Digestive System Flashcards
Hormones secreted by duodenum?
S cells: secretin > pancreas > bicarb
- cholecystkinin > gallblader > bile, and pancreatic digestive enzymes
What is the function of the small intestine?
- digestion and absorption
- breakdown of macronutrients via pancreatic and brush border enzymes
- absorbed by enterocytes as a.a., F.A., and monosac
Function of large intestine?
- absorb excess water from chyme
- only very small amount of absorption if any
Are macronutrients absorbed in the stomach? What is absorbed in the stomach?
Only proteins, Water and certain drugs
What digestion is the mouth capable of?
salivary amylase > sugars into oligo and disac
- lingual lipase, start of fat/lipid breakdown
Where is pepsinogen produced? Function?
- stomach
- zymogen, stomach acid > activ form pepsin
Where are brush border enzymes produced?
small intestine
- disachidases and peptidases
What are 3 sphincters in the GI tract?
ilocecal: small intestine and cecum
pyloric: stomach and duodenum of small intestine
lower esophogeal: esophagus to stomach, one of 2 in esophagus
upper esophogeal: pushes food down
what is the pH of the duodenum? How is this maintained?
6-7, panc secretes bicarb to neutralize acidic chyme
what are enterocytes? what is taken up by active vs passive transport?
cells of small intestine that take up amino acids, fatty acids, glucose/monosac
- glucose and Galac: secondary active transport
- -NaKATPase creates Na gradient > facilitates uptake via Na-Glut symporter (1 glu for every 2 Na)
- of note, sucrose is taken up by facilitated diffusion
Amino acids:
- secondary transport
Fatty acids:
- hydrophobic tail, thus passive diffusion, does not require energy
What is bile? what is its function?
mix of salts, cholesterol, and pigments
fx: dissolve/emulsify dietary fats
- break up larger fat globules into micells of Trig, more surface area to be broken down
Where is bile stored and where is it synthesized? how is it released?
synth: liver
store: gallbladder
released in response to cholecystkinin from the cells of duodenum
Step by step of fatty acid breakdown:
mouth: lingual lipase
gallbladder: bile (synth by liver, from gallbladder, in response to cholecystkinin) > fat into micelle
small intestine: pancreatic lipases > Trig into monoglyceride and fatty acids
small intestine: micelles diffuse into enterocytes > packed into chylomicrons (lipoprotein transport to other parts of body)
lacteals: vessels of lymphatic system, chylomicrons enter for transport
What are chylomicrons and lacteals?
lipoproteins involved in lipid packaging inside enterocytes for transport
- chylomicrons enter lacteals, small vessels of lymphatic system
what is the role of enteropeptidase? where is it secreted from?
- convert trypsinogen into trypsin > cleave Lys (K) or Arg (R)
- secreted by pancreas
Role of the mouth in digestion:
saliva:
- salivary amylase and lingual lipase
- Lysozyme: anti microbial, try and kill some bacteria but not all
parietal and chief cells, what can the stomach absorb?
- found in stomach
- secrete gastric acid (HCL and various salts)
- pH 1.5 - 3.5
chief cells > pepsinogen > pepsin (acidic environment)
- > pepsin: proteins > target regions of hydrophobic/aromatic
Absorb: aspirin, caffeine, small amounts of alc (20%)
What is intrinsic factor?
- produced by stomach, helps to absorb Vit B12, and produce water to dilute food bolus
How does the stomach protect itself?
- mucous epithelial cells produce bicarb rich mucus
- line stomach, neutralize acid
End stage product of food bolus from the stomach?
food bolus > chyme acidic mixture semi digested food and gastric juices
Small intestine anatomy:
folds: with villi (dense finger like projections)made up of intestional epithelal cells
- enterocytes > microvilli (hair like extensions on cell membrane)
- look like brush tissue > called brush border > enzymes like disacharidases and peptidases
Duodenum
- secretin > pancreas > bicarb > neutralize acidic chyme
- overall pH 6-7
- cholecystokinin > exocrine enzymes and bile (panc and gallbladder)
- lipid emulsification, think gallbladder > break up micelle > expose to lipase > absorb by enterocytes
Gallbladder
- store bile only
- bile salts are amphipathic > digest fats
- polar region bind with water, form micelle
- nonpolar region bind Trig
Liver functions
- secretes bile
- detoxifies compunds and metabolizes drugs/meds
- stores glyc and trig
- mobilize glucose and FA
- hepatic portal system, two capillar beds in liver and small intestine
