Gas exchange 4.3

4.3

how alveoli surface area help gas exchange

give lungs lots of internal surface area with hundreds of millions of them with a total surface area of 50-80m²

how alveoli blood vessels help gas exchange

well supplied with blood vessels so as much blood as possible is close to the air

how alveoli membranes help with gas exchange

very thin (only one cell thick) so gas molecules don’t have to travel far

where and why lungs are positioned

deep inside body to prevent excess evaporation of fluid that covers respiratory surfaces

what is the alveolus membrane covered with and why

covered by thin layer of moisture because gas can only diffuse when dissolved by fluid

why must there be constant changing of air in the alveoli

to ensure theres always a concentration gradient of oxygen and carbon dioxide between the air and the blood

where does the blood coming to the alveolus come from

it comes from the pulmonary artery into the capillaries around the alveoli

what has happened to the oxygen blood before it reaches the lungs

it has been through the bodies capillaries where a lot of the oxygen has been taken up by body cells, so it has a low concentration of oxygen
it has also picked up carbon dioxide as a product of cellular respiration

how does the actual oxygen and carbon dioxide get from the alveoli into the capillaries

the oxygen dissolves in the moisture on the inside of the alveoli and diffuses through the membrane, the walls of the alveoli and capillaries, and into the blood
the carbon dioxide does the opposite
both are moving from an area of higher concentration to an area of lower concentration

oxygen and carbon dioxide concentrations in inspired and expired air

inspired: oxygen 20.95%, carbon dioxide 0.04%
expired: oxygen 15.08%, carbon dioxide 4.30%

why does diffusion of gas into blood occur

because of the concentration gradient

how is the concentration gradient of the gases into and out of blood maintained

the constant flow of blood and the movement of air