The lung is primarily created from intrapulmonary bronchial tree, that is concerned with the conduction of air to-and- fro from the lung, and pulmonary units, that are concerned with the gaseous exchange inside the lung (for comprehensive structure see textbooks on Histology).

Bronchial Tree.

The bronchial tree is composed of main bronchus, lobar bronchi, terminal bronchioles, and respiratory bronchioles.

Primary Bronchi.

The trachea splits outside the lungs, in the level of the lower border of T4 vertebra, into 2 primary (main) bronchi– left and right for left and right lung, respectively:.

Right main bronchus is shorter, wider, and much more vertical. It’s about 1 inch (2.5 cm) long and is located more or less in line with the trachea.

Left main bronchus is narrower, longer, and much more horizontal than the right. It’s about 2 inches (5 cm) long and doesn’t be located consistent together with the trachea.

The long axis of right principal bronchus deviates about 25 ° from the long axis of the trachea, on the other hand long axis of the left main deviates about 45 ° from the long axis of the trachea.

The left main bronchus enters to the left below the arch of aorta and in front of the esophagus.

Clinical Significance

Aspiration Of Foreign Body Into The Right Principal Bronchus

The inhaled foreign bodies generally goes into in the right principal bronchus because it’s shorter, wider and in keeping with all the trachea. Since the inhaled foreign particles often goes into in the right principal bronchus, thus in the right lung. Consequently, lung abscess takes place more generally in the right lung.

Bronchoscopy.

It’s a process, where a flexible, fibreoptic bronchoscope is added in the trachea to visualize the inner part of the trachea and bronchi. The carina, a keel-like median ridge in the bifurcation of the trachea is an essential landmark observable via the bronchoscope. The widening and distortion of the angle between the main bronchi (distorting the position ofcarina) viewed in bronchoscopy is serious prognostic indication, since it generally signifies carcinomatous engagement of tracheobronchial lymph nodes. The carina of trachea is also an extremely sensitive area for cough reflex.

Bronchiogenic Carcinoma.

It’s the commonest cancer in the men notably in chronic cigarette smokers. It typically originates from epithelial lining of the bronchi and creates well-circumscribed gray white mass in the lung. A presence of circular shadow (popularly referred to as coin-shadow) in plane X ray chest (PA view) may be the only finding in an otherwise asymptomatic patient.

The bronchiogenic carcinoma may spread (metastasis) to brain by both arterial and venous paths as under:.

Arterial root.

Lung capillaries > pulmonary vein > left atrium > left ventricle > aorta > internal carotid and vertebral arteries > brain.

Venous route.

Bronchial veins > azygos vein > external vertebral venous plexus > internal vertebral venous plexus > cranial dural venous sinuses > brain.

 

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