Flexi Says: Capillary hydrostatic pressure and Bowman's space oncotic pressure are two mechanisms that governs filtration in the glomerulus and favor filtration into the tubule. The renal arteries, which carry blood into the kidneys, branch into the capillaries of the glomerulus of each nephron. The pressure of blood moving through these capillaries forces some of the water and dissolved substances in the blood through the capillary walls and into Bowman’s capsule. Bowman’s capsule is composed of layers. The space between the layers, called Bowman’s space, fills with the filtered substances. The process of filtering substances from blood in the glomerulus is called filtration. The fluid that collects in Bowman’s space is called filtrate.