Anatomy and Physiology II Practice Test 2026 - Free Anatomy Practice Questions and Study Guide

The correct answer is indeed the hormone that plays a crucial role in regulating the reabsorption of water in the kidneys, which is antidiuretic hormone (ADH), also known as vasopressin. ADH is secreted by the posterior pituitary gland in response to various stimuli such as increased plasma osmolality or decreased blood volume.

When ADH is released into the bloodstream, it travels to the kidneys, where it binds to specific receptors in the collecting ducts. This binding process increases the permeability of these ducts to water, allowing more water to be reabsorbed back into the bloodstream instead of being excreted in urine. As a result, this action helps to concentrate the urine and maintain the body's fluid balance, effectively preventing dehydration.

The other hormones listed have different functions; for instance, aldosterone primarily regulates sodium and potassium levels, while also influencing water retention indirectly. Renin, an enzyme, is part of the renin-angiotensin-aldosterone system that regulates blood pressure and fluid balance but does not directly control water reabsorption. Atrial natriuretic peptide is involved in reducing blood volume and pressure by promoting the excretion of sodium and water in the urine, opposing the effects of AD