Ultrafiltration

The diameter of the lumen of the afferent arteriole is larger than that of the efferent arteriole. Also, due to the pumping action of the heart, there is a high hydrostatic pressure in the glomerulus which forces plasma containing glucose, amino acid, water and urea, mineral salts except proteins and blood cells through the thin, differentially permeable and porous wall of the glomerulus into the Bowman's capsules.