Digestion 2 Flashcards
what are the organs of the lower GI tract
small intestine to anus
what are the two main functions of the lower GI tract
digest and absorb
eliminate indigestible and unabsorbed material
what does the small intestine absorb
most nutrients
most water
electrolytes
vitamins
what is the function of the duodenum
receives chyme from stomach
chemical digestion and absorption
gets accessory gland secretions from liver, gallbladder, and pancreas
what are the three structures in the small intestine that increase surface area
circular folds, villi, and microvilli
what do the circular folds of the small intestine do
folds made of mucosa and submucosa
increase surface area to increase nutrient absorption
slow movement of chyme
most found in duodenum and jejunum, some in the ileum
what do the villi of the small intestine do
simple columnar epithelium and lamina propria projections
increase surface area for absorption and secretion
most found in jejunum
have vessels for nutrient absorption and lacteals
what do lacteals do
lymphatic capillaries that absorb lipid and lipid soluble vitamins that are too large to be absorbed by the blood capillaries
what do the microvilli of the small intestine do
extensions of simple columnar cells
make up brush boarder
increase surface area
secrete brush boarder enzymes which complete chemical digestion of most nutrients
what are intestinal glands and what do they secrete
invaginations of mucosa between villi
secrete intestinal juice
what are paneth cells and what do they do
found in the base of intestinal crypts
secrete lysozyme and other antimicrobial agents that help the innate immune system
what does the duodenal submucosal gland do
produces viscous alkaline mucus that protects the duodenum from chyme
what are the three functions of the smooth muscle of the small intestine
mixes chyme with gland secretions
segmentation (back and forward motion)
propels contents through small intestine by peristalsis
what are the two main functions of the small intestine
chemical digestion
absorption of smaller, simpler molecules
explain the early intestinal phase
segmentation (mixing)
contractions initiated by pacemaker cells
more contractions/minute in duodenum, less in the ileum
slows everything down as it goes through to allow for nutrient absorption
frequency of contractions usually won’t change but the force can depending on the enteric nervous system
explain the late intestinal phase
peristalsis (moving) initiated by motilin hormone released by the duodenum
peristalsis contractions (migrating motility complex) move everything to large intestine
what does the gastroileal reflex
causes the ileum to contract
ileocecal spinchter relaxes and cecum relaxes
contents move from ileum to cecum
this all happens in response to food entering stomach
what are the three accessory digestive organs that release secretions into the duodenum
liver
gallbladder
pancreas
what is bile
secretion produced by the liver
stored, concentrated, and released by gallbladder
contains: bicarbonate ions, salts, pigments, cholesterol, lecithin
what is the biliary apparatus
network of ducts draining left and right lobes of liver drain into hepatic ducts
hepatic ducts merge to form single common hepatic duct
common hepatic duct merges with cystic duct from gallbladder to form common bile duct
what does the accessory pancreatic duct do
penetrates duodenal wall at minor duodenal papilla to release small amounts of pancreatic juice
what does the hepatopancreatic ampulla do
swelling on posterior duodenal wall where common bile duct and main pancreatic duct pierce duodenal wall
what does the major duodenal papilla do
projection within duodenum where duct penetrates wall
bile and pancreatic juice enters here
what does the hepatopancreatic sphincter do
regulates movement of bile and pancreatic juice into duodenum
what does the falciform ligament do
separates right and left lobes of liver
what is the round ligament a remnant of
remnant of fetal umbilical vein found at the bottom of the falciform ligament