Gastrointestinal System (Functions) Flashcards
Digestion
breaking down of larger food particles into molecules small enough to enter the body cells
ingestion
taking foods and liquids into the mouth
secretion
water, acid, buffers and enzymes secreted into the lumen
lumen
interior space
mixing and propulsion
alternating contractions and relaxations of smooth muscle mixes food
mechanical digestion
chewing/grinding food (mastication)
churning of food in the stomach and small intestine
consists of various movements that aid in chemical digestion; food must be pulverized by teeth
chemical digestion
enzymes break down food into smaller molecules
series of catbolic reactions that break down the large carbohydrate, lipd, and protein molecules that we eat, into smaller molecules usable by body cells
absorption
entrance of ingesed materials into epithelial cells that line the lumen of the GI tract
defecation
waste leaves the body; feces
teeth
cut, tear, and pulverize food
reduce to smaller particles for swallowing
extrinsic muscle (tongue)
move tongue from side to side and in and out
food (bolus) maneuvered for mastication and swallowing
intrinsic muscle (tongue)
alter shape of the tongue
swallowing and speech
taste buds
receptors for food stimulus
glands
secrete lingual lipase
breaks down triglycerides into fatty acids
major salivary glands (parotid, submandiable, sublingual
secrete saliva in the lining of the mouth and pharynx
softens moistens and dissolves food
cleanses mouth and teeth
saliva amylase splits polysaccharides into smaller particles
pharynx
pharngeal stage of swallowing (deglutition)
moves bolus from oropharynx to laryngopharynx and into the esophagus
closes air passage ways
esophagus
esophageal stage of swallowing: forces bolus down the esophagus
relaxation of upper and lower esophageal sphincter: permits entry of bolus from laryngopharynx into esophagus and eventually into the stomach
secretion of mucus lubricates esophagus for smooth passage of bolus
stomach
the primary digestive organ
mucosa
chief cells: secretes pepsinongen (breaks peptide bonds in protein
secretes gastric lipase (splits short chain triglycerides into fatty acids and monoglycerides
parietal cells
secretes hydrochloric acid (kills microbes in food, modifies the molecular structure of protein, inhibits secretion of gastrin)
secretes intrinsic factor (needed for absorption of vitamin B12
muscosa surface cells
secretes mucous (forms a protective barrier that prevents digestion of the stomach wall)
enteroendocrine cells
secretes gastrine (stimulates paretal cells to secrete HCL and chief cells to secrete pepsinogen, contracts lower esphageal sphincter, increase motility of the stomach, relaxes pyloric sphincter)
muscularis
mixing waves (masecerate food and mix with gastric juices to form chyme) peristalisis (froces chyme through pyloric sphincter)
pyloric sphincter
opens to permit passage of chyme to duodenum
pancreas
secondary organ aiding chemical digestion in the small intestine
pancreatic juice
buffers acidic gastric juices into chyme
stops the action of pepsin from the stomach
creates the proper pH balance for action of digestive enzymes in the small intestine
liver
heaviest gland in the body
second organ aiding in chemical digestion
liver (functions)
carbohydrate metabolism - maintains normal blood glucose level lipid metabolism protein metabolism removal of drugs and hormones exretion of bilirubin strorage of some vitamins and minerals avtivation of vitamin D
gallbladder
secondary organ aiding chemical digestion
store and concentrate bile
small intestine
major site of digestion and absorption
intestinal glands
secrete intestinal juices
duodeneal gland
secrete alkaline fluid to buffer stomach acids and mucous for protection and lubrication
microvilli
microscopic membrane covered projections of epithelial cells
increase surface are for absorption and digestion
villi
finger-like projections
sites for digestion of food
increase the surface area for digestion and absorption
circular folds
folds of the mucosa and submucosa that increase surface area for absorption and digestion
muscularis segmentation
alternationg contractions of circular fibers that produce segmentation/resegmentation of the small intestine
mixes chyme with digestive juices
chyme
semifluid mixture of parly digestive food and digestive secretions found in the stomach and small instestine during digestion of a meal
peristalsis
mild waves of contractions and relaxation of circular and longitudinal muscles
moves chyme foward through the samll intestine and towards the ileocecal sphincter
mucosa (large intestine)
secretes muscus to lubricate colon and protec mucosa
absorbs water and other soluble compounds to maintain water balance
solidifies feces
absorbs vitamins and some ions
lumen (large intestine)
bacterial activiy helps break down undigestied carbohydrates, proteins and amino acids into products that can be expelled in feces or absorbed
synthesizes certain B vitamins and vitamin K
muscularis (large intestine)
moves contents from the haustra to hasutra (pouch) by musular contraction
moves contents along length of the colon by contractions of cucular and longitudinal muscles
mass peristalsis forces contents into the sigmoid colon and rectum
defecation reflex eliminates feces by contractions in sigmoid colon and rectum
