GI 2: Salivary & Gastric Secretions Flashcards
what are the 3 pairs of salivary glands?
- parotid
- submandibular
- sublingual
what are the 4 things saliva contains?
- mucous
- bicarb and phosphate ions
- salivary amylase ptyalin
- lysozyme
what is the function of mucous in the saliva?
lubrication
what is the function of bicarb and PO4 in the saliva
pH neutralization
what is the function of salivary amylase ptyalin?
10% of carbohydrate digestion
what is the function of lysozyme in saliva?
anti-bacterial
~___L of saliva is secreted daily
1
salivary secretions are stimulated by ____ signals in response to taste, touch, sight, and smell
parasympathetic
lingual lyase breaks down ___
lipids
the pH is ~___ when it reaches the esophagus
6.5
the ____ layer of the stomach contains gastric pits
mucosa
function of surface mucous cells
secrete mucous to line and protect
function of the mucous neck cells
secrete HCO3 (act as buffer)
what are the 4 different types of cells in the gastric pits?
- mucous cells
- parietal cells
- chief cells
- endocrine cells
what are the 3 types of endocrine cells and the tings they secrete
- G cells = gastrin
- ECL cells = histamine
- D cells = somatostatin
what is the function of the mucous cells of the gastric pits?
secrete alkaline mucous to protect stomach from its low pH
what is the function of the parietal cells?
secrete HCL and intrinsic factor
what is intrinsic factor?
protein needed for absorption of B12
what is the function of the chief cells?
secrete pepsinogen
what does the suffix “ogen” mean?
secreted in inactive form
once activated, what is the function of pepsinogen?
breakdown peptides
what is responsible for the stomach’s low pH?
HCL secreted by parietal cells
what are the 5 functions of HCL secretion in the stomach?
- antibacterial
- denatures proteins
- transforma pepsinogen to pepsin
- inactivates salivary amylase
- activates lingual lipase
carbonic anhydrase converts ___ and __ into ___
CO2 and H20 into H2CO3
H+ is ____ (active/passive) transported in the stomach lumen via_____
actively; H+/K ATPase
HCO3 is ____ (active/passive) transported in the intestinal fluid via ____
passive; HCO3/Cl exchanger
CL is transported in the stomach lumen via ___
uniport channel
acid secretion in the stomach requires translocation of ___ from the cytoplasm to the apical membrane of the cell
H/atpases
translocation of the H/ATPases is activated by what 3 things?
- gastrin
- histamine
- ACh (PNS)
explain the potentiation of acid secretion involving histamine
histamine increases the cell’s sensitivity to gastrin and Ach, so the response is greater than the sum of the 3 individual effects
where are H/atpases typically found before their translocation?
vessicles
what is the role of somatostatin wrt H/ATPase?
reduces translocation to membrane
give 2 examples of drugs used to decrease gastric acid secretion
- proton-pump inhibitor (omeprazole)
2. histamine H2 receptor antagonists
explain how intrinsic factor helps with absorption of B12
intrinsic factor binds to b12 forming an indigestible complex that is then absorbed by the ileum by endocytosis
B12 is critical due to its role in ___ synthese
red blood cell (DNA synthesis)
list 4 posible causes of B12 deficiencies
- dysfunction of gastric parietal cells (pernicious anemia)
- resection (surgical removal) of terminal ileum
- catabolism of the vitamin by bacteria in the small intestine
- pancreatic insufficiency
adequate absorption of B12 from the diet depends on what 5 things?
- amount of dietary intake
- HCL and pepsin in stomach to free B12 from binding to dietary proteins
- pancreatic processes to free B12 from binding to R factors
- secretion of intrinsic factor by the gastric parietal cells
- intact ileum with functional receptors
B12 must be bound to ___ to be protected
protein
