12.6 Flashcards
Stereotyped layers of GIT:
Mucosa
Submucosa
Muscularis propria/externa
Serosa (or adventitia)
Layers of mucosa of GIT
Epithelium
Lamina propria
Muscularis mucosae (forming boundary of mucosa)
In oesophagus and rectum, epithelium is:
Stratified squamous
In all other parts of GI (i.e. not oesophagus and rectum), epithelium is:
Simple columnar
Muscularis externa - usually two layers of muscle: ___ and ___
Inner circular/circumferential and outer longitudinal.
Epithelium of serosa:
Simple squamous epithelium.
Two enteric nerve plexuses:
Myenteric - between circular and longitudinal muscle layers.
Submucous - in submucosa.
Special features of oesophagus histology:
Stratified squamous epi.
Submucosal seromucous glands.
In musc. externa, skeletal AND smooth muscle at different levels (skeletal = top third, mixed = middle third, smooth = bottom third).
Special features of stomach histology:
Simple columnar epi.
Thick muscularis mucosae, thick submucosa!
Thick muscularis externa - sometimes a third oblique layer of muscle!
Mucosa of stomach:
Rugae (low folds), but mostly flat.
Openings = gastric pits - openings to gastric glands in lamina propria of mucosa.
Special features of SI histology:
Simple columnar epi WITH MICROVILLI.
Villi on transverse folds (plica circulares).
Base of villi - tubular glands (crypts of Leiberkuhn).
GOBLET CELLS on villi!
Villi increase surface area by factor of ___, and plica circulares increase surface area by factor of ___.
10
2-3
So up to 600x in total.
SI absorbs approx. ___ litres of fluid, of which ___ is secreted into SI and 1L is from fluid intake
8.5 is absorbed.
Up to 8L is secreted into SI from crypts of Leiberkuhn.
Special features of LI histology:
Longitudinal muscle in 3 bands - teniae coli.
Many tubular glands (crypts of Leiberkuhn, mainly mucus).
Main cells in crypts are mucus producing cells.
