Structure and Functions in Living Organisms - Excretion (Paper 2)

Question 1

what is osmoregulation?

Answer 1

control of the water balance of the bloof, tissue or cytoplasm of a living organism

Question 2

what is the role of the kidney in excretion?

Answer 2

• renal artery transports oxygenated blood to the glomerulus under high pressure
• blood is filtered at high pressure to produce glomerular filtrate of water, glucose, salts and urea
• proteins and red blood cells are too large to be filtered through so remain in the blood
• glomerular filtrate enters the proximal convoluted tubule where all glucose is reabsorbed into surrounding capillaries (selective reabsorbtion)
• remaining filtrate flows through the collecting duct, where water is reabsorbed into the blood depending on levels of adh

Question 3

what is the role of the kidney in osmoregulation when water level is low?

Answer 3

• hypothalamus detects low levels of water in the body and stimulates the pituitary gland to produce more adh
• increase in adh causes membrane of collecting duct to become more permeable, increasing reabsorbtion of water into blood capillaries
• as more water is reabsorbed, water levels in the body return to normal
• urine becomes more concentrated and volume decreases

Question 4

what is the role of the kidney in osmoregulation when water level is high?

Answer 4

• hypothalamus detects high levels of water in the body and stimulates the pituitary gland to produce less adh
• decrease in adh causes membrane of collecting duct to become less permeable, decreasing reabsorbtion of water into blood capillaries
• as less water is reabsorbed, water levels in the body return to normal
• urine becomes less concentrated and volume increases

Question 5

what is in the nephron?

Answer 5

the bowman’s capsule, the glomerulus, the convoluted tubules, the loop of henle and the collecting duct

Question 6

what is the bowman’s capsule?

Answer 6

a cup-shaped sac that collects glomerular filtrate for entry into tubules for filtration

Question 7

what is the glomerulus?

Answer 7

a tuft of blood capillaries that filters blood under high pressure to produce glomerular filtrate

Question 8

what are the convolutes tubules?

Answer 8

a portion of nephron that includes the proximal convoluted tubule (PCT) and distal convoluted tubule (DCT) to carry out selective reabsorption of glucose into blood capillaries

Question 9

what is the loop of henle?

Answer 9

u-shaped portion of nephron that filters out salts to maintain water concentration in body

Question 10

what is the collecting duct?

Answer 10

long narrow tube that reabsorbs water to maintain water balance in body depending on levels of ADH produced

Question 11

what is in the urinary system?

Answer 11

the kidneys, the ureters, the bladder and the urethra

Question 12

what is the kidney?

Answer 12

a pair of bean-shaped organs that carry out filtration to remove waste products from body via excretion

Question 13

what is the ureter?

Answer 13

the tube that transports urine from kidney to bladder for storage prior to excretion

Question 14

what is the bladder?

Answer 14

the organ that stores urine produced by kidney for excretion

Question 15

what is the urethra?

Answer 15

the tube that connects the bladder to the exterior for removal of urine from body via excretion

Question 16

what happens during ultrafiltration?

Answer 16

• the renal artery transports oxygenated blood to the glomerulus under high pressure
• blood is filtered at high pressure to produce glomerular filtrate composed of water, glucose, salts and urea
• proteins and red blood cells are too large to be filtered through base membrane (material between glomerulus and bowman’s capsule) they will remain in blood

Question 17

what does urine contain?

Answer 17

excess water, excess salts and urea