Small Intestine

Question 0

What are the three subunits of the small intestine?

Answer 0

Duodenum (25cm)
Jejunum (2.5m)
Ileum (3.5m)

Question 1

How long is the small intestine?

Answer 1

6 metres from the pyloric sphincter to the illeocecal junction

Question 2

Describe the duodenum?

Answer 2

C-shaped
Shortest part
Head of pancreas lies in it
Superior part = intraperitoneal 
Descending, inferior and ascending parts all retroperitoneal

Question 3

What does the descending part of the duodenum contain?

Answer 3

The major and minor papillae which are ducts from the liver and the pancreas

Question 4

Describe the jejunum?

Answer 4

Extends from the duojejunal flexure to the ileum and is intraperitoneal

Question 5

Describe the ileum:

Answer 5

Extends from the jejunum to the large intestine at the ileocecal junction at the large intestine which contains the illeocecal valve
Intraperitoneal

Question 6

What layers does the duodenum have?

Answer 6

Inner mucosa
Submucosa
Muscularis (inner circular and outer longitudinal)
Serosa

Question 7

What does the mucosa of the duodenum contain?

Answer 7

ridges/folds that are permanent called plicae ciruclaris which enhances absorption as they increase the surface area and also contain villi

Question 8

Describe the villi of the plicae circularis

Answer 8

Covered by simple columnar epithelium with 4 cell types
about 40 per square mm of plicae
Each contain a blood capillary network of a lacteal (lymphatic capillary) and capillary
have their own microvilli

Question 9

What is the function of the lacteal in the villi of the plicae?

Answer 9

Food that is too large to go into the capillary network but still small enough (e.g fatty acids) goes into the lacteal and to the venous system

Question 10

What are the 4 cells type of the simple columnar epithelium of the duodenum and where are these cells produced and where do they move to?

Answer 10

1. Absorptive which produces digestive enzymes
2. Goblet which produces a protective mucous
3. Granular (paneth) protect the epithelium from bacteria by producing lysozymes
4. Endocrine which produce regulatory hormones
   These cells are produced in the intestinal glands Absorptive and goblet migrate to cover the surface and the granular and endocrine remain in the bottom

Question 11

Describe the Submucosa of the duodenum?

Answer 11

Contains coiled, tubular mucous glands called duodenal/brunner glands which open at the base of the intestinal glands

Question 12

Describe the Submucosa of the ileum?

Answer 12

Has lymphoid follicles called Peyer patches which initiate a response against microorganisms

Question 13

What happens as you go distally down the small intestine?

Answer 13

The plicae are less prominent and the thickness of the wall decreases