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4.1 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 (Urinary System)
Kidneys:
Pair of bean-shaped organs; filter blood, produce urine.
Ureters:
Two tubes; transport urine from kidneys to urinary bladder.
Urinary Bladder:
Muscular sac; stores urine.
Urethra:
Tube; carries urine from 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 bacterial.
Kidney Stone:
Hard deposits made of minerals and salts that form inside the kidneys.