Quiz, block 2- Digestive system Flashcards
what are the 3 parts of the digestive system?
- gastrointestinal (GI) tract: a long tube that extends from mouth to anus
- mouth: starts at oral (buccal) cavity, pharynx, esophagus, stomach, small intestine, large intestine
- accessory organs include salivary glands, liver, gall bladder, exocrine pancreas.
describe digestion process
breaking down of food into smaller particles and of macrophages in food into smaller, absorbable molecules. accomplished mechanically and by the actions of digestive enzymes, acid and bile.
describe secretion
release from exocrine glands of enzymes, bile, acid, water, ions and mucus into the lumen of the GI tract
describe absorption
movement of the molecules originally in food and drink resulting from digestion from the GI tract lumen across a layer of epithelial cells and into the body’s blood or lymph
describe motility
contractions of the smooth muscles in the GI tract wall that mix the luminal contents and propel them from mouth to anus.
what are the 4 processes in digestive system?
digestion, secretion, absorption, and motility
describe saliva that is secreted by salivary glands.
a. saliva is antibacterial
b. saliva contains mucus for lubricating food particles before swallowing
c. contain AMYLASE, an enzyme that begins polysaccharide digestion
d. dissolve molecules that can then interact with taste buds chemoreceptors that give rise to taste sensations
does GI system absorb everything?
yes, maximum absorption of glucose, water, Na+, etc.
indirectly regulate glucose so it can provide it to others for regulation.
Pharynx and esophagus can:
a. perform digestion
b. provide a pathway from oral cavity to stomach
c. a muscular walls control swallowing
d. b and c
d
upper esophageal sphincter
lower esophageal sphincter (can change in diamete)
stomach functions include:
a. produces the hormone gastrin
b. stores food
c. all of the above
c
what are the exocrine secretions in the stomach?
- hydrochloric acid into the lumen: kill bacteria, dissolves the particulate matter in food, which activate pepsinogen into pepsin.
- pepsin- digest proteins
- mucus- lubricating and protection
- intrinsic factor, for vitamin B12 for absorption in the SI. most vitamin has to be absorbed WHOLE.
what is the only process that the stomach do? not do?
ONLY absorb water, aspirin, and ethanol.
no digestion and absorption of carbs, fats, or proteins in the stomach
what is chyme?
the solution of partially digested protein, polysaccharide fragments, fat droplets, salt, water and other small molecules in the stomach, SI and LI
what are the components of small intestine?
duodenum, jejunum and ileum
what are the general functions of small intestine?
perform most digestion via hydrolytic enzymes and absorption of food molecules
list the 3 functions of small intestine
- small intestine secrete salts, water and mucus into its lumen. Liver/gallbladder secrete bile into its lumen
- beside absorbing monosaccharides, fatty acids, amino acids, it also absorbs vitamin, minerals and water
- SI motility mixes its luminal contents with various secretions, brings the contents into contact with epithelial surface of its wall where things can be absorbed, and slowly propels its contents toward the LI.
everything is absorbed in the SI, especially in the 1/4th of SI.
what are the dual functions of pancreas?
endocrine and exocrine function.
exocrine portion secretes pancreatic juice into the SI, which:
1. contain hco3- for maximally absorbing (necessary to prevent inactivation of pancreatic enzymes)
2. contain enzymes specific for digesting carbs, proteins, fats and nucleic acids
what are the 4 functions of liver?
a. secrete bile salts into the SI
b. secrete bicarbonate in the SI for acid neutralization
c. put some organic waste products and trace metals into the feces via the bile for elimination from the body
d. perform metabolic activities that help body handle carbs, amino acids/proteins, and fatty acids/lipid (including cholesterol).
e. all of the above
e
gallbladder functions:
a. stores and concentrates bile between meals and contract to secrete it into the duodenum
what are two components get dumped from the gallbladder and pancreas?
a. pepsin and gastrin
b. bile and pepsin
c. bile and pancreatic juice
d. hormones and salt
c: bile and pancreatic juice
functions of large intestine:
- secretes mucus into lumen for lubrication by goblet cells
- concentrates and temporarily stores undigested matter
- absorbs water and salt from it
- mixes and propel its contents
- don’t secrete many hormones
what are the 3 layers make up the innermost layer of GI wall?
mucosa.
1. mucosal epithelium- the epithelial layer plus
2. lamina propria: a layer of connective tissue containing blood, lymphatic vessels and nerve fibers, plus
3. muscularis mucosa- a thin layer of smooth muscle
what is the 2nd layer next to mucosa in the GI wall?
submucosa. a connective tissue layer just beneath the mucosa that contains a network of neurons (submucosal plexus), some neurons of which project to the mucosa, plus blood and lymphatic vessels
what’s the 3rd layer in the GI wall?
muscularis externa
composed to smooth muscle (plus a network of neurons between them- myenteric plexus) that contract to provide mixing and propulsion of the GI contents
what are the 2 muscle layers in the muscularis exerna?
