excretion Flashcards
(27 cards)
main role of kidney
Removers of waste, maintainers of balance
Maintain extracellular fluid composition and volume
Prevent build-up/depletion
Filtration followed by reabsorption
Produce some hormones (erythropoietin)
pathway of blood in kidneys
Aorta >Renal artery> blood enters kidney
Leaves kidneys >Renal Vein> Vena cava
Ureter
connects kidney to urinary bladder
Renal pelvis
huge drain to collect urine to funnel it to the ureter
Renal pyramid
bundles of tubules
Renal cortex
outer
Renal medulla
inner
Nephron
Tiny capillary delivering blood to tubule
Passes across boundary
Renal corpuscle
Glomerulus, Bowman’s capsule, site ultrafication
Glomerulus
“ball of wool”: tangle of porous capillaries
1. The wall of the capillary (endothelium)
2. The glomerular basement membrane
3. Podocytes (food processors)
what can and cannot go through glomerulus
CAN
Small molecules (<3nm)
Water, glucose, amino acids, urea, small ions like Na+ and K+
CANNOT
Large proteins
Blood cells (red and white)
Bowman’s capsule
surrounds glomerulus, absorb filtrate from it
Water pressure forces things out of capillaries into Bowman’s capsule
Proximal convoluted tubule
Lined with cells covered in microvilli
Main site of reabsorption of most solutes (glucose, Na+, amino acids, vitamins, bicarbonate)
Reabsorption of glucose in proximal convoluted tubule
Na+ is actively pumped out of the tubule, glucose is cotransported with Na+ via trans-membrane protein
active trans
Loop of Henle
Inside the medulla
Thin, Descending limb
Thick, Ascending limb
Assists in reducing the water content of urine
passive transport in loop of henle
Descending - water moves out as it goes down (reclaim water)
Ascending - thickened wall starts lower down, prevents water from moving across the wall of tubule
Amount of water is sort of locked in, stays the same
*Active pumping of Na+ and Cl- : stops water from flowing back into tubule via passive transport
Concentration of solutes are stronger as you descend further into the medulla
true
Distal convoluted tubal
Similar to proximal but shorter and with fewer microvilli
- Excess K+ is actively secrete into the nephron here, under control of Aldosterone
- Excess H+ is also secreted here, helping to maintain blood pH balance
Collecting duct
Collects urine produced from many nephrons and delivers it to the renal pelvis
Involved in water balance:
* Permeable to water
* Reabsorbs water under the influence of Vasopressin, produced in the hypothalamus
* Vasopressin increases the permeability of the collecting duct to water
The kidney filters the blood by…
20% plasma volume removed into nephron
70% of that is reabsorbed almost immediately in Proximal Convoluted Tubule
MEASURING GLOMERULAR FILTRATION RATE
GFR = (concentration in urine x urine flow rate (mL/min)) / concentration in blood
Inulin
plant carbohydrate, not reabsorbed at all by kidney
End up being urinate
How much goes in vs. how much comes out
How quickly this occurs
Creatinine
muscle breakdown byproduct - not reabsorbed
(and actually actively secreted a little)
Aldosterone
Produced by the adrenal gland (which sits on top of the kidney) in response to low blood pressure
Increased reabsorption of Na+ in the distal convoluted tubule and collecting duct
Therefore increases blood volume because water follows Na+ passively
