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
what is the ligament venosum a remnant of
remnant of ductus venous in embryo
what is the porta hepatis
where blood, lymph vessels, bile ducs, and nerves enter and leave liver
what are hepatic lobules
where the liver’s connective tissue capsule branches throughout the organ to form septa (walls) to partition the liver
(structural and functional units of liver)
made of hepatocytes (liver cells)
what are portal triads
found at the periphery of each hepatic lobule
made of bile ductule and microscopic branches of both hepatic portal vein and hepatic artery
what does the central (hepatic) vein do
found at the center of each hepatic lobule
drains the lobule’s blood flow
all central veins merge to form right and left hepatic veins which will empty into the inferior vena cava
what does the hepatic artery do
transports oxygenated blood to liver
delivers 25% of the liver’s blood
what does the hepatic portal vein do
transports deoxygenated and nutrient rich blood from capillary beds of GI tracts, spleen, and pancreas
delivers 75% of the liver’s blood
what are stellate (Kupffer) cells and what do they do
fixed macrophages found in the liver
engage in phagocytosis of potentially harmful substances
what is cirrhosis of the liver
hepatocytes are replaced by fibrous scar tissue
can compress blood vessels (hepatic portal hypertension)
causes: hepatitis B/C, alcoholism, injury
what are gallstones
condensations of cholesterol or calcium and bile salts
causes cholecystitis (inflammation of gallbladder)
may need to be removed (cholecystectomy)
what are the two main functions of the pancreas
produces and secretes insulin and glucagon (endocrine)
produces pancreatic juice to assist with digestive activities (exocrine)
what do acinar cells of the pancreas do
arranged in saclike acini
produce and release digestive enzymes
what is pancreatic juice
formed by acinar and pancreatic duct cells
alkaline fluid made of mostly water, bicarbonate, and digestive enzymes (amylase, lipase)
what is cholecystokinin and what does it do
hormone released from small intestine in response to fatty chyme
causes gallbladder to contract and release bile
causes pancreas to release pancreatic juice
relaxes smooth muscle within hepatopancreatic ampulla to allow bile and pancreatic juice into small intestine
inhibits stomach motility and release of gastric secretions
what is secretin and what does it do
released from small intestine if chyme gets too acidic
causes release of alkaline solution containing bicarbonate to neutralize acidic chyme
inhibits gastric sections and motility
what are the three functions of the large intestine
absorbs a little amount of water, electrolytes, and some vitamins
compacts watery chyme into feces
stores feces until eliminated
define peritonitis
infection of the peritoneal cavity due to something like a ruptured appendix
what are rectal valves and what do they do
thick, transverse folds of the rectum
ensure fecal mater is retained during the passing of gas
what are the levator ani muscles
pelvic floor muscles where the anal canal passes through
what are anal columns
longitudinal ridges in the anal canal
what are anal sinuses and what do they do
depressions between anal columns in anal canal
release mucous to lubricates canal during defecation
what are teniae coli and what do they do
thin, longitudinal bundles of smooth muscle
bunch large intestine into sacs called haustra
what are omental appendices
lobules of fat hanging off external surface of haustra
what is haustral churning
haustrum fills until its distended
distension stimulates reflex contractions in the muscularis
what are mass movements and what do they do
powerful, peristaltic-like contractions that involve teniae coli
proper fecal material towards the rectum
what are the two major reflexes of the nervous system that are associated with motility in the large intestine
gastrocolic and defecation reflex
what is the gastrocolic reflex and what does it do
initiated by stomach distension
causes a mass movement in an attempt to clear your intestines for incoming food
what is the defecation reflex and what does it do
filling of rectum initiates urge to defecate
signals go to spinal cord which increase parasympathetic output to sigmoid and rectum
decreases output to internal anal sphincter
what are the intestinal microbiota and what do they do
normal bacterial flora in large intestine
chemically breakdown complex carbs, proteins, and lipids
breakdown by bacteria releases gases and produces vitamins B and K
final product is feces
what is Crohn disease
a type of inflammatory bowel disease
intermittent and relapsing episodes of cramping and diarrhea throughout the whole colon
typically in young adults
what is ulcerative colitis
a type of inflammatory bowel disease
intermittent and relapsing episodes of cramping and diarrhea of large intestine
what is irritable bowel syndrome
abnormal function of colon
what are the three things used to test for colorectal cancer
fecal occult blood test
sigmoidoscopy
colonoscopy
what are hemorrhoids
dilated and inflamed veins around rectum and anus
what are anal fissures
oval shaped tears of the anus that often bleed
what is sorbitol
sugar substitute that acts as a laxative by preventing reabsorption of water within the intestine
where does most chemical digestion and absorption happen
small intestine
what do enteroendocrine cells do
release hormones like cholecystokinin (CCK) and secretin
what are the three functions of bile
1.) neutralizes acidic chyme through bicarbonate ions
2.) emulsifies lipids by bile salts and lecithin
3.) eliminates bilirubin