Excretion in Humans

Question 1

What are the organs that form the excretory system?

Answer 1

• Lungs
• Liver
• Kidneys
• Bladder
• Skin

Question 2

What do kidneys mainly excrete?

Answer 2

Excess water, salts and urea

Question 3

Def. Excretion

Answer 3

The process that eliminates waste or excess material from metabolic reactions in an organism

Question 4

Why is it important to remove waste material in the body?

Answer 4

To prevent build up of toxins and accumulation of ions (taking up space)

Question 5

What is the kidney?

Answer 5

Two bean shaped organs that filter the blood

Question 6

What is the ureter?

Answer 6

The tube that connects the bladder to the kidneys, transporting waste and excess substances

Question 7

What is the bladder?

Answer 7

An organ that stores urine (excess water, salts and urea) as it is being produced by the kidneys

Question 8

What is the urethra?

Answer 8

The tube that connects the bladder to the exterior of the body, where urine is then released

Question 9

What are the two functions of the kidney?

Answer 9

• They regulate the water and ion content of the blood
• They excrete the toxic waste products of metabolism (such as urea) and substances in excess of requirements (such as salts)

Question 10

Where and why is urea produced?

And what is first removed from the amino acid

Answer 10

Produced by the liver due to the deamination of excess amino acids

This means that any amino acids not used for protein production get sent to the liver to be assimilated (converted) into urea, meaning the Nitrogen/Amine group is removed, as it is toxic to cells, and is absorbed in the blood to be sent to the Kidneys. The rest is reused for other processes

Question 11

What is removed from amino acids before deamination

Answer 11

The Nitrogen group – amine group (NH₂) is first removed from the amino acids (deamination)

(This group is toxic to cells in the body)

Question 12

Where are kidneys found?

Answer 12

In the top of the abdominal cavity, underneath the diaphragm

Question 13

What is the renal vein?

Answer 13

A vessel that takes filtered blood away from the kidneys

Question 14

What is the renal artery?

Answer 14

The vessel that brings blood, with waste inside it, to the kidneys

Question 15

Name the parts of a kidney

Answer 15

• Pelvis
• Ureter
• Medulla
• Cortex

Question 16

How is blood filtered in the kidney?

Answer 16

1. Blood flows into the glomerulus under a high-pressure
2. Small particles (e.g. Sugar, Salt, Water & Urea) are forced into the bowman’s capsule (Ultrafiltration)
3. Useful molecules are reabsorbed into the blood, including glucose, some salt and some water (Selective Reabsorbtion)

Question 17

How and where is the amount of water absorbed controlled?

Answer 17

Controlled by a hormone called ADH (released by the pituary gland)

Question 18

What happens when there is not enough/too much water in the blood stream?

Answer 18

I there is too much, water will not be reabsorbed in large quantities, and instead added to urine
Otherwise, if the body is dehydrated, the water will be reabsorbed into the bloodstream, meaning less water is in the urine and it becomes more yellow

Question 19

What are the parts of a nephron?

Answer 19

• Glomerulus
• Bowman’s capsule
• Tubule (Consists of first coiled tubule and Loop of Henle)
• Collecting duct

Question 20

What is the part of the Kidney that filters blood?

Answer 20

Nephrons

Question 21

What process occurs when small substances are forced out of the glomerulus into the bowman’s capsule?

Answer 21

Ultrafiltration

Question 22

What process occurs when the necessary sunstances such as glucose, some water and some salts, reenter the bloodstream?

Answer 22

Selective Reabsorbtion

Question 23

Why is Urea removed from the body?

Answer 23

It is a toxic substance

Question 24

Explain what happens in a nephron

Answer 24

1. Blood passes through Glomerelus at high pressure
2. Small particles such as water, salts, glucose and urea are forced out into the Bowmans Capsule
3. These particles flow through the Tubule which in entwined with capillaries
4. The particles are selectively reabsorbed into the body, depending on what it needs

This takes part in Homeostasis

Question 25

What is the function of the liver in excretion?

Answer 25

• Separation of toxic amine/nitrogen group
• This is absorbed into the blood as urea
• Toxic substances and worn red blood cells are broken down
• Excretory substances such as chloresterol are used in bile
• All of this is called deamination