Excretion

Question 1

what is the definition of excretion?

Answer 1

a process by which metabolic waste products and toxic substances are removed from the body of an organism

Question 2

what do kidneys do?

Answer 2

• removes mainly nitrogenous waste products, excess water and mineral salts in the form of urine
• regulates salt and water balance of blood plasma
• regulates pH and composition of blood plasma

Question 3

what are the parts of the urinary system?

Answer 3

hilum; where renal arteries, veins and nerves are connected to the kidneys
kidney; removes urea and excess water from the blood through urine
ureter; tube that brings urine from kidney to the urinary bladder
urinary bladder; muscular bag that stores urine
sphincter muscle; controls urine flow into urethra
urethra; duct from the urinary bladder to outside of the body

Question 4

what is the internal structure of the kidney?

Answer 4

cortex; outer darker red region enclosed by fibrous capsule
medulla; inner thicker pale red region, contains pyramids

Question 5

what are the 5 parts of the nephron?

Answer 5

• loop of Henle
• proximal convoluted tubule
• distal convoluted tubule
• Bowman’s capsule
• collecting duct

Question 6

what is ultrafiltration?

Answer 6

• occurs in the glomerulus
• mechanical filtration that removes small molecules

Question 7

what are 2 conditions for ultrafiltration to occur?

Answer 7

1. high hydrostatic blood pressure in the glomerulus (difference in diameter between afferent and efferent arteriole)
2. partially permeable membrane

Question 8

what is selective reabsorption?

Answer 8

useful substances selectively reabsorbed from the filtrate of ultrafiltration

Question 9

what parts of the tubule reabsorb what?

Answer 9

proximal convoluted tubule; osmosis, active transport and diffusion - glucose, amino acids, mineral salts, water
loop of Henle; osmosis - water
distal convoluted tubule; diffusion - mineral salts
collecting duct; osmosis - water

Question 10

causes for kidney failure?

Answer 10

• high blood pressure
• diabetes
• alcohol abuse
• damage to the kidney
• complications from surgery

Question 11

what are the features of a dialysis machine and their functions?

Answer 11

• tubing is long, narrow and coiled; increase surface area to volume ratio
• contains no metabolic waste products with same concentration of essential nutrients; maintains steep concentration gradient
• direction of blood flow is opposite to dialysis fluid; maintains concentration gradient

Question 12

excretory products, their source and their excretory organ?

Answer 12

1. carbon dioxide; tissue respiration - lungs
2. nitrogenous waste; deamination of amino acids and diet - skin and kidney
3. bile pigments; breakdown of haemoglobin - liver
4. excess water; tissue respiration - kidney, skin, lungs

Question 13

why are metabolic waste products harmful?

Answer 13

harmful if accumulated in the body