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Transcript
216 CHAPTER 5 The Abdomen: Part II—The Abdominal Cavity
■■
EMBRYOLOGIC NOTES
■■
Development of the Suprarenal Glands
■■
The cortex develops from the coelomic mesothelium covering
the posterior abdominal wall. At first, a fetal cortex is formed;
later, it becomes covered by a second final cortex. After birth,
the fetal cortex retrogresses, and its involution is largely completed in the first few weeks of life.
The medulla is formed from the sympathochromaffin cells
of the neural crest. These invade the cortex on its medial side.
By this means, the medulla comes to occupy a central position and is arranged in cords and clusters. Preganglionic sympathetic nerve fibers grow into the medulla and influence the
activity of the medullary cells.
Three lateral visceral branches: the suprarenal artery,
renal artery, and testicular or ovarian artery
Five lateral abdominal wall branches: the inferior
phrenic artery and four lumbar arteries
Three terminal branches: the two common iliac arteries
and the median sacral artery (Fig. 5.72)
These branches are summarized in Diagram 5.1.
Common Iliac Arteries
The right and left common iliac arteries are the terminal
branches of the aorta. They arise at the level of the 4th
lumbar vertebra and run downward and laterally along the
medial border of the psoas muscle (Figs. 5.63 and 5.72).
Each artery ends in front of the sacroiliac joint by dividing
into the external and internal iliac arteries. At the bifurcation, the common iliac artery on each side is crossed anteriorly by the ureter (Fig. 5.72).
Susceptibility to Trauma at Birth
At birth, the suprarenal glands are relatively large because of
the presence of the fetal cortex; later, when this part of the
cortex involutes, the gland becomes reduced in size. During
the process of involution, the cortex is friable and susceptible
to damage and severe hemorrhage.
External Iliac Artery
The external iliac artery runs along the medial border of
the psoas, following the pelvic brim (Fig. 5.63). It gives off
inferior vena cava
cisterna chyli
hepatic veins
inferior phrenic artery
sympathetic trunk
suprarenal vein
celiac artery
suprarenal artery
renal vein
superior mesenteric artery
renal artery
y
lumbar arteries
inferior mesenteric artery
testicular artery
common iliac artery
external iliac
artery
internal iliac artery
deep circumflex iliac artery
inferior epigastric artery
median sacral artery
FIGURE 5.72 Aorta and inferior vena cava.
Basic Anatomy 217
inferior vena cava
celiac artery
(T12)
superior
mesenteric
artery
(L1)
xiphisternal joint
(T9)
transpyloric
plane (L1)
inferior mesenteric
artery
(L3)
intercristal
inter
cristal plane
(L4)
aorta
common iliac
vessels
anterior superior
iliac spine
external
iliac
vessels
symphysis pubis
internal iliac
vessels
FIGURE 5.73 Surface markings of the aorta and its branches and the inferior vena cava on the anterior abdominal wall.
left gastric artery
a. Celiac artery
splenic artery
hepatic artery
short gastric arteries (six)
splenic arteries (six)
left gastroepiploic artery
cystic artery
right gastric artery
gastroduodenal artery
right hepatic artery
left hepatic artery
right gastroepiploic artery
superior pancreaticoduodenal artery
jejunal and ileal arteries
1. Three anterior
visceral branches
inferior pancreaticoduodenal artery
b. Superior
mesenteric
artery
middle colic artery
right colic artery
ileocolic artery
anterior cecal artery
posterior cecal artery—appendicular artery
ileal artery
colic artery
left colic artery
c. Inferior
mesenteric
artery
sigmoid arteries (two or three)
superior rectal artery
a. Suprarenal artery
2. Three lateral
visceral branches
b. Renal artery
c. Testicular or ovarian artery
a. Inferior phrenic artery
3. Five lateral
abdominal
wall branches
4. Three terminal
branches
b. Four lumbar arteries
a. Two common iliac arteries
external iliac artery
internal iliac artery
b. Median sacral artery
DIAGRAM 5.1 Branches of Abdominal Aorta
218 CHAPTER 5 The Abdomen: Part II—The Abdominal Cavity
C L I N I C A L
Veins on the Posterior Abdominal
Wall
N O T E S
Inferior Vena Cava
Aortic Aneurysms
Localized or diffuse dilatations of the abdominal part of the
aorta (aneurysms) usually occur below the origin of the renal
arteries. Most result from atherosclerosis, which causes
weakening of the arterial wall, and occur most commonly
in elderly men. Large aneurysms should be treated by open
surgical repair. Endovascular repair can also be used by the
introduction of a stent graft through one of the iliac arteries
with access through the femoral arteries in the groin.
