Renal System

Question 1

What are the main functions of the kidneys?

Answer 1

Filtration of blood, excretion of waste, regulation of fluid/electrolyte balance, and pH control.

Question 2

What percentage of cardiac output goes to the kidneys?

Answer 2

20–25%.

Question 2

What hormone does the kidney produce to stimulate red blood cell production?

Answer 2

Erythropoietin.

Question 3

Through what vessels does blood flow into and out of the glomerulus?

Answer 3

Afferent arteriole (into), efferent arteriole (out of).

Question 4

What is the glomerular filtration rate (GFR)?

Answer 4

The amount of filtrate formed per minute, ~125 mL/min in humans.

Question 5

What factors determine GFR?

Answer 5

Hydrostatic pressure, oncotic pressure, and filtration membrane permeability.

Question 6

What is the functional unit of the kidney?

Answer 6

The nephron.

Question 7

Name the components of the nephron.

Answer 7

Glomerulus, Bowman’s capsule, proximal tubule, loop of Henle, distal tubule, collecting duct.

Question 8

What is tubular reabsorption?

Answer 8

Movement of substances from the filtrate back into the blood.

Question 9

Where does most reabsorption occur?

Answer 9

In the proximal tubule.

Question 10

What is tubular secretion?

Answer 10

Transfer of substances from blood into the tubular fluid.

Question 11

What are common substances secreted?

Answer 11

H⁺, K⁺, creatinine, drugs.

Question 12

How do reabsorption and secretion affect urine composition?

Answer 12

Reabsorption reduces, and secretion increases solute concentration in urine.

Question 13

What are normal components of urine?

Answer 13

Water, urea, creatinine, ions (Na⁺, K⁺, Cl⁻), and uric acid.

Question 14

What structures form the filtration barrier in the glomerulus?

Answer 14

Endothelium, basement membrane, and podocytes.

Question 15

What is filtered at the glomerulus?

Answer 15

Water, electrolytes, glucose, amino acids, urea—NOT proteins or cells.

Question 16

What key transport processes occur in the proximal tubule?

Answer 16

Reabsorption of Na⁺, glucose, amino acids, water, and secretion of some drugs/toxins.

Question 17

What is the function of the countercurrent mechanism in the loop of Henle?

Answer 17

To establish a vertical osmotic gradient in the medulla, enabling urine concentration or dilution.

Question 18

How does filtrate change in the descending vs ascending limbs?

Answer 18

Descending: becomes more concentrated; Ascending: becomes more dilute.

Question 19

What two conditions are required for water reabsorption in the kidney?

Answer 19

An osmotic gradient and water-permeable tubules.

Question 20

Which hormone makes distal and collecting tubules permeable to water?

Answer 20

Vasopressin (ADH).

Question 21

Where is vasopressin produced and stored?

Answer 21

Produced in the hypothalamus; stored in the posterior pituitary.

Question 22

What triggers vasopressin release?

Answer 22

Increased osmolarity and low blood volume/pressure.

Question 23

How does the vasa recta preserve the medullary osmotic gradient?

Answer 23

Through countercurrent exchange, minimizing solute washout.

Question 24

How does urine output and concentration change with hydration?

Answer 24

Normal: ~1 mL/min (isotonic), Overhydrated: ↑ (hypotonic), Dehydrated: ↓ (hypertonic).

Question 25

What controls bladder emptying?

Answer 25

Internal sphincter (involuntary) and external sphincter (voluntary); controlled by the micturition reflex.

Question 26

Where does most Na⁺ reabsorption occur in the nephron?

Answer 26

67% in the proximal tubule.

Question 27

Which hormone regulates Na⁺ reabsorption in the distal tubule?

Answer 27

Aldosterone.

Question 28

What activates the RAAS system?

Answer 28

Low ECF volume or blood pressure.

Question 29

What does aldosterone do?

Answer 29

Increases Na⁺ reabsorption and K⁺ secretion in the distal nephron.

Question 30

Where is K⁺ secretion regulated?

Answer 30

In the distal and collecting tubules.

Question 31

What directly stimulates aldosterone release for K⁺ balance?

Answer 31

High plasma K⁺.

Question 32

How does acidosis affect K⁺ excretion?

Answer 32

Reduces K⁺ secretion as H⁺ is excreted instead.

Question 33

What are the two main ways the body regulates pH?

Answer 33

CO₂ excretion (lungs) and H⁺/HCO₃⁻ regulation (kidneys).

Question 34

What is the most potent regulator of pH?

Answer 34

The kidneys.

Question 35

What are the major buffer systems in the body?

Answer 35

Bicarbonate (ECF), protein (ICF), haemoglobin (carbonic acid buffering), phosphate & ammonia (urine).

Question 36

What are the three renal mechanisms for pH regulation?

Answer 36

H⁺ excretion, HCO₃⁻ reabsorption, NH₄⁺ excretion.

Question 37

How is HCO₃⁻ added to plasma?

Answer 37

By secreting H⁺ into the tubule, which leads to HCO₃⁻ transfer to blood.