The respiratory system

Gas exchange:

External respiration -

Co2 from lung capillaries are transported to the alveoli sac to be exhaled out of the lungs.

Oxygen diffuses from the alveolar sac to the lung capillaries

Diffusion occurs because gases move from an area of higher concentration to an area of lower concentration.

We breathe in air that is a higher concentration than the blood in the capillaries surrounding the alveoli, so the air diffuses through the alveoli to the bloodstream.

In the alveoli = external respiration

In the tissues = internal respiration

After, oxygen enters the bloodstream where its transported around the body to cells and tissues, transported by gas transport.

Gas transport = haemoglobin molecules within red blood cells.

Oxygen + haemoglobin = Oxyhaemoglobin

Internal respiration -

Oxygen moving from the bloodstream to the tissues.

CO2 moving from the tissues to the bloodstream (using diffusion for both)