409.The answer is c.(Moore and Dalley, pp 326–329.)The diaphragm pos-
sesses three principal hiatuses shown in the diagram accompanying the ques-
tion: the hiatus for the inferior vena cava (answer a),the esophageal hiatus
(answer c),and the aortic hiatus (answer e).Potential diaphragmatic devel-
opmental defects include the foramen of Morgagni (answer b),just lateral to
the xiphoid attachment of the diaphragm, and the pleuroperitoneal canal of
Bochdalek(answer d),which is the most common site for congenital hernias.
The inferior vena cava and frequently small branches of the right phrenic
nerve pass through a hiatus (A)slightly to the right of the midline at the T8
level. The left phrenic nerve usually passes through the central tendon of the
diaphragm on the left side to innervate the left hemidiaphragm from below.
The esophageal hiatus (C)just to the left of the midline at the T10 level trans-
mits the esophagus, the left and right vagus nerves, and the esophageal
branches of the left gastric artery and vein. An acquired hiatal hernia usually
is the consequence of a short esophagus or of a weakened esophageal hiatus.
The two diaphragmatic crura are joined superiorly by the median
arcuate ligament to form an opening (E)at the T12 level. The aortic hiatus
transmits the aorta, thoracic duct, and a continuation of the azygos vein
into the abdomen. The splanchnic nerves penetrate the crura on each side
of the aortic hiatus to reach the abdomen.
410.The answer is d.(Moore and Dalley, p 338.)An aortic aneurysm.
This patient may have an abdominal aortic aneurysm. Risk factors for the
development of an abdominal aortic aneurysm include hypertension,
excessive weight and smoking. Males are about five times more likely to
have an aortic aneurysm than females. About 5% of men over 60 years of
age have abdominal aortic aneurysms. Ninety percent of the time abdomi-
nal aortic aneurysms develop inferior to the renal arteries. About two-third
of the time they extend inferiorly to include one of the common iliac arter-
ies. (What blood vessel comes off the aorta inferior to the renal arteries and
superior to the bifurcation into common iliac arteries? Answer: gonadal
and inferior mesenteric arteries.) Despite the retroperitoneal location of the
abdominal aorta, the high-pressure in the vessel typically makes ruptures
of abdominal aortic aneurysms fatal. Blood fills the peritoneal cavity and
the individual bleeds to death. If discovered prior to rupture they are typi-
cally repaired if greater than about 5.5 cm in diameter. Currently they tend
to be repaired intravascularly by placing a 6-inch Dacron tube with metal-
mesh cylinder into the aorta via the femoral artery. Anecdotally, abdominal
528 Anatomy, Histology, and Cell Biology