Function of kidneys: 

Filtration:

• Blood pressure within the glomerulus causes plasma to filter through capillary walls.

• Large molecules like red blood cells and plasma proteins remain within the capillary.

• The filtered fluid, resembling tissue fluid, mainly consists of water with dissolved ions, glucose, and urea.

Components of filtrate: 

Water: Essential solvent for transporting substances and maintaining hydration.

Urea: Nitrogenous waste product resulting from protein metabolism, secreted to maintain nitrogen balance.

Salts: Electrolytes such as sodium, potassium, chloride, and bicarbonate, crucial for cellular function and osmotic balance.

Glucose: Primary energy source for cells, filtered out of the blood to be reabsorbed and utilized by the body.

Reabsorption:

Filtrate collected in Bowman’s capsule travels down the renal tubule.

Surrounding capillaries reabsorb essential substances back into the bloodstream.

Initially, all glucose is reabsorbed along with a significant amount of water.

Some ions are selectively reabsorbed to maintain proper blood concentration.