Urinary System

Functions

• Cells produce waste that can become toxic if they accumulate

• The urinary system:• removes salts and nitrogenous wastes• maintains normal concentration of water and

electrolytes• maintains pH, controls red blood cell

production and blood pressure

Organs

• Two kidneys which produce urine

• Two ureters which carry urine to the urinary bladder where urine is stored

• Urethra passes urine to outside the body

Kidneys

• Bean-shaped, dark organs

• 5 in. long, 1 in thick• lie on either side of the

verebral column deep in the abdominal cavity

Nephrons

Renal Blood Vessels

• Renal arteries supply blood to the kidneys

• Renal vein joins the vena cava and takes away filtered blood

Pathway of waste

• Glomerulus

• proximal tubule

• nephron loop (also called loop of henle)

• distal tubule

• collecting duct

• bladder

Urine Formation

• glomerular filtration - urine formation begins, plasma is filtered

• tubular reabsorption - returns most of the fluid to the body

• tubular secretion - removes what is not needed; produces urine

Glomerular Filtration

• flow of fluid from the blood into the glomerular capsule (plasma without large proteins and rbcs)

• kidneys filter 48 gallons/day

Tubular Reabsorption

• Over 99% of the substances filtered in the glomerulus are reabsorbed back into the circulation at different sites along the nephron

Tubular Secretion

• process by which the kidneys remove unwanted substances from the blood into the lumen of the nephron

• Secreted substances include H+ and K+

Excretion (Urine Elimination)

• After urine forms in the nephrons, the ureters (starting with the renal pelvis) carry the urine away to the bladder

• Urinary bladder stores urine and forces it through the urethra

• Micturition expels urine by contracting the detrusor muscle and relaxing the external urethral sphincter

Video

Cause of hypertension

• Excess release of renin which (through a series of events) causes angiotensin II to be formed

• Angiotensin II vasoconstricts the efferent arteriole, which causes blood to back up into the glomerulus, thus raising glomerular capillary hydrostatic pressure

• Sodium and water are conserved

Kidney stones

• Composed of uric acid, calcium oxalate, calcium phosphate, or magnesium phosphate

• Form in the collecting ducts and renal pelvis• Passing into ureter causes sudden, severe pain • May cause nausea, vomiting, and blood in urine• 60% pass through body on their own• Can be shattered using intense sound waves• Is inherited or excess vitamin D or complication

of urinary tract infection

• Extracorporeal shock wave lithotripsy (ESWL) is a procedure used to shatter simple stones in the kidney or upper urinary tract.

• Ultrasonic waves are passed through the body until they strike the dense stones.

• Pulses of sonic waves pulverize the stones, which are then more easily passed through the ureter and out of the body in the urine.

Oh, bacteria!

• Cystitis – inflammation of urinary bladder

• Ureteritis – inflammation of ureter

• More common in women b/c urethral pathway is shorter

Overactive bladder

• sudden contractions of the bladder produce sensation of urgency, also more common in women

Hemolytic Uremic Syndrome

• Urine turns bloody, severe anemia, lack of platelets

• Caused from toxin produced by E. coli

• If the toxin travels to kidneys, it destroys the cells of capillaries that normally filter proteins and blood cells forming urine

                                          

                                 

Healthy red blood cells (upper left) are smooth and round. In hemolytic uremic syndrome (lower right), toxins destroy red blood cells. These misshapen cells may clog the tiny blood vessels in the kidneys.

Incontinence

• involuntary loss of urine • may lose a few drops of urine while running or coughing• Others may feel a strong, sudden urge to urinate just

before losing a large amount of urine • Pregnancy and childbirth, menopause, and the structure of

the female urinary tract account for more women than men having this

• Both women and men can become incontinent from neurologic injury, birth defects, stroke, multiple sclerosis, and physical problems associated with aging.

Kidney Transplant

• Tissues must be antigenically similar

• Donor kidney attached to renal artery and vein

• Donor ureter attached to urinary bladder

• Organ sale