Embolic Blockage of the Abdominal Aorta
The bifurcation of the abdominal aorta where the lumen suddenly narrows may be a lodging site for an embolus discharged
from the heart. Severe ischemia of the lower limbs results.
the inferior epigastric and deep circumflex iliac branches
(Fig. 5.72).
The artery enters the thigh by passing under the inguinal ligament to become the femoral artery. The inferior
epigastric artery arises just above the inguinal ligament. It
passes upward and medially along the medial margin of the
deep inguinal ring (Fig. 4.4) and enters the rectus sheath
behind the rectus abdominis muscle. The deep circumflex
iliac artery arises close to the inferior epigastric artery (Fig.
5.72). It ascends laterally to the anterior superior iliac spine
and the iliac crest, supplying the muscles of the anterior
abdominal wall.
Internal Iliac Artery
The internal iliac artery passes down into the pelvis in
front of the sacroiliac joint (Fig. 5.72). Its further course is
described on page 256.
Location and Description
The inferior vena cava conveys most of the blood from the
body below the diaphragm to the right atrium of the heart.
It is formed by the union of the common iliac veins behind
the right common iliac artery at the level of the 5th lumbar
vertebra (Fig. 5.72). It ascends on the right side of the aorta,
pierces the central tendon of the diaphragm at the level of
the 8th thoracic vertebra, and drains into the right atrium
of the heart.
The right sympathetic trunk lies behind its right margin and the right ureter lies close to its right border. The
entrance into the lesser sac separates the inferior vena cava
from the portal vein (Fig. 5.7).
The surface markings of the inferior vena cava are shown
in Figure 5.73.
Tributaries
The inferior vena cava has the following tributaries
(Fig. 5.72):
■■
■■
■■
■■
Two anterior visceral tributaries: the hepatic veins
Three lateral visceral tributaries: the right suprarenal
vein (the left vein drains into the left renal vein), renal
veins, and right testicular or ovarian vein (the left vein
drains into the left renal vein)
Five lateral abdominal wall tributaries: the inferior
phrenic vein and four lumbar veins
Three veins of origin: two common iliac veins and the
median sacral vein
The tributaries of the inferior vena cava are summarized in
Diagram 5.2.
If one remembers that the venous blood from the
abdominal portion of the gastrointestinal tract drains to
1. Two anterior visceral tributaries—the hepatic veins
a. Right suprarenal vein
(the left drains into the left renal vein)
2. Three lateral visceral tributaries
b. Renal veins
c. Right testicular or ovarian vein
(the left drains into the left renal vein)
3. Five lateral abdominal wall
tributaries
a. Inferior phrenic vein
b. Four lumbar veins
external iliac vein
4. Three tributaries of origin
a. Two common iliac veins
b. Median sacral vein
DIAGRAM 5.2 Tributaries of Inferior Vena Cava
internal iliac vein
Basic Anatomy 219
C L I N I C A L
N O T E S
Blunt trauma to the aorta is most commonly caused by headon automobile crashes. Rupture of the tunica intima and media
occurs and is quickly followed by rupture of the turnica adventitia. The initial rupture of the intima and media is probably mainly
caused by the sudden compression of the aorta against the
vertebral column, while the delayed rupture of the adventitia is
caused by the aortic blood pressure. Unless quickly diagnosed
by MRI, and surgical treatment instituted, death follows.
anatomic inaccessibility of the vessel behind the liver, duodenum, and mesentery of the small intestine and the blocking
presence of the right costal margin make a surgical approach
difficult. Moreover, the thin wall of the vena cava makes it prone
to extensive tears.
