Normal GIT Physiology Flashcards
What are the common structural layers of the GIT and which of these is the most varied? What is the role and general structure of each?
Mucosa (most diverse): epithelium, lamina propria, mucularis mucosae
Submucosa: dense CT for strength and elasticity with nerve, small ganglia and blood vessels
Mucularis externa: inner circumferential and outer longitudinal smooth muscle for gut movement, with myenteric ganglia in between
Serosa/adventitia: fluid-secreting simple squamous epithelium, thin layer of CT (adventitia is thicker CT joining GIT with surrounding structures)
What does the ENS regulate?
Absorption and secretion via submucous ganglia
Smooth muscle activity via myenteric ganglia
What kind of epithelium is present throughout the different segments of the GIT?
Oesophagus: non-keratinised stratified squamous
Stomach: simple columnar
Small intestine: simple columnar with villi
Colon: simple columnar
Rectum: simple columnar
Anus: non-keratinised stratified squamous
What are the 2 types of muscle in the oesophagus? Where are they located and what is their significance?
Striated in top 1/3 of oesophagus: under somatic control
Smooth in lower 2/3 of oesophagus: under autonomic control
What are the distinctive features of the stomach mucosa?
Gastric glands with mucous, parietal, chief and enteroendocrine cells
3rd oblique layer of smooth muscle
What is the role of the mucous cells?
Produce mucus
What is the role of the parietal cells?
Secrete HCl
What is the role of the chief cells?
Produce pepsinogen
What is the role of the enteroendocrine cells?
Release gastrin
Which cells are found in the cardia, antrum and pylorus of the stomach?
Mucous
What glands are found in the oesophagus?
Mucous glands
What cells are found in the body (corpus) of the stomach?
Parietal
Chief
How is the SA of the small intestine increased to aid absorption?
Plicae circulares: folded surface
Villi: extensions of mucosa
Microvilli: projections on enterocytes on villi
What are the crypts of Lieberkuhn?
Lumen between villi where glands of the small intestine empty
What is special about the lamina propria and muscularis mucosae in the small intestine?
Extends into the villi
Contains blood and lymph vessels, and immune cells
List the 5 epithelial cells of the small intestine and their roles
Enterocytes: fluid transport, absorption Goblet cells: mucus secretion EE cells: hormone release Paneth cells: anti-microbial secretions Stem cells: to renew epithelium
What are the distinctive features of the duodenum?
Highly coiled Brunner’s glands in submucosa
Low plicae circulares and long villi
What is the role of Brunner’s glands?
Release alkaline mucus to inactivate stomach enzymes and neutralise acid
Describe the histological structure of the entire GIT and all the important features
Oesophagus: non-keratinised stratified squamous epithelium, submucosal seromucinous glands
Stomach: simple columnar epithelium, mucus cells, parietal cells, chief cells, EE cells, oblique smooth muscle
SI: plicae circulares, villi, microvilli, crypts of Lieberkuhn, enterocytes, Paneth cells
Duodenum: Brunner’s glands, low plicae circularis, long villi
Ileum: Peyer’s patches, short villi, more goblet cells
Colon: taeniae coli, more goblet cells than SI
Rectum: more goblet cells
Anus: stratified squamous epithelium
What are the distinctive features of the ileum?
Peyer’s patches
Short villi
More goblet cells
What are the distinctive features of the large intestine?
Muscularis externa has 3 bundles of longitudinal muscle called taeniae coli
Straight tubular glands
More goblet cells than SI (esp in rectum)
What are the 4 main cell types in the large intestine?
Enterocytes
Goblet cells
EE cells
Stem cells
Describe the transition between the oesophagus and stomach
Abrupt junction between non-keratinised stratified squamous and columnar epithelium
Describe the transition between the rectum and anus
Abrupt junction between columnar and non-keratinised stratified squamous epithelium
