Human Physiology Ch 18
function of GI tract
transfer nutrients, water, and electrolytes from ingested food into bodys internal environment
four functions of digestive system
movement of food through body
chemical digestion is done by what?
swallowing is initiated by what?
involuntarily when bolus is pushed to back of mouth
what is vomitting?
what is the pH of the stomach
ph of 2
what pushes food through esophagus?
what does the esophogus secrete?
what is the bottom sphincter of the esophagus?
function of the stomach
store, mix, and prepare food for digestion
4 stomach secretions
sphincter at bottom of stomach
what is chyme?
liqufied mixture of food
what does the pyloric sphincter do?
controls the release of chyme into small intestine
what is pepsin used for?
what does salivary amylase do?
which has a bigger influence on saliva secretion? sympathetics or parasympathetics?
what do parietal cells secrete into stomach?
what do chief cells secrete into stomach?
what is pepsinogen converted into?
stomach factor that plays greatest role in gastric emptying
amount of chyme in stomach
what does fat do to gastric emptying?
what does acid do to gastric emptying?
delays it until it is neutralized
if small intestine is distended too much what happens?
gastric emptying is inhibited
how does SI handle stomach acid?
neutralizes it with bicarbonate
what is the site of most diegstion and absorption of nutrients?
three segments of small intestine
what is segmentation and where does it occur?
squeezing that mixes chyme and exposes it to more enzymes
what purpose do villi and microvilli serve in SI?
increase surface area to maximize absorption
where are water soluble particles absorbed? (proteins and carbs)
in capillaries in villi
where are fat soluble particles absorbed? (fats lipids)
where are enzymes in the small intestines?
within the brush border membrane of epithelial cells
what enzymes are in the brush border membrane of epithelial cells of the SI
do SI secretions contain enzymes?
where is fat digested?
lumen of small intestine
what enzyme digests fat?
functions of the large intestine
absorb water and electrolytes
formation and storage of fecal matter
sections of the large intestine
how is the large intestine different than the small intestine?
no digestive enzymes
not tightly coiled
intestinal microflora (bacteria)
how long does it take the stomach to empty?
how long does it take for food to transit through the colon
accessory organs of the GI tract
endocrine function of pancreas
secrete insulin and glucagon
exocrine function of pancreas
secrete pancreatic juices
what is a portal blood supply
which organ is the largest and most important in metabolism?
functions of liver
produces plasma protein
manufactures bile salts
removes and degrades toxins
why is stool brown?
due to liver removing bilirubin
where is bile made?
where is bile stored and concentrated?
where does bile go once it leaves the gall bladder?
what are bile salts?
derivatives from cholesterol
function of bile
where does bile go after digestion?
reabsorbed into blod
what are mycells?
smaller particles for lipase to breakdown
what is digestive motility and secretion regulated by?
autonomous smooth muscle function
intrinsic nerve plexuses
secreted by stomach in presence of protein
secreted by small intestine in the presence of fat
secreted by small intestine in presence of glucose
secreted by small intestine in presence of AA
increase HCO3- from pancreas, which decreases motility
phases of gastric secretion
initiated when receptors in head stimulated by senses (smell/taste/hear bacon)
begins when food reaches stomach
presence of protein increases gastric secretions
initiated by stimuli in intestinal tract (distension, acidity, etc)
amylase breaks down starches and forms it into what?
protein is broken down into what?
where do amino acids go?
hepatic portal vein
reassembled as triglycerides, then chylomicron, then lipoproteins
where do lipoproteins go?
into lacteals in small intestine then into circulation
what regulates hunger?
function of leptin
long term regulator
long term regulator
3 components of energy expenditure
basal metabolic rate
thermic effect of food
thermic effect of exercise
what component of energy expenditure is most variable?
thermic effect of food
BMR % of energy expenditure
TEF % of energy expenditure
TEE % of energy expenditure