3.4 Gastrointestinal Physiology Flashcards
How much does the parotid, submandibular, sublingual, and minor glands contribute to secretions?
parotid= 25-30% submandibular= 60-65% sublingual= 5-10% minor= 5-10%
why does parotid or submandibular produce more secretions?
submandibular produces more saliva bc it is more vascular and activated
*but depending on stimuli, both submandibular and parotid can produce about the same
composition of saliva?
1) lavage = water= 99.5%
2) lubrication= mucus
3) digestion= ptyalin and alpha amylase
4) buffers= HCO3-, PO4, HRPs, urea(ammonia)
5) antimicrobial
6) soft tissue repair
7) Ca++ binding phosphoproteins
urea is converted to? acts as a?
urea once converted to ammonia acts as a GREAT buffer
what percent of saliva is water?
99.5%
ptyalin is used for?
digestion in saliva
what type of amylase is found in saliva?
salivary amylase (or alpha amylase) *different from SI!!!
what are common salivary buffers?
HCO3-, PO4, HRPs, urea (ammonia)
What immunoglobulin is found in saliva?
IgA
what are antimicrobial aspects of saliva?
1) IgA
2) lysozyme
3) lactoferrin
4) lactoperoxidase
5) HRPs
how does lysozyme act as an antimicrobial?
destroys bacterial cell walls
how does lactoferrin act as an antimicrobial?
**
chelates iron
**binds up iron= so helps lysozyme do its job AND interferes with ALL bacteria metabolisms that REQUIRE iron
how does lactoperoxidase act as an antimicrobial?
kills microbes via oxidation
how does HRPs act as an antimicrobial?
bind to microbe cell walls and disrupt them
*HRP= histodine rich polypeptides
what growth factor helps with soft tissue repair in saliva?
nerve growth factor and epidermal growth factor
Ca++ binding phosphoproteins purpose in saliva?
examples?
they keep saliva in a state of super saturation
*examples are statherin, acidic proline-rich proteins, cysteine-containing proteins
HOW do Ca++ binding phosphoproteins work in saliva?
1) phosphoproteins bind Ca++ > increase CaPO salts
2) fermentation of carbohydrates > acid
3) low pH > protein release Ca++ and PO4
4) maintenance of tooth integrity and remineralization of early carious lesions
what is the most important buffer to prevent carries?
the ability to convert urea to ammonia
- a lot of credit is given to bicarbonate tho
- buffers are IMPORTANT to prevent carries (biggest difference to having a lot of carries or not)
what is xerostomia?
dry mouth
- NOT a disease, a condition caused by a disease
- has varied etiology
- results from diminished or arrested salivary secretions (asialism)
etiology means?
the cause of disease or conditions
what is asialism?
Diminished or arrested secretion of saliva. Also called aptyalia
xerostomia etiology?
independent study on this
usually caused by systemic disease and conditions that result in salivary gland hypofunction
*organic disease (of the organs themselves) induced by drugs, radiation, psychogenic conditions, decreased mastication
purpose of continuous secretions in esophagus?
1) protection against acid coming in or back up from stomach
2) protection from scratching (easy passage of food)
glands in the fundus and body of stomach secrete?
mucus
HCl-
Intrinsic factor
Pepsinogen
what secretion is only from the fundus and body of the stomach?
intrinsic factor
pepsinogen is the precursor for?
pepsin; a digestive enzyme that hydrolyzes peptide bonds
**pepsin is active form
glands in the antrum of stomach secrete?
mucus
pepsinogen
gastrin (endocrine hormone)-antrum only
what are the secretions to these endocrine cells
1) Mucous cells
2) Parietal cells
3) Cheif cells
4) G cells
1) mucus
2) HCl- and intrinsic factor
3) pepsinogen
4) gastrin
another name for parietal cells?
oxygenic cells (to make sour)
secretory cells are found in ____ pit
gastric pit of stomacj
function of HCl- secretion?
pH adjustment
pepsinogen activation
kills bacteria
HCl- secretion
1) type of transport
2) involves carbonic _____
3) results in exchange of what
4) _____ tide occurs in blood
1) primary active transport
2) involved carbonic anhydrase
3) intracellular HCO3- exchanged for extracellular Cl-
* **bicarbonate raises pH of blood
4) Alkaline tide occurs in blood
what causes alkaline tide during meals?
HCO3- goes to blood and Cl- goes to lumen
what does intrinsic factor do?
1) prevents destruction of vitamin B12
2) aids in vitamin B12 absorption in ileum and colon
* *only gastric secretion required for life
what is the only gastric secretion required for life?
intrinsic factor
what does gastrin do?
stimulates gastric motility and secretions
what does ‘intero’ mean?
intestine (and usually refers to SI)
what does the enterogastric reflex do for intestinal phase of gastric secretion regulation?
excess distention, osmolatity, irritation in intestine > decrease gastric secretion and motility
what does the hormonal inhibition do for intestinal phase of gastric secretion regulation?
acid, fat, protein in SI > GIP, CCK, and secretin (enterogastrones) > decrease gastric secretion and motility
function of pancreas?
1) endocrine= insulin and glucagon
2) exocrine= acinar cells and duct cells
bulk of pancreas is what type of cells?
exocrine
what regulates pancreatic secretions?
1) local/hormonal secretions
- presenceof nutriend-containing chyme and/or acid in SI
2) neural stimlation
- cephalic sense or gastric distension
is local/hormonal or neural stimulation more important for pancreatic secretion?
local/hormonal
role of acinar cells in the panaceas?
fattyacids and AA in SI > CCK > acinar cells > pancreatic enzymes
role of duct cells in the panaceas?
acid in SI > secretin > duct cells > bicarbonate solution
what are the pancreatic enxyme secretions?
1) amylase
2) lipase
3) trypsinogen
4) chymotrypsinogen
5) proelastase
6) carboxypeptidases
7) cholesterolesterase
what are and what does trypsinogen and chymotrypsinogen do?
pre-cursers for enzymes that break down protein once converted to acitve form
*endo= break in middle of chain
what does proelastase enzyme do?
breaks down elastin fibers
what does carboxypeptidases enzyme do?
breaks down ENDS of protein
*exo
what does cholesterolesterase enzyme do?
breaks down cholesterol
pancreatic enzymes are secreted as?
zymogens which means inactive precursors
what converts trpsinogen to trypsin?
enterkinase and trypsin
what converts chymotrypsinogen to chymotrypsin?
trypsin
what is special about enterokinase?
membrane bound; therefore trypsinogen MUST some in contact with it
what is the purpose of trypsin inhibitor?
peptide produced in acinar cells of pancreas that inactivates trypsin WITHIN the pancreas to prevent its digestion of the pancreas
where does carbs digestion happen?
mouth and SI
where does protein digestion start?
stomach
