GI #24
Fri, 02/21/03, 2pm
Dr. Roque
Scribe: Phi Le Tran
Page 1 of 4
HA: Blood, Lymph and Innervation (continued)
---continued from lecture at 1pm, starting with the Superior Mesenteric Artery.
--remember that the splenic artery supplies the stomach, pancreas, spleen and does not
supply the liver nor the gallbladder (this is how he’ll ask questions on the 3rd exam:
which of the following does this artery supply blood to or not supply blood to)
I.
Superior mesenteric a.
A. Inferior pancreaticoduodenal aa.
 supplies blood to head and uncinate process of pancreas; duodenum
 divides into two branches: anterior and posterior branches.
 the anterior inferior pancreaticoduodenal (anterior to the pancreas) aa. will
anastomose with the anterior superior pancreaticoduodenal aa. (this was


B.
C.
D.
E.
emphasized several times in class)
the posterior inferior pancreaticoduodenal (behind the pancreas) aa. will
anastomose with the posterior superior pancreaticoduodenal aa. (this was
emphasized several times in class)
remember that the superior pancreaticoduodenal aa. is from the
gastroduodenal aa. (which is from the common hepatic artery, a major
branch of the celiac trunk).
 pancreas is both derived from midgut and foregut; hence, it will be supplied
by branches of both the SMA and celiac artery.
Intestinal (jejunal/ileal) aa.
 Arise from the left side of SMA
 The same as the jejunal and ileal branches that supply jejunum and ileum,
respectively (forming arterial arcades and vasa rectae).
Ileocolic a.
 supplies blood to vermiform appendix, cecum, and part of ileum.
Right colic a.
 supplies blood to ascending colon
Middle colic a.
 supplies blood to transverse colon
II.
Inferior mesenteric a.
A. Left colic a.
● descending colon
B. Sigmoid aa.
● sigmoid colon
C. Superior rectal a.
● rectum; direct continuation of inf. mesenteric a.
III.
Marginal artery of Drummond
 Anastomoses among terminal branches of the superior and inferior mesenteric
arteries (ileocolic, right, middle, left colic arteries).
GI #24
Fri, 02/21/03, 2pm
Dr. Roque
Scribe: Phi Le Tran
Page 2 of 4


Forms a continuous “marginal” artery around the ascending, tranverse,
descending and sigmoid colons
A blockage in either inf. or superior mesenteric aa. will still have branches from
the other artery to supply blood to the colon.
IV. Portal vein
● [Two systems of vein: portal vein and caval(systemic) circulation.]
● Drains blood from GIT, spleen, and pancreas into the liver
● Supplies ~75% of blood to the liver
● Formed by union of superior mesenteric and splenic vv. Posterior to the head of
the pancreas.
● inferior mesenteric v. may drain into splenic vein or directly, into the portal vein
● paraumbilical vv.-drain into the portal vein.
V.
Portocaval Anastomoses
● Anastomoses between branches of portal and systemic (caval) circulations:
•1.Left gastric v.-azygos vv.
•2.Superior rectal v.-middle rectal v. and inferior rectal v.
•3.Paraumbilical vv.-ant. abdominal vv.
•4.Retroperitoneal vv.-lumbar vv.
•5.Veins in bare area of the liver-veins of diaphragm and internal thoracic v.
● Blood from gastrointestinal tract has to go through the portal vein (into the
liver) first before it drains into the inferior vena cava (systemic circulation).
● Therefore, when taking medications, the drugs will be metabolized in liver first
before they go to the heart and get distributed to the whole body (“FIRST PASS
SYSTEM” in Pharmacology).
VI. Portal Hypertension
● If portal vein is blocked, blood has to flow back where it came fromenlarged
organs or enlarged veins
● The blockage will cause an increase in pressure in the portal vein == portal
hypertension
●
Example: cirrhosis of liverblood can’t pass thru liverincrease pressure in
the portal veinportal hypertension.
