excretion

Question 1

What is the role of the liver?

Answer 1

breaks down harmful substances as well as toxic waste

breakdown of excess amino acids

Question 2

describe the structure of the liver?

Answer 2

composed of liver lobules

Each lobule is connected to hepatic vein and hepatic artery and hepatic portal vein

Question 3

What is the hepatic vein

Answer 3

the vein
which takes deoxygenated blood away from the liver, through the central vein

Question 4

What is the hepatic portal vein

Answer 4

contains the product of digestion

contains bile duct which transports bile to gall bladder to be stored

Question 5

What is a hepatic artery

Answer 5

responsible for supplying the liver with oxygenated
blood.

Question 6

Describe excretion in liver

Answer 6

Removal of amino group from amino acid to form ammonia and organic acids. (Deamination)

respiration of acids forms ATP or converted to carbohydrates

Ammonia is converted into urea by the addition of CO2

urea released by liver and filtered out by kidneys to produces urine

Question 7

What is the role of the kidney

Answer 7

excretion of waste products such as urea in the form of urine.

Question 8

Summary of kidney function

Answer 8

Blood enters kidney and passes capillaries in the cortex

waste products are filtered as it passes through nephrons which surround capillaries

selective reabsorption occurs which reabsorbs useful substances in the medulla

substances excreted pass along ureter and finally reach bladder where they are disposed of as urine

Question 9

Describe ultrafiltration

Answer 9

Blood enters glomerulus through afferent arteriole

blood leaves glomerulus though efferent arteriole

water containing less than 69,000 MR is able to leave capillary and enter the bowman’s capsule

fluid passes through holes in endothelium and then though epithelium of bowman’s capsule

Question 10

Describe selective reabsorption

Answer 10

Takes place in proximal convoluted tubule

100% glucose and amino acids are reabsorbed

Cells lining the PCT are adapted for this by having a large surface area and have many mitochondria

Question 11

describe the function of loop of Henle

Answer 11

produce low water potential in the medulla of kidney

descending limb is permeable to water so filtrates water potential decreases as it goes down.

ascending limb is impermeable to water but allows Na and Cl ions out of filtrate so water potential of filtrate rises

Question 12

Describe the process that happens when water potential is too low

Answer 12

osmoreceptors in the hypothalamus detect change in water potential

Hypothalamus sends nerve impulses to the posterior pituitary gland to release ADH

ADH causes walls of DCT and collecting duct to be more permeable

Question 13

How does ADH work

Answer 13

ADH binds to receptors in the plasma membrane of collecting duct cells

activates enzymes to produce cAMP

causes vesicle in collecting duct to fuse with plasma membrane

membranes of vesicles have aquaporins which make cells more permeable