Final answer:
The kidneys regulate blood pressure through the release of renin, which is part of the renin-angiotensin-aldosterone system affecting blood volume and pressure by promoting sodium and water retention.
Step-by-step explanation:
The kidneys regulate systemic arterial blood pressure primarily through the release of renin. Renin is part of the renin-angiotensin-aldosterone system that eventually leads to the retention of sodium (Na+) and water, thus raising blood volume and pressure. When blood pressure or volume decreases, renin enzymatically converts angiotensinogen to angiotensin I, which is then converted to angiotensin II, resulting in vasoconstriction and increased blood pressure. Angiotensin II also triggers the release of aldosterone, which stimulates sodium and water reabsorption in the kidneys. Apart from renin, the kidneys also release hormones like erythropoietin (EPO), which stimulates the production of red blood cells, aiding in greater oxygen delivery throughout the body.