The Glomerulus Flashcards
3 Functions of the kidneys
Maintain balance of salt, water and pH Endocrine function (secreting hormones) Excrete waste products
Each kidney receives what percentage of the cardiac output
10%
What is the arterial renal blood supply starting from the renal artery
Renal artery Interlobar artery Arcuate artery Interlobular artery Afferent arterial Glomerular/peritubular capillary
What is the importance of the peritubular capillary
Many of the tubular processes of secretion and reabsorption are active
Blood supply is crucial for providing this energy/oxygen
What 3 things occur between the glomerular capillaries and bowmans capsule
Glomerular filtration
Tubular secretion
Tubular reabsorption
How is the filtrate formed
Fluid passes from the blood into bowman’s space
What part of the nephron is responsible for secretion and reabsorption
Distal convoluted tubule
What determines an substances ability to cross the filtration barrier
Pressure Size Charge Rate of blood flow Binding to plasma proteins
Why can’t negatively charged anions cross the glomerular basement membrane
The glomerular basement membrane has a fixed negative charge
What protein is found in urine that is produced by tubules
Tamm horsfall protein.
How does a) hydrostatic p and b) osmotic p change across length of the capillary
a) constant
b) rises
What is glomerular filtration rate (GFR)
Filtration volume per unit time (minutes)
What is the filtration coefficient
Product of the permeability of the filtration barrier and the SA available for filtration
How is GFR calculated
GFR = Kf (HPgc - HPbs - 🥧GC
Filtration coefficient
🥧- oncotic pressure
Can you alter the net ultrafiltration pressure
Permeability and oncotic pressure can’t be altered
But there’s potential to alter HP or SA
What are 2 ways the GFR is decreased
Constriction of the afferent arteriole which decreases the pressure in the glomerular capillary
Or
Dilation of the efferent arteriole which decreased pGC
What are 2 things that increase the GFR
Constriction of the efferent arteriole which increase pGC
or
Dilation of the afferent arteriole which increases pGC
How is systemic arterial pressure auto regulated
Pressure within afferent arterioles rises which stretches the vessel wall
This triggers a contraction of smooth muscle so the arteriole constricts
This prevents an increase in systemic arterial pressure from reaching the capillaries
Reverse happens when systemic arterial pressure falls
What detects NaCl arrival in the distal tubule
Macula densa
How is the GFR of individual nephrons regulated
Rate at which filtered fluid reaches the distal tubule
What happens in response to reduced NaCl delivery
Macular densa cells release prostaglandins
This acts on granular cells triggering renin release
This activated the renin-angiotensin system
How is GFR measured. Give an equation relating to M
M is a marker substance
GFR = Um x urine flow rate / Pm
Um - [M] in urine
Pm - [M] in plasma
What is used to estimate GFR clinically
Creatinine - muscle metabolite
Give the equation for filtration fraction
FF = GFR / renal plasma flow
What is renal clearance
The volume of plasma completely cleared of a substance by the kidney per unit time
How does the composition of glomerular filtrate compare with that of plasma
Similar to plasma but no proteins or cells
What is the average GFR
120/125 ml/min
Give a value for filtration fraction
0.2
