The kidneys help to regulate blood pressure primarily by which mechanism?

• A. Releasing renin to activate the renin-angiotensin-aldosterone system (RAAS)
• B. Secreting insulin to increase glucose uptake by cells
• C. Producing bile to aid in fat digestion
• D. Releasing calcitonin to decrease blood calcium levels

Answer: (A)

Verified step by step guidance

1. Understand the role of the kidneys in blood pressure regulation, which primarily involves hormonal control rather than direct mechanical action.
2. Recognize that the kidneys release an enzyme called renin when blood pressure is low or when there is a decrease in sodium levels or blood volume.
3. Know that renin initiates the renin-angiotensin-aldosterone system (RAAS), a hormone cascade that ultimately leads to vasoconstriction and retention of sodium and water, increasing blood volume and pressure.
4. Eliminate options unrelated to kidney function in blood pressure regulation: insulin secretion (pancreas), bile production (liver), and calcitonin release (thyroid gland).
5. Conclude that the correct mechanism is the release of renin by the kidneys to activate the RAAS, which helps raise and regulate blood pressure.