Glomerular Filtration and RBF Flashcards
What is the location and function of juxtaglomerular cells?
Located next to the glomerulus. Secrete Renin.
What is the general structure of the capilaries inside the glomerulus?
Contain fenestrated endothelial cells with holes through the cells. Glomerular basement membrane separates the fenestrated endothelium from the glomerular epithelium/podocytes. Podocytes are connected with slit membranes.
What is the equation and forces that drive and oppose glomerular filtration (Starling Forces)?
GFR = K[(Pgc - Pt) - (PIgc - PIt)] where Pgc is the hydrostatic pressure in the blood plasma, Pt is the hydrostatic pressure from the tubule, PIgc is the osmotic pressure in the blood plasma, and PIt is the osmotic pressure in the tubule, and K is the reciprocal of the Resistance (R), or 1/R.
What affects blood flow through the glomerulus?
The pressure differential and the resistance of the vessel. Flow (Q) = (P1-P2)/R.
What are the typical values of Pgc, Pt, and PIgc, and what does this make the Net Filtration Pressure? What affect would a 15% increase in MAP have on NFP?
Pgc = 46 mmHg, Pt = 10 mmHg, PIgc = 30 mmHg. Thus NFP = (Pgc - Pt) - PIgc = 46-10-30 = 6 mmHg (
How does the kidney autoregulate the NFP and what is the range of autoregulation?
The kidney’s autoregulate the NFP by constricting or dilating the afferent and efferent arterioles in response to MAP (myogenic control). The range of autoregulation is MAP of 75-150, range is limited by the arteriole’s ability to constrict or dilate.
What is K in the Starling forces equation?
K = 1/R, or the reciprocal of the resistance. It is also equal to the total area of the glomerulus times the specific hydraulic conductivity “p”, so K=pA. The large area, A, of the glomerulus expalins why so much fluid can be filtered with only 6 mmHg pressure.
What is the general goal of kidney response to severe hypovolemia?
The kidneys must reduce their blood flow to help perfuse the the other vital organs, but must not shut down completely, thus they must maintain a filtration rate close to the normal rate.
How does the kidney achieve a reduction in RBF but maintain its GFR?
The kidney constricts both the afferent and efferent arterioles, allowing some blood enter, but filtering a greater proportion of that blood. This increase Filtration Fraction causes an increase in the PIgc and reduces the NFP and GFR somewhat, but maintains overall function.
