Flashcards in histology of the gut Deck (76):
name the functional compartments of the alimentary tract and their function
oral cavity - ingestion and fragmentation
simple passages (oesophagus and anus) - transport of food/waste
digestive tract (stomach and intestine) - digestion/absorption
what type of epithelium is found in the oral cavity?
what type of epithelium is found in the simple passages?
what makes up the digestive tract?
accessory glands like pancreas and liver
describe the stages of absorbing nutrients from ingested food from top to bottom
where does fragmentation of food occur and what aids it?
oral cavity and stomach
aided by saliva from the salivary glands
where does digestion occur and what aids it?
starts in the stomach but continues down the duodenum
pancreatic enzymes, bile salts and brush border enzymes
where does absorption occur and what aids it?
mostly in the jejunum and the ileum
enterocytes absorb nutrients
capillaries and lacteals transport these from the mucosa
where does elimination occur?
colon and anal canal
where is water absorbed from liquid residue?
where is solid faeces expelled from?
the anal canal
what are the four layers of the gut?
what are the layers of the mucosa?
what makes up the submucosa
a thick layer of fibrocollagenous tissue
what is a feature of the fibrocollagenous tissue?
what does the submucosa carry?
vessels and nerves and the submucosal neural plexus
what are the layers of the muscular propria?
where is adventitia found?
where the gut is retroperitoneal
most of the oesophagus
ascending and descending colon
what gives input to the enteric nervous system?
parasympathetic and sympathetic systems
what are the two plexuses of the enteric nervous system?
what does the submucosal plexus innervate?
what does the myenteric plexus innervate?
what does MALT stand for?
mucosa associated lymphoid tissue
what does MALT contain?
plasma cells of the lamina propria - IgA production
name the main structures of the alimentary tract
what is the main function of the oesophagus?
transport of fragmented food
what does swallowing involve?
relaxation of cricopharyngeal part of inferior constrictor muscle
what mediates peristalsis?
what type of epithelium is found in the mucosa of the oesophagus?
nonkeratinised stratified squamous epithelium
what does the submucosa of the oesophagus contain?
nerves and ganglion cells
describe the parts of the muscularis propria of the oesophagus and their function
top 1/3 - skeletal for swallowing
bottom 1/3 - smooth for peristalsis
what is the oesophagogastric junction?
the junction between the oesophagus and the stomach
how does the mucosa change at the oesophagogastric junction?
goes from stratified squamous to simple columnar
what is the function of the stomach?
acting in mechanical and chemical digestion
what does glandular mucosa in the stomach do?
produce gastric juice which helps reduce contents to chyme
what is the mucosa in the stomach covered in and why?
thick layer of mucous for protection from stomach acid
what are the parts of the stomach?
what are rugae?
ridges formed by the non-distended mucosa of the stomach
which cells in the stomach secrete mucus?
mucous neck cells
what substances are secreted into the stomach?
what regenerates epithelium?
how many layers to the muscularis propria in the stomach and what are they?
what is the pyloric sphincter?
thickening of the muscularis propria at the gastroduodenal junction
what are the functions of the small intestine?
continues the digestion started in the stomach
absorbs molecules from digested food
what are the parts of the small intestine?
what is the function of the duodenum?
digestion continues from the stomach
what glands are found in the duodenum and what do they secrete?
Brunner's glands in the submucosa
secrete alkaline mucus in response to luminal chyme
what does the duodenum receive and what does it receive this from?
bile and pancreatic juice via the Ampulla of Vater
what controls the Ampulla of Vater?
the Sphincter of Oddi
what is the function of the jejunum?
most absorption occurs here
what is the function of the ileum?
how is the surface area for absorption increased in the small intestine?
what are plicae circulares?
circular folds in the submucosa in the jejunum and ileum
what are vili?
extensions of the mucosa
what is found at the base of vili?
the intestinal glands (crypts of Lieberkuhn)
what is the brush border?
the apical processes on cells
what do microvilli do?
aids terminal digestion of proteins and carbohydrates
what connective tissue is in the lamina propria of villi?
areolar connective tissue
what is the function of enterocytes in the lining villus?
digestion using brush border enzymes and absorption
what is the function of enterocytes in the crypts?
secretion of watery intestinal juice
what is the function of goblet cells?
mucus secretion for protection/lubrication
where are goblet cells found in the small intestine?
scattered along villus
how does the distribution of goblet cells change along the digestive tract?
increase in numbers distally
where are endocrine cells found in the small intestine?
what is the function of endocrine cells?
regulation of gut function
what is the function of stem cells?
regeneration of epithelium
where are stem cells found in the small intestine?
where are paneth cells found in the small intestine?
what is the function of paneth cells?
how is the large intestine specialised for its functions?
enterocytes - water and salt absorption
mucus secretion - abundant goblet cells
where are villi found?
only in the small intestine
what are the taenia coli?
3 longitudinal bundles of muscularis propria of the large intestine
what are haustra?
small pouches of the colon
what is sacculation?
what is the function of the taeniae coli?
act to sacculated the colon to form haustra