The lungs are spongy, saclike respiratory organs in the chest cavity which, together with the heart, work to remove carbon dioxide from the blood and provide it with oxygen.
Anatomy of the lungs
The bronchi themselves divide many times before branching into smaller airways called bronchioles. These are the narrowest airways – as small as one half of a millimeter across. The larger airways resemble an upside-down tree, which is why this part of the respiratory system is often called the bronchial tree. The airways are held open by flexible, fibrous connective tissue called cartilage. Circular airway muscles can dilate or constrict the airways, thus changing the size of the airway.
Each lung is enclosed by a double-layered serous membrane, called the pleura. The visceral pleura is firmly attached to the surface of the lung. At the hilum, the visceral pleura is continuous with the parietal pleura that lines the wall of the thorax. The small space between the visceral and parietal pleurae is the pleural cavity. It contains a thin film of serous fluid that is produced by the pleura. The fluid acts as a lubricant to reduce friction as the two layers slide against each other, and it helps to hold the two layers together as the lungs inflate and deflate.
The lungs are soft and spongy because they are mostly air spaces surrounded by the alveolar cells and elastic connective tissue. They are separated from each other by the mediastinum, which contains the heart. The only point of attachment for each lung is at the hilum, or root, on the medial side. This is where the bronchi, blood vessels, lymphatics, and nerves enter the lungs.
Related entries• lung cancer
• lung cancer treatment
Related category• ANATOMY AND PHYSIOLOGY
Sources: National Cancer Institute and Merck
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