chapter 10 - excretory system

Question 1

organs involved in the excretory system

Answer 1

• lungs (carbon dioxide and water), skin/ sweat glands (urea, uric acid, water, salt), kidneys (water, salts, urea), alimentary canal (bile pigments, undigested food material), liver (amino acids)

Question 2

explain the structure of the kidney

Answer 2

• renal artery, renal medulla (pea shaped), nephron (attached to renal medulla), renal cortex (back of kidney), uretar (goes to bladder), renal vein

Question 3

explain function of the nephron

Answer 3

• remove wastes from the body and to keep substances required

Question 4

explain structure of the nephron

Answer 4

• afferent arteriole (bigger), efferent arteriole (smaller), glomerulus (knot of capillaries, semi permeable membrane), glomerular capsule, renal corpuscle (glomerulus and glomerular capsule), proximal consulting tubule, loop of henle, distal convoluting tubule, uretar

Question 5

three stages that take place in the nephron

Answer 5

• glomerular filtration
• selective reabsorption
• tubular secretion

Question 6

what happens during glomerular filtration

Answer 6

• occurs in renal corpuscle
• filters blood from renal artery
• fluid forced out of glomerulus into glomerular capsule (increased pressure in AA and EA)
  formed elements (RBC, WBC, platelets): renal artery -> afferent arteriole -> glomerulus -> efferent arteriole -> renal vein
• filtrate: enters capsule (H2O, NaCl, HCO3, K, AA, glucose, urea, creatinine, uric acid)

Question 7

what happens during selective reabsorption

Answer 7

• occurs in proximal convoluting tubule and loop of henle
• filtrate: substances that are useful must be reabsorbed (H2O, AA, NaCl, K, HCO3, O2, CO2)
• simple diffusion (osmosis H2O) -> peri tubular capillaries

Question 8

what is facultative reabsorption

Answer 8

• active process of water reabsorption under control of anti diuretic hormone (ADH) -> peri-tubular capillaries (surround nephron)
• ADH = going against diffusion gradient and makes capillaries are more permeable

Question 9

what happens during tubular secretion

Answer 9

• occurs in distal convoluting tubule
• adds materials to the filtrate (H, Na, creatinine, drugs) through passive / active transport
• removes unwanted materials from body, maintaining pH (7.4-7.5)
• increase pH = tubules secrete H and NH4 into filtrate (less acidic)

Question 10

what happens after tubular secretion

Answer 10

• filtrate drains from collecting ducts -> uretars -> urinary bladder -> urethra

Question 11

explain urine composition

Answer 11

• water (96%), urea (2%), various ions (1.5%) and other (0.5%)
• 99% of H2O that enters nephron is reabsorbed
• very small amounts of proteins
• no glucose
• 1.25L of blood passes through nephron / day
• 1.5L urine made / day

Question 12

structure vs function of nephron

Answer 12

• knot of capillaries
• one cell layer thin capillaries + glomerular capsule
• different size of AA and EA (increased pressure - increased filtration)
• glomerular capsule allows smaller substances through

Question 13

function of the liver

Answer 13

• process many substances so they can be secreted
• detoxifies alcohol / drugs
• deactivates hormones -> converts them -> can be secreted

Question 14

what is deamination

Answer 14

• removal of amino group (NH2) from amino acids and nitrogen bases (RNA) in the liver with the aid of enzymes

Question 15

why does deamination occur

Answer 15

• amino acids are used to make new proteins
• if protein is needed as an energy source, body metabolises it (however for this to occur amino group NH2 needs to be removed)

Question 16

what happens after deamination

Answer 16

• amino group is converted to liver cells to form ammonia (NH3) and then to urea because ammonia is highly toxic to cells
• amino acid + O2 -enzyme-> carbohydrate + NH3
• energy + CO2 + NH3 -> urea + water -> removed in urine and sweat

Question 17

what is the function of the skin

Answer 17

• protective covering over surface of body, regulate temperature, excretion of substances through sweat glands

Question 18

what are sweat glands

Answer 18

• located in the lower layers of the skin and secrete up to 500mL of water per day
• NaCl, urea, lactic acid, some drugs are dissolved in the water

Question 19

structure of the sweat glands

Answer 19

• duct carries to hair follicle or skin surface, opens as a pore, cells surrounding contract and squeeze sweat to skin surface

Question 20

function of the excretory system

Answer 20

the removal of metabolic wastes from the body

Question 21

what is excretion and elimination

Answer 21

• excretion: removal of metabolic wastes of metabolism from the body
• elimination: removal of indigestible material, bacteria and bile pigments from the body