7:12 Urinary System Excretory system Removes certain wastes and excess water from the body Maintains homeostasis Maintains acid-base balance 2 kidneys, 2 ureters, bladder, and urethra

Kidneys Bean-shaped organs Location Protection Cortex Medulla Hilum Nephrons

Ureters Muscular tubes about 10–12 inches long Extend from renal pelvis of each kidney to bladder Peristalsis moves urine through tube to bladder

Bladder Muscular sac Lined with mucous membranes Three layers of visceral muscle form walls Function Urge to void Circular sphincter muscles

Urethra Carries urine from bladder to the outside Urinary meatus Female and male systems Urine Conditions affecting urination

Diseases and Abnormal Conditions Cystitis Glomerulonephritis or nephritis Pyelonephritis Renal calculus or urinary calculus Renal failure Chronic renal failure Uremia Urethritis

Review of Kidney Function Urine is composed of approximately 96% water and 4% dissolved substances derived from food or waste products of metabolism. The actual composition of urine varies, depending on diet, metabolism, general health of the body, and health of the kidney. Urinalysis is performed to assess the urine’s composition as well as kidney function.

Review of Kidney Function Recall the urinary system consists of two kidneys, two ureters and the bladder.

Review of Kidney Function Also recall the role of blood - to bring nutrients and oxygen to cells of the body and to carry waste materials away from those cells. The kidney has the largest role in controlling the chemical composition of the blood in order to maintain proper cell function in the body.

Review of Kidney Function In the kidney, blood undergoes filtration and dialysis to separate waste compounds that will be removed from the body from those that will be returned to the circulating blood. Figure 1

Review of Kidney Function More specifically, the kidney has the functions of: removal of waste products from the blood retention of nutrients such as proteins and glucose maintenance of acid-base balance regulation of water and electrolyte (salt) content of the body hormone synthesis

Review of Kidney Function Urine is formed in the kidney structure called the nephron. Each kidney contains about one million nephrons. The nephron is made up of a glomerulus and a set of tubules. Cross section of a nephron

Review of Kidney Function The tubular portion of the nephron consists of several structures: Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct

Review of Kidney Function Urine is formed through a three phase process of: Filtration Reabsorption Secretion

Review of Kidney Function Filtration of the blood occurs within the specialized collection of capillaries in the glomerulus. The glomerulus permits water and small molecules and ions from the blood to enter a surrounding tubule called the Bowman’s capsule. This is called the filtrate. Blood cells and large protein molecules remain in the blood and return to the venous circulation.

Review of Kidney Function Reabsorption of essential chemicals the body needs (glucose, amino acids, NaCl and other salts, water and vitamins) occurs within the nephron’s proximal tubule, Loop of Henle, and distal tubule. Reabsorption prevents the loss of necessary body compounds but also adjusts the concentration of urine so it is more dilute when the body has more water (i.e., hydrated) and more concentrated when the body is short of water (i.e., dehydrated).

Review of Kidney Function Secretion of foreign chemicals the body does not need (ammonia, drugs, hormones, toxins) begins in the proximal tubules and continues in the distal tubule and the collecting duct. Secretion of excess ions such as H+ and K+ help establish electrolyte and acid-base balance.

Review of Kidney Function All three processes of filtration, reabsorption and secretion occur simultaneously as a result of complex cellular transport mechanisms and buffering mechanisms within the nephron tubules. The glomerular filtrate becomes more concentrated and acidic after it leaves the distal tubule and enters the collecting duct. The fluid that leaves the collecting duct is now urine.

Review of Kidney Function The processes of glomerular filtration and renal tubular reabsorption and secretion are can become affected when the kidney is compromised by disease. Loss of renal function can be caused by variety of conditions such as: congestive heart failure injury to the glomerulus or tubules caused by drugs, heavy metals and viral infections diabetes, hypertension and kidney stones.