The hormones that are required for water reabsorption in the collecting ducts are ADH and aldosterone.
Aldosterone is a steroid hormone that is produced by the adrenal cortex in response to low blood pressure or low blood volume. It acts on the kidneys to promote reabsorption of sodium and water, which increases blood volume and blood pressure.
ADH (antidiuretic hormone) is a peptide hormone that is produced by the posterior pituitary gland in response to increased plasma osmolality or decreased blood volume. It acts on the kidneys to promote reabsorption of water, which decreases urine output and helps maintain fluid balance.
ADH is produced in the hypothalamus and released from the posterior pituitary in response to increased plasma osmolality.
ADH is produced in the hypothalamus and released from the posterior pituitary in response to increased plasma osmolality. It increases water permeability in the collecting ducts and distal convoluted tubules by stimulating the insertion of aquaporin-2 channels into the apical membrane. This results in increased water reabsorption and a decrease in urine volume.
Aldosterone is produced by the adrenal cortex in response to decreased blood pressure or blood volume. It increases Na+ reabsorption in the distal convoluted tubule and collecting duct by stimulating the insertion of Na+/K+ ATPase pumps into the apical membrane. This results in increased Na+ retention and a decrease in urine volume.
Aldosterone is produced in the adrenal cortex and released in response to increased plasma renin activity.
Aldosterone, aminergic activation of the epithelial sodium channel, and antidiuretic hormone all contribute to the regulation of water reabsorption in the distal convoluted tubule and collecting ducts. The final step in the regulation of water homeostasis is urinary concentration, which is determined by the ratio of solute (mainly urea) to water in the inner medulla. The highest levels of solute (and thus the lowest levels of water) are found in the papilla, where urea is secreted into the renal pelvis by active transport.
ADH acts on the principal cells of the collecting ducts to increase water permeability.
ADH acts on the principal cells of the collecting ducts to increase water permeability. This allows water to flow from the tubular fluid back into the blood, thus concentrating the urine and preventing too much water loss.
Aldosterone acts on the principal cells of the collecting ducts to increase sodium chloride permeability.
Aldosterone acts on the principal cells of the collecting ducts to increase sodium chloride permeability. This leads to an increase in the osmotic gradient and reabsorption of water. Antidiuretic hormone (ADH) also increases water permeability in the collecting ducts and leads to increased water reabsorption.
The increased water and sodium chloride permeability leads to increased water and sodium chloride reabsorption.
There are two types of water reabsorption in the body: facultative and osmotic. Facultative water reabsorption occurs in the presence of a solute (usually sodium chloride) and is mediated by hormones, while osmotic water reabsorption occurs in the absence of a solute and is mediated by osmotic gradients.
The main hormone that regulates facultative water reabsorption is vasopressin, also known as antidiuretic hormone (ADH). ADH is produced by the pituitary gland and released in response to increased blood osmolarity (i.e. increased concentration of solutes). When ADH binds to receptors on the collecting ducts, it increases the permeability of the ducts to water and sodium chloride, leading to increased reabsorption of both molecules.
Aldosterone is another hormone that can regulate facultative water reabsorption. Aldosterone is produced by the adrenal cortex in response to decreased blood volume or increased plasma potassium concentration. When aldosterone binds to receptors on the collecting ducts, it increases the permeability of the ducts to sodium chloride, leading to increased sodium chloride reabsorption and thus increased water reabsorption (due to the osmotic gradient created by the higher concentration of sodium chloride).
The increased water reabsorption leads to decreased urine volume and increased plasma volume.
There are two types of water reabsorption in the kidney: obligatory and facultative. Obligatory water reabsorption occurs in the proximal convoluted tubule and the loop of Henle and is independent of antidiuretic hormone (ADH). In contrast, facultative water reabsorption occurs in the distal convoluted tubule and the collecting ducts and is stimulated by ADH.
ADH is produced by neurons in the hypothalamus and released into the bloodstream by the posterior pituitary gland. When plasma osmolality increases, ADH is released, which results in increased water permeability of the collecting ducts. This increased water permeability leads to increased water reabsorption from the kidney filtrate, resulting in decreased urine volume and increased plasma volume.
The increased sodium chloride reabsorption leads to increased blood pressure.
The increased sodium chloride reabsorption in the collecting ducts is facilitated by the hormones aldosterone and angiotensin II. These hormones cause the cells of the collecting ducts to absorb more sodium chloride from the filtrate, leading to an increase in blood pressure.