Anatomy and histology
Place dividing the trachea to the main bronchi (bifurcation) depends on age, sex and individual anatomic features; in adults is at level IV-VI of the thoracic vertebrae. Right bronchus wider, narrower and less deviates from the average axis than the left. The form of bronchial this bifurcation several funnel, then cylindrical with round or oval skylight.
In the area of the gate right lung main b is located in the pulmonary artery and left underneath.
B. main share in the secondary equity, or zone, B. Respectively lung regions distinguish the top, front, back and bottom of zone B. Each zonal bronchus branches into tertiary, or segmental (Fig. 1).

segmental bronchi divide
Fig. 1. Segmental bronchi divide: I - the main bronchus; II - top; III - front; IV - bottom; V - back zonal bronchus; 1 - top; 2 - rear; 3 - front; 4 - internal; 5 - external; 6 - bottom-front: 7 - lower-back; 8 - lower-internal; 9 - top; 10 - lower segmental bronchi.

Segmental bronchi, in turn, are divided into sub-segmental, midorikawa and vnutritrekovye B., which pass in the end terminal bronchioles. Branching B. forms in light of the bronchial tree. Terminal bronchioles dichotomously branching out, go into respiratory bronchioles I, II and III orders and end with the extension - arches, continuing in the alveolar moves.

the structure of pneumatic and respiratory departments light
Fig. 2. The structure of pneumatic and respiratory departments easy: I - the main bronchus; II - large zonal bronchus; III - the average bronchus; IV and V of the small bronchi and bronchioles (histological structure): I - multi ciliated epithelium; 2 - own layer of mucous membrane; 3 - muscle layer; 4 - submucosal shell with glands; 5 - hyaline cartilage; 6 - the outer casing; 7 - the alveoli; 8 - megaloblastnye partitions.

Histologically in the wall B. distinguish mucous membrane with submucosal layer, muscle and vibrotherapy and outer layers of connective tissue membrane (Fig. 2). Main, equity and segmental bronchi in its structure correspond to major B. according to the old classification. The mucous membranes are built of multi-row cylindrical ciliated epithelium, which contains a lot of goblet cells.
Electron on the free surface of epithelial cells of the mucous membrane of the bronchi, except cilia, found a significant number of microvilli. Under the epithelium is a network of longitudinal elastic fibers, and then layers of loose connective tissue rich in lymphoid cells, blood and lymph vessels and nerve cells. Muscle layer is formed by bundles of smooth muscle cells, oriented in the form of intersecting spirals; reduction causes a reduction in clearance and a shortening B. In segmental bronchi additional longitudinal bundles of muscle fibers, the number of which increases with lengthening B. Longitudinal muscle bundles causes the decrease B. in length, which contributes to its purification from secret. Vibrotherapy layer built from separate the different forms of plates hyaline cartilage, United dense fibrous tissue. Between muscle and fibrous layers are mixed mucous and albumen gland, excretory ducts which appear on the surface of the epithelium. Their secret with detachable goblet cells moisturizes the mucous membrane and adsorbs the dust particles. The outer casing consists of loose fibrous connective tissue. The unique structure sub-segmental bronchi is the prevalence argyrophilic connective tissue fibers in the frame walls, the lack of mucous glands and increase the number of muscle and elastic fibers. With the decrease of the caliber of the bronchi in fibrinoguenom layer decreases the number and size of cartilaginous plates, hyaline cartilage is replaced elastic and gradually disappears in sub-segmental B. the Outer casing is gradually transformed into midorikawa connective tissue. The mucous membrane vnutriposelkovykh bronchi thin; the epithelium double-row cylindrical, longitudinal muscle layer is absent, while the circular is weak. Terminal bronchioles lined single row cylindrical or cubic epithelium and contain a small amount of muscle bundles.
The blood supply b is bronchial arteries, the exhaust from the thoracic aorta and parallel bronchi, in their outer connective tissue layer. From them segmental depart smaller branches, penetrating into the wall B. and forming in her shells blood plexus. Artery B. widely anastomosis with other vessels of the mediastinum. Venous plexus are located in the submucosal layer and between muscle and vibrotherapy layers. According widely anastomosis front and rear bronchial veins the blood flowing to the right in the azygos vein, left - in pollonarrua.
Network of lymphatic vessels mucosal and submucosal layer fluid flowing through a lateral lymphatics to regional lymph nodes (kolobangara, bifurcation and ecolotrain). Lymphatic ways bronchi merge with pulmonary.
Bronchi innervated by the branches of wandering, sympathetic and spinal nerves. Nerves, penetrating the wall of the bronchus, form outwards and inwards from fibrogenesis layer two plexus, the branches of which end up in the muscle layer and the epithelium of the mucosa. In the course of the nerve fibers are nervous nodes up to the submucosal layer.
The differentiation of the constituent elements of the walls of the bronchi ends to 7 years of age. The aging process is characterized by atrophy of the mucosa and submucosa of the layer with the growth of fibrous connective tissue; marked to calcification of cartilage and changes elastic frame, which is accompanied by loss of elasticity and tone of the walls of the bronchi.