Intestine Microanatomy Flashcards
What does the smooth muscle on the lamina propria of the small intestine do?
Moves lymph through lacteals of villi
Rhythmic beating of villi
What cell types are found on the small intestine? (surface to crypt)
Columnar absorptive cells Goblet cells Enteroendocrine cells Undiff. Stem cells Paneth cells
Describe the features of columnar absorptive cells?
Microvilli to increase SA and localised mixing of contents due to force tranduction by actin filaments
Digestive enzymes in membrane to assist in digestion eg glycosidases
Glycocalyx on surface, rich in glycoproteins and acid micropolysaccharides, as a selective barrier
What do enteroendorcine cells produce an with what effect?
Secretin: arrival of acid, causes pancreas to secrete bicarbonate and reduce stomach acid production
Cholecystokinin: arrival of AA and FA’s, causes gall bladder contraction and pancreatic secretions containing enzymes
Somatostatin: Inhibits G cells, causes SM contraction and aids absorption
Serotonin: Increases peristalsis and secretions from all cells
What do paneth cells secrete?
TNF-a- inflammatory of nature in response to bacteria
lysozyme- anti-bacterial
Defensins- complement system
What are key features of the duodenum?
Brunners glands that secrete alkaline mucous (in submucosa)
pH in lumen changes from 1-2 to 7-8, think glands
Jejunum
more plicae
What are key features of the ileum?
has macroscopically visible lymphoid aggregates called Peyers patches containing B cells and M cells
What is unique about large intestine mucosa?
Smooth mucosa, with crypts. enterocytes and gobet cells (more prevalent at the end). Enterocytes absorb water, electrolyte and vit. B and K
LP has lymphatic tissue, GALTS
Muscularis externa has a thickening of the OL layer into three layers, making the teniae coli.
What does the tenia coli allow?
independent parts of the colon to contract
Pulls intestine into haustra
What can be said about the rectum?
Final part is the anal canal and is marked by longitudinal folds
Anal sphincter has two parts, inner SM and outer skeletal muscle
Where are undiff. stem cells loacted in the gut tube, and what is their turnover? (related to cancer drugs affecting mitosis)
Oesophagus: basal part; days
Stomach: near neck of glands; days for absorptive cells, gland cells is months
SI: lower half of crypts; surface is days, crypts is months
LI: lower third of crypts; days for absorptive cells
