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Digestive path
mouth - esophagus - stomach - small intestine - large intestine - rectum - anus
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digestion starts where, and how?
in mouth
alpha-amykase in saliva
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alpha amylase does what?
degrades starch into polysaccharides
increases surface area allowing more enzymes to work on food molecules
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How are food molecules pushed to esophagus?
peristaltic motion
(smooth muscle)
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What is primary function of the stomach?
mixes and stores food - reduces it to chyme
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exocrine glands in stomach
begins protein digestion with pepsin
low pH
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What is the pH of the stomach
2
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4 cell types in the stomach
mucous cells
chief cells
parietal cells
G-cells
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What do mucous cells do?
line stomach wall and exocrine glands
allows food to slide along without damaging the cell
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What are mucous cells composed of?
sticky glycoproteins and electrolytes
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What do chief cells do?
secrete pepsinogen
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What is pepsinogen? What is it activated by? What does it do?
pepsinogen = zymogen of pepsin
activated by low pH of the stomach
protein digestion
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What do parietal cells do?
secrete HCl
lowers pH of stomach and raise blood pH
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What are parietal cells stimulated by?
release of gastrin
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What do G-cells do?
secrete gastrin
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What is gastrin, and what does it do?
gastrin = peptide hormone
absorbed into the blood - stimulates parietal cells
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What are the major hormones that affect secretion of stomach juices?
acetylcholine, gastrin, and histodine
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3 parts of the small intestine and their functions
duodenum (most digestion)
ileum (absorption)
jéjunum (absorption)
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wall of small intestine contains what, and why?
microvili
increases surface area
(brush border in light microscope)
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What does lysozyme do?
regulates bacteria within the intestine
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Where does chime move to after the small intestine?
pancreas
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Main function of the pancreas
acts as an exocrine gland
secretes bicarbonate ions
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What is the pH in the small intestine and how?
pH = 6
bicarbonate ions released from small intestine
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Which enzyme activates all other zymogen forms released from the pancreas
trypsin
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major enzymes released from the pancreas and their function
trypsin and chymotrypsin = degrade proteins
amylase = polysaccharides into di and trisaccharides
lipase = degrades fat (triglycerides)
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Trypsin degrades proteins into small polypeptides. How are they reduced to amino acids?
when they reach the brush border
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bile - where is it produced, where is it stored, what does it do?
produced in liver
stored in gull bladder
emulsifies fat = increases surface area
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What happens to bile after it emulsifies fat molecules?
reabsorbed by small intestine and transported back to liver
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Primary function of large intestine
water reabsorption
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How is glucose absorbed into cells?
secondary active transport
down Na+ gradient
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How is fructose absorbed into cells
facilitated diffusion
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How are proteins absorbed into cells?
co=transport down Na+ gradient
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Do we want a high or low intracellular amino acid concentration?
low
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When fats are absorbed, they are first converted into what, how?
converted to fatty acids to brush border
diffuse through enterocyte membrane
return to triglycerides at smooth ER
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thoracic duct
delivers lymph to venous circulation
delivers fat to the blood
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Where does liver receive blood from?
capillary beds of the intestines, stomach, spleen, pancreas
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Why is there a secondary blood supply to the liver?
sent to oxygenate it
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Where does all of the blood received by the liver move to?
through flattened spaces
leads to vena cava
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liver funcitons (5)
- 1. blood storage and filtration
- 2. carb, fat, and protein metabolism
- 3. detoxification
- 4. erythrocyte destruction
- 5. vitamin storage
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When liver mobilizes fat or protein for energy, what happens to blood acidity levels?
increases
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Kidney (path)
afferent/efferent arterioles - glomerulus - Bowman's capsul - proximal convulated tubule - loop of Henle - distal convulated tubule - collecting duct - bladder/urethra
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uterer and urethra
uterer = carrries urine to the bladder
urethra = drains the bladder
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afferent and efferent arterioles
afferent = carries blood into nephron
efferent = carries filtered blood out of nephron
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what is the renal capsule
glomerulus and Bowman's capsule
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how does filtrate move from glomerulus to Bowman's capsule?
hydrostatic pressure
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What goes on in proximal tubule?
secondary active transport
wanted material is reabsorbed into capillary system
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glucose reabsorption in proximal tubule
in a healthy adult, glucose is completely reabsorbed
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Is insulin absorbed or excreted?
no
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loop of Henle - location
crosses border from renal cortex into renal medulla
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descending loop
only permeable to water
- H2O leaves loop and into medulla
- (because medulla is salty)
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filtrate osmolarity in descending loop
high osmolarity
hypertonic
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ascending loop
only permeable to salts
slats leave filtrate
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distal tubule
reabsorbs Na+ and Ca2+
secretes K+ , H+ and HCO3-
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collecting duct
collects waster products of multiple nephrons
transports waste to bladder
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ADH
increases permeability of water - water is absorbed into medulla (since it's salty)
Always Digging Holes
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Where is the urine concentrated?
descending loop of Henle
mostly in collecting duct
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What does aldosterone do?
increases Na+ and K+ membrane transport proteins
so it increases Na+ absorption and K+ secretion
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Juxttaglomerular Apparatus
monitors filtrate pressure in distal tubule
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