Flashcards in Digestion Deck (116):
used to break nutrients down into forms that can be used by the body for cell metabolism
where does the energy lie for the cells
within the bonds
what are the digestive processes? (7)
-alternating of smooth muscle contraction and relaxation
involuntary smooth muscle contraction
chewing and mixing food
rhythmic local contractions of the intestine
food broken down to monomers
release of water, acids, enzymes, and salt
end products from GI tract into blood or lymph
elimination of indigestible substances
what are the 2 main groups of the digestive system?
-alimentary canal//GI tract
What occurs in the mouth? (4)
1.analysis of material before swallowing
4.limited digestion by saliva
in the mouth there is limited ______ regulation
saliva contains (7)
breaks down polysaccharides into smaller fragments
salivary lipase (2)
-breaks down triglycerides
-only works at low pH (acidic) [stomach, not the mouth]
forms thick mucus when water is added
secretion of saliva is controlled by ____
autonomic nervous system (both sympathetic and parasympathetic)
the salivatory nuclei of the ___ ___ sends action potentials down the ____ and ____ nerves to stimulate salivation
medulla oblongata; facial and glossopharyngeal
is there absorption in the oral cavity?
very little in the mouth, some lipid soluble substances
oral phase of saliva release? what does it result in? (2)
-chemoreceptors (stimulated by acidic substances)
-activation of the parasympathetic nervous system->saliva released
cephalic phase of saliva release? what does it result in?
thought, sight, smell of food
-activation of the parasympathetic nervous system->saliva released
what happens during sympathetic stimulation during saliva release? (2)
-a smaller production of viscous saliva with little enzyme content
-due to constriction of blood vessels feeding the glands
what are the functions of the stomach? (5)
-primarily a food storage
-mechanically breaks up food particles
-liquefies the food to produce chyme
-limited digestion of protein and lipids
-helps sterilize food
what type of tissue lines the stomach?
simple columnar epithelium that is a secretory sheet
the epithelium of the stomach is organized into?
what are they lined with?
at the base?
-gastric pits which are shallow depressions
-mucous epithelium (release mucin)
what are the cells of the gastric glands? (4)
mucous neck cells of gastric glands (2)
-located at the top of the gland
parietal cells of gastric glands (2)
-produce intrinsic factors that binds to B12-> absorbed by small intestine
caused by a drop in B12 production which is need to produce red blood cells
what is the purpose of HCl? (5)
-break down plant walls
-converts ferric(fe3) to ferrous (fe2)
how is acid (HCl) produced in the stomach? (4)
1. carbon dioxide diffuses into cell from the blood
2. carbonic anhydrase produces H and HCO3
3. H/K ATPase pump out H in exchange for K
4. Cl shift into cell as HCO3 goes into the blood
chief cells of gastric glands (2)
-produce rennin and gastric lipase in infants
is converted to pepsin by HCl
digests proteins to shorter peptide chains
g cells of gastric gland
what does gastrin stimulate?
the secretion of parietal (acid) and chief (pepsin) cells
-produced by D cells
-weekly inhibits gastrin release
-released when stomach is very acidic
regenerative cells (2)
-at the base of the gland
gastric secretion contains (4)
mucous, acid, enzymes, and hormones
the regulation of gastric secretion is controlled by what?
nervous and hormonal mechanisms
what are the 3 phases of gastric secretion?
cephalic phase of gastric secretion (4)
- directed by ANS
-occurs before food enters the stomach
-triggered by sight, smell, or thought of food
-PNS nerve fibers travel down vagus nerve
gastric phase of gastric secretion (2)
-occurs once food reaches the stomach
-important stimulus is distention, peptides and low acidity
when stimulated these make:
gastrin (G cells)
how are gastric effects similar to positive feedback loop?
gastrin stimulates HCl from parietal cells, which causes more gastrin to be released
how are gastric effects similar to negative feedback loop?
when gastrin is released in which the pH drops below 2 somatostatin is released
intestinal phase of gastric secretion (2)
-starts when chyme enters the small intestine
-main function is to control the entrance of acidic chyme into duodenum
what hormones are involved in the intestinal phase of gastric secretion? (4)
-gastric inhibitory polypeptide (GIP)
-released from the small intestine if pH of chyme is less than 3
-inhibits gastric secretion
CCK and GIP (2)
-released from small intestine in the presence of fatty acids and lipids
-inhibit gastric secretion
site of digestion and almost all absorption
3 regions of the small intestine
gastric emptying is primarily accomplished via?
