Each of these divides into two respiratory bronchioles, which in turn divide to form 2 to 11 alveolar ducts, from which the alveolar sacs and alveoli arise. There are 50 to 80 terminal bronchioles in each lobe. There are about 10 bronchopulmonary segments in the right lung and 8 in the left, the actual number varying. The pattern of distribution of these into the segments of each lobe is important in pulmonary and thoracic surgery. These further divide into a great number of smaller bronchioles. The primary bronchi divide into secondary bronchi, one for each of five lobes. Two primary bronchi, one on each side, extend from the trachea. Behind this is the hilum, through which the blood vessels, lymphatics, and bronchi enter and leave the lung.Īir travels from the nasal passages to the pharynx, larynx, and trachea.
The left lung has an indentation (the cardiac depression), for the normal placement of the heart. The total capacity of the lung varies from 3.6 to 9.4 L in men and 2.5 to 6.9 L in women. Respirations per minute are 12 to 20 in an adult. The lungs contain 300,000,000 alveoli, and their respiratory surface is about 70 sq m. The right lung has three lobes and the left two. The lungs include the lobes, lobules, bronchi, bronchioles, alveoli (air sacs), and pleural covering. The base of each lung rests on the diaphragm, and each lung apex rises from 2.5 to 5 cm above the sternal end of the first rib, the collarbone (clavicle), supported by its attachment to the hilum or root structures. The lungs are connected with the pharynx through the trachea and larynx.
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