B. Mechanisms involved in performing functions 1. Ultrafiltration a. Blood is filtered to form a filtrate. Substances move from the blood to the filtrate. Kidney forms a tubule filtrate. Reabsorption a. Substances move from the filtrate back into the blood.
Water moves back into the blood because of high osmotic pressure.
Secretion a. Substances move from the blood to the filtrate. The kidney actively and selectively transports solutes into the filtrate. C. Structures required to perform function 1. Bowman's capsule epithelial cells called podocytes surround each capillary and form filtration slits through which the filtrate passes together with other epithelial cells not in contact with the capillaries, podocytes form a space in which the initial filtrate is collected b. Formation of the ultrafiltrate ii.