Excretion

Question 1

Define catabolic reaction

Answer 1

Reactions that break up complex molecules into simpler molecules

Question 2

Define anabolic reaction

Answer 2

Reactions which build up simpler molecules into complex molecules

Question 3

Define excretion

Answer 3

The removal of toxic materials and the waste products of metabolism from organisms

Question 4

Why is excretion important

Answer 4

Waste products from metabolism can be harmful and prevent the maintenance of a steady state in the body if allowed to accumulate

Question 5

Define egestion

Answer 5

The elimination of undigested material from the alimentary canal

Question 6

Function of kidney

Answer 6

Contains numerous kidney tubules which remove urea, excess water and heat from blood to form urine.
Responsible for osmoregulation(process which keeps water potential of the body fluids constant)

Question 7

Function of ureter

Answer 7

Tube that connects kidney to urinary bladder. Urine flows from kidneys to bladder through the ureter

Question 8

Function of bladder

Answer 8

Muscular bag which stores urine

Question 9

Function of urethra

Answer 9

Muscular tube through which urine flows from bladder to exterior

Question 10

Name five parts of kidney

Answer 10

Nephrons, cortex, medulla, renal pelvis, renal pyramid

Question 11

Define ultrafiltration

Answer 11

Ultrafiltration is a non-selective filtering process which occurs at the glomerulus.

Question 12

Describe the process of ultrafiltration(refer to textbook for details)

Answer 12

• splitting of renal artery
• high blood pressure+reason
• blood plasma is forced out
• what remains in blood

Question 13

Describe process of selective reabsorption(refer to textbook for details)

Answer 13

PCT - glucose, amino acids, vitamins
LoH - water and ions
DCT - water and small conc. of Na and CL ions
CD - remaining water required by body

Question 14

Define selective reabsorption

Answer 14

The transport of useful substances from the filtrate back to the bloodstream. Useful solutes are reabsorbed back by active transport and facilitated diffusion. Water reabsorbed by osmosis.

Question 15

Define osmoregulation

Answer 15

The maintenance of a correct balance between water and dissolved solute in blood to maintain constant water potential in the body

Question 16

How is ADH produced

Answer 16

Produced by the hypothalamus and released by the pituitary gland

Question 17

Describe effectors involved in osmoregulation when water potential in blood increases

Answer 17

• Pituitary gland releases less ADH into bloodstream, transported to kidneys via
• Walls of DCT and CD less permeable to water
• Less water reabsorbed into blood
• Urine more diluted, higher volume

Question 18

Describe effectors involved in osmoregulation when water potential in blood decreases

Answer 18

• Pituitary gland releases more ADH into bloodstream, transported to kidney
• Walls of DCT and CD more permeable to water
• More water reabsorbed into blood
• Urine more concentrated, smaller volume

Question 19

Causes of kidney failure

Answer 19

High blood pressure, diabetes, alcohol abuse, accidents or infections

Question 20

Describe hemodialysis

Answer 20

Blood drawn by fistula, passed through dialyser, dialysis fluid introduced, small molecules diffusion, blood returned

Question 21

Features of the dialyser

Answer 21

• Tubing narrow to speed up rate of diffusion between blood and fluid
• Fresh dialysis fluid in contact with tubing where blood about to enter patient, no waste product enters patient
• Direction of blood flow opposite to flow of dialysis fluid. Maintains concentration for removal of waste products

Question 22

Contents of dialysis fluid

Answer 22

Contains same concentration of essential substances as healthy blood, if there is lack of these substances, substances can diffuse into blood

Question 23

Why are there no metabolic waste products in dialysis fluid

Answer 23

Sets up suitable concentration gradient for waste products to diffuse out tubing into dialysis fluid. Maintains correct solute concentration and water potential of blood