digestive system Flashcards
tubular gastrointestinal tract
mouth, esophagus, stomach, small intestine, large intestines and rectum
accesory organs
liver, pancreas, gall bladder
salivary glands
four layes tunics of the GI tract
- ) mucusa
- ) submucosa
- ) muscularis
- )Serosa
saliva
99.5% water, 0.5% solutes mucous, lysozyme, urea, amylase, lingual lipase, bicarbonate ions Produced by parotid gland cleanses mouth and teeth dissolves food to begin digestion mucus lubricates food for swallowing lysozyme destroys bacteria amylase: initiates starch digestion lingual lipases is activated in the stomach
digestive processes of the oral cavity
mastication (chewing)
salivary amylase
deglutition (swallowing)
gastric secretions
hydrochloric acid
pepsinogen
pepsin
mucus
hydrochloric acid
. hydrochloric acid: destroys bacteria in food acid pH denatures proteins converts pepsinogen to pepsin inhibits gastrin secretions stimulates secretin and CCK secretions
pepsinogen
inactive form of pepsin (prevents pepsin from digesting proteins in chief cells where it is produced)
pepsin
breaks peptide bonds in proteins –> peptides
mucus
protective barrier, prevents digestion of stomach wall
the hormone gastrin
stimulates parietal cells to secrete HCl chief cells to secrete pepsinogen Function: increased secretion of gastric juice decreased pH of gastric contents indirectly: increased motility of the stomach and gastric emptying
time of stomach emptying
stomach generally empties 2 to 4 hours after a meal
fluids: least time
carbohydrates less time than proteins
fats spend the longest time in the stomach
fatty acids in chyme stimulate CCK release which delays gastric emptying
intrinsic factor
is required for absorption of vitamin B12
is required for erythropoiesis
pernicious anemia:
inadequate production of intrinsic factor leads to insufficient erythropoiesis
movements within the small intestine
segmentation
localized contraction of circular muscle fibers in regions that contain food
mixes chyme with digestive juices
brings food into contact with mucosa for absorption
peristalsis
successive muscle contractions similar to but weaker than those in esophagus and stomach
pushes chyme forward through small intestine
types of glandular tx in the pancreas
endocrine pancreatic islets alpha cells secrete glucagon beta cells secrete insulin exocrine -acini: acinar cells secrete pancreatic juices
liver lobule flow
hepatocytes secrete bile into bile canaliculi which join to form bile ducts
bile
produced by hepatocytes
bile salts role in digestion
Break down
emulsify dietary fats in chyme (aqueous environment)
break down large lipid globules into small droplets (larger surface area for digestion)
Transport lipids to the lymph
“Micelles”
bilirubin
is formed from the breakdown of hemoglobin (from “heme” portion )
liver removes waste bilirubin from the blood and secretes it in bile
intestinal bacteria in the GI tract breakdown bilirubin to form urobilinogen
– urobilin (stercobilin) - gives feces brown colour
functions of the liver
carbohydrate metabolism lipid metabolism protein metabolism detoxification excretion of bilirubin synthesis of bile salts storage: glycogen, vitamins, iron phagocytosis activation of vitamin D
the gallbladder
storage and concentration of bile until bile required by small intestine
the large intestine
digestive process
mechanical:
Haustra – pouches on large intestine =haustral churning
peristalsis
mass peristalsis
defecation reflex
chemical
** bacterial
fermentation of any remaining carbohydrates
bilirubin stercobilin
production of vitamin K and some B vitamins
movements in the large intestine
haustral churning moves contents to next haustra
peristalsis moves contents along length of intestine
mass peristalsis is a strong contraction that pushes contents into sigmoid colon and rectum
flatulence
A factor of these variables:
The bacteria in your colon
Type of food consumed
Motility time
