Bronchi

The bronchi are the air-conducting tubes that branch off from the trachea, forming the bronchial tree that distributes air to the different regions of the lungs.

The bronchi are cartilaginous and membranous tubes that continue from the trachea after its bifurcation. The trachea divides into two main bronchi (or primary bronchi), a right and a left, each entering the corresponding lung at the pulmonar hilum. These main bronchi then branch into lobar bronchi (or secondary bronchi), which supply specific lung lobes. The lobar bronchi, in turn, divide into segmental bronchi (or tertiary bronchi), and then into progressively smaller bronchioles, forming the bronchial tree. The wall of the bronchi is similar to that of the trachea, composed of cartilaginous rings or plates (less regular and complete as the bronchi branch), smooth muscle, connective tissue, and a mucous membrane lined with pseudostratified ciliated epithelium containing goblet cells.

The general organization of the bronchial tree is similar in mammals, but variations exist, particularly concerning the presence of tracheal bronchi and lung lobation:

• Ruminants (Cattle, Sheep): As in dogs, cattle and sheep also possess a tracheal bronchus for the right cranial lobe, which emerges from the trachea before the main bifurcation. The bronchial arborization is then similar, with lobar bronchi for the different lung lobes.

  • Horse, Dog, Cat: They don't havea tracheal bronchus. The trachea divides into right and left main bronchi, which then branch into lobar bronchi. Lung lobation is less pronounced in horses than in other species.

In humans, bronchial anatomy is similar to that of cats and horses, meaning there is no tracheal bronchus.