15.5 Structure And Function Of The Mammalian Kidney Flashcards
Main roles of the kidney in the body
Excretion
Osmoregulation
Blood vessel taking blood to the kidney
Renal artery
Blood vessel taking blood away from the kidney
Renal vein
Ureter
Tubes carrying urine from the kidney to the bladder
Urethra
Tube through which urine exits the body
Sphincter
Controls flow of urine out of the body
Sphincter
Controls flow of urine out of the body
3 main areas of the kidney
Cortex
Medulla
Pelvis
Cortex
Dark outer layer
Filtering of blood takes place
Dense capillary network carrying blood from renal artery to nephrons
Medulla
Lighter in colour
Contains tubules of nephrons which form pyramids of kidney and the collecting duct P
Pelvis in the kidney
Central chamber of kidney where urine collects before passing down the ureter
Bowman’s capsule
C shaped structure containing the glomerulus (tangle of capillaries)
More blood enters glomerulus than leaves due to ultrafiltration process
Proximal convoluted tubule
First coiled region after BC
Found in cortex of the kidney
Reabsorption takes place
Loop of Henle
Long loop of tubule that creates region with very high solute concentration in tissue fluid in medulla
Descending loop - from cortex to medulla
Ascending loop - from medulla to cortex
Distal convoluted tubule
Second twisted tubule
Adjust water balance of the body
Permeability of the walls are affected by ADH
Collecting duct
Urine passes down the collecting duct through the medulla to the pelvis
Walls of collecting duct are sensitive to ADH
Concentration of substances in blood leaving the kidney
Lower levels of urea
Glucose, amino acids are similar to the blood entering the kidneys
How to observe nephrons during dissection of kidney
Drop of hydrogen peroxide added to cut surface of the kidney
Rapid effervescence
After this, renal tubules, collecting duct and loops of Henle are clearer to see by strings of bubbles
Difference between DCT and PCT
PCT has brush border
DCT have larger lumen, which are more open
Thickness of walls of ascending loop and descending loop of Henle
Ascending - thicker walls
Descending - thinner walls
Ultrafiltration
Forms tissue fluid in capillary beds of the body
Blood enters glomerulus under high pressure, so smaller molecules are forced out
Fluid passes through the basement membrane - made of network of collagen fibres and other proteins (sieve)
What can pass through basement membrane?
Most of the plasma contents
Blood cells and proteins are retained in the capillary due to size
Podocytes
Podocytes have extensions - pedicels- that wrap around capillaries forming slits so any cells, platelets or large plasma proteins do not get through into the tubule
Reabsorption
Ultrafiltration removes urea, water, glucose, salts
Some of these substances are needed by the body
After Bowman’s capsule, most of the filtered substances are returned back to the blood
Adaptations of PCT
Covered in microvilli - increasing SA
Many mitochondria to provide ATP needed in active transport
How is the loop of Henle a counter current multiplier?
It uses energy to produce concentration gradients that cause movement of substances from one area to another
Water balance in descending Loop of Henle
Upper part of descending limb is impermeable to water
Lower part of descending limb is permeable and runs down into the medulla -
