5.1.2: Excretion as an example of homeostatic control

Question 1

Define excretion

Answer 1

The removal of metabolic waste from the body

Question 2

Define metabolic waste

Answer 2

Substances that could be toxic or produced in excess by reactions in cells

Question 3

Give 2 examples of metabolic waste and how it is removed

Answer 3

CO2 = waste product from respiration excreted in lungs

Nitrogenous waste urea = created from excess amino acids in diet and broken down in liver to ammonia then into urea which is excreted by kidneys

Question 4

Compare excretion and secretion

Answer 4

Excretion is removal of unwanted metabolic waste, secretion is useful products released from glands

Both require ATP and both substances travel in blood

Question 5

Give an example of a secreted and excreted substance

Answer 5

Oestrogen vs urea

Question 6

What is the function of kupffer cells and where are they found ?

Answer 6

Within sinusoids. Protect against disease by engulfing foreign particles and phagocytose bacteria which have entered via hepatic portal vein from digestive system.

Question 7

What is the function of the hepatic artery ?

Answer 7

Takes oxygenated blood into liver

Question 8

What is the function of the hepatic vein ?

Answer 8

Where blood leaves the liver

Question 9

What is the function of the hepatic portal vein ?

Answer 9

Supplies the liver with its own blood from deoxygenated digestive system

Question 10

In which vessel in the liver is pressure the highest and why ?

Answer 10

Hepatic artery as blood has come from aorta

Question 11

Describe the composition of blood entering the liver from the digestive system

Answer 11

Rich in amino acids and lower O2 concentration than hepatic artery as O2 used in digestive system

Question 12

What are the function of hepatocytes ?

Answer 12

Liver cells which make bile

Question 13

Give adaptions of hepatocytes which enable a high metabolic rate of cells in the liver

Answer 13

• Many mitochondria to supply ATP
• Prominent golgi apparatus
• Large nuclei

Question 14

What is the function of the bile duct and give features of it ?

Answer 14

Surrounded by hepatocytes (no cell wall) and passes bile into gall bladder where it is stored. Bile is secreted from hepatocytes when they break down old blood cells then travel through bile duct.

Question 14

What is a section of the liver called ?

Answer 14

A lobule

Question 15

What are the function of sinusoids ?

Answer 15

Spaces surrounded by hepatocytes where blood from hepatic artery and hepatic portal vein mix so blood becomes partially oxygenated

Question 16

Give adaptations of the liver

Answer 16

• Hepatic artery divides into many branches to carry blood to lobules
• Branches divide to form many sinusoids which are narrow and lined with many hepatocytes enabling lots of blood to flow past lots of liver cells

Question 17

List the 3 functions of the liver

Answer 17

• Storage of glycogen
• Detoxification
• Formation of urea

Question 18

What is the overall function of the kidney ?

Answer 18

Responsible for excretion of nitrogenous waste and osmoregulation

Question 19

How does the liver carry out its role of glycogen storage ?

Answer 19

In response to insulin, hepatocytes absorb excess glucose from blood and covert it to glycogen. In response to glucagon, glycogen is hydrolysed back to glucose and released into blood by hepatocytes

Question 20

How does the liver carry out its function of detoxification ?

Answer 20

Liver contains enzymes to neutralise and breakdown toxic chemicals

Question 21

How does the liver carry out its function to form urea ?

Answer 21

Amino acids are deaminated (reacted with oxygen) to ammonia + keto acid . Ammonia is then reacted with CO2 in the ornithine cycle to form urea and water

Question 22

Give 4 metabolic roles of the liver

Answer 22

• Protein synthesis
• Use amino acids in respiration
• Gluconeogenesis
• Produces bile

Question 23

What is the renal artery ?

Answer 23

Supplies the kidney with unfiltered blood

Question 24

What is the renal vein ?

Answer 24

Carries filtered blood away from kidney

Question 25

Give the sequence of events from kidney to urethra

Answer 25

Kidneys - ureter - bladder - urethra