The kidneys and excretion Flashcards
What do the kidneys do?
- They excrete waste products
- They regulate the water potential of the blood
where does blood enter the kidneys
through the renal artery, and then passes through capillaries in the cortex of the kidney
What is ultrafiltration
when substances are filtered out of the blood
What is selective reabsorption
when useful substances are absorbed back into the blood from the medulla and cortex
filtered blood passes out of the kidneys through the……………
Renal vein
What are nephrons
and how many are there in each kidney
long tubules with a bundle of capillaries
THIS IS WHERE THE BLOOD IS FILTERED
- around one million nephrons in each kidney
Process: What happens at the nephron
1) blood enters from the renal arteries enters the arterioles in the cortex
2) Each arteriole splits into a glomerulus- a bundle of capillaries looped inside a hollow ball ( bowman’s capsule)
3) Blood gets taken into and out of each glomerulus via different arterioles.
4) High pressure in the glomerulus forces small molecules that are in the blood out of the capillaries and INTO the bowman’s capsule
5) The small molecules and liquid have to pass through 3 layers to get into the Bowman’s capsule and enter the nephron tubule
- basement membrane, epithelium of the bowman’s capsule, LARGE molecules eg PROTEINS can not pass through and stay in the blood
6) Filtrate ( the small molecules) pass along the rest of the nephron and useful substances are reabsorbed along the way.
7) Filtrate flows through the collecting duct and passes out of the kidney along the ureter
Where does ultrafiltration take place
In the Bowman’s capsule
where does the afferent arteriole take the blood
Takes the blood into each glomerlus
Where does the efferent arteriole take the blood
Takes the filtered blood away from the glomerulus
why is the blood in the glomerulus under high pressure
The diameter of the efferent arteriole is SMALLER than the diameter of the afferent arteriole
where does Selective reabsorption take place
Takes place along the PCT and along the DCT
PROCESS|: Selective reabsoeption
1) useful substances leave the tubules of the nephron and enter the capillary network
2) Microvilli on the epithelium wall of the PCT provides a large surface area for the reabsorption of useful substances from the filtrate
3) Glucose, amino acids, vitamins, salt are reabsorbed along the PCT by A.T and F.D
4) some urea reabsorbed by diffusion
5) The water potential of the blood is lower than the water potential of the filtrate, so water enters the blood by osmosis. and water is reabsorbed from the loop of henle, DCT and the collecting duct.
6) The filtrate that remains in the urine passes along the ureter to the bladder.
What molecules are reabsorbed along the PCT by active transport and facilitated diffusion?
Glucose, amino acids, salt, vitamins
During selective reabsorption what substance is reabsorbed by diffsion
Urea
