Alveoli and gas exchange

Location of blood vessels:

blood capillaries located close to the walls of the alveoli = short diffusion pathway for efficient gas exchange.

Elastin

alveoli walls contain elastic tissue which

allows the air sacs to stretch during inspiration

recoil during expiration to help force the air out

Surfactant:

The bronchioles secrete a protein substances that acts as a surfactant preventing the alveoli walls from sticking together. It reduces the surface tension of the water in the alveoli.

Concentration gradient:

Concentration gradient from high to low oxygen from alveoli to blood and the other way round for carbon dioxide is maintained by regularly replacing the air in the alveoli by breathing and by the constant movement of blood in the capillaries so deoxygenated blood continuously replaced the newly oxygenated blood

Moisture:

The alveoli have a layer of moisture to prevent the lungs from drying out and to facilitated diffusion of dissolved gases from blood to alveoli and from alveoli to blood.

Walls of alveoli

squamous epithelial cells.

walls as thin as possible to allow for the shortest possible diffusion pathway

Walls of blood vessels:

The capillary walls are made of squamous endothelial cells, one cell thick to further shorten the diffusion pathway.

check powerpoint for diagram