Because of the multiple anastomoses of the tributaries of the
inferior vena cava (Fig. 5.75), it is impossible in an emergency to
ligate the vessel. Most patients have venous congestion of the
lower limbs.
Obliteration of the Abdominal Aorta and Iliac Arteries
Compression of the Inferior Vena Cava
Trauma to the Abdominal Aorta
Gradual occlusion of the bifurcation of the abdominal aorta,
produced by atherosclerosis, results in the characteristic clinical symptoms of pain in the legs on walking (claudication) and
impotence, the latter caused by lack of blood in the internal iliac
arteries. In otherwise healthy individuals, surgical treatment by
thromboendarterectomy or a bypass graft should be considered.
Because the progress of the disease is slow, some collateral
circulation is established, but it is physiologically inadequate.
However, the collateral blood flow does prevent tissue death in
both lower limbs, although skin ulcers may occur.
The collateral circulation of the abdominal aorta is shown in
Figure 5.74.
Trauma to the Inferior Vena Cava
Injuries to the inferior vena cava are commonly lethal, despite
the fact that the contained blood is under low pressure. The
the liver by means of the tributaries of the portal vein, and
that the left suprarenal and testicular or ovarian veins drain
first into the left renal vein, then it is apparent that the tributaries of the inferior vena cava correspond rather closely
to the branches of the abdominal portion of the aorta.
Inferior Mesenteric Vein
The inferior mesenteric vein is a tributary of the portal
circulation. It begins halfway down the anal canal as the
superior rectal vein (Figs. 5.22, 5.26, and 5.48). It passes up
the posterior abdominal wall on the left side of the inferior
mesenteric artery and the duodenojejunal flexure and joins
the splenic vein behind the pancreas. It receives tributaries
that correspond to the branches of the artery.
Splenic Vein
The splenic vein is a tributary of the portal circulation.
It begins at the hilum of the spleen by the union of several veins and is then joined by the short gastric and left
gastroepiploic veins (Figs. 5.22 and 5.48). It passes to the
right within the splenicorenal ligament and runs behind
the pancreas. It joins the superior mesenteric vein behind
the neck of the pancreas to form the portal vein. It is
joined by veins from the pancreas and the inferior mesenteric vein.
The inferior vena cava is commonly compressed by the enlarged
uterus during the later stages of pregnancy. This produces edema
of the ankles and feet and temporary varicose veins.
Malignant retroperitoneal tumors can cause severe compression and eventual blockage of the inferior vena cava. This
results in the dilatation of the extensive anastomoses of the
tributaries (Fig. 5.75). This alternative pathway for the blood
to return to the right atrium of the heart is commonly referred
to as the caval–caval shunt. The same pathway comes into
effect in patients with a superior mediastinal tumor compressing
the superior vena cava. Clinically, the enlarged subcutaneous
anastomosis between the lateral thoracic vein, a tributary of
the axillary vein; and the superficial epigastric vein, a tributary
of the femoral vein, may be seen on the thoracoabdominal wall
(Fig. 5.75).
Superior Mesenteric Vein
The superior mesenteric vein is a tributary of the portal circulation (Figs. 5.22, 5.26, and 5.48). It begins at the ileocecal
junction and runs upward on the posterior abdominal wall
within the root of the mesentery of the small intestine and
on the right side of the superior mesenteric artery. It passes
in front of the third part of the duodenum and behind the
neck of the pancreas, where it joins the splenic vein to form
the portal vein. It receives tributaries that correspond to the
branches of the superior mesenteric artery and also receives
the inferior pancreaticoduodenal vein and the right gastroepiploic vein (Fig. 5.22).
Portal Vein
The portal vein is described on page 194.
Lymphatics on the Posterior
Abdominal Wall
Lymph Nodes
The lymph nodes are closely related to the aorta and form
a preaortic and a right and left lateral aortic (para-aortic or
lumbar) chain (Fig. 5.76).
