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