- circular muscle: fibers of which encircle the tube and thus narrow its lumen diameter when they contract for mixing
- longitudinal muscle: fibers of which they run along the tube and thus shorten the tube when they contract.
what are the connections between the plexuses in GI wall?
neurons of myenteric plexus are innervated by neurons from the autonomic nervous system, and are connected with neurons of the submucosal plexus.
what is the 4th layer in the GI wall?
serosa.
- the think layer of CT forming outer surface of GI tube
a. outer tunic in the esophagus is called adventitia, rather than serosa.
b. in the abdominal cavity, sheets of CT connect the serosa to the abdominal wall.
what are the projects called that extend from the luminal surface of the SI into its lumen?
villi
what are the smaller projections sticking out of villi? their functions?
microvilli, aka brush border.
they increase the SI surface area.
what is the function of lacteal locating in the center of each villus?
most absorbed fat enters the lymhp via the lacteal
what is the route that the SI, LI, pancreas and part of stomach that drain into instead of the inferior vena cava?
they drain into the hepatic portal vein
what do products of digestion has to undergo before entering the general circulation?
they are absorbed into the SI blood and are processed (metabolized, detoxified, stored, etc.) by liver enzymes before entering the general circulation.
what is peritoneum in the digestive system?
a serous membrane, similar to the pleural and pericardial membranes, that covers the external surface of many digestive organs and also lines the inner surface of abdominopelvic cavity wall.
what does the peritoenum encapsulate?
a peritoneal cavity that is filled with a thin layer of lubricating serous fluid.
what is the function of mesentery?
a fused, double layer of peritoneal membrane that extends from the body wall to some digestive organs. Mesentery hold organs in place and provides routes for blood vessels, lymphs, and nerves to reach the organs.
what is the enzyme in the mouth called?
amylase in saliva, that provides a small amount of starch digestion, but is inactivated by acid in the stomach.
what is the amylase in pancreatic juice serve?
it is secreted into the small intestine to perform carb digestion.
what are other enzymes embedded in the luminal membranes of SI mucosal epithelial cells?
lactase, sucrase, maltase or alpha-dextrinase. they protrude into the SI lumen when they can be contacted by chyme.
what do the brush border enzymes and pancreatic amylase result in?
perform water-soluble monosaccharide, that are absorbed across the SI mucosal epithelium into blood capillaries, then moved to the liver via the hepatic portal vein.
in carb digestion, how is Na+ gradient set up using secondary active transport?
Na+/K+ pump using ATP, pump Na+ out of cells to create a high con outside and low inside the cell
in carb, how does Na+ get transported inside the cell from the lumen?
Na+ enter the cells by bringing glucose with it through SGLT-1
how does glucose get transported into the capillaries once entered the cell via Na+?
glucose undergo facilitate diffusion via the GLUT2 (no energy expended).
2. glucose undergo simple diffusion into the capillaries
what GLUT brings fructose into the interstitium?
fructose is absorbed into SI mucosa epithelial cells via the membrane-bound carrier protein called GLUT-5 that does not require ATP.
how does glucose and galactose enter the SI mucosal epithelial cells?
via secondary active transport that uses a Na+-glucose. Want to expend energy to get all of it in.
what does the stomach secrete that involved in protein digestion?
stomach secrete pepsin and is secreted into the stomach lumen. breaks proteins into peptide fragments.
what are the 2 pancreatic enzymes that also produce peptide fragments?
trypsin and chymotrypsin, acting on small intestine.
what are the pancreatic enzymes that further break down peptide fragments into the free amino acids?
carboxypeptidase, aminopeptidases, or dipeptidase that are embedded in SI muscosal epithelial cell membranes.
how do free amino acids enter epithelial cells?
sodium co-transport
what is one way that a chain of 2 or 3 amino acids move into the cells?
by secondary active transport coupled to H+ rather than Na+. then these chains are hydrolyzed into free amino acids within the cells. this required ATP
what are the mode of transports of amino acids from the cells into the interstitial fluid, and then into the blood? require ATP?
- enter the interstitial fluid by facilitated diffusion involving many carrier molecules.
- enter the blood by diffusion through capillary pores.
- don’t required ATP
T/F Intact proteins can be absorbed without being digested first
F. very small amounts of intact proteins can be absorbed without being digested. they are engulfed via endocytosis.
what pancreatic enzyme is secreted by the pancreas into the small intestine involved in fat digestion?
pancreatic enzyme, lipase, involved in lipid digestion
is ingested lipids water or lipid soluble? how this limit the action of lipase which is water soluble?