● There are other cases where the liver is relatively normal but still have portal
hypertension
● Example: a tumor at the head of the pancreas wil compress the portal vein
behind the pancreasincrease pressure in the portal veinportal hypertension
● Example: right side heart failure, tricuspid valve stenosisincrease blood
volume in the right atriumblood is backed up into the inf. vena ca (results in
passive congestion of the liverincrease pressure in portal veinportal hypertension
(still not as bad as hepatic cirrhosis)
Clinical Manifestations of Portal Hypertension include:
GI #24
Fri, 02/21/03, 2pm
Dr. Roque
Scribe: Phi Le Tran
Page 3 of 4
●
Hematemesis-fresh bleeding from esophageal varices (enlarged esophageal vv.
drain into left gastric v.)
● Caput medusae-enlarged paraumbilical vv. which drain into portal v.
● Hematochezia-fresh bleeding from hemorrhoids (enlarged superior rectal v. is a
direct continuation of the inf. mesenteric v.)
● Splenomegaly-enlarged spleen from blood in splenic v.
--tape stopped recording here
--Dr. Roque followed the outlines in the ppt closely
--Any additions or corrections will be sent in email later
--corrections (by Dr. Roque) are in bold and underline.
VII.
Nerve supplyImportant to know embryological origin of various organs since blood supply
and nerve supply can be easily remembered based on this.
A. Sympathetic nerves
•1.Greater thoracic splanchnic nn.
•2.Lesser thoracic splanchnic nn.
•3.Least thoracic splanchnic nn.
•4.Lumbar splanchnic nn.
•5.Sacral splanchnic nn.
•
THORACIC SPLANCHNIC NERVES SUPPLY FOREGUT AND MIDGUT
DERIVATIVES, WHILE THE LUMBAR AND SACRAL SPLANCHNICS
SUPPLY THE HINDGUT DERIVATIVES. LUMBAR SPLANCHNICS
SUPPLY DESCENDING COLON TO SIGMOID COLON; SACRAL
SPLANCHNICS SUPPLY THE RECTUM.
B. Parasympathetic nerves (relaxed sphincter, increase peristalsis)
•1.Vagus nn.
•2.Pelvic splanchnic nn.
•VAGUS NERVES SUPPLY FOREGUT AND MIDGUT DERIVATIVES;
PELVIC SPLANCHNICS SUPPLY THE HINDGUT.
KNOW THE ANATOMICAL LOCATION AND DISTRIBUTION OF THE
COMPONENTS OF THE AUTONOMICS
GI #24
Fri, 02/21/03, 2pm
Dr. Roque
Scribe: Phi Le Tran
Page 4 of 4
VIII. Sympathetic nerves
A. Spinal cord-thoracolumbar outflow
B. Preganglionic sympathetic fibers-remember the thoracic splanchnic nerves
that you dissected near the vertebral column along the sympathetic trunk
during study of the Cardiovascular System? These are the same nerves.
•1. Greater thoracic nn.-T5-T9 (know these well)
•2. Lesser thoracic nn.-T10-T11
•3. Least thoracic nn.-T12
•4. Lumbar nn.-L1-L2
•5. Sacral nn.-S1-S4
D. Sympathetic ganglia-around aorta and associated with the large arteries
such as the celiac, superior mesenteric, inferior mesenteric arteries.
Preganglionic fibers pass through and synapse in the sympathetic ganglia.
E. Postganglionic sympathetic fibers-pass in the mesenteries to reach the viscera
IX. Parasympathetic nerves
A. Spinal cord-craniosacral outflow
B. Preganglionic parasympathetic fibers-fibers pass through the (sympathetic)
ganglia around the large arteries WITHOUT SYNAPSING, then through the
mesenteries to reach the viscera.
•1 Vagus (CN X)-found anterior and posterior to the esophagus and stomach
•2. Pelvic splanchnic nn. (S2-S4)
C. Parasympathetic ganglia-in the wall of the the viscera, distributed within the
•1. Myenteric (Auerbach’s) plexus – the muscular layer
•2. Submucous (Meissner’s) plexus – in the submucosa
C. Postganglionic sympathetic nn.-very short; within the wall of the viscera
EXPECT QUESTIONS SUCH AS:
Question: What type of autonomic fibers found in the mesenteries should be avoided
during surgery?
Answer: Postganglionic sympathetic fibers
Preganglionic parasympathetic fibers