Summary Pathology & Therapeutics I

UNIT 7 & 8 - Major key summaries for unit 7 and 8! - Essentials of Anatomy & Physiology Pathology & Therapeutics I (George Brown College) UNIT 7: THE URINARY SYSTEM 1. List the functions of the urinary system and its role in homeostasis. The urinary system is one of the anatomically simpler systems of the body. The kidneys play more roles than are commonly realised: • Excretion of Metabolic Wastes: The kidneys excrete metabolic wastes, notably nitrogenous wastes. Urea is the primary nitrogenous end product of metabolism in humans, but we also excrete some ammonium, creatinine, and uric acid. Urea is a by-product of amino acid metabolism. The break- down of amino acids in the liver releases ammonia, which the liver rapidly combines with carbon dioxide to produce urea. Ammonia is very toxic to cells, but urea is much less toxic. Some ammonia (NH3) is also excreted as ammonium ion (NH4+). Creatine phosphate is a high-energy phosphate reserve molecule in muscles. The metabolic breakdown of creatine phosphate results in creatinine, which is excreted. The breakdown of nucleotides, such as those containing adenine and thymine, produces uric acid. Uric acid is rather insoluble. If too much uric acid is present in blood, crystals may form and precipitate out in the joints, producing a painful ailment called gout. • Osmoregulation: A principal function of the kidneys is osmoregulation, the maintenance of the appropriate balance of water and salt in the blood. Blood volume is intimately associated with the salt balance of the body. Salts, such as NaCl, have the ability to cause osmosis, the diffusion of water—in this case, into the blood. The more salts there are in the blood, the greater the blood volume and the greater the blood pressure. In this way, the kidneys are also involved in regulating blood pressure. The kidneys also help maintain the appropriate level of other ions, such as potassium (K+), bicarbonate (HCO –), and calcium (Ca2+), in the blood.