Physiological correlates of renal disease II Flashcards
the PCT is permeable to:
- water
- salt
what is the osmolarity in the PCT in comparison to plasma?
isoismotic
how is the permeability of the collecting duct described?
variable permeability according to hormonal control
what are the two requirements for forming a concentrated urine?
- high osmolarity of renal medullary interstitial fluid
- high level of ADH
the ascending loop is permeable to:
salt
what structure serves as a counter current exchanger in order to minimize washout of solutes from the interstitium?
vasa recta
what is the role of the vasa recta?
serves as counter current exchanger to minimize washout of solutes from the interstitium
as you go deeper into the interstitium, how does osmolarity change?
higher osmolarity
why is the counter current exchange system necessary?
necessity to maintain osmolarity in the medulla
how does an increase in fluid osmolarity and plasma sodium concentration affect osmoreceptor cells?
osmoreceptor cells shrink
what causes osmreceptor cells to shrink?
increase in fluid osmolarity and plasma sodium concentration
after osmoreceptor cells shrink, what occurs in the hypothalamus? which nucleus?
release of ADH from supraoptic nucleus
the degree of dilution or concentration of the urine is controlled by what hormone?
ADH
an increase in plasma ADH has what effect on distal tubules and collecting ducts?
water permeability increases
fluctuation in NaCl delivery to the distal tubule is sensed by what structure?
juxtaglomerular apparatus
what controls the GFR by a feedback mechanism acting on the renal arteriolar resistance?
juxtaglomerular apparatus secondary to fluctuation in NaCl delivery to the distal tubule
what comprises the juxtaglomerular complex? where are these components located?
- macula densa (initial distal tubule)
- juxtaglomerular cells (wall of arterioles)
what are two functions of the macula densa?
- sense the delivery of salt
- decide how much renin is released
what type of adrenergic innervation stimulates renin release?
B1
angiotensin II formation is regulated by changes in ________
BP
how does angiotensin II affect sodium and water reabsorption? how does it do this?
- increases sodium and water reabsorption
- constricts efferent arterioles
- directly stimulates sodium tubular reabsorption
- stimulates aldosterone secretion
where does aldosterone act? what is its role?
- cells of cortical collecting tubule
- increases sodium reabsorption and potassium secretion
levels of what compounds affect the level of aldosterone? what are these levels specifically?
- high Na decreases plasma aldosterone
- high K increases plasma aldosterone
an increase in activity of renal sympathetic nerves results in an increase of sodium and water reabsorption due to what three factors?
- reduction in GFR by constriction of renal arterioles
- increase in tubular sodium reabsorption
- increase in renin release and angiotensin II formation, further stimulating tubular sodium reabsorption
definition: renal clearance
volume of plasma that is completely cleared of the substance by the kidney per unit of time
what are the uses of renal clearance?
- quantify the rate at which blood flow through the kidneys
- basic kidney function
what is the best overall index of kidney function?
GFR
what is the renal clearance equation?
C = (V x U) / P
C = clearance V = urine flow rate U = urine concentration of x P = plasma concentration of x
what is inulin? what is its clinical use?
- polysaccharide molecule not produced by our body
- used to assess GFR
what is the clniical significance of creatinine?
cleared from body entirely by glomerular filtration
if a substance is completely cleared from the plasma, the clearance rate of that substance is equal to what measurement?
total renal plasma flow
definition: filtration fraction
fraction of renal plasma flow (RPF) that is filtered into bowman’s capsule at the glomerulus
what is the equation for GFR in terms of RPF and FF?
GFR = RPF x FF
how does HTN exacerbate kidney injury?
alteration of renal hemodynamic and tubular reabsorption
what type of kidney lesions promote HTN? what are 3 examples of these?
- lesions that reduce the ability of the kidney to excrete sodium and water
- increased renal vascular resistance
- decreased glomerular capillary FF
- excessive tubular sodium reabsorption
what is acute kidney injury (acute renal failure) in the context of time frame, GFR, and sequelae?
- syndrome that results in a sudden decrease in kidney function or damage from few hours to few days
- rapid decline in GFR accompanied by accumulation of waste products in the blood and inability to maintain fluid and electrolyte balance
what is the cause of pre-renal AKI?
kidney hypoperfusion
what is the cause of renal AKI?
- vessel and glomerular injury
- tubular epithelial injury
- renal interstitial injury
what are the 4 sites of renal AKI?
- vascular
- glomerular
- tubular
- interstitial
what is the cause of post-renal AKI?
urinary tract obstruction
what are the physiological consequences of AKI?
- water and sodium overload (edema, HTN)
- hyperkalemia
- metabolic acidosis
- anuria (severe AKI)
what is the cause of chronic kidney failure?
disorders of blood vessels, glomeruli, tubules, renal intersitium, and lower urinary tract
