Renal Function Flashcards
What are the 3 layers of the Glomerular Filtration Barrier?
- Capillary Endothelium
- Glomerular Basement Membrane
- Podocyte Epithelium
What are the layers from internal to external of the Glomerular Basement Membrane?
- Lamina Rara Interna
- Lamina Densa
- Lamina Rara Externa
What are the Lamina Rara Interna and Externa of the Glomerular Basement Membrane composed of?
Proteoglycans
- Specifically, Heparin Sulfate
What is the purpose of the Proteoglycans in the Lamina Rara Interna and Externa in the Glomerular Basement Membrane?
Provide Electronegative charge that repels negatively charged substances like proteins
What in the Capillary Endothelium of the glomerular filtration barrier forms a sticky biogel in the capillary lumen?
Glycocalyx
What is the job of the Glycocalyx in the Capillary Endothelium of the glomerular filtration barrier?
Repels charged proteins and forms initial barrier for filtrates to pass through
- found in the fenestrations of the capillary endothelium
List of the order of things that a filtrate would encounter from first to last if it were attempting to be filtered at the Glomerulus
Glycocalyx Capillary Endothlium Lamina Rara Interna Lamina Densa Lamina Rara Externa Podocyte Epithelium
If something is reabsorbed while in the nephron of the kidney, where does it get taken?
From the nephron back INTO the BLOOD
Urinary Excretion calculation equation?
= Amount filtered - Amount reabsorbed + Amount secreted
Can things get secreted from the blood into the nephron once past the glomerulus?
YES - “amount secreted”
What goes into the kidney, must come out.
Arterial input =
Venous output + Urine output
Ux stands for?
Urinary concentration [x]
= Concentration/Volume
V stands for?
Urinary FLOW rate
= Urine Volume/Time
What is the equation for urine excretion rate of x?
Ux * V
What is Renal Clearance?
Rate at which a certain substance is removed from the plasma and excreted in the urine
What is the equation for Renal Clearance of x?
Urine excretion rate of x/plasma [x]
Cx = Ux * V/Px
What is Glomerular Filtration Rate?
Volume of plasma filtered into both kidneys per unit time
What is Glomerular Filtrate?
Fluid filtered into Bowman’s Capsule
GFR
Glomerular Filtration Rate
GFR is about ___% of Renal Blood Flow (RBF)
20%
What is the Filtration Fraction?
= GFR/RBF (ratio)
- Usually about 20%
- Amount of filtered fluid at the kidney compared to the TOTAL Amount of fluid that reached the kidney
If the Filtration Fraction increases, the oncotic pressure of which arteriole increases and why?
Efferent arteriole oncotic pressure increases
- Due to more fluid being filtered and more solutes left in the efferent arteriole
- The increased oncotic pressure will increase tubular reabsorption!
What is a normal GFR?
125 mL/min
What can you use to estimate GFR?
Renal Clearance - if molecule is not reabsorbed or secreted
If you are estimating GFR using Renal Clearance, what is the equation?
GFR = Ux * V/ Px
What are 2 molecules to use to calculate GFR (via Renal Clearance estimation)?
Inulin
Creatine
Filtered load equation for x?
= GFR * Px
Sympathetic effect on which arteriole through what receptor?
Vasoconstriction of afferent arteriole through alpha -1
Sympathetic effect on Juxtaglomerular Cells through what receptor?
Increased Renin release through beta -1
Sympathetic effect on Tubular Epithelial cells?
Na+/K+ ATPase to increase sodium reabsorption through alpha -1
Starling forces that FAVOR filtration at the glomerulus
- Hydrostatic pressure of Glomerular Capillary
2. Oncotic pressure of Bowman’s Capusle
Starling forces that DO NOT favor filtration at the glomerulus
- Hydrostatic pressure of Bowman’s Capsule
2. Oncotic pressure of Glomerular Capillary
Based on the starling forces, if the number is (+), did filtration occur?
YES
What is the Ultrafiltration Pressure (Puf)?
Hydrostatic pressure of Glomerular Capillary
(minus) - Hydrostatic pressure of Bowman’s capsule
(minus) - Oncotic pressure of glomerular capillary
What are the 3 physical factors that contribute to the GFR?
- Hydraulic Conductivity (permeability)
- Surface Area for filtration
- Capillary Ultrafiltration Pressure (Puf)
Hydraulic conductivity (Lp) X Surface area for filtration (Sf) is equal to?
Ultrafiltration Coefficient (Kf)
Based on the physical factors, what is the GFR equation?
GFR = Kf X Puf
Besides the hydraulic conductivity and surface area for filtration, what else can alter the Ultrafiltration Coefficient (Kf)?
Mesangial cells!
- Contractile properties alters the surface area for filtration
What 2 sites are the sites of regulation for hydrostatic pressures?
Afferent and Efferent Arterioles
Vasoconstriction of the afferent arteriole will have what effect on the GFR?
Vasoconstriction will DECREASE Puf (ultrafiltration pressure) which will DECREASE GFR
Vasodilation of the afferent arteriole will have what effect on the GFR?
Vasodilation will INCREASE Puf (ultrafiltration pressure) which will INCREASE GFR and Renal Blood Flow
Vasoconstriction of the efferent arteriole will have what effect on the GFR?
Vasoconstriction will INCREASE Puf (ultrafiltration pressure) which will INCREASE GFR
Vasodilation of the efferent arteriole will have what effect on the GFR?
Vasodilation will DECREASE Puf (ultrafiltration pressure) which will DECREASE GFR but increase Renal Blood flow
There are more alpha-1 receptors on which arteriole?
Afferent
Job of: Sympathetics (catecholamines) Endothelin Angiotensin 2 ATP
Vasoconstriction
Job of: Prostaglandins Bradykinin Nitric Oxide ACE inhibitors
Vasodilation
What maintains Renal Blood Flow and GFR across a range of arterial pressures?
Autoregulation
What are the 2 mechanisms for Autoregulation?
- Myogenic
2. Tubuloglomerular feedback
What is the myogenic (smooth muscle) response to Autoregulation?
High pressures results in vasoconstriction of the afferent arteriole and vasodilation of the efferent arteriole in order to protect the glomerular capillaries from the high pressures
What 3 things are involved in the Juxtaglomerular Apparatus?
Macula Densa Cells - on distal tubule
Juxtaglomerular Cells - on afferent arteriole
Mesangial cells - beyond glomerulus
What does the Juxtaglomerular Apparatus sense?
NaCl in the tubule
What does the Tubuloglomerular feedback mechanism maintain?
Constant sodium delivery to the distal tubule and a constant GFR
Describe the order of events that will occur if the Macula Densa senses HIGH NaCl
- Increased Na+ reabsorption into cell using NKCC2 channel
- ATP and Adenosine are released from cell
- ATP and Adenosine bind to receptors
- Calcium is released to vascular smooth muscle surrounding the Afferent Arteriole
- Vasoconstriction occurs of arteriole
- DECREASED GFR and Renin release
Describe the order of events that will occur if the Macula Densa sense LOW NaCl
- Decreased Na+ reabsorption into cell
- Less ATP and Adenosine are released
- No Calcium is released to smooth muscle
- Afferent Arteriole vasoDILATES
- INCREASES GFR and Renin release
Renin secretion is promoted by ____ NaCl delivery to the Macula Densa
DECREASED
Renin secretion is also promoted by sympathetic stimulation of?
Beta-1 receptors on the JG apparatus
What is the Fractional Excretion?
% of what was filtered that actually got excreted
What is the equation for the Fractional Excretion?
(Ux * V)/(GFR * Px)
= (Ux * Pcr)/(Px * Ucr)
