Kidneys

• Carbon dioxide must be removed after respiration as it dissolves to form an acidic solution (carbonic acid)
• Digestion of proteins result in excess amino acids that need to be excreted safely. Amino acids are deanimated to form ammonia, which is toxic. It is immediately converted to urea for safe excretion.
• Urea and water are released from the liver cells, into the blood stream and transported to the kidneys. Blood is filtered here and the urea is excreted.
• ADH from the pituitary gland causes tubules in the kidneys to reabsorb more water into the blood stream
• If water levels in the blood stream are too high, less ADH is made so more water is sent to the bladder to leave the body as urine
• Water levels in the blood is controlled with negative feedback