Urinary System Reviewer
Overview
The urinary system, also known as the excretory system, removes waste products from the
body, regulates water and electrolyte balance, and maintains blood pressure. Its primary product
is urine.
Main Components of the Urinary System
1. Kidneys:
○ Bean-shaped organs located in the lower back.
○ Functions:
■ Filter blood to remove waste, toxins, and excess ions.
■ Regulate blood volume, pressure, and pH.
■ Produce hormones like erythropoietin (stimulates red blood cell
production) and renin (regulates blood pressure).
2. Ureters:
○ Thin tubes that transport urine from the kidneys to the bladder.
○ Use peristalsis (wave-like contractions) to move urine.
3. Bladder:
○ A muscular, hollow organ that stores urine until it is excreted.
○ Can hold approximately 400-600 mL of urine.
4. Urethra:
○ Tube that carries urine from the bladder to the outside of the body.
○ Longer in males (also carries semen); shorter in females.
How the Urinary System Works
1. Filtration (in Kidneys):
○ Blood enters the kidneys through the renal artery.
○ Filtration occurs in the nephrons, the functional units of the kidneys.
○ Waste, water, and small molecules form filtrate.
2. Reabsorption and Secretion:
○ Useful substances (e.g., glucose, water) are reabsorbed into the blood.
○ Waste and excess ions are secreted into the filtrate.
3. Excretion:
○ Urine (water, urea, salts, and toxins) is collected in the renal pelvis, flows into
the ureters, and is stored in the bladder.
○ Urine exits the body through the urethra.
Key Functions of the Urinary System
1. Excretion: Removes nitrogenous wastes (e.g., urea, uric acid) from the body.
2. Regulation:
○ Maintains water and electrolyte balance.
○ Controls blood pH by excreting hydrogen ions and reabsorbing bicarbonate.
○ Regulates blood pressure through renin and water balance.
3. Hormone Production:
○ Erythropoietin: Stimulates red blood cell production.
○ Renin: Regulates blood pressure.
Common Disorders
1. Urinary Tract Infection (UTI):
○ Infection in the urinary tract, often caused by bacteria.
○ Symptoms: Frequent urination, pain or burning sensation.
2. Kidney Stones:
○ Hard deposits of minerals and salts that form in the kidneys.
○ May block urine flow and cause severe pain.
3. Chronic Kidney Disease (CKD):
○ Gradual loss of kidney function.
○ May require dialysis or kidney transplant in severe cases.
4. Incontinence:
○ Loss of bladder control, leading to accidental urine leakage.
Quick Facts
● Kidneys filter about 50 gallons of blood daily.
● The average person produces 1-2 liters of urine per day.
● The bladder's stretching triggers the urge to urinate when it is about 200-300 mL full.
