Urology Flashcards
(35 cards)
What is the role of the peritubular arteries
Exchange and reabsorption
And supply the nephron with O2 and nutrients
Difference between internal and external sphincter
Internal = involuntary control to prevent urination, smooth muscle External = voluntary control to prevent urination, striated muscle
What is the trigone
Area on destructor muscle
When the trigone is stretched, a signal is sent to the brain that you need to urinate
What does the bulbourethral gland do
Secretes lubricant which promotes sperm survival
Why does the cortex have a granular appearance and the medulla have a striated appearance
The loops of henle and collecting ducts extend into the medulla, giving it a striated appareance
But the bowman’s capsules are in the cortex, giving it a granular appearance
Describe the difference between the superficial nephrons and the juxtamedullary nephrons
Superficial nephrons
- bowman’s capsule is towards outer part of cortex
- loop of henle extends into outer medulla
Juxtamedullary nephrons
- bowman’s capsule is near the border of cortex and outer medulla
- loop of henle extends into inner medulla
There are approx 10 times more superficial nephrons than juxtamedullary
Constituents of the juxta glomerular apparatus
Macula densa (cells on distal convulsed tubule) Juxta glomerular cells (secrete renin into afferent arteriole) Extra glomerular mesangial cells
Functions of the juxta glomerular apparatus
GFR regulation through the tubulo glomerular feedback mechanism
Blood pressure regulation through renin secretion
How is fluid driven through the semi permeable membrane in the passive process of filtration in bowman’s capsule
By the hydrostatic pressure of the heart
Doscrube the filtration apparatus of the bowman’s capsule
Capillary walls have fenestrae which allow small molecules and water to pass through
Bowman’s capsule wall have epithelial podocytes. Between each podocyte is a slit with a slit diaphragm which has holes in to allow small molecules and water to filter through into the nephron
Difference between hydrostatic and oncotic pressure
Hydrostatic
- Exerted by fluid molecules
- fluid molecules and small solutes are pushed out
Oncotic
- exerted by proteins and large solutes
- fluid molecules are pulled in across semi permeable membrane
How to calculate net ultrafiltration pressure
Hydrostatic pressure in glomerular capillaries - oncotic pressure in glomerular capillaries - hydrostatic pressure in bowman’s capsule
What is the cardinal feature of renal disease
Gall in GFR (indicates excretory products in the plasma)
How to calculate GFR
GFR = net ultrafiltration pressure x ultrafiltration coefficient
What does ultrafiltration coefficient depend on
Membrane permeability
SA for exchange
Healthy GFR ranges for adults
Male = 90-140 ml/min Female = 80-125 ml/min
What is GFR
The amount of fluid filtered from the glomeruli into the bowman’s capsule, across both kidneys, per unit time (ml/min)
2 feedback mechanisms for regulating GFR
1) myogenic feedback mechanism
- afferent arteriole bp increases so it stretches
- smooth muscle in afferent arteriole contracts to constrict the vessel and increase resistance
- decreases blood flow and stabilises GFR
2) tubulo glomerular feeedback mechanism
- GFR increase
- NaCl in loop of henle increases and this is detected by the macula densa
- macula densa increases ATP and adenosine discharge which causes the afferent arteriole to constrict
- reduces blood flow and stabilises GFR
(Opposite actions for decreased GFR)
What is renal clearance
The number of litres of plasma that are completely cleared of a substance per unit time (ml/min)
Renal clearance x conc of substance in plasma = rate of urine production x conc of substance in urine
What about creatinine can indicate renal failure
Low renal clearance of creatinine or high plasma conc
What about creatinine levels could indicate renal failure
High plasma levels
Or low renal clearance
What is filtration fraction
FF = GFR/RPF
Which molecule can be used to determine RPF
PAH (para amino hippurate)
The amount of PAH that enters the kidneys is equal to the amount that is excreted - all the PAH in the blood that enters the kidneys is excreted
There is no PAH left in the blood after the kidneys
So the GFR of PAH = the RPF
(Renal plasma flow is the volume of blood that enters the kidneys per unit time)
How does coupled transport work
The movement of one substance down its electrochemical gradient provides energy for the second substance to move against its electrochemical gradient
