Regulates amount of salts and the ratios of various ions to each other. Removes waste products. This is an osmotic problem because water is required for their elimination. 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.