Renal System Flashcards
How many nephrons in a kidney?
Human kidney has approx 1.5million nephrons per kidney
What role do nephrons play?
Important role in controlling:
- Glomerular filtration
- Tubular reabsorption
- Urine formation
What are the different components of the kidney?
- Bowman’s capsule (ultrafiltration takes place)
- Proximal convoluted tubule (PCT)
- Thin descending limb
- Loop of henle
- Thin ascending limb
- Thick ascending limb
- Distal convoluted tubule (DCT)
- Collecting duct
Where do each part of the nephron sit in the kidney?
Bowmans Capsule - Cortex
Thick Descending and Ascending limbs - Outer medulla
Loop of henle & thin limbs - Inner medulla
What are the components of the juxtaglomerular apparatus of the kidney?
ALL SURROUNDED BY BOWMANS CAPSULE
- Efferent arteriole
- Glomerulus
- Granular cells
- Afferent arteriole
OUTSIDE THE BOWMANS CAPSULE
Macula densa cells - sense DCT flow and release factors that affect afferent arteriole diameter
What is glomerular filtration dependent on?
- Capillary permeability
- Hydrostatic pressure in the capillaries
- Hydrostatic pressure in the tubules
- Osmotic pressure of plasma in glomerular capillaries
- Osmotic pressure of tubular filtrate
What are the forces occurring during glomerular filtration?
GFR = (Pcap + §bc) - (Pbc + §cap)
§ = colloid osmotic pressure (protein movement which is usually 0 as little proteins in Bowmans Capsule)
What is the equation for the glomerular filtration rate?
GFR = Kf (Pcap - Pbc - §cap)
Kf - Filtration coefficient (gives an indication of permeability)
What occurs when afferent vasoconstriction takes place?
- Increased resistance
- reduced pressure in capillary
- GFR decreases
What occurs when efferent vasoconstriction takes place?
- Increased pressure in capillary
- Pressure rises
- GFR increases
What occurs in the proximal convoluted tubule?
70% of filtrate is reabsorbed back into the body
What is is the average GFR per day?
180L per day (equivalent to 125ml per min
-Average person has only 3L of plasma therefore it is filtered many times a day
What occurs at the proximal convoluted tubule?
- Active reabsorption of Na+
- Reaborption of glucose an bicarbonate (HCO-)
- Some ions and molecules are secreted into the tubular filtrate (H+ ion secretion is important in reabsorption of bicarbonate)
What are the features of the loop of henle?
Descending limb: -Filtrate (isosmotic) 300mosm/kg
- Permeable to water
- No active ion transport
Ascending limb:
- Filtrate (hypo-osmotic 180mosm/kg
- Active reabsorption of Na+
- Impermeable to water
Bottom of loop:
FIltrate (hyper-osmotic) 1200mosm/kg
What is the need for the loop of henle?
Creates an osmotic gradient in the medullary interstitium
increase in filtrate concentration as you descend and the reverse as you ascend
What is the need for the loop of henle?
Creates an osmotic gradient in the medullary interstitium
increase in filtrate concentration as you descend and the reverse as you ascend
What occurs in the loop of henle?
- Descending limb gives rise to hyper-osmotic medulla (essential in regulation of urine volume)
- Fluid entering the cortex from the ascending limb is hypotonic to plasma
- Countercurrent multiplier (facilitates the reabsorption of water from the collecting ducts toward the hyper-osmotic interstitium
What occurs at the distal convoluted tubule?
Active reabsorption of Na+
Secretion of K+ and H+ ions
Stimulated by the actions of aldosterone
What occurs at the collecting duct?
- Urea is free to move out of the collecting duct in the presence of anti-diuretic hormone (ADH)
- ADH opens water channels, thereby increasing reabsorption of water and concentrating urine
