The Genitourinary System (38) Flashcards by Daria Ditri

What are the functions of the kidney?

excretion of useless metabolic products: urea, uric acid, creatinine
excretion of foreign substances: drugs
regulation of body fluids, electrolytes and acid-base balance
control of blood pressure
secretion of hormones: erythropoietin, renin

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What is the structure of the kidney?

cortex- outer layer
medulla- middle region
renal artery- blood in
renal vein- blood out
ureter- urine out

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What is the passage of blood into and out of the kidney?

renal artery–> segmental artery–> interlobar artery–> arcuate artery–> interlobular artery–> afferent arteriole–> glomerular capillaries–> efferent arteriole–> peritubular capillaries–> interlobular vein–> arcuate vein–> interlobar vein–> renal vein

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What is the function of the detrusor muscle in the bladder?

contracts to build pressure in the urinary bladder to support urination

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What is the function of the trigone in the bladder?

stretching of this triangular region to its limit signals the brain about the need for urination

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What is the function of the internal sphincter in the bladder?

involuntary control to prevent urination

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What is the function of the external sphincter in the bladder?

voluntary control to prevent urination

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What is the function of the bulbourethral gland?

produces thick lubricant which is added to watery semen to promote sperm survival

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What is the structure of the nephron?

glomerulus
Bowman’s capsule
proximal convoluted tubule
loop of Henle
distal convoluted tubule
collecting duct

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What is reabsorbed into the bloodstream at the proximal convoluted tubule?

Na+
Cl-
most solutes
water follows bc dec. osmolarity in tubule (higher w.p.)

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What occurs at the loop of Henle?

countercurrent flow
pump salt out at the top of the thick, ascending loop
salt gradient generated
lots of mitochondria here in epithelial cells bc pumping activity
water leaves at thin descending limb bc interstitial fluid = hyperosmolar (N.B. ascending limb impermeable to water)
epithelial cells here have low density of mitochondria bc passive movement

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What occurs at the distal convoluted tubule?

impermeable to water

- salt pumped, so epithelial cells rich in mitochondria

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What cells are rich in mitochondria at the collecting duct of the nephron?

intercalated cells, whereas principal cells have low mitochondrial

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What are the 2 types of nephron?

superficial/cortical nephron: glomeruli in outer portions of renal cortex, short loops of Henle
juxtamedullary nephrons: glomeruli in juxtamedullary region of cortex, long loops extending down into medullary pyramids
only 15% of human’s nephrons have long loops

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What is the juxtaglomerular apparatus?

between glomerulus and DISTAL convoluted tubule
macula densa (distal convoluted tubule)
extraglomerular mesangial cells
juxtaglomerular cells (afferent arteriole)

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What are the functions of the juxtaglomerular apparatus?

GFR regulation through tubulo-glomerular feedback mechanism
renin secretion for regulating blood pressure

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What is glomerular filtration?

passive process
fluid is ‘driven’ through the semipermeable glomerular capillaries into the Bowman’s capsule space by the hydrostatic pressure of the heart
the filtration barrier (size and charge dependent)= highly permeable to fluids and small solutes; impermeable to cells and proteins

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What features enable glomerular filtration?

fenestrated endothelium of glomerular capillaries, surrounded by glomerular basement membrane
podocytes w/ numerous pseudopodia that interdigitate to form filtration slits

What is hydrostatic pressure?

a force that compels a fluid to move out of a vessel

fluid exerts this pressure

What is oncotic pressure?

type of osmotic force exerted on fluids by presence of proteins in blood and tissues

What are the participating pressures involved in glomerular filtration?

blood hydrostatic pressure exerted–> drives fluid into
lower oncotic pressure from interstitial fluid bc no proteins vs. there are proteins in blood–> attempts to draw fluid molecules in
HPgc drives fluid into primary urine
HPbw works against this = -ve pressure
πgc of plasma proteins in gc = -ve pressure

What is the equation for net ultrafiltration pressure (Puf)?

Puf= HPgc - HPbw - πgc

What is glomerular filtration rate?

amount of fluid filtered from the glomeruli into the Bowman’s capsule per unit time (ml/min)
sum of filtration rate of all functioning nephrons
GFR= Puf X Kf ultrafiltration coefficient (membrane permeability and SA available for filtration)

What is a healthy GFR?

