The bronchus is one of a pair of large tubes (plural bronchii) that branch off from the trachea (windpipe) in the mammalian and vertebrate body. Human bronchii, like those of other animals, branch off and one goes into each lung.
Each bronchus is relatively short because it soon branches out into many much narrower tubes called bronchioles that also diverge into many branches and eventually end in many thousands of tiny tubes that have an air sac called an alveolus at the end of them.
Bronchii have rings of cartilage to keep them always open during the movements that draw air into the lungs and then push it out again. Glands in the wall of each bronchus secrete a slimy mucus that is constantly propelled upwards to the back of the throat by millions of tiny hairs that are on the surface of the cells. This protects the lungs by removing any dust and other particles that are breathed in with the air.
Each bronchus is relatively short because it soon branches out into many much narrower tubes called bronchioles that also diverge into many branches and eventually end in many thousands of tiny tubes that have an air sac called an alveolus at the end of them.
Bronchii have rings of cartilage to keep them always open during the movements that draw air into the lungs and then push it out again. Glands in the wall of each bronchus secrete a slimy mucus that is constantly propelled upwards to the back of the throat by millions of tiny hairs that are on the surface of the cells. This protects the lungs by removing any dust and other particles that are breathed in with the air.