Urinary System: The Excretion of Waste

Kidneys: Structure and Function  The urinary system is made up of two kidneys, a pair of ureters, the urinary bladder, and the urethra  Kidneys filter the blood to remove wastes from it, thus maintaining the homeostasis of the body fluids

Kidneys: Structure and Function  Your kidneys are located just above the waist, behind the stomach  One kidney lies on each side of the spine, partially surrounded by the ribs

Ureters  Each kidney is connected to a tube called an ureter, which leads to the urinary bladder

Urinary Bladder  Urinary bladder is a smooth muscular bag that stores a solution of wastes

Nephron: The Unit of the Kidney  Each kidney is made up of about one million tiny filters  A filter is a devise that removes impurities from a solution  Each filtering unit is called a nephron

Nephron: The Unit of the Kidney  Blood entering a nephron carries wastes produced by body cells  As blood enters the nephron, it is under high pressure and immediately flows into a bed of capillaries called glomerulus

Nephron: The Unit of the Kidney  Because of the pressure, water, glucose, vitamins, amino acids, protein waste products (called urea), salts, and ions from the blood pass out of the capillaries into a part of the nephron called Bowman’s capsule

Nephron: The Unit of The Kidney  Blood cells and most proteins are too large to pass through the walls of the capillary, so these components stay within the blood vessels  Most of the other nutrients are reabsorbed when passed out of Bowman’s capsule

Formation of Urine  The liquid that remains in the tubules- composed of waste molecules and excess water and ions- is urine  You produce about 2L of urine a day  Waste fluids flow out of the kidney, through the ureter, into bladder, then out a tube called the urethra

Homeostasis  Waste products- ammonia and urea- come from the breakdown of proteins  Both compounds are toxic to your body and must be removed from the blood regularly

Homeostasis  Kidneys are also in control of the level of sodium in blood by removing and reabsorbing sodium ions; regulates osmotic pressure of the blood  Kidneys also regulate the pH of blood by filtering out hydrogen ions and allowing bicarbonate to be reabsorbed back into the blood