Regulation

The function of the urinary system is regulated by various hormone axes within the body.

In this section we shall consider the role of antidiuretic hormone (ADH), also known as vasopressin. It is a small peptide hormone that is responsible for regulating the body’s retention of water and is one of only two hormones secreted by the posterior pituitary gland.

We will then look at the Renin-Angiotensin-Aldosterone-System (RAAS). This is the hormone system within the body that is responsible for the regulation of blood pressure and fluid balance.The system is mainly comprised of the three hormones renin, angiotensin II and aldosterone. It is mainly regulated by the rate of renal blood flow.

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Flowchart showing ADH regulation: increased plasma osmolality or decreased blood volume and pressure stimulate hypothalamic ADH synthesis, storage in the posterior pituitary, and release into the bloodstream. ADH increases kidney water reabsorption and urine concentration, raising plasma volume and lowering osmolality through negative feedback.

Antidiuretic Hormone

Diagram of bicarbonate reabsorption across a proximal convoluted tubule cell, showing hydrogen ion and sodium transport, carbonic anhydrase reactions, and movement between the tubular lumen and bloodstream.

Urinary Regulation of Acid-Base Balance

Diagram of a nephron showing the glomerulus, proximal convoluted tubule, descending and ascending loops of Henle, distal tubule, and collecting duct, with explanatory text about filtration, reabsorption, and secretion.

Water Filtration and Reabsorption

Renin-Angiotensin-Aldosterone System

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