Gaseous Exchange

• The lungs are in the upper part of the bidy - Thorax.
• They are protected by the ribcage
• They are seperated from the lower part of the body (the abdomen) by the diaphagm.

• The breathing systme takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air.
• Vantilation is the movement of air into and out of the lungs - breathing in and out

• Intercostal muscles contract pulling the ribcage up and out,
• The diaphragm contracts and flattens
• The thorax volume increase
• this decreases the pressure, drawing air in.

Throught the lungs:

Trachea -> Brachi -> Branchioles -> Alveoli -> gas exchange

• Intercostal muscles relax and the ribcage drops in and down,
• The diaphragm relaxes and moves down
• The thorax volume decreases
• This increases the pressure, so air is forced out.

• Artifical ventilators are machines that move air (often with extra oxygen) into and out of the lungs.
• They help people who can't breathe by themeselves
• E.g. if someone is under general anaesthetic/ has a lung injury or disease

Old Method:

• Used to be a giant case ('ron lung') from the neck to the abdomen
• Air was pumped into the case, pressure dropped, the lungs expanded and so air was drawn into the lungs.
• than air was pumped into the case, pressure increased, lungs decreased and so air was forced out of the lungs,
• However they could interfere with blood flow to the lower body.

New Method:

• Most ventilators work by pumping  air into the lungs.
• This expands the ribcage.
• When they stop pumping th ribcage relaxes and pushes air back out of the lungs.
• This doesnt interfer with blood flow
• BUT it can cause damage (e.g. burst alveoli) if the lungs can't cope with the artificial air flow.