excretion

Question 1

what is excretion

Answer 1

Excretion: the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements.

Substances should include carbon dioxide, urea and salts.

Question 2

function of the kidney

Answer 2

Removal of urea and excess water and the re-absorption of glucose and some salts

Urea is formed in the liver from excess amino acids

Question 3

function of the liver

Answer 3

Urea is formed in the liver from excess amino acids

Alcohol, drugs & hormones are broken down in the liver

Question 4

function of kidney cortex

Answer 4

contains Bowman’s capsules and coiled tubules

Question 5

function of ureter

Answer 5

carries urine from kidney to bladder

Question 6

function of medulla

Answer 6

contains loops of Henlé and collecting ducts

Question 7

function of loop of henle

Answer 7

selectively absorbs water/solutes

Question 8

function of collecting ducts

Answer 8

reabsorbs water into blood and store wastes until they are passed into ureter

Question 9

function of urethra

Answer 9

carried urine from bladder to the outside.

Question 10

function of bladder

Answer 10

stores urine

Question 11

function of renal capsule

Answer 11

filters from blood: water, glucose, urea and salts.

Question 12

function of tubule

Answer 12

(yellow) reabsorbs 100% of glucose, most of the water and some salts back into the blood (red), leading to concentration of urea in the urine as well as loss of excess water and salts into the tubule.

Question 13

function of renal artery

Answer 13

brings wastes and water from blood

Question 14

function of renal vein

Answer 14

reabsorbs water and useful molecules and leaves wastes behind

Question 15

process in the kidney

Answer 15

Ultrafiltration: blood from renal artery enters the glomerulus. Water, urea, salts and glucose are forced into the Bowman’s capsule. Blood cells and large proteins cannot pass through.

Selective reabsorption: in the proximal tubule two thirds of the salt and water and all the glucose moves out of the nephron, by active transport. These substances are reabsorbed back into the blood capillary.

Loop of Henlé: this part of the loop of Henlé is permeable to water but not salt. Water passively diffuses out of the nephron because of the low water potential of the medulla tissue fluid.

Loop of Henlé: this part is permeable to salt but not water. The loss of water from the filtrate in the previous stage increases the salt concentration. Some salt passively diffuses out of the loop here.

Collecting duct: the remaining substances move through the second coiled tubule (distal tubule), into the collecting duct. The permeability of this part of the nephron to water is controlled

Question 16

what is kidney dialysis

Answer 16

When a kidney machine takes a patient’s blood and cleans it, then returns the blood to circulation.

Question 17

how does kidney dialysis work

Answer 17

Blood enters machine from patient

The pump passes the blood passes the dialysis tubing which is semi-permeable therefore acting as a filter

The surrounding liquid contains some salts, glucose but no urea so waste materials pass from blood by diffusion;

The ‘cleaned’ blood returns to patient’s circulation/body

Question 18

pros of kidney dialysis

Answer 18

-Do not need to find kidney

Question 19

cons of kidney dialysis

Answer 19

• More expensive in the long run
• Need a machine & must live near one
• Very disruptive (three 6-8 hrs sessions per week)

Question 20

pros of kidney transplant

Answer 20

• Less expensive in the long run
• Not very disruptive (only have to take medication)
• Can go anywhere, anytime

Question 21

cons of kidney transplant

Answer 21

• Need a kidney

- risk of rejection