Flexi Says: Blood circulates throughout the body and it is filtered on entering the kidney. The process of filtering substances from blood in the glomerulus is called filtration. The fluid that collects in Bowman’s space is called filtrate. It is composed of water, salts, glucose, amino acids, and urea. Larger structures in the blood—including protein molecules, blood cells, and platelets—do not pass into Bowman’s space. Instead, they stay in the main circulation. From Bowman’s space, the filtrate passes into the renal tubule. The main function of the renal tubule is reabsorption. Reabsorption occurs in the proximal tubule and is the return of needed substances in the filtrate back to the bloodstream. From the proximal tubule, the filtrate passes through the loop of Henle. The loop of Henle carries the filtrate from the cortex down into the medulla and then back up to the cortex again. Its primary purpose is to reabsorb water and salt from the fluid filtrate. The remaining fluid enters the distal tubule. The distal tubule carries the fluid, now called tubular fluid, from the loop of Henle to a collecting duct. The collecting ducts are the site of urine formation.
