Renal Flashcards
Urinary excretion rate =
Urinary excretion rate = Filtration rate - (Reabsorption rate + Secretion rate)
Creatinine in kidneys
Are only filtered not reabsorbed nor excreted
Filtration = Excretio
Na, Cl ions and others are
Freely filtered and partially reabsorbed
Excretion = Rate of filtration - Rate of reabsorption
Amino acids and glucose
Freely filtered and completely reabsorbed from tubules
No excretion
Organic acids and bases
Freely filtered not reabsorbed but additional substances secreted from capillary to tubule
Excretion rate = Filtration + secretion rate
Filtration fraction =
Filtration fraction = GFR/Renal plasma flow
The GC has 3 layers
1 endothelium
2 basement membrane
3 epithelial cell podocyte
Normal GFR
125 ml/min 180L/day
Filtrate devoid of protein, rbc, half of Ca bound and fatty acid
Fenestrations in gc are endowed with
that hinder passage of plasma proteins
negative charges
Filterability of solutes are determined by
Size
Electrical charge
Proteinuria/Albuminuria occurs in minimal change disease bec of
loss of negative charge on the basement membrane proteoglycan
Net filtration pressure =
Net Filtration Pressure = (GCh - Bh) - (GCc+Bc)
Glomerular Filtration Rate =
Glomerular Filtration Rate =
Kf x (Net filtration pressure)
Kf x [(GCh-Bh)-(GCc+Bc)]
Kf normal
12.5 ml/min/mmHg
Kf = GFR/NFP Kf = 125/10mmHg
DM alters Kf by
Inc thickness of bm and damaging functional capillary less surface area
In obstructive renal disease such as calcium or uric stones, GFR is markedly dec bec of
Inc Bowman capsule hydrostatic pressure from backflow limiting filtration
Inc glomerular capillar colloid osmotic pressure : GFR
Decreases GFR
BY:
Inc arterial plasma colloid osmotic pressure, inc glomerular capillary colloid osmotic and dec GFR
Inc filtration fraction concentrating plasma proteins, inc colloid osmotic, dec GFR
A greater rate of blood floe into glomerulus: GFR
Lower rate of blood flow into glomerulus: GFR
Increases
Decreases
Primary means of physiologic regulation of GFR
Glomerular hydrostatic pressure
Glomerular hydrostatic pressure is determined by (3)
1 arterial pressure (inc AP, inc GFR)
2 afferent arteriole (vasoconstriction dec GFR and vice versa)
3 efferent arteriole (vasoconstriction inc GFR slightly as long as the inc does not reduce renal blood flow)
too much efferent vasoconstriction eventually dec GFR bec dec renal blood flow can promote inc filtration fraction and inc colloid osmotic pressure DEC GFR)
Oxygen consumption of kidney is related to
High rate of active sodium reabsorption by tubule
Renal blood flow =
Renal blood flow =
(Renal artery pressure1 - Renal vein pressure2)/Total renal vascular resistance
Total renal vascular resistance come from
Interlobular arteries
Afferent arteriole
Efferent arteriole
Strong activation of renal sympathetic nerves and autacoids (NE, Epi, Endothelin) such as in defense rx, ischemia brain, or severe hemorrhage
Dec GFR
Otherwise in mild to mod vasoconstriction, little influence on blood flow
Angiotensin II acts preferentially on the efferent arteriole when activated to
Promote flow in the glomerulus
Prevent dec glomerular hydrostatic pressure and prevent dec GFR
Efferent constriction causes reduction in renal blood flow leading to dec flow in peritubular capillaries and sodium and water reabsorption increases
Autoregulation of kidneys depend on:
1 sodium chloride concentration at macula densa
2 control of renal arteriolar resistance
GFR autoregulation is accomplished by
1 renal autoregulation
2 glomerulotubular balance (adaptive mech in renal tubules)
Tubuloglomerular feedback components:
1 afferent arteriolar feedback
2 efferent arteriolar feedback
depending on juxtaglomerular complex
JGC components
1 macula densa (initial distal tubule)
2 juxtaglomerular cell (afferent and efferent)
Macula densa cells sense change in volume delivery at distal tubule when
Dec GFR slows flow rate at LOH
INC reabsorption of NaCl ions in ascending LOH
Dec concentration of NaCl at macula densa
Dec of NaCl at macula densa cause:
Dec resistance to blood flow in afferent arteriole Inc GFR
Inc renin release in JGC (RAAS)
Angiotensin II inc GFR by
Vasoconstricting afferent arterioles
Myogenic mechanisms in renal arteriole has important protective function against
Hypertension-induced kidney i
Filtration =
Filtration = Glomerular filtration x Plasma conc
Reabsorption across tubular epi into interstitial fluid occurs by
active or passive transport
Transport from interstitial fluid into peritubular capillary involve
ultrafiltration (bulkflow)
Moves solute against electrochemical gradient requires energy from metabolism
active transport
Transport coupled to an energy source such as hydrolysis of ATP is called
Primary Active Transport
Transport coupled indirectly to energy source such as ion gradient
Secondary active transport
ex glucose
Diffusiob from a region of low solute to high solute concentration
Diffusio
Primary active transport in kidneys (4)
Na/K
H ATPase
H/K
Ca ATPase
Na enters apical membrane from tubular lumen by
Electrochemical gradient established by NaK ATPase
Na is transported across basolateral membrane by
Electrochemical gradient by NaK ATPase
Na is reabsorbed from interstitial fluid into peritubular capillary by
Ultrafiltration
Reabsorption or secretion of solutes across cells
Transcellular