Topic 2: Kidney function intro

Question 1

How much blood is delivered to the kidneys per min?

Answer 1

• Renal arteries deliver 1/4th of cardiac output per min

Question 2

Describe the nerve supply to the kidneys

Answer 2

• Via sympathetic fibers from renal plexus
• No parasympathetic supply to kidneys

Question 3

How many times per day is body’s plasma filtered?

Answer 3

• 60 times per day

Question 4

What is the filterate from kidneys?

Answer 4

• Blood plasma minus proteins

Question 5

Describe urine

Answer 5

• <1% of total filtrate
• Contains metabolic wastes + unneeded
  substances

Question 6

Give the arterial pathway to the nephron

Answer 6

1) Aorta
2) Renal artery
3) Segmental artery
4) Interlobar artery
5) Arcuate artery
6) Cortical radiate artery
7) Afferent arteriole
8) Glomerulus = capillaries

Question 7

Give the venous pathway from the nephron

Answer 7

1) Efferent arteriole
2) Peritubular capillaries and vasa recta
3) Cortical radiate vein
4) Arcuate vein
5) Interlobar vein
6) Renal vein
7) Inferior Vena Cava

Question 8

Define nephrons

Answer 8

• Structural + functional units = form urine
• 1 million per kidney

Question 9

Give the 2 parts of nephron

Answer 9

1) Glomerulus: cluster of capillaries
2) Renal tubule: cup-shaped capsule surrounding glomerulus

Question 10

Give the composition of urine

Answer 10

1) Water
2) Nitrogenous waste = urea
3) Salts
4) H+/ions
5) Drugs/vitamins

Question 11

Explain urine formation

Answer 11

1) Glomerular filtration: in the glomerular
capsule
2) Tubular reabsorption: in the proximal
tubule and loop of Henle
3) Tubular secretion: distal tubule
4) Concentration of Urine: collecting duct

Question 12

Describe pressure filtration

Answer 12

• Blood enters glomerulus from afferent arteriole
• BP forces small molecules out of the capillaries into capsule

Question 13

Which substances leave the blood?

Answer 13

• Water
• Salts
• Nutrients = glucose + amino
• Urea/waste

Question 14

Describe selective reabsorption

Answer 14

• Location: proximal tubule + loop of Henle
• H2O + nutrients + salts reabsorbed back into blood
• Na+ ions, glucose, amino acids = move
  back into the peritubular capillaries by
  active transport
• Cl- follow the positive charge of Na⁺ passively
• H2O reabsorbed by osmosis

Question 15

What is the function of the Loop of Henle?

Answer 15

• Remove as much water from filtrate as possible + return to blood

Question 16

Describe Loop of Henle

Answer 16

• Descending limb: permeable to water not salt
• Ascending limb: permeable to salt not H2O = Na+ actively pumped of limb

Question 17

Describe the medulla

Answer 17

• Hypertonic = high conc of Na+
• H2O leaves tubule via osmosis + enters medulla → peritubular capillaries

Question 18

Describe tubular secretion at distal tubule

Answer 18

• Excess H+ ions/drugs move from blood → nephron via active transport
• Ions secreted/kept to maintain pH

Question 19

Describe reabsorption of water

Answer 19

• More water reabsorbed into blood from collecting duct
• Collecting duct = in hypertonic medulla = water drawn out by osmosis

Question 20

Describe urine excretion

Answer 20

• When ready to be extreted = collects in renal pelvis → ureter → bladder

Question 21

How is the composition of blood in the renal
artery different from that in the renal vein?

Answer 21

• Renal vein has less urea = large amounts of urea is removed via the nephrons to form
  urine
  – Less water + solutes/ions = amount
  removed will depend on the hydration
  status of the individual