rigid-hulled inflatable boat
  • Romanian International Bank
  • Routing Information Base

This article is about the bones called ribs. For other meanings, see rib (disambiguation).

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The thoracic cavity (or chest cavity) is the chamber of the human body (and other animal bodies) that is protected by the thoracic wall (thoracic cage and associated skin, muscle, and fascia).
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The abdominal cavity is the body cavity of the human body (and other animal bodies) that holds the bulk of the viscera and which is located below (or inferior to) the thoracic cavity, and above the pelvic cavity.
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In animal physiology, respiration is the transport of oxygen from the ambient air to the tissue cells and the transport of carbon dioxide in the opposite direction. This is in contrast to the biochemical definition of respiration, which refers to cellular respiration
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In animal physiology, respiration is the transport of oxygen from the ambient air to the tissue cells and the transport of carbon dioxide in the opposite direction. This is in contrast to the biochemical definition of respiration, which refers to cellular respiration
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lungs flank the heart and great vessels in the chest cavity.[1]]]

The lung is the essential respiration organ in air-breathing vertebrates, the most primitive being the lungfish.
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Intercostal muscles are several groups of muscles that run between the ribs, and help form and move the chest wall.

There are three principal layers;
  • the external intercostal muscles, which aid in quiet and forced inhalation.

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An antagonist is a kind of muscle that acts in opposition to the movement generated by the agonist and is responsible for returning a limb to its initial position.

Antagonistic pairs in houses

These antagonistic muscles are found in pairs called antagonistic pairs.
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Cuvier, 1812

Classes and Clades

See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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Goodrich, 1916

  • Anapsida
  • Diapsida
  • Reptilia Laurenti, 1768
Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane, and members of the class
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human voice consists of sound made by a human using the vocal folds for talking, singing, laughing, crying, screaming etc. The vocal folds, in combination with the lips, the tongue, the lower jaw, and the palate, are capable of producing highly intricate arrays of sound.
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