Anatomy 3: Intestines

Where is the position of the small intestine?

It lies in the central and lower parts of the abdomen with some coils hanging into the pelvic cavity

What are the parts of the small intestine?

The small intestine is divided into 3 parts:

1) Duodenum: it is the proximal part.

2) Jejunum: follows the duodenum.

3) Ileum: it is the distal part.

What are the general properties of the jejunum and the ileum?

Length:

• 6 meters

Postions:

• Most of the jejunal loops lie above the umbilicus

• Most of the ileal loops lie below it.

Shapes:

• Coils or loops

Peritoneal covering:

• Suspended from the posterior abdominal wall by a large fold of peritoneum called mesentery.

Extents:

• Jejunum: joins the duodenum at the duodenojejunal flexure,

• Ileum: joins the beginning of large intestine (caecum) at the ileocaecal junction

Compare the jejunum and the ileum

What is the definition, its site, and the parts of the large intestine?

It is the distal part of the GIT

Site:

• Encircles the coils of the small intestine

Parts:

• Caecum.

• Descending colon.

• Anal canal.

• Ascending colon.

• Pelvic colon.

• Transverse colon.

• Rectum.

What is the main characters of the large intestine?

1) Taenia coli:

• 3 longitudinal bands in wall of colon

• This part represents the longitudinal muscle layer

2) Sacculations: (Haustration)

• The presence of sac-like dilatations in the wall of the large intestine.

Formed because the length of the taeniae coli is shorter than the true length of the large intestine

3) Appendices epiplocae:

Small fat-filled sacs of peritoneum attached along the taenia.

Compare the small and large intestine

What is the definition, position, width, length, and the peritoneal covering of the caecum?

It is the blind beginning of the large intestine.

Position:

• In the right iliac fossa, above the lateral half of the inguinal ligament

Width:

• The most dilated part of the large intestine.

Length:

• 3 inches

Peritoneal covering:

• Completely covered except the upper part of its posterior wall

List and describe the openings of the caecum

What are the relations of the caecum?

What is the blood supply of the caecum?

Arterial:

• Anterior & posterior caecal arteries

Venous:

• Into the superior mesenteric vein

What is the definition, length, opening, and peritoneal covering of the vermiform appendix?

It is the blind beginning of the large intestine.

Length:

• 2 - 20cm

Opening:

• Opens into the posteromedial aspect of the caecum about 1 inch below the ileocaecal valve.

Peritoneal covering:

• Completely covered with a short mesentery called the mesoappendix

What is the special feature of the appendix?

• 3 taeniae coli of the caecum meet at the base of the appendix to form a continuous longitudinal muscle coat in the wall of the appendix.

The taenia coli is taken as a guide to reach the appendix.

What is the position of the appendix?

What is the blood supply of the appendix?

What is the surface anatomy of the appendix?

Compare the ascending, transverse, and descending colon

Compare the right and left colic flexures

What does the portal venous consist of, and what does it drain?

Consists of the portal vein & its tributaries & their blood pour directly into liver.

It drains the G.I.T, spleen, pancreas & gall bladder.

What is the formation, course, termination and tributaries of the splenic vein?

What is the formation, course, termination and tributaries of the superior mesenteric vein?

What is the formation, course, termination and tributaries of the inferior mesenteric vein?

What is the formation, course, termination and tributaries of the portal vein?

What is the definition and sites of the porto-systemic anastomosis?

The communication between tributaries of the portal vein and systemic veins.

Sites:

• Lower end of oesophagus

• Lower end of anal canal.

• Inside liver.

• At bare area of liver.

• At umbilicus.

• Reteroperitoneal

What is the portosystemic communication at the lower end of the esophagus?

Portal: Esophageal tributaries of the left gastric vein

Systemic: Esophageal tributaries of the azygos vein.

What is the portosystemic communication at the lower end of the anal canal?

Portal: Superior rectal vein

Systemic: Middle and inferior rectal veins.

What is the portosystemic communication inside the liver?

Portal: Branches of the portal vein

Systemic: Tributaries of the hepatic veins

What is the portosystemic communication at the bare area of the liver?

Portal: Branches of the portal vein

Systemic: Phrenic veins

What is the portosystemic communication at the umbilicus?

Portal: Paraumbilical veins

Systemic: Epigastric veins

What is the consequence of portal hypertension?

Lower end of esophagus:

• Esophageal varices

• Possible complication of haematemesis

Lower end of anal canal:

• Piles or hemorrhoids

• Possible complication of bleeding piles

Inside liver:

• Hepatomegaly

• Possible complication of liver failure

Bare area of liver:

• Ascites

Umbilicus:

• Caput medusae

What happens when a portal vein is obstructed?

They may establish a collateral circulation.

Visceral veins have no valves, this aids their dilation during portal vein obstruction.

(The veins are thin walled and could burst. This is not part of the lecture)