Describe the histological structure of lungs.
Answers
The principle function of the lung is to provide oxygen to the blood and in exchange rid the blood from carbon dioxide. Inhaled air passes through the trachea that branch into two bronchi, each supplying one of the two lobes of lung. In the lung, each bronchus branches into narrower bronchi that eventually terminate in bronchioles. The wall of bronchioles consist of ciliated cuboidal epithelium and a thin layer of smooth muscle. As opposed to upper parts of the respiratory tract, it lacks hyaline cartilage. The main cell types of the bronchioles are similar to the ones in the bronchi namely, basal cells, neuroendocrine cells, ciliated cells, serous cells, Clara cells and goblet cells. Goblet and ciliated cells decrease in number as one approaches the terminal bronchioles, whereas the number of Clara cells increases proportionally. The Clara cells have a secretory function and represent the main progenitor cell after bronchiolar injury. They are columnar to cuboidal in shape and project above the ciliated cells into the airway lumen.