Flashcards in GI system III Deck (20):
What are the features of the small intestine mucosal epithelium?
1. Mainly absorptive columnar cells with well developed striated brush borders2. Goblet cells - increase in numbers as ileum is approached
What are the features of the small intestine mucosal lamina propria?
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
What are the features of the intestinal glands (crypts of Lieberkuhn)?
1. Lined by simple columnar epithelium 2. Glands open between villi3. Simple tubular4. Paneth cells, enteroendocrine glands, stem cells
What are Paneth cells?
1. Found in intestinal glands2. Secrete lysozyme, defensins, TNFa3. Extend into right colon
What are the features of the small intestine submucosa?
1. Moderately dense CT2. Submucosal (Meissner's) plexus3. Blood and lymph vessels
What is the signature feature of the duodenum?
What is the function of Brunner's glands?
1. Secrete mucous and human EGF2. Well developed proximally
How is the large intestine mucosa different from the small intestine mucosa?
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)
What are the features of the large intestine muscularis externa?
Outer layer of smooth muscle does not completely surround the large intestine (3 teniae coli bands instead)
What are the features of the appendix?
1. Lymphatic nodules found in lamina propria and submucosa2. Lacks teniae coli and villi
What are the plicae transversales recti (transverse rectal folds, valves of Houston)?
Folds of circular muscle of externa, submucosa, and mucosa
What are the anal columns?
1. Longitudinal folds of submucosa and mucosa2. Anal valves located between distal adjacent anal columns with anal sinuses lateral to valves
What is the pectinate line?
1. Stratified squamous, nonkeratinized epithelium superior2. Stratified squamous keratinized epithelium inferior
What are the anal cushions?
1. Composed of CT, smooth muscle, blood vessels2. Functions in anal continence
What is the internal anal sphincter?
1. Formed by inner circular smooth muscle layer of muscularis externa2. Becomes thickened
What are false diverticula?
Outpouchings of colonic wall, only involves mucosa and submucosa
What is a true diverticulum?
Involves all wall layers
How are colonic polyps formed?
In response to robust proliferative activity of colonic crypt cells
What are the features of ulcerative colitis?
1. Confined to large intestine and perhaps distal ileum2. Involves mucosa and submucosa