Small Group Session II

(answers in red)

Visceral Blood Supply

Answer the following questions upon completion of your dissection of the vascular
supply to the gut.

I. Arterial Supply:

A. Indicate in the space provided whether the named artery is "free" or "retroperitoneal".

1. Splenic artery: retroperitoneal for most of course, then becomes free while passing through the
lieno-renal ligament.
2. Inferior pancreatico-duodenal artery: Retroperitoneal. It is the first branch of the SMA and
passes posterior to the head of the pancreas.
3. Middle colic artery: Is free as it passes through the transverse mesocolon to the transverse
colon.
4. Right colic artery: Is retroperitoneal or fixed to the right posterior wall as a consequence of
the fixation of the ascending colon.
5. Sigmoid arcade: The terminal branches of the IMA, is free within the sigmoid mesentery.
6. Ovarian/Testicular artery: In the male it is retroperitoneal. The paired artery arises from the
abdominal aorta and passes behind peritoneum to the deep inguinal ring in the male. In the
female the proximal part of the artery is retroperitoneal, while the distal portion as it supplies
the ovary becomes free as it passes through the infundibulopelvic ligament, the broad ligament
then through the mesoovarium to the ovary.

B. What are the major differences between the vascular patterns of the proximal jejunum
compared to the more distal ileum?

The jejuneum has relatively few arcades and long vasa recti; while in the ileum, there are
multiple arcades and relatively shorter vasa recti.

C. What is the functional significance of the arterial arcades, especially in the jejunum?

The arterial arcades provide a mechanism to reduce the pulsitile flow of blood and provide a
redundant supply of blood to the gut mucosa. Since the mucosa is sensitive to oxygen tension,
it is a necessary requirement that blood flow be maintained in the event of occlusion of a
supplying branch.

D. What is the functional significance of the arterial vasa recti?

The vasa recti are the terminal branches of the arterial arcades. They are straight branches that
alternatively pass on either side of the gut proper; thus, upon expansion of the gut with feces
and gas during digestion, the blood supply is not compromised.

E. In severe cases of "abdominal angina", the superior mesenteric artery commonly exhibits
atherosclerosis or narrowing of the vessels. Under these conditions, how may blood still fill the
branches to the small intestine?

Blood flow may still be maintained through supply from the inferior mesenteric artery via the left
colic artery, marginal artery, and right branch of the middle colic artery.

II. Portal Venous System:

A. What are the major differences in the vascular pattern between the portal system of veins
and the arterial supply to the small and large intestine?

The major named vessels of the portal tributaries generally follow the arterial pattern of named
vessels; i.e. middle colic, right colic etc.; however, the inferior mesenteric vein does not follow
the artery, but departs and independently drains into the splenic vein or near the portal. There
are no venous arcades, nor are there vessels that correspond to the vasa recti since this is a
low pressure venous return system.

KIDNEYS AND POSTERIOR WALL

A. On your cadaver, what structures overlie the hilum of the right kidney?

Generally the 2nd part of the duodenum.

B. On your cadaver, what muscle groups lie posterior to the left kidney?

The muscular bed of the kidney is formed by the psoas (medially), quadratus lumborum
(inferior and lateral), and transversus abdominus (laterally).

C. Based on your knowledge of the relative position of the kidney, describe a surgical
procedure to remove the left kidney via a retro-peritoneal approach. Include the direction of
the skin incision, the muscles transected and the compartments exposed. Be specific as to
the vertebral level, and the consequences of the surgical approach; i.e. denervation and
subsequent nerve loss (sensory and motor); and important blood vessels ligated. Include
possible injury to adjacent organs.

Surgical approach: Retroperitoneal. This approach avoids entry into the peritoneal cavity and
displacement of visceral organs; especially those fixed to the posterior wall. Ribs 11 and 12
are displaced, the intercostal muscles divided and kidneys and perirenal fat.visualized within
the renal capsule.

Vertebral level(s): T12 - Lumbar 2.

Skin incision: A skin incision extending lateral below the 12th rib forward and diagonally to the
left midaxillary line. This provides access to the L1 vertebral renal space. The 12th rib is
displaced downward.

