Unit 13 - excretion in humans

Question 1

definition of excretion

Answer 1

the removal of toxic materials, the waste products of metabolism, and substances in excess of requirements from the body

Question 2

examples of substances which are excreted

Answer 2

urea, co2 , salts (ions), sweat

Question 3

Organs involved in excretion, (4) and what they excrete

Answer 3

• skin : water + mineral ions
• lungs : co2 + water
• kidneys : water, mineral ions, + urea
• liver: produces urea from amino acids

Question 4

what is urea made by , what is this process called

Answer 4

made from the breakdown of amino acids in the liver , process is called deamination

Question 5

what does the urethra do

Answer 5

facilitates removal of urine from the body

Question 6

what does the ureter do

Answer 6

transport urine from the kidneys to the bladde

Question 7

why are kidneys important

Answer 7

for maintaining the water and ion balance in the body, also filter urea out of blood and excrete it

Question 8

main roles of the kidneys (3)

Answer 8

1. removal of urea from bood
2. adjustment of ions in the blood
3. adjustment of water in the blood

Question 9

what is urea and why is it removed from the body

Answer 9

• waste of deamination is urea, filtered out by the kidneys
• urea is a toxic waste product so must be excreted before it reaches high concentration.

Question 10

how are ions ingested and excreted

Answer 10

• ions such as sodium taken into the body in food
• excess ions are removed by the kidneys

Question 11

how is too little water content in blood adjusted

Answer 11

1. hypothalamus detects and pituitary releases ADH
2. more ADH enters kidneys- more water is reabsorbed
3. so less urine which is concentrated is produced.

Question 12

how is too much water in the blood adjusted

Answer 12

1. hypothalamus detects and pituitary releases less ADH
2. less ADH enters kidneys - less water reabsorbed
3. so more urine which is less concentrated is produced

Question 13

what does ADH stand for

Answer 13

anti-diuretic hormone

Question 14

what and where is the hypothalamus

Answer 14

in the brain, monitors the water content of the blood

Question 15

what is the glomerulus

Answer 15

a knot of blood vessels surrounded by the renal capsule

Question 16

What is ultrafiltration

Answer 16

high blood pressure in the glomerulus forces water, ions, urea and glucose out the blood.

Question 17

what happens in the renal tubule (selective reabsorption )

Answer 17

• all glucose is reabsorbed
• sufficient ions/salts are reabsorbed using active transport
• sufficient water is also reabsorbed
  all using active transport

Question 18

cortex function

Answer 18

blood is filtered by the nephrons

Question 19

renal artery function

Answer 19

transports unfiltered blood from the aorta into the kidney

Question 20

renal vein function

Answer 20

transports filtered blood back to the heart

Question 21

function of medulla

Answer 21

reabsorption of water to maintain water balance

Question 22

what are proteins turned into after assimilation, what is assimilation

Answer 22

proteins eg fibrinogen
when food molecules are converted to other molecules that the body needs

Question 23

deamination definition

Answer 23

the removal of the nitrogen-containing part of amino acids to form urea.