Lungs in situ

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What does in situ mean? If we were to remove the anterior wall of the thorax without removing or altering any of the structures beneath it, we would see the lungs in their original place, or in situ. Examining the lungs in situ allows us to appreciate their normal anatomy, topography and relations with other structures of the thorax.

The lungs are located either side of the mediastinum, surrounded by the thoracic cage and superior to the diaphragm. Hence, each lung has a mediastinal, costal and diaphragmatic surface. Both lungs are enveloped by visceral and parietal pleura, between which is a potential space known as the pleural cavity.

Inferior and anterior to the lungs are two potential spaces called pleural recesses to which the pulmonary tissue does not extend (or extends only during a forced inspiration), called the costodiaphragmatic and costomediastinal recesses, respectively.

Each lung has an apex and a base, as well as the anterior, posterior and inferior borders. The apices of the lungs project outside of the superior thoracic aperture, while base rests on the ipsilateral hemidiaphragm. Although paired organs, the left and right lungs differ anatomically. The inferior border is located around the level of the sixth rib at the midclavicular line, eighth rib at the midaxillary line, and tenth rib posteriorly at the scapular line. The anterior border of right lung is located deep to the right margin of the sternum, extending between the second and sixth costal cartilages; the anterior border of the left lung begins deep to the sternum at the level of the second intercostal space before running inferolaterally to the sixth intercostal space, about three centimeters from the left margin of the sternum.

The following video tutorial will provide you with a detailed overview of the location, anatomical features and relations of the lungs.

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Summary