Kidneys Flashcards
What may cause a hypertonic blood
Too much sweating
Not drinking enough water
Lots of ions in diet
What may cause hypotonic blood
Drinking too much water
Not enough salt in diet
Structure of nephron
Afferent arteriole leading into nephron Branches into smaller capillaries called the glomerulus inside the renal capsule Leading into proximal convoluted tubule Loop of henle Distal convoluted tubule Collecting duct
What’s in urine
Water
Dissolved salts
Urea
Small substances like hormones
NO PROTEIN OR BLOOD
Kidney function
Filter blood to remove waste and selectively reabsorbed useful substances into blood
Why no proteins in wee
Too large to be filtered out
Why no glucose in wee
All absorbed in selective reabsorption by active transport in PCT
4 steps for filtering and reabsorption
Ultrafiltration
Selective reabsorption
Loop of henle
DCT and collecting duct
What causes the high hydrostatic pressure in ultrafiltration
Blood enters through afferent arteriole and spots into lots of smaller capillaries which make up the glomerulus
Adaptation of cells lining PCT
Microvilli provide a large surface area for reabsorption
Lots of mitochondria since need energy for active transport of glucose
Function of loop of henle
Maintains a sodium ion gradient to enable reabsorption of water
Ascending vs descending limb
Ascending is permeable to water, descending impermeable
Hypotonic blood, osmoregulation
Osmoreceptors in hypothalamus detect rise in water potential
Water enters osmoreceptors via osmosis
Triggers posterior pituitary gland to secrete less ADH
Less travels in blood to kidneys
Decreases permeability of distal convoluted tubule and collecting duct to water
By causing less vesicles to fuse with the cell membrane of these cells
Large volume of urine produced
Dilute
Less water reabsorbed at DCT and collecting duct
Hypertonic blood, osmoregulation
Osmoreceptors in hypothalamus detect fall in water potential
Water leaves osmoreceptors via osmosis
Triggers posterior pituitary gland to secrete more ADH
More travels in blood to kidneys
Increases permeability of distal convoluted tubule and collecting duct to water
By causing more vesicles to fuse with the cell membrane of these cells
Small volume of urine produced
Concentrated
More water reabsorbed at DCT and collecting duct
How is urea removed from the blood
Hydrostatic pressure caused by fenestrations of capillary wall
Causes ultrafiltration at renal capsule/glomerulus
Through basement membrane which acts as a filter
Enabled by small size of urea molecules
How is a glomerular filtrate produced
How does ultrafiltration work
Higher than normal hydrostatic pressure caused by fenestrations in capillary endothelium
Water, glucose, urea pass through basement membrane which acts as a filter
Pass through spaces between branches of podocytes
Protein and blood molecules too large to stay behind
Explain the reabsorption of water and glucose
Sodium ions actively transported out of the cells lining the proximal convoluted tubule
Into blood capillaries to reduce sodium concentration in cells
Via sodium potassium pump which required ATP from many mitochondria
Allowing sodium ions from filtrate to move into surrounding cells via facilitated diffusion via co-transport with glucose
Allowing glucose to be reabsorbed
Thicker medulla
Longer loop of Henle
Sodium ion concentration gradient can be maintained over a longer length
More sodium ions actively transported out of ascending loop of henle
More water reabsorbed
How is urea concentrated in the filtrate
Reabsorption of water by osmosis
At the PCT/Descending loop of henle
At the DCT/CD active transport of ions/glucose
How does ADH cause movement of water from lumen to collecting duct
Vesicles containing aquaporins inserted into cell membranes of CD
Water enters via osmosis through aquaporins
Down a water potential gradient
From cell to capillary
Via interstitial fluid
How do the descending and ascending loops work
Filtrate enters descending limb and exits ascending limb
Sodium ions actively transported out of the Ascending limb using ATP
Sodium ions enter Descending limb
Lowering water potential between the two limbs
Water drawn out of permeable descending limb by osmosis into medulla
As the ascending limb is impermeable to water little/no water leaves that part of the loop
Water from the descending limb then enters capillaries returning to the blood
DCT
Makes final adjustment to the water and salts that are reabsorbed
Permeability of its walls alters under influence of certain hormones
Water continues to move out by osmosis the counter current multiplier ensures there is always a water potential gradient
Water out of CD into tissue fluid then surrounding capillaries