90-140ml/min in males
90-125ml/min in females
a low GFR is the cardinal feature of renal disease–> buildup of excretory products in plasma

How do we regulate GFR?

1. myogenic mechanism: arterial pressure inc.--> afferent arteriole stretches--> arteriole contracts to resist stretch--> vessel resistance rises--> blood flow reduces--> GFR stays the same 2. tubulo-glomerular feedback mechanism: inc./dec. GFR--> inc./dec. NaCl in loop of Henle--> change detected by macula densa--> inc./dec. ATP and adenosine discharged--> afferent arteriole constricts/dilates--> GFR stabilises

What is renal clearance?

``` the number of litres of plasma that are completely cleared of the substance per unit time C= (U x V)/P ml/min U= conc. of substance in urine V= rate of urine production P= conc. of substance in plasma ```

What is the ideal molecule to use to practically determine GFR?

- ideal molecule: inulin - plant polysaccharide - freely filtered and neither reabsorbed nor secreted - not toxic - measurable in urine and plasma N.B. not found in mammals, so needs to be infused

Why is creatinine commonly used to determine GFR?

- waste product from creatine in muscle metabolism, so amount of creatinine released= fairly constant (if muscle mass= constant) - if renal function is stable--> creatinine amount in urine is stable bc freely filtered and not reabsorbed (BUT a small amount is secreted) - high plasma creatinine/ low creatinine clearance may indicate renal failure

What substance do we use to measure renal plasma flow (RPF)?

PAH (para aminohippurate) bc all is removed from plasma passing through kidney by filtration and secretion

What is the filtration fraction (FF)?

the ratio of the amount of plasma which is filtered and which arrives via the afferent arteriole - 0.15-0.20 (15/20% of plasma has been filtered) - FF= GFR/RPF

What is 2y active/coupled transport?

- a type of active transport - movement of 1 solute down its electrochemical gradient provides energy for the other solute to move against it - symport e.g. Na+- glucose symporter - antiport e.g. Na+- H+ antiporter

What is a paracellular pathway?

- transfer of substances across an epithelium by passing through the intercellular space BETWEEN cells (gap junctions) - water moves like this, bringing ions w/ it e.g. Ca2+, K+,Cl-, urea etc...

What is a transcellular pathway?

- transfer of water THROUGH cells using aquaporins - Na+/K+ ATPase transporter for transcellular Na+ reabsorption (bc 3 sodium out, 2 potassium in)--> leads to downhill movement of sodium coupled to other things

How are sodium and bicarbonate reabsorbed in the early proximal convoluted tubule?

carbonic anhydrase converts H+ and HCO3---> CO2+H20--> then back in cell--> H+ brings a sodium in w/ Na+ H+ antiporter--> Na+ and HCO3- move out into blood w/ symporter

What is 100% reabsorbed in the PCT?

glucose

How does angiotensin regulate Na+ reabsorption in the PCT?

increases the number of Na+- H+ antiporters

How is glucose reabsorbed in the early proximal convoluted tubule?

- Na+ - glucose symporter brings in sodium and glucose (bc low sodium in cell due to Na+/K+ ATPase pump) - glucose then dissolves from cell through GLUT2 transporter into blood down gradient

How are Na+ and Cl- actively pumped/reabsorbed in the loop of Henle?

- at thick ascending limb (vs. passively moved in thin ascending limb) - Na+ K+ 2Cl- symporter into cell and K+ Cl- symporter out into blood - cations Na+, Ca2+ etc... reabsorbed by paracellular pathway

How are Na+ and Cl- reabsorbed in the early distal convoluted tubule?

- Na+ Cl- symporter (dependent on Na+/K+ ATPase pump) and K+ Cl- symporter out into blood

How is Ca2+ actively reabsorbed at the distal convoluted tubule?

- Na+ Ca2+ antiporter bring sodium into cell (bc Na+/K+ ATPase pump takes sodium out) and Ca2+ goes into blood

How does ADH regulate water reabsorption at the distal DCT and collecting duct?

causes aquaporins to move to membrane--> inc. water reabsorption

How does aldosterone increase sodium reabsorption at the collecting ducts?

increases apical Na+ channels and basolateral Na+K+ ATPase pumps

How doe we maintain acid-base balance in the collecting ducts?

- alpha intercalated cells: HCO3- reabsorption and H+ secretion - beta intercalated cells: HCO3- secretion and H+ reabsorption