The Urinary System & Excretion Detoxification of the Blood

The Urinary System

Remember! The liver detoxifies the blood by removing poisonous substances and detoxifying them. the Deamination of amino acids produces ammonia, a poison, which is then converted to urea. Drug metabolism – break down of toxic substances like alcohol and medicinal products like tylenol,acetominaphen. These products are then removed by the kidneys in the production of urine.

Functions of the Urinary System The kidneys produce urine that is eliminated from the body. Four functions occur during this production to help maintain homeostasis.

1. Excretion of Metabolic Wastes The most common is nitrogenous wastes. Amino acid breakdown ends in urea production. NH 3 + CO 2  Some ammonia, NH 3 is excreted as ammonium, NH 4. Creatine phosphate is a high energy reserve of phosphates for ATP production in muscles cells. Creatinine is the metabolic waste. Nucleotide breakdown results in uric acid waste.

2. Maintenance of Water-Salt Balance The kidneys help maintain blood pressure at its set point or homeostasis. 120/80 mmHg Blood volume is closely linked to salt content! Salts such as NaCl, have the ability to cause osmosis. The more salts in the blood, the greater the blood volume, the greater the blood pressure. Other ion maintenance in the blood such as K +, HCO 3 -, & Ca 2+.

3. Maintenance of Acid-Base Balance Blood pH remains between the body’s set point of 7.38 and 7.4. If blood pH drops, becomes acidic, H + are secreted,(excreted) and HCO 3 - are reabsorbed. If blood pH rises, the opposite occurs. H + + NH 3  NH 4, if conditions are acidic. Which substance acts as a buffer? Urine has a pH of ~ 6 due the acidic nature of foods eaten.

4. Secretion of Hormones The kidneys aid the endocrine system with hormone production and secretion. Renin is produced by the juxtaglomerular apparatus and released in response to low blood pressure. This leads to the release of aldosterone from the adrenal cortex which promotes the reabsorption of Na +. Kidneys also secrete erythropoietin in response to the low oxygen carrying capacity of the blood and rbc production is increased. Kidneys help activate vitamin D, a hormone-like substance to promote Ca 2+ absorption from the digestive tract.