IGCSE Biology – 2i: Excretion in Humans
Excretion
Definition
o Excretion is the removal from the body of waste products of the body’ metabolism.
o The metabolism is all of the chemical processes happening in our bodies.
Excretion in the Lungs
Equations for Respiration
o Word equation –
Glucose + oxygen carbon dioxide + water + energy
o Chemical equation –
C₆H₁₂O₆ + 6O₂ 6CO₂ + 6H₂O + ATP
Explanation
o The carbon dioxide diffuses into the blood before travelling back to the heart
through the veins.
o It is then pumped through the pulmonary artery and into the capillaries in the lungs,
where it travels down a concentration gradient by diffusion and into the air in the
lungs to be expelled.
Excretion in the Kidneys
The Role of the Kidneys
o The kidneys filter your blood.
o They also separate urea, water, and excess mineral ions.
What is Excreted?
o Urea made by the liver gets filtered into the kidneys.
o It then travels into the bladder to make urine which is expelled from the body.
Excretion in the Skin
Excretory Product
o Sweat is the excretory product of the skin.
o It is made of water and salts.
Where is it Produced?
o Sweat is produced by the sweat glands.
o The main aim of sweat is to keep you cool through evaporation.
Excretion
Definition
o Excretion is the removal from the body of waste products of the body’ metabolism.
o The metabolism is all of the chemical processes happening in our bodies.
Excretion in the Lungs
Equations for Respiration
o Word equation –
Glucose + oxygen carbon dioxide + water + energy
o Chemical equation –
C₆H₁₂O₆ + 6O₂ 6CO₂ + 6H₂O + ATP
Explanation
o The carbon dioxide diffuses into the blood before travelling back to the heart
through the veins.
o It is then pumped through the pulmonary artery and into the capillaries in the lungs,
where it travels down a concentration gradient by diffusion and into the air in the
lungs to be expelled.
Excretion in the Kidneys
The Role of the Kidneys
o The kidneys filter your blood.
o They also separate urea, water, and excess mineral ions.
What is Excreted?
o Urea made by the liver gets filtered into the kidneys.
o It then travels into the bladder to make urine which is expelled from the body.
Excretion in the Skin
Excretory Product
o Sweat is the excretory product of the skin.
o It is made of water and salts.
Where is it Produced?
o Sweat is produced by the sweat glands.
o The main aim of sweat is to keep you cool through evaporation.
