<Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> A bronchus, is a passage of airway in the respiratory system that conducts air into the lungs . The first bronchi to branch from the trachea are the right main bronchus and the left main bronchus . These are the widest and enter the lungs at each hilum, where they branch into narrower secondary bronchi known as lobar bronchi, and these branch into narrower tertiary bronchi known as segmental bronchi . Further divisions of the segmental bronchi are known as 4th order, 5th order, and 6th order segmental bronchi, or grouped together as subsegmental bronchi . The bronchi when too narrow to be supported by cartilage are known as bronchioles . No gas exchange takes place in the bronchi . </P> <P> The trachea (windpipe) divides at the carina into two main or primary bronchi, the left bronchus and the right bronchus . The carina of the trachea is located at the level of the sternal angle and the fifth thoracic vertebra (at rest). </P> <P> The right main bronchus is wider, shorter, and more vertical than the left main bronchus . It enters the right lung at approximately the fifth thoracic vertebra . The right main bronchus subdivides into three secondary bronchi (also known as lobar bronchi), which deliver oxygen to the three lobes of the right lung--the superior, middle and inferior lobe . The azygos vein arches over it from behind; and the right pulmonary artery lies at first below and then in front of it . About 2 cm from its commencement it gives off a branch to the superior lobe of the right lung, which is also called the eparterial bronchus . Eparterial refers to its position above the right pulmonary artery . The right bronchus now passes below the artery, and is known as the hyparterial branch which divides into the two lobar bronchi to the middle and lower lobes . </P>

The point at which the trachea divides into the two mainstem bronchi is called the