What are the functions of the bronchi?

The Bronchi are a complex system of airway tubes that carry air in and out of the Lungs.

They look like little tiny branches with your blood vessels wrapped around them
the bronchi which are like the branches of a tree. The bronchi carry the gases deep into the lungs
The bronchi are a complex system of airway tubes that carry air into and out of the lungs. The bronchi do not absorb oxygen or exchange it for carbon dioxide; gas exchange only occurs in the alveolar sacs at the very ends of the bronchial network. The trachea (windpipe) divides into two mainstem bronchi, each of which divides into 2 or 3 lobar bronchi. Each lobar bronchus divides into 8 to 10 segmental (or tertiary) bronchi, and each segmental bronchus divides into many primary bronchioles, each of which divides into terminal bronchioles which divide into respiratory bronchioles which divide into alveolar ducts. Each of the hundreds of alveolar ducts supplies air to several pulmonary alveolar sacs where oxygen is exchanged for carbon dioxide.
The trachea branches off into two main bronchi, your left and right primary bronchi, which lead to the left and right lung respectively. Your right lung is slightly wider, shorter, and taller that the left, which makes it more vulnerable to foreign invasion. At this point in breathing, the air has been moistened, purified and warmed.

Each bronchi enters its lung and begins on a series of branches, called the bronchial or respiratory tree. The first of these branches is the lobar (secondary) branch. On the left, there are two lobar branches, while on the right, there are three. Each lobar branches into one lobe. The next branch is called the segmental (tertiary) branch. Each branch continues to branch into smaller and smaller bronchioles. The final branch is called the terminal bronchioles. These bronchioles are smaller than 0.5 mm in diameter.

The first few levels of bronchi are supported by rings of cartilage. Branches after that are supported by irregularly shaped discs of cartilage, while the latest levels of the tree have no support whatsoever.
There are two primary bronchi which are the first divisions branching off from the trachea to take air into the lungs. The primary bronchi then subdivide into lobar bronchi and then again into tertiary bronchi which continue to divide until they are tiny bronchioles which supply each of the alveoli in the lungs.

The left primary bronchus leads to the left lung and the right primary bronchus leads into the right lung. The bronchi contain rings of hyaline cartilage which help to provide flexible support to the airways.
They serve as air passages