Excretory System Assessment

Antidiuretic Hormone (ADH)

ADH is produced in the hypothalamus and released from the posterior pituitary gland. It targets the collecting ducts of the kidneys, where it increases water reabsorption into the bloodstream. This reduces urine output and helps maintain blood volume and pressure, especially during dehydration or high blood osmolality.

Aldosterone

Aldosterone is secreted by the adrenal cortex, specifically the zona glomerulosa. It acts on the distal convoluted tubule and collecting ducts in the kidneys. Its role is to increase sodium reabsorption and potassium excretion, which leads to water retention, thereby increasing blood volume and stabilizing blood pressure.

Atrial Natriuretic Peptide (ANP)

ANP is produced by the atrial cells of the heart in response to increased blood volume or pressure. It targets the kidneys, where it inhibits sodium reabsorption and promotes sodium and water excretion. This reduces blood volume and pressure, acting as a natural counter to aldosterone and ADH.

Renin

Renin is released by the juxtaglomerular cells of the kidney in response to low blood pressure or low sodium levels. It initiates the Renin-Angiotensin-Aldosterone System (RAAS) by converting angiotensinogen (from the liver) into angiotensin I, which is then converted into angiotensin II. Angiotensin II causes vasoconstriction and stimulates aldosterone release, both of which help increase blood pressure and fluid retention.