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40 Cards in this Set
- Front
- Back
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nephron
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functional unit of kidney
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cortex
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outer
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medulla
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inner
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cortical nephron
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short loop of Henle, doesn't go to medulla. 80-85% of nephrons
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juxtamedullary nephron
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long loop of henle, goes to medulla, 15-20% nephrons
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renal blood supply
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20-25% resting cardiac output
1200ml/min 2 arterioles (afferent and efferent) 2 capillary beds (glomerular and peritubular) |
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glomerulus
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ball shaped capillary, sits between 2 arterioles , rather than an arteriole and venule
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kidney functions
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blood ionic composition via electrolyte balance
blood pH (acid base balance) blood volume and BP conserve/eliminate H20 in urine hormonal pathways maintain blood osmolarity |
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calcitrol
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calcium homeostasis stimulated by PTH
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EPO
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erythropoetin ( RBC) erythropoesis
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renal corpuscle
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blood plasma is filtered.
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afferent
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to
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efferent
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from
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filtration and secretion
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put things into fluid in tubule
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reabsorption
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taking things out of fluid
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excretion
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excretion= filtration + secretion - reabsorption
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major nephron processes
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filtration- substance out of plasma and into nephron
reabsorption- nephron to plasma secretion- from cells of nephron into nephron excretion- removal from body as urine |
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filtration
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1st step in urine formation
movement of water and solutes from blood plasma across glomerular capillaries, glomerular capsule and into renal tubule |
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pressure driving filtration
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GBHP- glomerular blood hydrostatic
CHP- capillary hydrostatic pressure BCOP- blood colloid osmotic pressure NFP= GBHP-CHP-BCOP=10mmHg |
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GBHP
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glomerular blood hydrostatic pressure- BP in capillaries, it forces H20 and solute from blood plasma thru filtration membranes
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CHP
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Capillary hydrostatic pressure- opposes filtration, exerted against filration membrane by fluid already in capsular space and renal tubule
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BCOP
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Blood colloid osmotic pressure, opposes filtration, presence of plasma proteins
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GFR
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glomerular filtration rate
measurement of filtration volume of plasma filtrate that passes through the glomerulus every minute, evaluates function of the renal system 125mL/min for men 105mL/min for women |
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GFR too high
GFR too low |
too high, substances pass quickly thru tubule and are not reabsorbed
too low, nearly all substances are reabsorbed, so waste products are not necessarily excreted. affected by changes in BF and pressures of NFP |
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Clearance =GFR
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when a substance's clearance =GFR, freely filtered neither reabsorbed nor secreted.
includes Inulin and Creatinine evaluates function of renal system |
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clearance formula
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clearance "x"= Ux *V/Px
Ux= urine concentration(mg/ml) V=volume of urine flow (ml/min) Px (plasma concentration (mg/mL) |
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GFR is regulated by
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renal autoregulation
neural regulation hormonal regulation |
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renal autoregulation
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regulates GFR
maintains constant GFR despite arterial BP changes 1)myogenic mechanism- increase in local blood flow, stretches afferent arteriole, so the smooth muscle contracts and reduces its size to normal in seconds 2)tubularglomerular feedback- increase in local blood flow, raises the GFR, the substance is moving too fast so reabsorption can't occur properly. vasoconstrictors are released, afferent arterioles constrict and reduce in size. |
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neural regulation
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regulates GFR
@rest- renal vessels are maximally dilated, b/c sympathetic activity is limited so renal autoregulation occurs -moderate stimulation, sympathetic activity for afferent and efferent vessels, reduce GFR equally extreme sympathetic stimulation (exercise/hemorrhage) - vasoconstriction of afferent arteriole reduces GFR it slows urine output and forces blood flow to other tissues |
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hormonal regulation
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regulates GFR
1) Atrial natriuretic peptide (ANP) increase GFR. an increase in blood volume causes atria to stretch, ANP is released. relaxes glomerular cells and capillary surface area to increase GFR 2) Angiotensin II. decreases GFR potent vasoconstriction narrows afferent and efferent arterioles, promotes water retention as it increases BP |
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reabsorption
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movement of substances from renal tubule to the bloodstream.
cells reabsorb 99% of filtered water and solutes return to blood as it flows thru peritubular capillary and vasa recta |
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secretion
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removal of substance from the blood and into the cell
dumping of wastes from blood into tubular fluid composition of fluid changes along diff parts of nephron |
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proximal tubule
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site of reabsorption and secretion
largest amount of solute and H20 reabsorbed Na+ and glucose , amino acids secretion of H+ ions and drug residue |
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Loop of Henle
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site of reabsorption and secretion
descending- reabsorbs H20 secretes NACl ascending- impermeable to H20, reabsorbs NaCl at this site, greatest ability to produce concentrated urine |
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distal tubule and collecting duct
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sensitive to ADH, aldosterone and ANP
ADH dependent on water (urea) reabsorption Aldosterone, dependent on Na reabsorption, K secretion ANP- can suppress secretions of ADH or aldosterone Acid/base dependent H+ ions can reabsorb or secrete |
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hormonal control of reabsorption and secretion
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1) renin-angiotensin, aldosterone- renin secretion when BV is high, angiotensin lowers GFR with vasoconstriction stimulationg aldosterone, aldosterone reabsorbs Na, Cl and secretes K
2) ADH- increases permeability to water in cells of distal tubule, increase reabsorption 3) ANP- inhibits aldosterone and ADH, decrease in Na and water reabsorption |
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osmosis
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net movement of solvent thru a selectively permeable membrane
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osmolarity
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protecting long term by the kidneys
a solute exerts force (osmotic pressure) causing H20 movement across the cells osmolarity is proportional to the # of solute particles in a L of H20 ratio of solute:solvent (osmo/L) is inverse to H20 concentration |
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COP
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colloid osmotic pressure
osmolarity of plasma proteins - 25mmHg increased COP retains fluid in intravascular compartment influences magnitude of fluid movement in/out of plasma |
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steady state
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when input=output
if output<input, positive balance, can cause renal failure output >input, negative balance, excessive salt and water loss |
