Excretory System

Excretion

Definition: The process of removal of metabolic waste products and excess substances from the body of an organism.

Organs and their Excretory Products

• Kidneys: Primary excretory organs, remove nitrogenous wastes (urea, uric acid, creatinine), excess salts, and water from the blood to form urine.
• Sweat Glands (Skin): Excrete excess water, salts, and a small amount of urea through sweat.
• Lungs: Excrete carbon dioxide and water vapor during respiration.

Renal Excretory System

The urinary system is the main excretory system in humans.

• Kidneys:
  • Location: A pair of bean-shaped organs located on either side of the spine, just below the rib cage.
  • Function: Filter blood to remove waste products and produce urine.
• Ureters:
  • Location: Two tubes extending from the kidneys to the urinary bladder.
  • Function: Transport urine from the kidneys to the urinary bladder.
• Urinary Bladder:
  • Location: A muscular sac located in the pelvis.
  • Function: Stores urine until it is ready to be expelled from the body.
• Urethra:
  • Location: A tube extending from the urinary bladder to the outside of the body.
  • Function: Carries urine from the bladder out of the body.

Role of Kidneys in Filtration

Kidneys contain millions of tiny filtering units called nephrons. Blood enters the kidneys, and within the nephrons, waste products, excess salts, and water are filtered out from the blood to form urine. Essential substances are reabsorbed back into the blood.

Common Disorders of the Urinary System

• Urinary Tract Infection (UTI): An infection in any part of the urinary system, often caused by bacteria.
• Kidney Stone: Hard deposits made of minerals and salts that form inside the kidneys.