1. 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

2. Kidneys Bean-shaped organs Location Protection Cortex Medulla Hilum
Nephrons

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

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

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

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

7. 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.

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

9. 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.

10. 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

11. 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

12. 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

13. 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

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

15. 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.

16. 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).

17. 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.

18. 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.

19. 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.