1.2 regulation of GIT (secretion) Flashcards
what are GI secretions
group of enzymes and fluids which aid in the liberation of nutrients from food, as well as mucus which facilitates transport of food down the alimentary tract
what colors are GI fluid (2 colors)
colorless and pale yellow
what are exocrine glands
they excrete substances onto epithelial surfaces through a duct
what are endocrine glands
they are ductless glands that secrete products straight into blood
the 3 exocrine modes of cellular secretion
Merocrine (aka eccrine)
- Secretory vesicles fuse with apical plasma membrane to release their products into a duct
- e.g. secretion of saliva
Apocrine
- A portion of the cell’s cytoplasm pinches off with the secretory products and enters into a duct
- e.g. secretion of lipid droplets in the mammary glands
Holocrine
- Secretory products accumulate in the secretory cells, which then die and the entire cells and its secretory products are released into a short duct
e.g. secretion of an oily, lipid-rich product by sebaceous glands in the skin
main components of saliva
- mucous
- amylase
- proteins and enzymes
- electrolytes
- water
what shouldn’t be in saliva and what does that mean
glucose, could mean diabetes
stomach cells and their functions
- parietal cells
- produces hydrochloric acid
- chief cells
- produces pepsinogen (zymogen) that breaks down proteins
- Pepsinogen will be converted into pepsin
- Pepsinogen needs a low pH to be converted into pepsin
- surface mucous cells and mucous neck cells
- They produce mucus that cover the cells of the stomach and avoid the cells from getting destroyed by hydrochloric acid and pepsinogen
- G cells
- they produces gastrin (hormone)
what stimulates the secretion of stomach cells
- acetylcholine
- gastrin
- histamine
what happens in cephalic phase
- Conditioned reflex or sight/smell/taste of food
- Through vagus (CN X), gastrin secretion and histamine
- Increase stomach motility
- Increase HCl and pepsinogen secretion
what happens in gastric phase
- Stimulation of chemo and mechano receptors in stomach lead to the release of gastrin and histamines
- A local negative feedback loop operates if gastric pH is <3
what happens in intestinal phase
- When food leaves stomach and enters duodenum
- The presence of chyme in the duodenum inhibits acid secretion and motility via the release of secretin, GIP and CCK
what promotes stomach mucosa growth
gastrin
how does cholecystokinin, secretin, GIP and VIP works
Cholecystokinin and secretin - stimulates the pancreas to release sodium hydrogen carbonate and water to act as buffer
Cholecystokinin also stimulates the gall bladder to release bile to help digest food in duodenum
Secretin inhibits gastrin release
GIP and VIP inhibits release of HCl
what promotes intestinal mucosa growth
cholecystokinin and enteroglucagon
