Lecture 29: GI

Stomach pH = ____: necessary for activating pepsinogen into _____- self cleaves, also denatures proteins, kills bacteria

2 pepsin

Large surface area- absorption completed within first ~_____ of intestine length

20%

reabsorbed ~ ____L

8.9

ingested/secreted ~ ____L

9

similar to glucose, amino acids are absorbed across small intestine apical membrane via _____ transporters (Na+ linked to co-transport) and the ____________ membrane by facilitated diffusion

AA basolateral

_________________ eventually exocytose out of basolateral membrane of cell into interstitial fluid

Chylomicrons

__________ apparatus further packages triglycerides into chylomicrons

Golgi

Secretes gastric juice (_____ and protease) to degrade food bolus into "_______"

HCl chyme

____________ crypts secrete bicarbonate rich fluid

Lieberkuhn

__________________ transport lipids/cholesterol around the body via the bloodstream to cells

Lipoproteins

GI system maximizes ________- regardless of whether nutrients are needed

absorption

_______- of nutrients: small intestine, large intestines

absorption

final digestion occurs near ______________

absorption

small intestine anatomy has evolved for maximum ___________

absorption

stomach expands to _________ food

accomodate

parietal cells: secrete _______

acid

pepsin cannot cleave full length proteins into substituent ________ acids

amino

monosaccharides are absorbed into brush border ________ membrane

apical

LDL = _____ cholesterol = low protein content

bad

Protective layer of mucus and _________ secreted from neck and goblet cells

bicarbonate

liver secreted ______ enters duodenum. (can be stored in gallbladder) Bile salts aid in ________ digestion

bile lipid

Bile synthesis: derived from __________- gallbladder stores bile, bile duct transports bile from liver and/or _________ to duodenum

bilirubin gallbladder

Teeth, tongue, and saliva help shape food into a "______" which is swallowed

bolus

Intestinal capillaries and lacteal absorb "________ _______" nutrients

broken down

Microvili form "______ _______" to increase surface area even further

brush border

____________ mediated transport- energy from Na+/K+ ATPase on basolateral membrane

carrier

Bile saltsa re amphipathic derivatives of __________ that aide in lipid digestion

cholesterol

pepsin can only __________ at certain amino acid consensus sequences (after: The, Leu, Glu)

cleave

__________ (large intestine) functions to: reabsorb some water and a few vitamins (K, thiamine, riboflavin), and cincentrate/stored "____________" feces (until elimination)

colon indigestible

proximal segment circular muscle __________, while distal segment circular muscle __________, contents propelled forward

contracts relaxes

_________- to small molecules: (ex. protein- amino acids) mouth, stomach, _______ intestine

digestion small

Pancreatic amylase secreted into small intestine continue digestion to small ____________

disaccharides

fat droplets slowly "__________" as they transit the small intestine

dissolve

wastes/toxin elimination: ______/poisons, ________ metals

drugs trace

pancreatic juice enters ________- containing a wide variety of _________ enzymes

duodenum digestive

Three divisions of SI: __________, jejunum, __________

duodenum ileum

_________ volume = 50 mL, full volume = 100 mL

empty

accessory organs ________ in SI

empty

____________: ex. beta-islet cells secrete ________ into bloodstream. Insulin causes ________- to be taken into cells (away from bloodstream)

endocrine insulin glucose

___________ split polypeptides at interior peptide bonds

endopeptidases

Brush border proteases: ______________ activates trypsin

enterokinase

Villi increase surface area of ___________

epithelium

upper and lower __________ ___________ regulate passage- open during swallowing

esophageal sphincter

___________: muscular tube (dorsal to trachea) carries food from pharynx to stomach

esophagus

_______________: ________ cells produces pancreatic juice- rich in bicarbonate (neutralizes chyme) and multiple enzymes stored in ________ granules that can degrade ______ 4 macromolecules: amylases, lipases, proteases, nucleases

exocrine acinar zymogen all

_____________ cleave off amino acids from ends of polypeptide

exopeptidase

amphipathic lipids are apoproteins on _______________

exterior

Lipids don't mix well with stomach and intestinal contents- instead they form _______ droplets that float on top of ________

fat chyme

Failure of lower esophageal sphincter results in _______ ________ (heartburn)

gastric reflux

The _______________ system digests food into absorbable nutrients

gastrointestinal

glucose- ___________

glycogen

HDL = _______ cholesterol = high protein content

good

_________ artery provides liver with "own" fresh blood supply

hepatic

nutrients travel from liver to heart (for general circulation) via __________ vein

hepatic

Autonomic nervous system modulates: parasympathetic: __________ contraction/motility sympathetic: __________ contraction/motility

