The Excretory System

• The excretory system removes cellular waste from the body.
• Without excretion, poisonous wastes can accumulate in blood, cells, and tissues.
• Build up of toxins from lack of excretion can lead to serious illness and death.

Structures of the Excretory System

• Skin
• Lungs
• Liver
• Large Intestine
• Urinary System

Skin

• Wastes such as excess water, salt, urea, and uric acid are removed from the body through sweat.

Lungs

• Excess carbon dioxide is removed from the body when exhaling.

Liver

• Detoxifies blood by filtering bacteria, alcohol, drugs, and toxic substances
• Changes harmful substances into inactive or less toxic forms.
• Excretes bile, containing worn-out red blood cells, bile salts, and cholesterol.

Large Intestine

• Removes solid, undigested food from the body after it passes through the digestive system.
• Waste is stored in the rectum and excreted as solid waste.
• The large intestine handles waste not produced by the cells.

Urinary System

• Eliminates nitrogenous or liquid waste in the form of urine through urination, micturition, or voiding
• Maintains fluid and electrolyte balance.
• Regulates blood composition, volume, and pressure.

Kidney

• A bean-shaped structure against the posterior abdominal wall
• Positioned at the last thoracic and first three lumbar vertebrae.
• Responsible for urine formation through filtration, reabsorption, and secretion.

Nephron

• The waste filtering unit of the kidney found in the cortex and the medulla.
• Considered the functional unit of the kidney.
• There are approximately 1.25 million nephrons in each kidney.
• Nephron's main function is to form urine.

Urine

• Is the final waste fluid excreted by the excretory system.
• It is composed of water, urea, and various salts.
• Typically, 1-1.5 liters of urine are produced every 24 hours.

Composition of Urine

• Water accounts for approximately 1.5 liters per day on average.
• Urea, a waste product of protein and amino acid metabolism.
• Uric acid, a waste product of muscle metabolism of purines by the liver.
• Creatine, another waste product of muscle metabolism.
• Electrolytes include potassium (K), sodium (Na), calcium (Ca), and chloride (Cl).
• Hormones and their breakdown products
• Vitamins, particularly water-soluble vitamins B and C.
• Drugs, such as aspirin, penicillin, and sulfa.
• Abnormal constituents: glucose, albumin, red blood cells, kidney stones.

Ureters

• A pair of tubes extending from the kidneys to the urinary bladder, facilitating urine passage.

Urinary Bladder

• A collapsible bag of smooth muscle lined with mucosa for temporary urine storage.

Urethra

• A musculo-membranous tube lined with mucosa that opens to the exterior via the urinary meatus.
• In males, it is longer and serves as a passage for both urine and semen.
• In females, it is shorter and functions only for urine passage.

Diseases of the Excretory System

• Bladder and kidney infections can occur when bacteria from the colon/rectum enter the urethra.
• Kidney stones are formed by the crystallization of mineral salts and uric acid, blocking urine passage.
• Gout is a form of arthritis where excess production of uric acid leads to crystal deposits in joints.