GASEOUS EXCHANGE IN THE LUNGS AND BODY
TISSUES
Gaseous exchange is the movement of
oxygen into the body, and carbon dioxide out of the body. The
gaseous exchange takes place in the lungs by diffusion through the
alveolar surface. There are millions of aveoli in the lungs, which
gives it around 70m2 of exchange surface.
The complex sequences of events which
take place during gaseous exchange are as follows:
The squamous epithelial cells of the
aveoli are what exhaled or inhaled gases must cross. They also
diffuse past tissue fluid between the alveoli and the blood
capillaries, and a single layer of cuboidal cells on the walls of
blood capillaries. The rate and direction of diffusion depends on
the pressure gradient, and whatever distance is involved.
