Alimentary Canal Anatomy (second Half)

Question 1

Stomach

Answer 1

• bolus converted into chyme
• food enters cardioesophogeal sphincter from the esophagus, then leaves into small intestine at the pyloric sphincter
• C-shaped, very elastic
• has cardia, fundus, greater and lesser curvature, and pyloric valve

Question 2

Stomach histology

Answer 2

• mucosa: simple columnar (almost all mucous cells)
• gastric pit: surface epithelium, leading to gastric glands that secrete gastric juice
• mucosa lined by mucosal barrier
• muscularis includes a third layer (oblique, allowing churning)

Question 3

Stomach mucosa cells (in gastric pit)

Answer 3

• chief cells
• parietal cells
• mucous neck cells
• enteroendocrine cells

Question 4

Chief cells

Answer 4

-produces protein-digestive enzymes (pepsinogens)

Question 5

Parietal cells

Answer 5

-produces HCl that activates enzymes

Question 6

Mucosa neck cells

Answer 6

-produces thin mucus (different from the ones produced by the mucous cells of the mucosa)

Question 7

Enteriendocrine cells

Answer 7

-produced local hormones (gastrin)

Question 8

Small intestine

Answer 8

• 2-4 m
• major site of chemical digestion and absorption
• muscular tube extending from pyloric sphincter to the ileocecal valve
• suspended from the posterior abdominal wall by the mesentary
• splits into: duodenum, jejenum and ileum

Question 9

Histology of small intestine

Answer 9

• all three regions have similar histology with some structural adaptations:
• increased surface area for food absorption that decrease in number towards the end
• has villi, microvilli, circular folds, and intestinal crypts

Question 10

Villi

Answer 10

-fingerlike projections formed by the mucosa

Question 11

Microvilli

Answer 11

-tiny projections of the PM with brush border enzymes

Question 12

Circular folds

Answer 12

• (plicae circulares)

- deep folds of the mucosa and submucosa. Causes chyme to spiral

Question 13

Intestinal crypts

Answer 13

-secretes intestinal juice and hormones

Question 14

Large intestine

Answer 14

• 1.5 m
• from ileocecal valve to the anus
• absorbs H2O, molecules made by bacteria, stores and eliminates residue
• parts: cecum, appendix, colon, and rectal Valves

Question 15

Cecum

Answer 15

-sac-like first part

Question 16

Appendix

Answer 16

• vestigial organ
• hangs on cecum
• can get inflamed by the accumulation of lymphoid tissue

Question 17

Colon

Answer 17

• ascending: turns at right comic (hepatic) flexure
• transverse: turns at left colic (splendic) flexure
• descending: down the left side
• sigmoid, S-shaped, enters pelvis

Question 18

Rectal Valves

Answer 18

• separates gas from feces
• anal canal ends in two sphincters
• internal anal sphincter (smooth muscle)
• external anal sphincter (skeletal muscle)
• goblet cells produce alkaline mucus to lubricate passage of feces