Connected to trachea that has half ring cartilage to prevent collapsing, and goblet cells for secretion of mucus trapping dust particles and pathogens, also cilia to prevent pathogens entering the lungs.
Has bronchus that separate for the two side of the lungs.
Bronchus has cilia too and has goblet cells that secret mucus to trap the dust particles and pathogens. These pathogens can be swiped upwards to the throat by cilia that are on the surface of ciliated epithelial cells.
This mucus reaches the throat to be swallowed and so pathogens can be killed by stomach acid.
Bronchus has a complete ring of cartilage.
Bronchioles have no cartilage.
And have no goblet cells, but they do have cilia.
This is to prevent any mucus reaching down in the bronchioles blocking the thin air way of bronchioles.
Bronchioles are very small and so they do not need cartilage to stay open, as smooth muscles are sufficient enough.
Alveoli have elastics fibers in their walls to allow recoiling when exhaling, and expanding when inhaling
Preventing alveoli walls from bursting.
Also to allow maximum oxygen to enter the blood (by diffusion).
Alveoli have many network of capillaries surrounding it to get as much oxygen as possible for RBC and release carbon dioxide carried by RBC.
Alveoli is moist, this allows it to have faster diffusion rate as the gasses dissolve in this fluid.