1. The diaphragm
(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
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2. The oesophagus
(a) Is 40 cm in length
(b) In the thorax passes behind the left main bronchus
(c) Is lined by stratified squamous epithelium in the upper two-thirds
(d) Is lined by transitional epithelium in the lower one-third
(e) Drains all of its blood into the azygos and hemiazygos veins
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only b and c are right . The oesophagus is 25 cm in length. The oesophagogastric junction lies 40 cm from the incisors. The oesophagus is lined by both striated (upper two-thirds) and smooth (lower third) muscle. The lower third is line by columnar epithelium. The venous drainage is into the inferior thyroid, azygos and left gastric veins. The communication between the azygos and left gastric veins is an important portosystemic anastomosis that can be the site of oesophageal varices.
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3. The radial nerve
(a) Is the principal branch of the posterior cord of the brachial plexus
(b) Is derived from the posterior primary rami of the C5 to T1 nerve roots
(c) Is the main nerve supply to the extensor compartments of the arm and forearm
(d) Gives rise to the anterior interosseous nerve
(e) Supplies sensation to the extensor aspect of the radial three and a half digits
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a , c , e are the right answers . The radial nerve is the main branch of the posterior cord of the brachial plexus. Other branches of the posterior cord include the axillary, thoracodorsal and upper and lower subscapular nerves. All roots of the brachial plexus arise from the ""anterior"" primary rami. The radial nerve supplies the forearm and wrist extensors; A radial nerve palsy results in a classical 'wrist drop'. The anterior and posterior interosseus nerves are branches of the median and radial nerves respectively.
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4. The thymus gland
(a) Lies within the posterior mediastinum
(b) Develops from the fourth pharyngeal pouch
(c) Decreases in size with age
(d) Is made up of cells of endodermal origin
(e) Descends anterior to the brachiocephalic vein
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The thymus lies within the anterior mediastinum. It develops with the inferior parathyroid gland from the third pharyngeal pouch. The cells of the thymus are of endodermal origin. It is at its largest in childhood and decreases in size with age.
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5. Scalenus anterior
(a) Is an accessory muscle of respiration
(b) Separates the subclavian vein from the subclavian artery and brachial plexus
(c) Is pierced by the phrenic nerve
(d) Inserts into the scalene tubercle on the second rib
(e) Lies anterior to the suprascapular artery
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only a and b are correct . Scalenus anterior arises from the transverse processes of the third to six cervical vertebrae. It inserts into the scalene tubercle of the first rib. The subclavian vein passes anteriorly. The subclavian artery and brachial plexus pass posteriorly. The phrenic nerve lies on the anterior surface.
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6. The axilla contains
(a) The cords of the brachial plexus
(b) The superior thoracic artery
(c) The latissimus dorsi muscle in its medial wall
(d) The thoracodorsal nerve in its posterior wall
(e) The long thoracic nerve in its medial wall
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a , b , d , e are the right answers . The axilla contains the cords of the brachial plexus. The latissimus dorsi muscle forms the posterior wall of the axilla. It is supplied by the thoracodorsal nerve. The long thoracic nerve supplies serratus anterior and lies on the medial wall.
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7. The common bile duct
(a) Lies in the free edge of the lesser omentum
(b) Lies anterior to the portal vein
(c) Lies to the right of the hepatic artery
(d) May open into the duodenum independent of the pancreatic duct
(e) Lies anterior to the first part of the duodenum
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only e is false . The common bile duct lies in the free edge of the lesser omentum, anterior to the portal vein and to the right of the hepatic artery. It passes posterior to the first part of the duodenum before opening into the second part.
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8. The following structures pass under the inguinal ligament
(a) The tendon of psoas major
(b) The femoral branch of the genitofemoral nerve
(c) The long saphenous vein
(d) The superficial epigastric vein
(e) The superficial femoral artery
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only a and b are right . The tendon of psoas major and the femoral branch of the genitofemoral nerve both pass under the inguinal ligament. The long saphenous vein terminates in the femoral vein about 3 cm below the inguinal ligament. The external iliac becomes the common femoral artery at the inguinal ligament. The superficial epigastric vein passes in front of the inguinal ligament
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9. The pancreas gland
(a) Lies anterior to the left kidney
(b) Derives part of its blood supply from the splenic artery
(c) Has parts in both the supracolic and infracolic compartments
(d) Is pierced by the middle colic artery
(e) The junction of the splenic and superior mesenteric veins lies behind the gland
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only d is wrong . The tail of the pancreas crosses the left kidney as it passes to the hilum of the spleen. The blood supply is from the splenic, superior and inferior pancreaticoduodenal arteries. The gland is pierced by the superior mesenteric artery. The middle colic arises from the lower border.
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10. A common peroneal nerve palsy
(a) Can occur following a fracture of the neck of the fibula
(b) Causes loss of extension of the big toe
(c) Causes a characteristic foot drop
(d) Causes loss of inversion of the foot
(e) Produces anaesthesia of the sole of the foot
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a , b , c are right . The common peroneal nerve is a branch of the sciatic nerve. It winds around the neck of the fibula before dividing into the superficial and deep peroneal nerves. The latter is responsible for eversion of the ankle and dorsiflexion of the foot. Inversion is not lost as this is partially controlled by tibialis posterior supplied by the tibial nerve. Sensation to the sole of the foot is by the medial and lateral plantar branches of the tibial nerve.
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