Absorption Flashcards
nervous innervation of absorption occurs via the ____
Meissner’s Plexus (Submucosal plexus)
function of Meissner’s Plexus (submucosal plexus)
allow for secretion of digestive enzymes required for absorption of nutrients
innervations of mouth
CN V, VII, IX, X
primary function of mouth
mechanical breakdown (mastication/chewing)
surface area of food in the mouth will be ____
increased
what nutrients are digested in the mouth?
carbohydrates
fats
what is the function of amylase?
digests starch (amylose) to maltose in the mouth
what is the function of salivary lipase?
digests triacylglycerols to glycerol + FAs in the mouth
what foods require chewing for digestion?
vegetables (plants)
what are the 3 phases of swallowing?
voluntary
pharyngeal
esophageal
voluntary stage of swallowing
starts the swallowing process
pharyngeal phase of swallowing
- close off trachea: inhibit breathing and approximate vocal cords
- upper sphincter relaxes, peristalsis begins: pass food further down esophagus
esophageal phase of swallowing
final movement of food before stomach
patients with CN injury will have an extremely hard time completing what phase of swallowing?
pharyngeal
(IX + X swallowing reflex)
the upper 1/3 of the esophagus contains ____ muscle and has a ____ contraction
striated skeletal
strong
the lower 2/3 of the esophagus contains ____ muscle and has a ____ contraction
smooth
weaker
what are the 2 major types of peristalsis?
primary & secondary
primary peristalsis
- initiated by medulla
- affects striated muscle (upper 1/3)
secondary peristalsis
- initiated by enteric system
- affects smooth muscle (lower 2/3 & upper esophageal sphincter)
the general anatomy of the stomach allows for ____ movements by the ____
mixing movements by the high pressure antral pump
what nutrients are digested in the stomach?
proteins
fats
function of pepsin
converts proteins to peptides in the stomach (active at pH2)
function of gastric lipase
digests triacylglycerols to glycerol + FAs in the stomach
directly after a meal, the volume of food in the stomach ____
increases
what stimulates the myenteric reflex?
- increased gastric volume reduces available space for additional food
- outward pressure of food stimulates myenteric reflex
what is the function of the myenteric reflex?
- increase rate of emptying in the stomach
- release gastrin
the common bile duct enters the ____ of the small intestine through the ____
duododenum
sphincter of Oddi
function of sphincter of Oddi
allows both bile & pancreatic enzymes into duodenum
when fatty chyme and amino acids from the stomach enter the duodenum, the hormone ____ is released
cholecystokinin (CCK)
actions of cholecystokinin
- relax (opens) sphincter of Oddi
- cause release of pancreatic enzymes
- contract gallbladder to release bile, necessary for action of pancreatic lipase
- Decrease gastric emptying
- cause brain to feel satiated
nutrients absorbed in the jejunum
proteins, carbohydrates, lipids
proteins enter the portal blood as ____
amino acids
carbohydrates enter the portal blood as ____
monosaccharides
fats enter the ____ as ____
lymph
chylomicrons containing TAGs
function of dipeptidase & tripeptidase
proteins in jejunum -> AAs in portal blood
function of disaccharidases
carbohydrates in jejunum -> monosaccharides in portal blood
surface area of the jejunum is increased by ____
villi and microvilli
what happens to blood flow to the villi of the small intestine when food arrives?
increases (8x)
what happens when blood flow to the villi of the small intestine is increased?
increased absorption and contraction of smooth muscle at appropriate rate
what 2 factors could increase blood flow to villi of the small intestine?
- arrival of food
- increased GI secretions
decrease in blood flow to the GI tract is usually associated with ____
sympathetic stimulation
what is ischemia?
reduced blood flow to an area of the body
what part of the GI tract is particularly sensitive to ischemia?
villi of SI
what is the effect of ischemia on the GI tract?
decreased rate of absorption in that area of the gut
where is vitamin B12 absorbed, and what is required for its absorption?
ileum & ileocecal valve
intrinsic factor
function of ileocecal valve
- prevent backflow from LI to SI
- promote emptying into colon when stimulated (backup = pathOLogy)
primary function of large intestine
absorption of water & electrolytes
(some vitamins produced by bacteria & absorbed: vitamin K, biotin)
what is the surface specialization of the large intestine?
crypts of Lieberkuhn
(no villi)
mucus secretion mostly occurs in the ____
large intestine
what is the goal of mass movements?
push food through the LI, from transverse colon to rectum
what reflexes initiate mass movements?
gastrocolic
duodenocolic
(ENS and ANS both involved)
function of mixing movements in the Large intestine?
mix chyme -> helps with electrolyte absorption
what are the 3 levels of control of the rectum & anus?
- intrinsic
- spinal cord reflex
- high center (medulla)
intrinsic control of rectum & anus
enteric nervous system which is activated by presence of feces entering rectum
spinal cord innervation of rectum & anus
S2, S3, S4
control of rectum & anus by medulla
efferent signals from brain down spinal cord to local level of innervation
internal anal sphincter is under ____ control, while the external anal sphincter is under ____ control
autonomic
voluntary
