Right main bronchus

The right main bronchus is the first major air-conducting tube that branches from the trachea at the tracheal bifurcation, channeling air to the right lung.

The right main bronchus is the more direct and often wider of the two main bronchi, emerging from the trachea at the tracheal carina. It extends caudally and laterally to enter the right lung at its hilum. Its wall consists of cartilaginous rings or plates, smooth muscle, and a ciliated respiratory mucosa. In some species, it gives rise to specific lobar bronchi shortly after its origin, while in others, a lobar bronchus may even branch off the trachea before it.

The origin and initial ramifications of the right main bronchus show significant variations:

• Ruminants (Cattle, Sheep): In these species, the right main bronchus is generally shorter than the left. A distinctive feature is the presence of a tracheal bronchus (or right cranial lobar bronchus) that branches directly from the right side of the trachea, before the main tracheal bifurcation. Consequently, the right main bronchus, after the carina, ventilates the right middle, caudal, and accessory lung lobes.

• Cat, Dog and Horse: In cats, dogs and horses, there is no tracheal bronchus. The right main bronchus is the first branch of the trachea at the carina. It then gives rise to the lobar bronchus for the right cranial lobe, followed by the bronchi for the other lobes of the right lung.

In humans, the right main bronchus is generally shorter, wider, and more vertical than the left main bronchus. It branches off the trachea at the carina. As in cats and horses, there is no tracheal bronchus in humans; the right main bronchus gives rise to the lobar bronchi for the three lobes of the right lung (superior, middle, inferior). Its more vertical trajectory makes it more susceptible to foreign body aspiration compared to the left main bronchus.