1. The diaphragm (find true statements)
(a) Develops from the septum transversum and cervical myotomes
(b) Receives a nerve supply from both the phrenic and intercostal nerves
(c) An opening in the central tendon transmits the left phrenic nerve
(d) The inferior vena cava passes through the diaphragm at the level of the T12 vertebra
(e) The aorta passes through the diaphragm at the level of the T8 vertebra
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only a and b are true . The diaphragm develops in the neck and hence receives its nerve supply from the cervical spinal cord (C4-C5). It is made up of structures arising from the septum transversum, pleuroperitoneal membranes, the dorsal mesentery and body wall. The septum transversum forms the central tendon. The motor nerve supply arises from the phrenic nerve. The sensory nerve supply is from the lower six intercostal nerves. The IVC, oesophagus and aorta pass through the diaphragm at the levels of T8, T10 and T12 respectively. an opening in the central tendon transfers the right phrenic nerve .
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 caval—and a series of smaller ones are described.
The aortic hiatus is the lowest and most posterior of the large apertures; it lies at the level of the twelfth thoracic vertebra. Strictly speaking, it is not an aperture in the diaphragm but an osseoaponeurotic opening between it and the vertebral column, and therefore behind the diaphragm; occasionally some tendinous fibers prolonged across the bodies of the vertebræ from the medial parts of the lower ends of the crura pass behind the aorta, and thus convert the hiatus into a fibrous ring. The hiatus is situated slightly to the left of the middle line, and is bounded in front by the crura, and behind by the body of the first lumbar vertebra. Through it pass the aorta, the azygos vein, and the thoracic duct; occasionally the azygos vein is transmitted through the right crus.
The esophageal hiatus is situated in the muscular part of the diaphragm at the level of the tenth thoracic vertebra, and is elliptical in shape. It is placed above, in front, and a little to the left of the aortic hiatus, and transmits the esophagus, the vagus nerves, and some small esophageal arteries.
The vena caval foramen is the highest of the three, and is situated about the level of the fibrocartilage between the eighth and ninth thoracic vertebræ. It is quadrilateral in form, and is placed at the junction of the right and middle leaflets of the central tendon, so that its margins are tendinous. It transmits the inferior vena cava, the wall of which is adherent to the margins of the opening, and some branches of the right phrenic nerve.
Of the lesser apertures, two in the right crus transmit the greater and lesser right splanchnic nerves; three in the left crus give passage to the greater and lesser left splanchnic nerves and the hemiazygos vein. The gangliated trunks of the sympathetic usually enter the abdominal cavity behind the diaphragm, under the medial lumbocostal arches.
On either side two small intervals exist at which the muscular fibers of the diaphragm are deficient and are replaced by areolar tissue. One between the sternal and costal parts transmits the superior epigastric branch of the internal mammary artery and some lymphatics from the abdominal wall and convex surface of the liver. The other, between the fibers springing from the medial and lateral lumbocostal arches, is less constant; when this interval exists, the upper and back part of the kidney is separated from the pleura by areolar tissue only.
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.
Nerves.—The diaphragm is supplied by the phrenic and lower intercostal nerves.
Actions.—The diaphragm is the principal muscle of inspiration, and presents the form of a dome concave toward the abdomen. The central part of the dome is tendinous, and the pericardium is attached to its upper surface; the circumference is muscular. During inspiration the lowest ribs are fixed, and from these and the crura the muscular fibers contract and draw downward and forward the central tendon with the attached pericardium. In this movement the curvature of the diaphragm is scarcely altered, the dome moving downward nearly parallel.
(a) Develops from the septum transversum and cervical myotomes
(b) Receives a nerve supply from both the phrenic and intercostal nerves
(c) An opening in the central tendon transmits the left phrenic nerve
(d) The inferior vena cava passes through the diaphragm at the level of the T12 vertebra
(e) The aorta passes through the diaphragm at the level of the T8 vertebra
-------------------------
only a and b are true . The diaphragm develops in the neck and hence receives its nerve supply from the cervical spinal cord (C4-C5). It is made up of structures arising from the septum transversum, pleuroperitoneal membranes, the dorsal mesentery and body wall. The septum transversum forms the central tendon. The motor nerve supply arises from the phrenic nerve. The sensory nerve supply is from the lower six intercostal nerves. The IVC, oesophagus and aorta pass through the diaphragm at the levels of T8, T10 and T12 respectively. an opening in the central tendon transfers the right phrenic nerve .
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 caval—and a series of smaller ones are described.
The aortic hiatus is the lowest and most posterior of the large apertures; it lies at the level of the twelfth thoracic vertebra. Strictly speaking, it is not an aperture in the diaphragm but an osseoaponeurotic opening between it and the vertebral column, and therefore behind the diaphragm; occasionally some tendinous fibers prolonged across the bodies of the vertebræ from the medial parts of the lower ends of the crura pass behind the aorta, and thus convert the hiatus into a fibrous ring. The hiatus is situated slightly to the left of the middle line, and is bounded in front by the crura, and behind by the body of the first lumbar vertebra. Through it pass the aorta, the azygos vein, and the thoracic duct; occasionally the azygos vein is transmitted through the right crus.
The esophageal hiatus is situated in the muscular part of the diaphragm at the level of the tenth thoracic vertebra, and is elliptical in shape. It is placed above, in front, and a little to the left of the aortic hiatus, and transmits the esophagus, the vagus nerves, and some small esophageal arteries.
The vena caval foramen is the highest of the three, and is situated about the level of the fibrocartilage between the eighth and ninth thoracic vertebræ. It is quadrilateral in form, and is placed at the junction of the right and middle leaflets of the central tendon, so that its margins are tendinous. It transmits the inferior vena cava, the wall of which is adherent to the margins of the opening, and some branches of the right phrenic nerve.
Of the lesser apertures, two in the right crus transmit the greater and lesser right splanchnic nerves; three in the left crus give passage to the greater and lesser left splanchnic nerves and the hemiazygos vein. The gangliated trunks of the sympathetic usually enter the abdominal cavity behind the diaphragm, under the medial lumbocostal arches.
On either side two small intervals exist at which the muscular fibers of the diaphragm are deficient and are replaced by areolar tissue. One between the sternal and costal parts transmits the superior epigastric branch of the internal mammary artery and some lymphatics from the abdominal wall and convex surface of the liver. The other, between the fibers springing from the medial and lateral lumbocostal arches, is less constant; when this interval exists, the upper and back part of the kidney is separated from the pleura by areolar tissue only.
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.
Nerves.—The diaphragm is supplied by the phrenic and lower intercostal nerves.
Actions.—The diaphragm is the principal muscle of inspiration, and presents the form of a dome concave toward the abdomen. The central part of the dome is tendinous, and the pericardium is attached to its upper surface; the circumference is muscular. During inspiration the lowest ribs are fixed, and from these and the crura the muscular fibers contract and draw downward and forward the central tendon with the attached pericardium. In this movement the curvature of the diaphragm is scarcely altered, the dome moving downward nearly parallel.
1 comment:
"Through it pass the aorta, the azygos vein, and the thoracic duct; occasionally the azygos vein is transmitted through the right crus."
Kindly site your reference. Gray's Anatomy 39th Ed (pg 1026) says it can pass through either aortic orifice or right crus. No percentages are available anywhere on the incidence of each though!
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