URINE

Question 1

Name and describe the three stages of urine formation and their location

Answer 1

a. Glomerular filtration
- Water and small dissolved solutes move from the glomerulus into the glomerular capsule

b. Tubular reabsorption
- Water and important substances are returned from the filtrate in the tubule back into the blood 

c. Tubular secretion The transfer of unwanted substances from the blood into the urine (or removal of H+ from the blood)

Question 2

Describe the four ways in which the renal system contributes to maintaining homeostasis of the cardiovascular system

Answer 2

• Kidneys maintain fluid balance in the blood by controlling the amount of urine produced
• Kidneys control blood volume and blood pressure by regulation of Na+ and water balance.
• Kidneys produce renin which initiates the RAAS pathway when blood pressure is lowered.
• Kidneys produce erythropoietin which stimulates the production of red blood cells.

Question 3

State the effects of ageing on the urinary system

Answer 3

Kidneys shrink as nephrons decrease in size and number- Decreased renal function and glomerular filtration rate, Inability to compensate for fluid overload

Tubule cells become less efficient as concentrating urine - Inability to compensate for dehydration
Decreased blood supply - results in decreased GFR, and damage to blood vessels in glomeruli

Bladder capacity and tone decrease (also detrusor instability) - leading to frequent micturition, nocturia and often incontinence

Prostate enlargement is a common problem of older men - can result in urinary retention and difficulty with initiating or stopping flow.

Question 4

State the eight functions of the kidney.

Answer 4

• Regulating blood electrolytes by secreting excessive ions into the urine.
• Regulating blood pH by excreting/conserving H+ or bicarbonate ions.
• Regulating blood volume by conserving or eliminating water.
• Regulating blood pressure (by regulating blood volume and by RAAS, ANP).
• Maintaining blood osmolarity by secreting excessive Na+ into the urine.
• Excreting waste products: ammonia, urea and creatinine
• Producing hormones: EPO, calcitriol, and produces the enzyme renin which leads to the production of angiotensin and aldosterone.
• Regulating blood glucose.

Question 5

Identify the role of aldosterone, antidiuretic hormone and atrial natriuretic peptide in the management of fluid balance AND identify the effect of these on urine output.

Answer 5

ANP/ANH (same thing) - decrease blood pressure, increase urine output

ADH (part of RASS pathway) - increase blood pressure, decrease urine output

Aldosterone (part of RASS pathway) - increase blood pressure, decrease urine output