Ingested lipids are not water soluble, thus form large lipid droplets.
lipase is water soluble, so it its digestive action occur ony at the surface of the droplets
what is emulsification?
breaking each droplet into smaller droplets, which increase the surface area accessible to lipase.
what are two mechanisms that are achieved by emulsification?
- mechanical disruption due to churning activity in the stomach
- emulsifying agents contained in the bile: bile salts and phospholipid lecithin.
what are special about bile salt or lecithin?
they have nonpolar part that is soluble in fat and thus dissolves in the surface layer of a fat droplet, and
-a POLAR part, which is water soluble and is left exposed at the water surface of small fat droplet where it repels other lipid droplets.
what’s the difference between micelles and emulsified small fat droplets?
micelles- are much smaller, consists of fatty acids, monoglycerides, bile salts and phospholipids with POLAR ends facing the surface of micelle.
can micelles diffuse through the lipid bilayer? how?
no. micelles by breaking down and reforming can release fatty acid and monoglycerides, which they can diffuse through.
what other molecules resemble micelles but much smaller that are pinched off the ER and move through the golgi and then get exocytosed?
chylomicrons!
what barriers prevent chylomicrons from entering capillaries? what does it pass through instead?
basement membranes associated with blood capillaries prevent chylomicrons from entering capillaries; insteady chylomicrons pass into lacteals.
is there energy expenditure in fat absorption via diffusion?
a. yes
b. no
no
what are the fat-soluble vitamins?
A,D,E,K (follow the same fat absorption pathway)
what are the water-soluble vitamins?
vit B and C
absorbed by diffusion and some by carrier-mediated transport
vitamin B-12 (large charged molecule that is not easily absorbable)
what does B-12 has to be combined with in order to be absorbed?
B-12 binds to intrinsic factor in the ileum, where B-12 is absorbed by endocytosis.
**EXCEPTION: this occurs at 2/3 of the small intestine.
what is B-12 required for? what happened when it’s deficient?
B-12 is required for red blood cell production.
-its deficiency result in pernicious anemia (not enough rbc/hemoglobin)
what is the main mechanism that water occurs as?
mainly in osmosis. it’s not digested. small amounts of water are absorbed in the stomach.
*about 80% of ingested and secreted water get absorbed in the SI.
what are 2 mechanisms that allow Na+ to enter the epithelial cells to also bring other ions into the cells as well?
Na+ move down its electrochemical gradient from the chyme into epithelial cells by moving through ION CHANNELS or by CO-TRANSPORT mechs that also bring amino acids, glucose, galactose, or chloride ions into the cells.
do potassium, magnesium, calcium, zinc, iodide and other minerals absorb actively or passively?
active via various mechs.
esophagus function is to carry food from the pharynx to the stomach. however, it ____ secrete digestive enzymes.
does not secrete digestive enzymes into its own lumen
what are the important methods by which the ECF (plasma) concentration of calcium is increased at times when plasma calcium is below its set point?
- parathyroid hormone (PTH) acts on bone tissue to increase the resorption (breakdown) of bone
- PTH acts on the kidney to increase the tubular reabsorption of calcium
- 1,25 dihyroxycholecalciferol (1,25 dihydroxyvitamin D) acts on intestine to increase the absorption of dietary calcium
Liver contains ___ (reticuloendothelial) cells that cleanse the blood of bacteria as blood flows through the liver.
Kupffer
Sprue is a disorder of what organ?
small intestine
which vitamin becomes dissolved in a micelle and, later, in a chylomicron, and is then absorbed across the intestinal mucosal epithelium into a lacteal rather than into a blood capillary?
vitamin A
describe digestion!
the use of muscle contraction and of enzymes, bile, and acid to break the large particles and macrophages in food down into smaller particles and smaller molecules.
what are some of the absorbable products of the digestion of dietary carbohydrates?
galactose molecules
If water diffuses out of a hypothalamic osmoreceptor, causing the osmoreceptor to shrink, what is the result?
the osmoreceptor causes the hormone ADH to be secreted
what is the mechanism by which “loop” diuretics such as furosemide and bumetanide increase the rate of urine volume output?
they inhibit the Na-Cl-K co-transporter located in the thick ascending limb of the loop of Henle
most if not all aminopeptidase is ___ and is involved in the digestion of __.
embedded in the plasma membrane of mucosal epithelium cells of the small intestine; proteins
ANP functions directly to:
decrease the kidney’s tubular reabsorption of sodium
ADH increases the permeability of the wall of the late DT and CD to ___; therefore, an increase in the rate at which ADH is secreted by the pituitary will ___.
water; decrease the rate at which water is excreted in the urine
giving a drug that inhibits ACE enzyme would be expected to ___ the person’s rate of renin secretion.
increase
