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
