Excretory
System
, Excretory System
Function of excretion Homeostasis
Excretion: removal of metabolic waste, vital in homeostasis, Process of keeping balance in body. Important
for survival. Oxygen & digested food are
maintenance of constant internal environment.
absorbed/carried by blood to cells, used in cell
Egestion: removal of undigested substance, not products respiration/other metabolic processes.
of metabolism, never inside cells.
Metabolism
Secretion: release of useful substances produced by cells The chemical processes occurring in living organism. Provide
energy & products for growth/maintenance. Also produce
for important functions, (digestive juices, hormones & milk) waste products (CO2) & nitrogenous waste (urea, uric acid
& ammonia). Metabolic waste products build up in cells,
Waste products not removed changes composition of tissue fluid become toxic & eventually stop metabolic processes. Need
efficient waste disposal systems.
surrounding cells/cell cytoplasm
Change pH, temperature & water potential of cells disrupt metabolism, death of cells/organism
Organ Excretory product Origin of this product
Lungs CO2, water vapour Product of cellular respiration
Skin(sweat glands) Mineral salts, little urea, water Extracted from blood
Deamination of excess amino acids, break down
Liver Urea, bile pigment of haemoglobin
Gut Bile pigment, excess mineral salt From liver, haemoglobin breakdown
Deamination of excess amino acids in liver
Kidneys Urea, mineral salts Excess taken in with food
Role of the main excretory organs
Major organs: lungs, kidneys & skin. Liver & alimentary play minor role
Lungs excrete CO2 as waste product of cellular respiration, transported to lungs from cells
via circulatory system, also excrete water vapour & heat.
Kidneys & bladder form urinary system. Removes waste material from
bloodstream, regulates amount of water salts. Kidneys produce urine, liquid:
water & nitrogenous waste products (urea, uric acid, creatinine & ammonia)
Skin, Sweat is salty fluid secreted by sweat glands in skin. Skin excretes small
amount of urea, water & salts. As sweat evaporates, heat is lost from body.
Liver breaks down extra amino acids in bloodstream into glucose & urea. Urea
carried in bloodstream to kidneys, excreted in urine, breaks down haemoglobin to bile
pigments, carried in bile to duodenum of alimentary canal.
