GI system III

Question 1

What are the features of the small intestine mucosal epithelium?

Answer 1

1. Mainly absorptive columnar cells with well developed striated brush borders2. Goblet cells - increase in numbers as ileum is approached

Question 2

What are the features of the small intestine mucosal lamina propria?

Answer 2

1. Loose CT that extends into villi2. Intestinal glands (crypts of Lieberkuhn)3. Well endowed with blood and lymphatic vessels (lacteals)4. Smooth muscle, leukocytes, plasma cells

Question 3

What are the features of the intestinal glands (crypts of Lieberkuhn)?

Answer 3

1. Lined by simple columnar epithelium 2. Glands open between villi3. Simple tubular4. Paneth cells, enteroendocrine glands, stem cells

Question 4

What are Paneth cells?

Answer 4

1. Found in intestinal glands2. Secrete lysozyme, defensins, TNFa3. Extend into right colon

Question 5

What are the features of the small intestine submucosa?

Answer 5

1. Moderately dense CT2. Submucosal (Meissner’s) plexus3. Blood and lymph vessels

Question 6

What is the signature feature of the duodenum?

Answer 6

Brunner’s glands

Question 7

What is the function of Brunner’s glands?

Answer 7

1. Secrete mucous and human EGF2. Well developed proximally

Question 8

How is the large intestine mucosa different from the small intestine mucosa?

Answer 8

1. No plicae circulares (but does have plicae semilunares)2. No villi3. Numerous and longer intestinal glands4. Goblet cells more numerous in large intestine5. Lymphatic channels poorly developed in lamina propria (better for cancer prognosis)

Question 9

What are the features of the large intestine muscularis externa?

Answer 9

Outer layer of smooth muscle does not completely surround the large intestine (3 teniae coli bands instead)

Question 10

What are the features of the appendix?

Answer 10

1. Lymphatic nodules found in lamina propria and submucosa2. Lacks teniae coli and villi

Question 11

What are the plicae transversales recti (transverse rectal folds, valves of Houston)?

Answer 11

Folds of circular muscle of externa, submucosa, and mucosa

Question 12

What are the anal columns?

Answer 12

1. Longitudinal folds of submucosa and mucosa2. Anal valves located between distal adjacent anal columns with anal sinuses lateral to valves

Question 13

What is the pectinate line?

Answer 13

1. Stratified squamous, nonkeratinized epithelium superior2. Stratified squamous keratinized epithelium inferior

Question 14

What are the anal cushions?

Answer 14

1. Composed of CT, smooth muscle, blood vessels2. Functions in anal continence

Question 15

What is the internal anal sphincter?

Answer 15

1. Formed by inner circular smooth muscle layer of muscularis externa2. Becomes thickened

Question 16

What are false diverticula?

Answer 16

Outpouchings of colonic wall, only involves mucosa and submucosa

Question 17

What is a true diverticulum?

Answer 17

Involves all wall layers

Question 18

How are colonic polyps formed?

Answer 18

In response to robust proliferative activity of colonic crypt cells

Question 19

What are the features of ulcerative colitis?

Answer 19

1. Confined to large intestine and perhaps distal ileum2. Involves mucosa and submucosa

Question 20

What are the features of Hirschsprung’s disease?

Answer 20

1. Agangliosis of myenteric and submucosal plexuses2. Always involves rectum and may also involve more proximal segments