increases decreases

bile salts work by ____________ surface are of lipid droplets- by breaking large droplet into several small droplets = ____________-

increasing emulsification

hydrophobic lipids on _____________

interior

Chylomicrons are too _________ to directly access capillaries, instead enter __________ system first

large lymph

lipases (secreted mostly from pancreas) are water soluble can only act on ________ molecules near fat droplet edge

lipid

Lingual lipase starts to digest _________

lipids

__________ face a special problem in digestion and absorption, they are not ________ soluble

lipids water

chylomicrons are a type of _____________

lipoprotein

lipids- ___________

lipoproteins

Absorbed nutrients pass through/converted in ________ prior to general circulation

liver

___________ modifies ratio of lipid/protein of lipoproteins

liver

bile salts recycled by __________

liver

synthesized in _________ (stored in gall bladder) - delivered as "______" to the duodenum

liver bile

Brush border enzymes and transport proteins also __________ here

localize

Digestion begins with __________ (chewing) to break food down into smaller particles

mastication

Intestinal capillaries drain to _______ veins- then to _________ capillaries via hepatic portal vein

mesenteric liver

brush border enzymes finish digestion to ______________ (maltase digests maltose to two glucose molecules)

monosaccharides

__________- smooth muscle contraction propagates food through system

motility

Order of GI tract

mouth - esophagus - stomach - small intestine - colon - rectum - anus

Liver has ________ functions- in addition to processing nutrients

multiple

___________ and ___________- also exist on brush border to facilitate digestion of nucleic acids and proteins

nucleases peptidases

Liver functions to "process" ___________

nutrients

hollow tube- 15 feet long- lumen = "________" body

outside

__________ secretes many molecules: endocrine and exocrine

pancreas

___________ absorption - follows Na+ and absorbed nutrients... Na+ actively pumped out of _____ via Na+/K+ ATPase- duodenum and jejunum epithelial cells have "_______" tight junctions

passive GI leaky

_________ initiates digestion of ingested protein

pepsin

protein enzyme = __________, secreted as pepsionegn (Hal and "self" activates)

pepsin

Chief cells: secrete __________

pepsinogen

Stomach gastric pits secrete __________ (chief cells) and _________ (parietal cells)

pepsinogen acid

_________: propels contents forward (ex. esophagus)

peristalsis

___________: shared between food and air

pharynx

_________ protein and hormone synthesis: (ex. albumin, angiotensinogen)

plasma

Indigestible _______________ (ex. cellulose) pass through GI as "fiber"

polysaccharides

______________ digestion begins in mouth and finishes in small intestine

polysaccharides

Absorbed nutrients travel in blood to liver for "____________" before entering general circulation

processing

Peptides need further processing by other __________ enzymes

proteolytic

_________ sphincter regulates passage of chyme between stomach and small intestine

pyloric

small intestine smooth ER ___-____________ triglycerides from incoming fatty acids

re-manufactures

__________ = folds that flatten upon expansion

rugae

_________ amylase acts in mouth

salivary

glucose absorbed at apical membrane via ___________ active so transport with Na+ (driven by basolateral Na+/K+ pump). then across basolateral membrane (down concentration gradient) via ____________ diffusion

secondary facilitated

_________- of fluid and digestive enzymes. salivary glands, stomach, pancreas, small intestine, liver

secretion

___________- saliva acts as a lubricant, and salivary amylase begins to digest _____________ (ex. starch)

secretion carbohydrates

__________ contractions mix chyme

segmental

_____________: mixes contents (stomach)

segmentation

Pacemaker cells, mechanoreceptors, gap junctions control smooth muscle contraction for _____________/______________

segmentation peristalsis

_________________ enteric nervous system controls digestion

semiautonomous

fatty acid monomers absorb into epithelial cell via _________ diffusion or form _________- which continue to release lipids for absorption

simple micelles

Chyme slowly released into ________ intestine

small

protein digestion finishes in ________ intestine

small

________ intestine is the primary site of _________ and absorption

small digestion

__________ muscle contraction allows movement of GI contents

smooth

low pH of stomach inhibits _______- digestion

starch

SI: coiled, hollow tube 8-10 ft long between __________ and large intestine

stomach

___________ stores and continues digestion of swallowed food (protein)

stomach

protein digestion begins in ____________

stomach

Large intestine (colon) subdivisons: ascending, _________, descending, ___________

transverse sigmoid

lipases release fatty acid monomers from ______________

triglycerides

pancreatic proteases: _________, chymotrypsin, _____________

trypsin carboxypeptidase

____________ is reabsorbed primarily in the small intestine, 95% reabsorbed

water

pancreatic proteases are stored as inactive __________ granules, secreted by exocytosis and activated by proteolysis

zymogen