Lecture 7: Histology of the SI and LI Flashcards
What is the plicae circulares?
folds in the jejunum wall with submucosal core, increases surface area
Intestinal villi:
Epithelium?
Features?
Contains?
- simple columnar epithelium
- finger like folds on surface in SI with enterocytes and goblet cells in the epithelium
- vessels and lacteals (extension of lymphatics that are important for fat digestion)
What is the importance of enterocytes and goblet cells?
Enterocyte: has lots of microvilli (increased SA) and secretes enzymes for digestion
Goblet cells: releases mucus for protection
Characteristics of intestinal mucosa:
Epithelium?
Contains?
- simple columnar epithelium
- lamina propia and muscularis mucosae
Characteristics of intestinal submucosa:
Type of CT?
Contains?
- dense irregular CT
- NV, lymphatics and glands
Characteristics of the intestinal muscularis externa
Characteristics of the intestinal serosa
- inner circular and outer longitudinal muscle layers
- loose CT covered with visceral peritoneum
Intestinal glands
Epithelium
Features
- simple columnar epithelium
- tubular glands and continuous with epithelium that covers villi
Enteroendocrine cells (intestine): Function?
-secrete peptide hormones for gut motility, and regulate secretion of enzymes
Paneth cells
Found where?
Features
Function
- base of the intestinal glands
- pyramid shaped cells, eosinophilic, granular apical surface (stains differently from the rest of the gland)
- secretes anti-microbial substances like lysozyme and a-defensins
Intestinal stem cells
where?
function?
- crypta base of the intestinal gland
- repopulating the epithelium with new cells that move up to the surface
M (Microfold) cells:
Found where?
Function?
- epithelial cells found in the ileal mucosa by Peyer patches
- pocket contains immune cells that transport pathogens , apical surface has receptors that bind Gram (-) bacteria
Gastroduodenal Junction
Pyloris vs. Duodenum
-transitiion between pylorus and duodenum
Pyloris: thick wall due to the sphincter muscle
Duodenum: Lots of Brunner’s glands deep to the MM
Duodenum
Hallmark features
Functions
Brunner’s glands
Brunner’s neutralizes acidic chyme from stomach
hepatopancreatic ampulla collects bile and secretions
Jejunum
Hallmark features
Contains?
- Longer finger like villi with lacteal in the core, no submucosal glands
- Lamina propia has lymphoid nodules
Ileum
Hallmark features
-shorter finger like villi, Peyer’s patches (lymphoid nodules) with paneth cells at the base of the intestinal glands
Ileoceccal Junction
Hallmark features
-ileoceccal valve that propels food into cecum, abrupt transition from small SI villi to glandular LI villi + thickened muscularis externa
Colon:
Epithelium?
Hallmark features?
simple columnar epithelium
-tubular intestinal glands (crypts of Lieberkuhn), has glands and goblet cells with no villi
Characteristics of colon mucosa:
Colon submucosa:
Colon muscularis externa
- has colonocytes, goblet cells, extensive GALT
- dense irregular CT
- outer layer has taeniae coli forming the haustra of LI, serosa at intraperitoneal portions of the colon
Hirschsprung’s Disease
Cause
Clinical
Treatment
RET mutation = failure of NCC migration resulting in lack of ganglionic plexus in distal colon = difficulty of bowel movements due to colon always contracted
- constipation, abd. distention, delayed BM <48 hours post birth
- surgical removal of affected segment
What comprises the rectum?
What type of epithelium does the rectum proper have?
Upper part: rectum proper
Lower part: Anal canal
simple columnar
Portions of the anal canal (in to out):
Colorectal zone
Anal transitional zone
Squamous zone
Epithelium transitions of the anal canal
C zone: simple columnar epithelium
ATZ: simple columnar > startified squamous
Squamous: stratified squamous (continuous with skin)
