The kidneys and water balance

What are the 2 functions of the kidneys?

They regulate the water content. They excrete toxic waste and substances that are in excess.

What happens as blood passes through the kidneys?

It is filtered as the waste products move from the blood plasma to the kidneys.

How does blood enter the kidney?

Through the renal artery.

How does blood leave the kidney?

Through the renal vein.

What is the cortex?

The outermost region of the kidney.

What is the medulla?

The inner section of the kidney.

What is the renal pelvis?

The tube linking the kidney to the ureter.

What is the capsule?

The outer membrane of the kidney.

Where are nephrons located?

Between the cortex and medulla.

Where does the blood flow to after the renal artery?

The glomerulus.

What is the glomerulus?

A knot of capillaries.

Why is there a high pressure in the glomerulus?

Because the blood vessel leaving it is narrower than the one entering it so the blood backs up and creates high pressure.

What is the effect of the high pressure in the glomerulus?

The pressure forces plasma fluid and small molecules out of the blood and into the Bowman's capsule.

What is this process known as?

Ultrafiltration.

What small molecules can get forced into the Bowman's capsule?

Water, salts, glucose and urea.

What do the walls of the capillaries act as in ultrafiltration?

A very fine filter.

When and where does selective reabsorption occur?

As the filtrate moves through the nephron tubules. This mainly happens in the proximal convoluted tubule.

How do glucose and amino acids get reabsorbed into the blood?

ALL the glucose and amino acids get reabsorbed through diffusion and active transport.

What 2 structures regulate the amount of salt and water in the body?

The loop of Henle and collecting duct reabsorb all the extra water and salt.

What happens when you have not drunk much water?

The kidneys reabsorb more water → volume of urine produced is less → urine is very concentrated → dark yellow/orange.

What happens when you have drunk enough water?

The kidneys excrete more water → a large quantity of urine is produced → urine is diluted → pale yellow.

Where is ADH released from?

The pituitary gland.

What happens when more ADH is released?

More water gets reabsorbed in the tubules of the kidney as they become more permeable to water.

What happens when less ADH is released?

Less water gets absorbed by the tubules of the kidney as they become less permeable to water.