The document discusses splanchnic circulation, including its definition, blood flow characteristics, and regulatory mechanisms. It details the amount of blood flowing to the liver and describes factors that affect splanchic circulation, such as intrinsic and extrinsic regulations and nervous control. The importance of sympathetic vasoconstriction during exercise and its impact on blood distribution within the body is also highlighted.

1. SPLANCHNIC CIRCULATION
•Definition
•Blood flow amount
•Characteristics
•Regulation
•Factors affecting it
Year 3 Medicine, UST Sana‘a, Spring 2010

2.  Definition:
 Portal circulatory system + arterial blood flow into
the liver
Portal circulatory system:
COP known amount of blood vessels of
intestine spleen portal venous system
liver

3. Main artery Main tributaries arteries Main areas supplied
1. Coiliac trunk common hepatic (branches: Liver, parts of
right gastric and stomach,dudenum and
gastrodudenal) pancreas
Splenic Spleen , parts of stomach
and pancreas
Lt gastric Parts of stomach and lower
esophagus
2.Superior mesenteric Inferiorpancreatinodudenal Small intestine,
artery , Intestinal, iliocolic , right caecum,ascending colon,
colic, middle colic most of the transverse
colon, parts of duodenum
and pancreas
Left colic,segmoid,superior Descending and sigmoid
3.Inferior mesenteric artery rectal colon, parts of transverse
colon and rectum

4. Blood flow amount
 About 1100 ml of portal blood enters liver each
minute
 Plus 350ml of blood from the hepatic artery enters
liver each minute
 total blood flow = about 1450ml or 29% of the
circulating blood flow.
 Oxygen consumption during rest is approximately
20-35% of the body‘s total needs.

5.  Characteristics:
 The splanchnic blood flow participates in the
regulation of circulating blood volume as well as
the systemic blood pressure.
 In case of acute hypovolaemia, such as in case of
hemorrhage, the splanchnic circulation becomes
markedly reduced to be able to supply more vital
or essential organs such as the brain and heart.
 The splanchnic circulation is also an important source
of inflammatory mediators.

6.  Characteristics continued:
 The blood flow to the mucosa is greater than that to
the rest of the intestinal wall and it responds to
changes in the metabolic activity (such as after
meal, the blood flow doubles in the intestine and
lasts up to 3 hours)

7. Types of regulations
 Regulation:
 1)intrinsic regulation
 2)extrinsic regulation

8. :Regulation
 1)intrinsic regulation
2. Local metabolic control & myogenic control
3. Local reflexes
4. Locally produced vasoactive substances
 2)extrinsic regulation
6. Sympathetic innervations
7. Circulatory vasoactive substances
8. Systemic hemodynamic changes

9. Intrinsic regulation(1
 Local metabolic control: responds by local
vasodilators eg. oxygen and cellular
metabolism
 Myogenic control: a response caused by an
increase in the vascular transmural pressure by
arterial vasoconscriction
 These two are important for maintaining adequate
blood flow for metabolic needs

10. Intrinsic regulation cont‘d
 Local reflexes: occurs as a response of the
presence of luminal contents
 Locally produced vasoactive substances
3) gastrin
4) secretin
5) cholecystokenin

11. Extrinsic regulation(2
t Sympathetic nervous activity: this dec. blood flow
by increasing the vascular resistance of the
arteries and arterioles.
e Circulatory vasoactive substances eg:
catecholamine
Alpha adrenoreceptors results in vc
Beta adrenoreseptors results in vd
Adrenaline is predomenantly active on alpha
receptors thus vascular resistance in the intestine.

12. Factors affecting the splanchinic
circulation
n glandular secretion
i motility
i oxygen availability local VD
A Peptide hormones
eg: gastrin
secretin
cholecystokenin
kenin

13. Factors affecting cont‘d
5) Nervous control:
2 Parasympathetic to stomach and lower
colon . It blood flow and secretions .
l Sympathetic causes vc and blood
flow .but that last for few minutes then it return to
normal ……….. WHY?

14. Factors affecting cont‘d
 This is because of a mechanism known as Auto
regulatory escape ……… local vasodilators
mechanisms elicited by ischemia- hence the activity
of the vasodilator metabolites ……..returns blood
flow to the GIT and muscles.

15. Importance of sympathetic
:vasoconstriction
1. Shutting off splanchenic circulation during exercise
when inc, blood flow is needed by the skeletal
muscle
2. It causes strong vc of intestine and mesenteric
artery which doesn‘t escape but blood volume
and thus displaces large amount of the blood to
other parts of the circulation

16. Thank you