220 CHAPTER 5 The Abdomen: Part II—The Abdominal Cavity
right subclavian artery
left subclavian artery
intercostal
posterior intercos
arteries
internal thoracic
artery
thoracic part of aorta
musculophrenic
c artery
diaphragm
diaph
superior epigastric
c
artery
phrenic artery
phre
left renal artery
middle colic artery
superior mesenteric
artery
abdominal aorta
right colic artery
lumbar arteries
marginal artery
ileocolic artery
left colic artery
inferior epigastric artery
inferior mesenteric
artery
fourth lumbar
artery
sigmoid
arteries
sig
deep circumflex
x
iliac artery
internall iliac artery
superio
superior rectal
artery
middle rectal artery
arter
median
sacral
artery
inferior rectal a
artery
FIGURE 5.74 The possible collateral circulations of the abdominal aorta. Note the great dilatation of the mesenteric arteries
and their branches, which occurs if the aorta is slowly blocked just below the level of the renal arteries (black bar).
The preaortic lymph nodes lie around the origins of the
celiac, superior mesenteric, and inferior mesenteric arteries
and are referred to as the celiac, superior mesenteric, and
inferior mesenteric lymph nodes, respectively. They drain
the lymph from the gastrointestinal tract, extending from
the lower one third of the esophagus to halfway down the
anal canal, and from the spleen, pancreas, gallbladder, and
greater part of the liver. The efferent lymph vessels form the
large intestinal trunk (see Fig. 1.18 and below).
The lateral aortic (para-aortic or lumbar) lymph nodes
drain lymph from the kidneys and suprarenals; from the
testes in the male and from the ovaries, uterine tubes, and
fundus of the uterus in the female; from the deep lymph
vessels of the abdominal walls; and from the common iliac
nodes. The efferent lymph vessels form the right and left
lumbar trunks (see Fig. 1.18 and below).
Lymph Vessels
The thoracic duct commences in the abdomen as an elongated lymph sac, the cisterna chyli. This lies just below the
diaphragm in front of the first two lumbar vertebrae and
on the right side of the aorta (Fig. 5.76).
The cisterna chyli receives the intestinal trunk, the right
and left lumbar trunks, and some small lymph vessels that
descend from the lower part of the thorax.
Basic Anatomy 221
brachiocephalic
subclavian vein vein
superior vena cava
first rib
axillary vein
azygos vein
hemiazygos veins
internal thoracic vein
lateral thoracic vein
diaphragm
inferior vena cava
ascending lumbar
vein
lumbar veins
inferior epigastric vein
superficial epigastric
vein
external iliac vein
inferior mesenteric
vein ascending to
portal vein
superior rectal vein
internal iliac vein
inguinal ligament
middle rectal vein
femoral vein
great saphenous
vein
inferior rectal vein
FIGURE 5.75 The possible collateral circulations of the superior and inferior venae cavae. Note the alternative pathways that
exist for blood to return to the right atrium of the heart if the superior vena cava becomes blocked below the entrance of the
azygos vein (upper black bar). Similar pathways exist if the inferior vena cava becomes blocked below the renal veins (lower
black bar). Note also the connections that exist between the portal circulation and systemic veins in the anal canal.
Lymphatic Drainage of the Gonads
The importance of the lymph drainage of the testis was
emphasized on page 132.
Nerves on the Posterior Abdominal
Wall
Lumbar Plexus
The lumbar plexus, which is one of the main nervous pathways supplying the lower limb, is formed in the psoas muscle from the anterior rami of the upper four lumbar nerves
(Fig.5.77).The anterior rami receive gray rami
communicantes
from the sympathetic trunk, and the upper two give off
white rami communicantes to the sympathetic trunk. The
branches of the plexus emerge from the lateral and medial
borders of the muscle and from its anterior surface.
The iliohypogastric nerve, ilioinguinal nerve, lateral
cutaneous nerve of the thigh, and femoral nerve emerge
from the lateral border of the psoas, in that order from
above downward (Fig. 5.34). The iliohypogastric and
ilioinguinal nerves (L1) enter the lateral and anterior
abdominal walls (see page 124). The iliohypogastric nerve
supplies the skin of the lower part of the anterior abdominal
wall, and the ilioinguinal nerve passes through the inguinal
canal to supply the skin of the groin and the scrotum or
labium majus. The lateral cutaneous nerve of the thigh