kidney Flashcards
(25 cards)
What is the function of the kidney?
- excretion
- osmoregulation
- filter nitrogenous waste products out of urea
- maintain water balance of blood and pH
What is the function of ureter?
Carries urine to bladder
What is the function of bladder?
Muscular sac that stores urine
What is the function of urethra?
Where urine passes out of the body from
What is the function of renal artery?
Brings oxygenated blood to the kidney
What is the function of renal vein?
Takes deoxygenated blood away from kidney
Where does ultrafiltration take place?
- renal artery leads to smaller arterioles in Cortex
- arteriole splits into glomerulus (bundle of capillaries looped in a hollow ball) and hollow ball is called bowmans capsule
What is the afferent arteriole?
The arteriole that takes blood into each glomerulus of the nephron
What does the efferent arteriole do?
Takes filtered blood away from glomerulus
- smaller in diameter than afferent arteriole so blood in glomerulus is under high pressure
- the high pressure forces liquid and small molecules in the blood out of the capillary and into bowmans capsule
Describe ultrafiltration
- substances are filtered out of the blood and enter tubules in kidneys
- blood enters glomerulus, bundle of capillaries looped inside a hollow ball called bowman’s capsule
- blood in glomerulus in under high pressure because it enters through afferent arteriole and leaves via the smaller efferent arteriole
- high pressure forces liquid and small molecules in blood out of capillary and into bowman’s capsule
- liquid and small molecules pass through capillary wall, basement membrane, epithelium of bowman’s capsule
- larger molecules like proteins and blood cells can’t pass through so stay in blood
What are the 3 layers to enter the bowman’s capsule?
Capillary wall
Basement membrane
Epithelium
What is selective reabsorption?
- useful substances leave tubules of nephrons and enter capillary network that’s wrapped around them
- epithelium of wall of PCT has microvilli for large surface area for reabsorption of useful materials from filtrate in tubules to blood in capillaries
- useful salutes such as glucose, amino acids, vitamins, salts are reabsorbed along PCT via active transport and diffusion
- some urea is reabsorbed by diffusion
- water enters blood via osmosis as water potential is lower than of filtrate
- water is reabsorbed from loop of Henle, DCT, collecting duct
- filtrate that stays is urine which passes to ureter and bladder
What is urine usually made up of?
Water
Dissolved salts
Urea
Other such as hormones and excess vitamins
What does urine not usually contain?
Proteins and blood cells - as too big to be filtered out of blood
Glucose, amino acids and vitamins - actively reabsorbed back into the blood
What happens if water potential of blood is too low? Aka dehydration
More water is reabsorbed by osmosis into the blood from tubules of the nephrons
So urine is more concentrated so less water is lost during excretion
What happens if the water potential of the blood is too high? Aka too hydrated
Less water is reabsorbed by osmosis into the blood from tubules of nephrons
Water is more dilute so more water is lost during excretion
Where does regulation of water potential happen?
loop of henle
Distal convulated tubule
Collecting duct
Volume of water reabsorbed is controlled by hormones
What mechanism helps reabsorption of water?
Countercurrent multiplier mechanism - helps to reabsorb water back into the blood
Set up by ascending limb and descending limb of loop of henle
Explain the counter current multiplier mechanism
- Na+ and Cl- ions are actively pumped out of top of ascending limb out to the medulla. ascending limb is impermeable to water so water stays inside the tubule. creates low water potential in medulla as there is a high concentration of ions.
- lower water potential in medulla than in descending limb so water moves out of descending limb to medulla by osmosis. makes filtrate more concentrated as ions cant diffuse out since its impermeable to ions, water in medulla is reabsorbed into blood through capillary network.
- at the bottom of ascending limb, Na+ and Cl- ions diffuse out into medulla which further lowers water potential in medulla. ascending limb is impermeable to water so water stays in the limb.
- first 3 stages increase ion concentration in medulla which lowers water potential. causes water to move out of collecting duct by osmosis. water in the medulla is reabsorbed back into the blood through capillary network.
how is the volume of water reabsorbed from the collecting duct controlled?
The permeability of the collecting duct changes
What is the benefit of having a long loop of henle for animals that live in areas with little water?
longer the loop of henle, the more water that can be reabsorbed from the filtrate.
when there is a longer ascending limb, there are more ions that are being actively pumped out into the nephron creating a low water potential in the medulla. This means more water moves out of the nephron and collecting duct into the capillaries which gives a very concentrated urine.
Animals living in areas with little water have long loops to save as much water as possible.
What is water reabsorption controlled by?
hormones
What monitors the water potential of the blood?
it is monitored by cells called osmoreceptors in the part of the brain called hypothalamus.
How does ADH act if your dehydrated?
- water content of blood reduces so water potential lowers
- omsoreceptors are stimulated by low water potential
- hypothalamus sends nerve impulses to posterior pituitary gland to release more hormone ADH into the blood
- ADH makes the walls of the DCT and collecting duct more permeable.
- More water is reabsorbed from the tubules into the medulla and in the blood by osmosis.
- small amount of highly concentrated urine is produces do less water is lost
