Gastrointestinal System Flashcards
what are the types of digestion
mechanical and chemical
what are the stages of nutrient intake
digestion (mechanical and chemical), absorption
what are two factors that can help with digestion and absorption
motility and secretion
label the organs of the GI system
main points: mouth, pharynx, esophagus, stomach, small and large intestine, rectum, anus
label the accessory glands of the GI system
main points: liver, salivary glands, gallbladder, pancreas
what are the main layers of the GI tract wall
mucosa, submucosa, muscularis externa, serosa
draw a diagram of the GI tract wall with the main parts
….
what are the functions of the mouth
- chewing
- lubrication and breakdown of food with saliva
- (tongue) manipulation of food
describe the stomach and its function
- swelling of esophagus
- has gastric pits with secretory cells
- acidic
- chemical and mechanical digestion (chyme)
what are the secretory cells of stomach gastric pits
neck, chief, parietal, G-cells
what is the stomach lining protected by
gastric mucosal barrier
draw a diagram showing the anatomy of the stomach
….
what are neck cells responsible for
secretion of mucus
what are chief cells responsible for
secretion of pepsinogen
what are parietal cells responsible for
secretion of acid
what are the divisions of the small intestine (start to end)
duodenum, jejunum, ileum
what is the purpose of the ascending, descending, transverse colon
absorption of water and ions from chyme
what is the purpose of the sigmoid colon
storage
what are the divisions of the colon
ascending, transverse, descending, and sigmoid
antibiotics are a type of medicine that can kill harmful bacteria from infections; however, it can also kill good bacteria that is present in the body. how will this affect the body and how can this bacteria be re-accounted for?
- microbiome important for digesting fibre, and producing vitamin K (blood clotting; form and maintain bone structure) and B7 (body system support –> hair, skin, eyes, liver, nervous system)
- taking probiotics (yogurt, kombucha, kefir)
describe carbohydrate digestion
- salivary and pancreatic amylase limitedly break down polysaccharides
- resulting products are digested by brush border enzymes in small intestine
- only monosaccharides are absorbed by body
why are amylases limited in their ability to digest polysaccharides
amylases can’t break polysaccharide bonds at branch points (limit dextrins) or between glucose monomers at the very end of the chain (disaccharides)
what are the brush border enzymes
- dextrinase
- glucoamylase
- sucrase
- lactase
- maltase
what does dextrinase breakdown, and what is the resulting product
limit dextrins → glucose
what does glucoamylase breakdown, and what is the resulting product
polysaccharides → glucose
what does sucrase breakdown, and what is the resulting product
sucrose → fructose + glucose
what does lactase breakdown, and what is the resulting product
lactose → galactose + glucose
what does maltase breakdown, and what is the resulting product
maltose → 2 glucoses
define absorption
transport of nutrients from lumen to blood
what are the way(s) that glucose is absorbed by the body
- co-transport with sodium across apical membrane
- facilitated diffusion across basolateral
what are the way(s) that galactose is absorbed by the body
- co-transport with sodium across apical membrane
- facilitated diffusion across basolateral membrane
what are the way(s) that fructose is absorbed by the body
facilitated diffusion across both membranes
draw a diagram of the brush border between the lumen and capillary that depicts how maltose is digested and absorbed
….
what are the enzymes that digest proteins
endopeptidases and exopeptidases
how do endopeptidases digest proteins
by splitting polypeptides at interior peptide bonds into small peptide fragments
how do exopeptidases digest proteins
by cleaving amino acids from one end of the polypeptide
describe protein digestion
- started by pepsin converted from pepsinogen and acidity in stomach
- pancreatic proteases in small intestine, and brush border enzyme enterokinase complete protein digestion into amino acids, di, and tri peptides
what is a zymogen
inactive form of a substance that converts into an enzyme when activated (by another enzyme)
what does trypsinogen convert into when active and how
- trypsin
- enterokinase
what does chymotrypsinogen convert into and how
- chymotrypsin
- trypsin
what does procoarboxypeptidase convert into and how
- carboxypeptidase
- trypsin
draw out how small peptides and amino acids are able to absorb thru the apical membrane/basolateral membrane
….
why is it more difficult to digest and absorb lipids
- non-water soluble
- don’t mix with stomach or intestinal contents
- make fat large droplets
what enzymes are able to digest lipids in small intestine
ligual lipase, gastric lipase, pancreatic lipase
describe ligual lipase
lipase enzyme in saliva and remains active in stomach
describe gastric lipase
lipase enzyme secreted into the gastric lumen
describe pancreatic lipase
lipase enzyme that mixes with chyme in small intestine
how are bile salts able to help with lipid droplet digestion
- surface area increases due to emulsification which helps more lipid to expose to water
- exposure to water on edges makes a polar coating that helps lipid to mix better in water
describe bile salts
- amphipathic molecule w hydrophilic polar groups on one side of molecule and other side is hydrophobic
- synthesized in liver from cholesterol
- secreted in bile to duodenum
draw out how pancreatic lipase works to free fatty acids and monoglycerides from fat droplets
….
how do free fatty acids and monoglycerides absorb into the body
thru simple diffusion into intestinal cells
how are bile salts recycled
by liver using enterohepatic circulation
water absorption is considered a(n) ____________ process
passive
how do free fatty acids enter circulation
- enter smooth ER first and re-form into triglycerides and other lipids
- lipids enter Golgi and become chylomicrons (enterocyte that made triglyceride-rich lipoprotein)
- chylomicrons secreted by exocytosis from basolateral membrane into interstitial fluid
- chylomicrons enter lymphatic system thru lacteal and eventually enter circulation
why do fat droplets shrink as they move thru intestine
by action of pancreatic lipase
