Thoracic diaphragm

From Morphome.net

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.

1 Function
2 Pathology
3 Anatomy
4 Additional images
5 See also
6 References
7 External links

[edit] Function

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.

[edit] Pathology

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.

[edit] Anatomy

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:

Part	Origin
sternal	two fleshy slips from the back of the xiphoid process.
costal	the inner surfaces of the cartilages and adjacent portions of the lower six ribs on either side, interdigitating with the Transversus abdominis.
lumbar	aponeurotic 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.

[edit] Innervation

The diaphragm is innervated by the phrenic nerve.

[edit] 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.

[edit] 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.

opening	level	structures
caval opening	T8	inferior vena cava, and some branches of the right phrenic nerve
esophageal hiatus	T10	esophagus, the vagus nerves, and some small esophageal arteries
aortic hiatus	T12	the aorta, the azygos vein, and the thoracic duct
two lesser aperture of right crus		greater and lesser right splanchnic nerves
three lesser aperture of left crus		greater and lesser left splanchnic nerves and the hemiazygos vein
behind the diaphragm, under the medial lumbocostal arches		gangliated 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 arches		This 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.

[edit] Variations

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.

[edit] Additional images

Gray391.png Inferior view of the human diaphragm	Gray806.png The phrenic nerve and its relations with the vagus nerve.	Gray845.png Plan of right sympathetic cord and splanchnic nerves.	Gray846.png Thoracic portion of the sympathetic trunk.
Gray1032.png The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind.	Gray1034.png Front view of the thoracic and abdominal viscera.	Gray1098.png The duodenum and pancreas.	Gray1224.png Topography of thoracic and abdominal viscera.
BauchOrgane wn.png Organs of abdomen	Peritoneopericardial diaphragmatic hernia.JPG Peritoneopericardial diaphragmatic hernia in a cat.	Hiatalhernia.gif Hiatal hernia	Diaphragm def 1707.png Probably the first dictionary definition of "diaphragm"