Small Intestine Anatomy

Question 1

Circular folds

Answer 1

Large (about 10mm) ridges of the mucosa and submucosa that increase SI surface area

Question 2

Villi

Answer 2

Smaller (about 1mm) finger-like projections of the GI mucosa running along the surfaces of the circular folds. They profoundly increase the surface area of the SI and acts as sort of a functional absorptive unit, as the lamina propria of each villus has a capillary bed and a lacteal for absorption of nutrients

Question 3

Microvilli

Answer 3

Microscopic (about 1 micron) projections on the apical surface of intestinal absorption cells. They are supported by actin filament and greatly increase the surface area of the SI. They’re so small in situ, that they resemble a fuzzy “brush” under a light microscope

Question 4

Simple columnar epithelium

Answer 4

The type of mucosal epithelium lining the lumen of the SI

Question 5

Absorptive cell

Answer 5

The primary epithelial cell type of the GI. They are the simple columnar epithelium cells lining the mucosa

Question 6

Goblet cell

Answer 6

Mucous-producing cells interspersed with simple columnar cells of the intestinal mucosa

Question 7

Paneth cell

Answer 7

Specialized cells of the intestinal mucosa that secrete lysozyme for innate immunological function/ They can also act as fixed macrophages

Question 8

S, CCK, K cells

Answer 8

Enterdenocrine cells lining the intestinal glands and secrete digestive and absorptive hormones into the lumen of the SI

Question 9

Intestinal glands

Answer 9

Crypts of Lieberkuhn. Depressions between the villi of the intestinal mucosa. Similar to gastric pits and holding Paneth and enteroendocrine cells. Still in contact with the SI lumen

Question 10

Aggregated lymphatic follicles

Answer 10

Peyer’s patches. Groups of lymphatic nodules clustered together in the ileum

Question 11

Lacteal

Answer 11

A lymphatic capillary running within the lamina propria of the villus. Dietary lipids are absorbed into the lacteal

Question 12

Duodenal glands

Answer 12

Brunner’s glands. Within the intestinal submucosa, they secrete an alkaline mucous to neutralize the scarring acidity of the stomach

Question 13

Brush border

Answer 13

Name given to the apical surface of intestinal absorptive cells, given the presence of microscopic microvilli that blur under the scope into a fuzzy “brush.” The brush border houses digestive enzymes that accomplish digestion at the apical surface of the intestine, and absorptive proteins

Question 14

Segmentations

Answer 14

Apposiontal-like contractions of the intestinal muscularis. They move only in a superficial to deep direction, about once every 5 seconds alternating compressing different sections of the intestine. The movement sloshes the chyme in and out of the circular folds, facilitating chemical digestion and absorption

Question 15

Migrating motility complexes

Answer 15

Essentailly peristalsis. Alternating contraction of circular smooth muscle rings proximally to the chyme, and contraction of longitudinal sheets distal to the chyme, with the overall result of moving the chyme distally down the SI