The cardiovascular system

The superior mesenteric artery (Fig. 5.44) branches fromthe aorta between the coeliac artery and the renal arter-

It passes through a second capillary bed, the hepaticsinusoids, in the liver before entering the general circula- tion via the inferior vena cava. In this way blood with aies. It supplies the whole of the small intestine

proximal half of the large intestine.The inferior mesenteric artery (Fig. 5.44) arises

and thehigh concentrationach and intestines, tain modifications

of nutrients, absorbed from the stom-goes to the liver first. In the liver cer-

take place, induding the regulation offrom the

aorta about 4 em above its division into the common iliacnutrient supply to other parts of the body.arteries. It supplies the distal half of the large

and part of the rectum.intestine

Portal veinThis is formed by the union of the following veins (Figs5.47 and 5.48), each of which drains blood from the area supplied by the corresponding artery:

Venous return from the abdominal organsThe inferior vena cava is formed when right and left

com-mon iliac veins join at the level of the body of the 5th lum-bar vertebra. This is the largest vein in the body and it conveys blood from all parts of the body below the •

••••

splenic veininferior mesenteric vein superior mesenteric vein gastric veinscystic vein.

The splenic vein drains blood from the spleen, the

diaphragm to the right atrium of the heart. It passesthrough the central tendon of the diaphragm at the levelof the 8th thoracic vertebra.

Paired testicular, ovarian,the inferior vena cava.

renal and adrenal veins join

Blood from the remaining organs in the abdominal pancreas and part of the stomach.The inferior mesenteric vein returns the venous blood

from the rectum, pelvic and descending colon of the large intestine. It joins the splenic vein.

The superior mesenteric vein returns venous blood fromthe small intestine and the proximal parts of the large

via the portal circulationcavity passes through thebefore entering the inferior

livervena cava (Fig. 5.45).

Portal circulationIn all the parts of the circulation which have been intestine, i.e. the caecum, ascending and transverse

colon. It unites with the splenic vein to form the portal vein.

The gastric veins drain blood from the stomach and the distal end of the oesophagus, then join the portal vein.

described previously, venous blood passes from the tis-sues to the heart by the most direct route through only one capillary bed. In the portal circulation, venous blood passes from the capillary beds of the abdominal part of the digestive system, the spleen and pancreas to the liver.

105

The cystic vein which drains venous blood fromgall bladder joins the portal vein.

the

Hepatic artery Liver (turned up) Coeliac artery

Cystic artery _

ifF--It---=::; ....L---=-----'l.~~:=.\-- Left gastric arteryHepatic artery----=~!i>=:e=="=l--Stomach

Spleen

Gastroduodenal al1el)'-------'

Head of pan

Right gastroepiploic artery--------T7f''"'-.;..IIIIl::,LJ

Left gastroepiplo.ic artery

Right gastric artery Splenic artery

Figure 5.45 The coeliac artery and its branches, and the inferior phrenic arteries.