Topic 6C: Kidneys Flashcards
Function of Kidneys
- excretes waste products like urea
- regulates water potential of the blood(osmoregulation)
Structure of Kidneys
- Cortext (outlayer)
- medulla (inner layer)
- Renal Artery
- Renal Vein
- Ureter
- Bladder
- Urethra
What is a Nephron?
Long tubules along with bundle of capillaries where the blood is filtered
How many nephrons in one kidney?
One million
Stages in Ultrafiltration
- Blood enters the through the afferent arteriole from the renal artery
- because the diameter of the afferent a is bigger than the efferent a it causes a HIGH hydrostatic pressure at the glomerulus
- forces small molecules and liquid in the blood out of the capillaries into the bowmans capsule.
- goes through three layers
- produces the a glomerular filtrate in the bowmans capsule.
- proteins are too large to enter through
-
What layers are involved in ultrafiltration?
- Capillary wall
- Basement membrane
- Epithelium of bowmans capsule
Why cant proteins pass through to the bowmans capsule?
they are too large so they stay in the blood
Structure of Nephron
Afferent arteriole Glomerulus Efferent arteriole Bowmans Capsule Proximal Convoluted Tubule Loop of Henle Distal Convoluted Tubule Collecting Duct
What is in the medulla?
Loop of Henle and Collecting Duct
What happens in the PCT?
- Useful substances like glucose leave the tubules and into the capillary network by AT and FD
- Water enter the blood by osmosis because the wp of water in blood is lower than filtrate.
Adaptations of PCT
- microvilli on the epithelium wall of PCT increases the SA for selective reabsorption
- lots of mitochondria provides ATP for active transport
What is urine made up of?
- water
- dissolved salts
- urea
- hormones and excess vitamins
What is osmosregulation?
When the kidneys regulate the water potential of blood so that the body has just the right amount of water.
If water potential of blood is too low..
- more water is absorbed into the blood
- urine is more concentrated so less water is lost during excretion
If water potential of blood is too high
Less water is absorbed into the blood
-urine is dilute so more water is lost during excretion.
What does the Loop of Henle do?
Maintains a sodium ion gradient
- this is for the cotransport of glucose and amino acids with Na+
How many limbs does loop of Henle have?
Descending and ascending limb
Stages of Loop of Henle
1) Top of a limb Na+ are actively transported out into the medulla
- water stays inside because a limb is impermeable to water.
2) Creates a low water potential in the medulla because there is a high concentration of ions.
- WP gradient established
3) Water from the d limb and collecting duct diffuse out into the medulla by osmosis
- this makes the filtrate more concentrated
4) The water in the medulla is reabsorbed into the blood through the capillary network
What causes the Na+ to be actively transported out to the medulla from the top of the ascending limb?
Near the bottom of the ascending limb there is an increase of Na+ions which diffuses out into the medulla.
What happens at the distal convulted tubule?
Water diffuses out of the distal convoluted tubule by osmosis and is reabsorbed into the blood.
What happens in the collecting duct?
- In the medulla there is a low water potential as a result of the loop of henle
- This causes water to move out of the CD by osmosis leaving the filtrate to remain in the collecting duct
What type of cells monitors the water potential of blood?
osmoreceptors
Where are osmorecptors located in the body
part of the brain called the hypthalamus
What does ADH stand for?
Antidiuertic Hormone
What happens to ADH when you are dehydrated?
- water potential of the blood drops
- detected by osmoreceptors in the hypothalmus
- sends a signal to the posterior pituitary gland (PPG)
- (PPG) is stimulated to release MORE ADH into the blood
- More ADH means that DCT and CD are more permeable to water
- so more water is reabsorbed into the blood by osmosis
What happens to ADH when you are hydrated
- water potential of the blood rises
- detected by osmoreceptors in the hypothalmus
- sends a signal to the posterior pituitary gland (PPG)
- (PGG) is stimulated to release LESS ADH into the blood
- Less ADH means that DCT and CD are less permeable to water
- so LESS water is reabsorbed into the blood by osmosis
What kind of urine do you produced if you are hydrated?
A large amount of dilute urine is produced and more water is lost.
What kind of urine do you produced if you are dehydrated?
A small amount of highly concentrated urine is produced and less water is lost.
Animals which live in drier climates will have
Animals which live in drier climates will have longer loops of Henle
What are the effects of having a longer loops of Henle? (For animals living in drier climates)
- Greater amount of ions pumped out of ascending limb (filtrate) into blood.
- Creating a much lower water potential in medulla tissue
- Steeper water potential gradient created
- More water reabsorbed from collecting duct by osmosis
- Urine has a lower water potential(more concentrated)
