The lungs are organs that facilitate respiration, the process of taking in oxygen and expelling carbon dioxide. They are located within a protected space in the upper body.
Anatomy of the Thoracic Cavity
The thoracic cavity, also known as the chest cavity, is a large, cone-shaped space in the human body. Its boundaries are formed by a bony and muscular framework designed for protection and movement. The rib cage, comprising the ribs and the sternum (breastbone) anteriorly, and the thoracic vertebrae posteriorly, forms the protective walls of this cavity.
Inferiorly, the thoracic cavity is separated from the abdominal cavity by a dome-shaped muscle called the diaphragm. This structure completes the enclosure of the thoracic space. The cavity is wider at its base and narrows towards the top, providing a secure environment for the organs it contains. Its primary role involves housing and safeguarding vital organs, including the lungs and heart.
Precise Location of the Lungs
The lungs are situated centrally within the thoracic cavity, with one lung positioned on each side. The right lung typically has three lobes, while the left lung has two, being slightly smaller to accommodate the heart.
A central compartment, the mediastinum, separates the two lungs. This space contains several important structures, including the heart, major blood vessels, the trachea (windpipe), and the esophagus. The lungs are positioned laterally to this mediastinum, resting against its sides. The apex of each lung extends upwards, just above the first rib, while their broader bases rest directly on the diaphragm.
How the Thoracic Cavity Supports Lung Function
The thoracic cavity provides both physical protection and mechanical support for the lungs. The rigid framework of the rib cage and sternum acts as a shield, safeguarding the delicate lung tissue from external impact and trauma.
The mechanics of breathing are directly facilitated by the thoracic cavity. The diaphragm and intercostal muscles work together to change the volume of this cavity. During inhalation, the diaphragm contracts and moves downward, while the external intercostal muscles pull the ribs upward and outward, expanding the chest cavity. This increases volume, reducing pressure within the lungs and drawing air inward.
Conversely, during exhalation, the diaphragm and external intercostal muscles relax, causing the thoracic cavity to decrease in volume. This increases pressure within the lungs, forcing air out.
Surrounding each lung are two layers of a serous membrane called the pleura: the visceral pleura covers the lung surface, and the parietal pleura lines the inner chest wall. Between these layers lies the pleural cavity, which contains lubricating pleural fluid. This fluid allows the pleurae to slide smoothly, minimizing friction as the lungs expand and contract. It also helps maintain the lungs’ expanded state by creating surface tension.