(1) Gaseous exchange takes place within the lungs by diffusion from the alveoli to blood capillaries.
(2) Lungs in the vertebrates are madeup of several thousands of small chambers called Alveoli. (alveolus – singular)
3) Alveolus is the structural and functional unit of the lung.
(4) Each alveolus is supplied with a branch of the bronchiole and with capillaries, which bring the deoxygenated blood. The alveolus as well as capillaries are one celled thick gaseous exchange between the two.
(5) Blood, dark red in colour, flows from the heart through capillaries and collects oxygen from the alveoli.
(6) At the same time, carbondioxide passes out of the capillaries and into the alveoli. When we breathe out, we get rid of this carbondioxide.
(7) The bright red oxygen rich blood is returned to the heart and pumped out to the body.
(8) As a result of gaseous exchange, the composition of inhaled and exhaled air is different.