opening and closing of pyloric sphincter
what stimulates opening of the pyloric sphincter? (2)
-stretch of the stomach
what stimulates closing of the pyloric sphincter? (3)
-stretch of the small intestine
-chemical receptors for acid, amino acids, and lipids
-secretion of CCK, GIP, and secretin
-smallest region of the small intestine
-received pancreatic juice, bile, and stomach contents
common bile duct
common entry point from gall bladder and pancreas
attaches the stomach to the intestine
jejunum vs illeum
jejunum : more digestion than absorption
illeum: more absorption than digestion
what features are added to increase surface area of the small intestine? (2)
plica circulate (2)
-deep folds of the inner surface
-shape causes chyme to spiral
fingerlike projections of the mucosal surface of the intestine
microvilli=____where are they located?
-on villi and become progresssively smaller in more distal regions of the small intestine
cells of the villi? what are they called?
simple columnar cells; absorptive cells
what are the cells found in the intestinal crypts (glands)? (4)
what are the cells of the submucosal layer of the small intestine? (3)
dense lymphoid nodules
the pancreas has 2 ducts that it can use to empty into the duodenum, what are they?
-pancreatic duct which fuses with gallbladder to form common bile duct (larger)
pancreas has an endocrine portion known as ______, and a exocrine portion that is organized into _____.
islets of langerhan; acini (small clusters of glandular epithelial cells)
islets of langerhan:
beta cells release _____
alpha cells release ______
composition of the pancreatic juice (3)
-electrolytes (sodium bicarbonate)
what are the 4 enzymes in pancreatic juice?
break peptide bonds
trypsinogen is activated by ______, a brush border enzyme. it is then converted to _______.
pancreatic lipase (2)
-cleaves 2 fas leaving 1 fas and a monoglyceride
RNA and DNA enzyme
pancreatic secretion is primarily under _____ control. What 2 hormones are released to release pancreatic enzymes and juices?
hormonal;secretin and CCK
one of the functions of the liver is to?
synthesize and secrete bile
-produced by the liver
-is a yellow-green alkaline solution
-role in digestion is as fat emulsifer
-stored in the gallbladder
what is the composition of bile? (5)
bile salts (5)
-contain polar and nonpolar ends
-act as detergents for lipids
-recycled by enterohepatic circulation
bile pigments (2)
-most is bilirubin (waste product of heme)
-give feces its brown color (break down of urobilinogen)
what are the 4 regions of the large intestine?
what are the functions of the large intestine? (3)
-absorption of lots of water
-elimination of feces
indigestible carbs produce _____
what are some examples of chemical digestion by bacteria observed in the large intestine? (3)
-fermentation of indigestible carbs
-cellulose digested to glucose
-synthesis of B vitamins
the enzymatic breakdown of polymers into monomers is achieved by ____
-a glucose polymer
-not much in diet
monosaccharides (3). What is the significance of this monomers when it comes to digestion?
-they can quickly be absorbed
glucose + galactose
pancreatic amylase (2)
-takes about 10 minutes to work in SI
-produce maltose and 3 to 9 glucose chains
dextrinase and glucoamylase
-works on small glucose polymers
-yields maltose and glucose
galatose converts to _______ immediately once it enters the small intestine
glucose and galatose are transported ______ by _____ dependent transporters. While fructose is transported by ____ . All monosaccharides are transported paracellularly via _______
facilitated diffusion; solvent drag
STOMACH: During protein digestion, pepsinogen->pepsin. It attacks bonds involving ____ and _____.
tyrosine and phenylalanine
carboxypeptidase (CPA) is what type of enzyme (2)
SMALL INTESTINE: Trypsin and chymotrypsin
reduce the sizes of the polypeptide by attacking internal bonds
CPA removes the _____end of the amino acid, while aminopeptidase/dipeptidase removes the ____ end of the amino acid.
carboxyl group; amine group
-both work best in neutral pH
infants absorb proteins via _____
protein digestion occurs in the ?
lipid digestion occurs in the ?
stomach and small intestine
ALL in small intestine
micelle made up of (4)
fatty acids + monoglycerides + phospholipid (from bile) + bile salts
once inside the cell, the fatty acids and monoglycerides are resynthesized into _______. These then combine with cholesterol and ______ to make up ______.
triglycerides; phospholipid; lipoprotein
lipoprotein formed in the cell
where do most chylomicrons go?
lacteals or left overs are taken to the liver