Histology of the SI and LI Flashcards
Plicae circulares
Transverse folds with a submucosal core.
Visible in jejunum, less so in ileum.
Enterocytes
Simple columnar cells that produce enzymes for digestion.
Goblet cells
Secrete mucous for protection from abrasion.
Enterocyte microvilli
‘Striated border’
Glycocalyx coat assists in nutrient uptake.
What permits contraction of microvilli?
Terminal web
Innervation of SI/LI
ANS (motility) Enteric NS (submucosal plexus of Meissner and myenteric plexus of Auerbach)
Simple tubular glands have (5)
Simple columnar epithelium Enteroendocrine cells Paneth cells Intestinal stem cells M cells
Enteroendocrine cell
Secretes peptide hormones to control gut motility, regulate secretion of enzymes, HCl, bile, etc.
Paneth cells
Pyramid cells at base of glands.
Function in innate immunity by secreting antibiotic substances.
May be found in small numbers, but increase when there is pathology.
Intestinal stem cells reside:
In a niche at crypt base near Paneth cells
M cells
Overlie Peyer’s patches.
Has microfolds and thin glycocalyx.
Houses immune cells.
M cells function as: “ “
Ag-transporting cells. The express receptors specific for macromolecules and gram-negative bacteria.
Hallmarks of duodenum (3)
Brunner’s glands in submucosa.
Leaf-like villi.
Tubular intestinal glands in mucosa.
Hallmarks of jejunum (3)
No submucosal glands.
Elongated, fingerlike villi.
Tubular intestinal glands in mucosa.
Hallmarks of ileum (3)
Peyer’s patches.
Fingerlike villi.
Tubular intestinal glands in mucosa.
Ileocecal junction is noted by:
Abrupt transition from villi of SI to glandular epithelium of LI.
What is special about the ileocecal valve?
It has a thickened muscularis mucosae to limit reflux back into the ileum. Muscularis externa may also be thickened.
Hallmark of the LI
Intestinal glands, gobelt cells and NO intestinal villi.
Veriform appendix
Diverticulum of cecum.
Mucosa of simple columnar epithelium and goblet cells.
Submucosa contains dense irregular CT and adipocytes.
Covered in serosa.
Hirschsprung’s disease
“Aganglionosis” in distal colon.
Mutation in RET gene needed for migration of NCC.
Short segment HD
85% of cases. Confined to rectosigmoid region.
Long segment HD
10% of cases. Extends past rectosigmoid region to splenic flexure.
Total colonic aganglionosis HD
5% of cases. Affects entire colon.
Presentation of HD
TTM of HD
Constipation, poor feeding, abdominal distention.
Surgical removal of colon segment.
