Bronchi and Bronchial Tree

In the mediastinum, at the level that the 5th thoracic vertebra, the trachea divides right into the right and also left major bronchi. The bronchi branch into smaller and smaller passageways till they terminate in small air sacs dubbed alveoli.

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The cartilage and mucous membrane the the main bronchi are similar to the in the trachea. Together the branching proceeds through the bronchial tree, the amount of hyaline cartilage in the walls decreases till it is absent in the smallest bronchioles. Together the cartilage decreases, the quantity of smooth muscle increases. The mucous membrane additionally undergoes a shift from ciliated pseudostratified columnar epithelium to straightforward cuboidal epithelium to straightforward squamous epithelium.

The alveolar ducts and also alveoli consist primarily of straightforward squamous epithelium, which permits quick diffusion of oxygen and also carbon dioxide. Exchange that gases in between the air in the lungs and also the blood in the capillaries occurs throughout the walls of the alveolar ducts and alveoli.

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Lungs

The two lungs, which contain every the components of the bronchial tree beyond the main bronchi, occupy most of the space in the thoracic cavity. The lungs space soft and also spongy since they are mainly air spaces surrounding by the alveolar cells and elastic connective tissue. They room separated native each various other by the mediastinum, which has the heart. The only suggest of attachment because that each lung is at the hilum, or root, top top the medial side. This is whereby the bronchi, blood vessels, lymphatics, and nerves get in the lungs.

The appropriate lung is shorter, broader, and also has a greater volume 보다 the left lung. The is separated into 3 lobes and also each lobe is supplied by one of the second bronchi. The left lung is longer and narrower 보다 the best lung. It has an indentation, called the cardiac notch, top top its medial surface ar for the apex the the heart. The left lung has two lobes.

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Each lung is attached by a double-layered serous membrane, called the pleura. The visceral pleura is steady attached to the surface ar of the lung. In ~ the hilum, the visceral pleura is continuous with the parietal pleura the lines the wall of the thorax. The small space in between the visceral and also parietal pleurae is the pleural cavity. It consists of a slim film that serous liquid that is produced by the pleura. The liquid acts together a lubricant to mitigate friction as the two layers slide versus each other, and it help to organize the 2 layers with each other as the lungs inflate and deflate.