Muscles transected: Transverse abdominus.and quadratus lumborum with incision below the
12th rib

Nerves transected: Subcostal (T12) (may be displaced), iliohypogastric (may be displaced),
ilioinguinal (occassional).

Sensory/motor nerve loss: Sensory loss to skin of suprapubic area extending laterally to skin
incision. Motor loss to muscles of rectus sheath (pyramadalis m.); partial loss to external
abdominal, internal abdominal oblique. [Remember, these muscles receive innervation from
three spinal levels].

Arterial vessels ligated: Superficial branches of external iliac circumflex, segmental arteries of
T1and Lumbar segmental aa. Left renal artery and inferior superrenal artery. Also don't
forget accessory renal arteries from the aorta that usually enter into the lower pole of the kidney.

Important anastomoses required to maintain proper blood supply: Superficial: segmental arteries
of T11 and superficial inferior epigastric artery. Deep visceral: Superior and middle suprarenal
arteries to supply suprarenal gland. Segmental arteries to supply the remaining ureter.

Venous vessels ligated: Superficial veins of skin. Deep visceral: Renal vein(s). The suprarenal
vein on the left side should be left intact; along with the left testicular/ovarian veins i.e. a close
ligature at the hilum of the kidney.

Important alternate venous drainage after venous ligation: With removal of the left kidney, the
suprarenal vein should be spared; if not then suprarenal may be removed. If testicular vein is
ligated, then alternate flow is through minor deferential veins or through cremasteric veins. If
ovarian vein is ligated, venous drainage is through uterine veins.

Compartments entered (in order of sequence): Renal compartment only which is behind the
renal fascia and parietal peritoneum.

Other organs/structures cut and or removed during this procedure: In addition to the removal of
the kidney, the renal artery and a short piece of the renal vein (keeping the suprarenal vein and
testicular/ovarian venous drainage intact). The ureter is cut at a high level (L1- L2), the end
ligated and tacked to the psoas fascia. Under some circumstances, such as an enlarged
kidney, the 11th and/or 12th ribs may be removed.

Adjacent organs that may be injured: The main organ that can be injured is the left suprarenal
gland. While the gland is in a separate compartment from the kidney and therefore separated by
a fascial layer, in tumors of the kidney that fuse with the fascia, the gland may be firmly
attached to the kidney, requiring its removal [Remember we have two suprarenal glands].

D. Name each of the arteries that supply the male ureters and the extent of their distribution.

1) renal artery
2) abdominal aorta
3) testicular artery
4) common iliac, internal iliac, vesicle arteries

Which of the above branches is replaced in the female, and what is its contribution?

Ovarian for the testicular artery; and uterine artery for much of the vesicular arteries in the male.

E. Describe the contents of each of the following compartments that surround the bladder
and indicate its clinical importance.

(1) Retropubic space: Lies posterior to the pubic symphysis and anterior to the bladder above
the urogenital diaphragm, and is sub-peritoneal. It is occupied by the prostatic venous plexus
in the male [drainage of the deep dorsal vein of the penis]. The space is approached using a
suprapubic entry to the anterior lobes of the prostate; however, it is a bloody approach with
uncontrolled bleeding. It is not clinically significant in the female.

(2) Utero-vesicle space: It is a sub-division of the lower peritoneal cavity between the antiverted
uterus and the bladder. With the uterus in the retroverted position, the space is enlarged.

(3) Recto-vesicle space: Exists in the male only. It is a sub-division of the lower peritoneal
cavity between the bladder and the upper rectum. It may contain a portion of loops of the small
intestine. It is the most dependent space in the peritoneal cavity in the upright position, and in
the cases of acites, will fill with fluid.

(4) Pre-vesicle space: It is a sub-division of the lower peritoneal cavity that exists between the
upper bladder and anterior body wall. It is more defined with a filled bladder.

(5) Recto-uterine space: A sub-division of the lower peritoneal cavity in the female between the
lower uterus and the upper rectum. It lies adjacent to the posterior fornix of the vagina. It may
contain loops of small intestine. Clinically important in abortion procedures where a sharp
instrument is passed through the posterior fornix into the recto-uterine space and possibly into
small intestine; thus allowing enteric bacteria into the peritoneal cavity.