Excretion

Question 1

What are the organs of excretion?

Answer 1

Lungs, kidney, skin

Question 2

What do the lungs excrete?

Answer 2

Carbon dioxide

Question 3

What does the skin excrete?

Answer 3

Sweat (salt, water and urea)

Question 4

What are the excretory products of the kidney?

Answer 4

Urea
Ions/salt
Water

Question 5

How do the kidneys excrete products?

Answer 5

Filtering things out of blood under high pressure and reabsorb the things the body needs.

Question 6

What is the end product of kidney excretion?

Answer 6

Urine

Question 7

What are nephrons?

Answer 7

Filtration units in the kidneys
About 1 million per kidney
Carry out ultrafiltration, reabsorption and release of wastes

Question 8

What is the glomerulus?

Answer 8

A bundle of capillaries at the start of the nephron

Where ultrafiltration happens

Question 9

What is the Bowman’s capsule?

Answer 9

Structure that surrounds the glomerulus

Contains the glomerular filtrate

Question 10

What is the composition of the glomerular filtrate?

Answer 10

Water, urea, ions and glucose

Question 11

What are the stages of ultrafiltration?

Answer 11

1. Blood from the renal artery flows through the glomerulus.
2. A high pressure is built up in the glomerulus which squeezes water, urea, ions and glucose out of the blood and into the Bowman’s capsule
3. The filtered liquid is known as the glomerular filtrate.
   (The glomerulus acts like a filter so big molecules eg protein and blood cells are mot squeezed out)

Question 12

What are the stages of reabsorption?

Answer 12

1. All the glucose is reabsorbed using active transport from the proximal convoluted tubule (to be used in respiration).
2. Sufficient (not excess) ions are reabsorbed.
3. Sufficient water is reabsorbed from the collecting duct into the bloodstream by osmosis.

Question 13

How are wastes released?

Answer 13

The remaining water, ions and urea form urine. This goes out of the nephron, through the ureter and to the bladder, where it is stored before being releases via the urethra.

Question 14

What is osmoregulation?

Answer 14

The body balancing the water coming in against the water going out.
eg If a person is sweating a lot (losing water), the kidneys reabsorb more water so less is lost in the urine.

Question 15

What is ADH and what does it do?

Answer 15

Anti-diuretic hormone
Secreted by the pituitary gland
Causes collecting duct to become more permeable and reabsorb more water
Dehydration -> more ADH released

Question 16

What does urine contain?

Answer 16

Water, urea and salts

Question 17

What is selective reabsorption?

Answer 17

The kidney reabsorbing the molecules which have been filtered out.