Anatomy of the Gastrointestinal Tract: Arterial Supply and Accessory Organs

Lectured by Bien Nillos, MDReference: Gray’s Anatomy, Ellis Clinical Anatomy 11th ed.

The Peritoneal Cavity

In the male, the peritoneal cavity is completely closed, but in the female it is perforated by the openings of the uterine tubes which constitute a possible pathway of infection from the exterior

Divided into greater and lesser sac The right extremity of the lesser sac opens

into the main peritoneal cavity via the epiploic foramen or foramen of Winslow

Subphrenic Spaces

Below the diaphragm are a number of potential spaces formed in relation to the attachments of the liver. One or more of these spaces may become filled with pus (a subphrenic abscess) walled off inferiorly by adhesions. There are five subdivisions of clinical importance.

1. The right and left subphrenic spaces - lie between the diaphragm and the liver, separated from each other by the falciform ligament.

2. The right and left subhepatic spaces - lie below the liver. The right is the pouch of Morison and is bounded by the posterior abdominal wall behind and by the liver above. The left is the lesser sac.

3. The right extraperitoneal space - lies between the bare area of the liver and the diaphragm.

The Esophagus

Blood supply is from the inferior thyroid artery, branches of the descending thoracic aorta and the left gastric artery.

The Stomach

the left gastric artery—from the celiac artery

the right gastric artery—from the hepatic artery

the right gastroepiploic artery—from the gastroduodenal branch of the hepatic artery

the left gastro-epiploic artery—from the splenic artery

the short gastric arteries—from the splenic artery

The Duodenum

The superior pancreaticoduodenal artery- arises from the gastroduodenal artery

the inferior pancreaticoduodenal artery - originates as the first branch of the superior mesenteric artery

These vessels both lie in the curve between the duodenum and the head of the pancreas, supplying both structures.

Jejunum and Ileum

The Large Intestine

Midgut (Mid-duodenum to Distal transverse colon)

1. the inferior pancreaticoduodenal artery;2. jejunal and ileal branches—supplying the

bulk of the small intestine;3. the ileocolic artery, supplying terminal

ileum, caecum and commencement of ascending colon and giving off an appendicular branch to the appendix—the most commonly ligated intra-abdominal artery;

4. the right colic artery—supplying the ascending colon;

5. the middle colic artery—supplying the transverse colon.

Hind-gut

1. the left colic artery—supplying the descending colon;

2. the sigmoid branches—supplying the sigmoid;

3. the superior rectal artery—supplying the rectum

Portal System of Veins The portal venous

system drains blood to the liver from the abdominal part of the alimentary canal (excluding the anal canal), the spleen, the pancreas and the gall-bladder and its ducts.

The inferior mesenteric vein ascends above the point of origin of its artery to enter the splenic vein behind the pancreas.

The superior mesenteric vein joins the splenic vein behind the neck of the pancreas in the transpyloric plane to form the portal vein, which ascends behind the first part of the duodenum into the anterior wall of the foramen of Winslow and thence to the porta hepatis.

Here the portal vein divides into right and left branches and breaks up into capillaries running between the lobules of the liver. These capillaries drain into the radicles of the hepatic vein through which they empty into the inferior vena cava.

The Liver This is the largest organ in the body. It is

related by its domed upper surface to the diaphragm, which separates it from pleura, lungs, pericardium and heart

Its external secretion, the bile, is collected after passing through the bile capillaries by the bile ducts

The internal secretions are concerned with the metabolism of both nitrogenous and carbohydrate materials absorbed from the intestine and carried to the liver by the portal vein. 

divided into a larger right and small left lobe, separated superiorly by the falciform ligament and postero-inferiorly by an H-shaped arrangement of fossae

The cross-bar of the H is the porta hepatis.

anteriorly and to the right—the fossa for the gallbladder;

posteriorly and to the right—the groove in which the inferior vena cava lies embedded;

anteriorly and to the left—the fissure containing the ligamentum teres;

posteriorly and to the left—the fissure for the ligamentum venosum.

Lying in the porta hepatis (which is 2 in (5 cm) long) are:

1. the common hepatic duct—anteriorly;2. the hepatic artery—in the middle;3. the portal vein—posteriorly.

The liver is made up of lobules, each with a solitary central vein which is a tributary of the hepatic vein which, in turn, drains into the inferior vena cava.

In spaces between the lobules, termed portal canals, lie branches of the hepatic artery (bringing systemic blood) and the portal vein, both of which drain into the central vein by means of sinusoids traversing the lobule.

The Biliary System The right and left hepatic ducts fuse in

the porta hepatis to form the common hepatic duct

The CHD joins with the cystic duct, draining the gall-bladder, to form the common bile duct

The CBD commences about 1 in (4 cm) above the duodenum, then passes behind it to open at a papilla on the medial aspect of the second part of the duodenum

The gallbladder a conical or pear-shaped

musculomembranous sac, lodged in a fossa on the under surface of the right lobe of the liver, and extending from near the right extremity of the porta to the anterior border of the organ

acts as a bile concentrator and reservoir.

the organ is divided into fundus, body and neck, the latter opening into the cystic duct

The gall-bladder is supplied by the cystic artery (a branch usually of theright hepatic artery) which lies in the triangle made by the liver, the cysticduct and the common hepatic duct (Triangle of Calot)

The Pancreas a compound racemose gland,

analogous in its structures to the salivary glands, though softer and less compactly arranged than those organs

Its secretion, the pancreatic juice, carried by the pancreatic duct to the duodenum, is an important digestive fluid.

lies retroperitoneally in roughly the transpyloric plane.

For descriptive purposes it is divided into head, neck, body and tail.

The head lies in the C-curve of the duodenum and sends out the uncinate process which hooks posteriorly to the superior mesenteric vessels as these travel from behind the pancreas into the root of the mesentery.

Blood is supplied from the splenic and the pancreaticoduodenal arteries;

the corresponding veins drain into the portal system.

The pancreas macroscopically is lobulated and is contained within a fine capsule; these lobules are made up of alveoli of serous secretory cells draining via their ductules into the principal ducts.

Between these alveoli lie the insulin-secreting islets of Langerhans.

The main duct of the pancreas (Wirsung) runs the length of the gland and usually opens at the ampulla of Vater in common with the common bile duct;

occasionally it drains separately into the duodenum

The accessory duct (of Santorini) passes from the lower part of the head in front of the main duct, communicates with it, and then opens into the duodenum above it.

Occasionally it is absent.

End of Lecture

“Is life worth living? It all depends on the liver” – William James

Or is it?

Quiz

1. Also known as the right subhepatic space2. Also known as the Accessory duct of the

Pancreas3. Fusion of the cystic duct and common

hepatic duct4. Also known as the Main Duct of the

Pancreas5. Acts as bile concentrator and reservoir

6 – 8. 3 Blood supplies of the esophagus9. – 10. 2 Blood supplies of the Duodenum11. -12. The portal vein is formed by what 2

veins?13. What organ forms and secretes the bile?14. The left colic artery supplies blood to

which part of the large intestine?15. insulin-secreting cells of the Pancreas