Urinary 2 Flashcards
measures the volume of plasma cleared of a. substance in a given time
renal clearance
clearance equation
RC = (urine concentration x urine flow rate) / plasma concentration
closely approximates GFR and is useful for assessing kidney function
inulin clearance
- involves active or passive transport of substances like H+ ions, penicillin, and K+ ions into the filtrate
- plays a role in controlling the body’s pH balance
tubular secretion
- vasa recta capillaries exchange water for salt as they travel down into the medulla
- system ensures ECF retains high salt levels for water movement out of the nephron
countercurrent exchange mechanism
- maintains high medullary concentration to aid water reabsorption from the nephron
- saltier medulla pulls water out of the descending limb, while salts are pumped out in the descending limb
countercurrent multiplier
countercurrent mechanisms
- countercurrent multiplier
- countercurrent exchange mechanism
what hormone promotes active tubular secretion of potassium and reabsorption of sodium ions in the distal convoluted tubule and collecting ducts
aldosterone
what area of the nephron is responsible for the reabsorption of the most water from the filtrate as well as most nutrients
proximal convoluted tubule
true or false:
Under normal conditions, the proximal convoluted tubule (PCT) reabsorbs nearly all of the glucose, lactate, and amino acids in the filtrate and 65% of the Na+ and water.
true
the kidney are stimulated to produce renin by
a decrease in the blood pressure
contains fluid that becomes more concentrated as it moves down into the medulla
descending limb
effect of ADH on cells of the CD
causes aquaporins to be inserted into apical membranes
true or false:
Filtrate becomes less concentrated as it flows down the medullary collecting ducts, toward the renal pelvis.
false
why does alcohol act as a diuretic
inhibits the release of ADH
- 125ml of filtrate is formed each minute by pushing plasma across the fenestrae of glomerular capillaries into the proximal convoluted tubule.
- Most objects are too large to pass through the small (7nm) barrier
- Plasma proteins and RBCs (>7nm) remain in the capillary, while small hormones and minerals (<7nm) pass through.
filtration membrane
consists of the glomerulus and bowman’s capsule
renal corpuscle / filtration membrane
forces at the filtration membrane
- glomerular blood pressure (GP)
- colloid osmotic pressure (COP)
- capsular hydrostatic pressure (CP)
net filtration pressure (NFP) =
Glomerular Pressure - (Colloid Osmotic Pressure + Capsular Hydrostatic Pressure)
NFP = GP - (COP + CP), with GP pushing water and solutes out, while COP and CP push in the opposite direction.
filtration will still occur as long as
glomerular blood pressure is high enough
how much water is reabsorbed in the nephron and how much is lost as urine
Approximately 123.75ml of water is reabsorbed in the nephron, leaving only 1.25ml/min lost as urine.
plays a significant role in the collecting duct, concentrating urine up to 4 times.
ADH
causes Na+ reabsorption and K+ secretion, leading to water reabsorption in the DCT
aldosterone
impermeable to water, with Na+, K+, and Cl- transported out into interstitial fluid
ascending limb
reabsorbs 15% of filtrate due to high interstitial solute concentration.
descending limb
- 65% of filtrate is reabsorbed here, including amino acids, glucose, and ions like Na+, K+, and Cl-.
- Water moves out by osmosis, transported against concentration gradients into peritubular capillaries.
proximal convoluted tubule
involves vasoconstriction and dilation of afferent and efferent arterioles of the glomerulus
autoregulation
directed by the macula densa of the distal convoluted tubule (DCT)
tubuloglomerular feedback mechanism
monitor filtrate concentration and flow, adjusting GFR accordingly.
macula densa cells
types of regulation of filtration
- intrinsic (autoregulation and tubuloglomerular feedback mechanism)
- extrinsic (sympathetic stimulation (neural) and renin-angiotensin mechanism (hormonal))
leads to arteriole dilation at rest, with norepinephrine causing vasoconstriction of renal vessels.
sympathetic stimulation
aims to increase blood pressure by converting angiotensinogen to angiotensin II
renin-angiotensin mechanism
is angiotensin a vasoconstrictor or a vasodilator
vasoconstrictor
normal value of GP
55 mmHg
typical COP value
30 mmHg
typical CP value
15 mmHg
increased blood pressure =
vasoconstriction of afferent arteriole
decreased blood pressure =
vasodilation of afferent arteriole
increased GFR =
rapid flow in DCT; vasoconstriction of afferent arteriole
decreased GFR =
sluggish flow in DCT; vasodilation of afferent arteriole
what is the stimulus for the renin-angiotensin mechanism
drop in blood pressure
aldosterone release =
increase reabsorption of Na+ and water
increased Na+ and water =
increased blood pressure
ADH works most strongly in which areas of the nephron
DCT and CD
decreased BP and increased K+ =
increased aldosterone = increased sodium and water retention
increased BP and decreased K+ =
decreased aldosterone = decreased BP, increased urine output
caused by ADH insufficiency
diabetes insipidus
decreased BP = __ ADH and __ H2O retention
increased
increased water retention =
increased BP, decreased urine
increased BP = _____ ADH and _____ H2O retention
decreased ADH and decreased H2O retention
decreased ADH and decreased H2O retention =
decreased BP, increased urine
