Describe how solute is reabsorbed in the kidney including the important hormones involved

ADH

Concentrated urine is formed when ADH is secreted and water is reabsorbed from the collecting ducts. In contrast, dilute urine (hypo-osmotic), more water is allowed to pass out the tubules without being reabsorbed. This occurs when ADH is not secreted, the collecting ducts are impermeable to water and dilute urine is formed. 

ADH, (or vasopressin), increases water reabsorption in the distal convoluted tubule and collecting duct by increasing the number of aquaporin water channels. 

Synthesised by the hypothalamus and released by the posterior pituitary gland

Aldosterone

Aldosterone promotes sodium reabsorption and potassium excretion in the distal tubule and collecting duct. Sodium balance is regulated by aldosterone, which increases reabsorption of sodium from the urine into the blood by the distal convoluted tubule of the kidneys. Potassium balance is regulated by the kidneys, mainly by aldosterone

Atrial Natriuretic Peptide

ANP inhibits sodium reabsorption in the DCT and collecting duct, promoting sodium and water excretion

Filtration, re-absorption, and excretion rates of solutes

Tmax refers to the maximum reabsorption rate of solutes. The filtration rate of solutes is directly proportional to the plasma solute concentration. The renal threshold indicates the concentration at which a solute will first appear in the urine

proximal convoluted Tubule

The PCT is the primary site for solute reabsorption, recovering almost 100% of glucose, amino acids, and many vitamins. This is achieved through both active and passive transport

active reabsorption (PCT)

Substances like sodium, glucose, and amino acids are actively transported across the PCT wall using energy from ATP

passive reabsorption (PCT)

Water, chloride ions, and other solutes are passively reabsorbed along their concentration gradients

loop of Henle

The descending limb of the loop of Henle reabsorbs water via osmosis, while the ascending limb actively pumps sodium, potassium, and chloride ions out of the filtrate

Distal convoluted tubule and collecting duct

Filtrate enters distal tubule, which drains into a collecting duct. Fine regulation of salt and water balance takes place; Controlled by hormones - ADH & aldosterone. Alterations to reabsorption and secretion - determines final concentration of filtrate/urine. Final osmolality of urine can be 50 - 1200 mOsm