Excretory System Overview

The Excretory System

• The excretory system, also known as the urinary system, removes waste and excess fluids from the body.
• Key structures include the kidneys, ureters, bladder, and urethra
• The kidneys are the primary organs filtering blood.
• The ureters carry urine from the kidneys to the bladder.
• The bladder stores urine until it is expelled from the body.
• The urethra is the tube through which urine is discharged.

Purpose of the Excretory System

• Removes waste products like urea (a by-product of protein breakdown).
• Removes unneeded substances.
• Protein breakdown in the liver results in ammonia, which is converted into less toxic urea.
• Blood transports urea to the kidneys for removal.

Kidney Function and Urine Formation

• Four phases are involved in urine formation in the kidneys:
  • Filtration: Blood is filtered, removing water and small molecules. Blood cells remain in the blood.
  • Reabsorption: Essential substances like water, salts, and glucose are reabsorbed into the bloodstream.
  • Secretion: Other waste products are added to the filtrate.
  • Excretion: The remaining waste products are expelled from the body as urine.
• About 119 ml of the filtered fluid is reabsorbed back into the blood.
• The remaining 1 ml of the filtered fluid is excreted as urine.
  • Urine is approximately 95% water and 5% waste.

Kidney-Related Diseases

• Kidney stones: Hard deposits of minerals and salts formed in the kidneys or urinary tract.
• Gout: Arthritis caused by uric acid crystals in the joints.
• Urinary Tract Infections (UTIs): Infections caused by bacteria in the urinary tract. Common types include urethritis (urethra infection), cystitis (bladder infection), and pyelonephritis (kidney infection).

Kidney Dialysis

• A procedure used to remove waste and excess fluid from the blood when the kidneys cannot function properly.
• Two types:
  • Hemodialysis (HD): Blood is filtered outside the body. The process takes 3-4 hours, 3 times a week.
  • Peritoneal Dialysis (PD): A solution is placed in the abdomen, and waste products are removed via osmosis/diffusion. The procedure takes 30 minutes, 4 times a day and can be done at home.