Chapter 20: Urinary System Flashcards
filtration pressure
- main force that moves substances by filtration through the glomerular capillary wall is hydrostatic pressure of blood inside glomerulus
- resistance in efferent arteriole increases blood pressure in glomerulus, which favors filtration
net filtration pressure
force favoring filtration - force opposing filtration
force favoring filtration
glomerular capillary hydrostatic pressure
force opposing filtration
glomerular capillary osmotic pressure, capsular hydrostatic pressure
glomerular filtration rate
GFR; directly proportional to the net filtration pressure
AVG= 125 ml/min, 180 L/day
control of filtration rate
- autoregulation
- RAA system
- atrial natriuretic peptide & ventricular natriuretic peptide (+ADH)
- increased sympathetic impulses keep GFR constant in changing BP conditions, by causing afferent and efferent arteries to constrict simultaneously
RAA system
responds to a decrease in blood pressure; through vasoconstriction, and secretion of ADH and aldosterone, it results in a conservation of Na and H, and an increase in blood pressure; keeps GFR constant
tubular reabsorption
movement of substances from renal tubules to the interstitial fluid, where they then diffuse into the peritubular capillaries
tubular secretion
movement of wastes from peritubular capillaries into renal tubules
characteristics of tubular reabsorption
- 70% occurs in proximal convoluted tubule
- active transport
- osmosis
- endocytosis
active transport (tubular reabsorption)
- movement of substances against concentration gradient; limited transport capacity due to # of carrier proteins
- renal plasma threshold is reached when there is more transported substance in the plasma than the active transport mechanism can handle; excess spills into forming urine
- ex. glucose, amino acids, creatine, lactic, citric, uric, & ascorbic acid, ions
characteristics of tubular secretion
- substances move from plasma to peritubular capillaries into the fluid of renal tubules
- these substances are wastes, destined to be excreted in the urine
- active transport mechanisms function in tubular secretion, but they work in the opposite direction of tubular reabsorption
what does low ADH do (to urine)
dilutes urine
what does high ADH do (to urine)
concentrates urine; tubule cells become permeable to water
urea
- by product of amino acid catabolism
- plasma concentration reflects the amount of protein in diet
- enters renal tubules by glomerular filtration and undergoes both tubular secretion and reabsorption
