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Pink silhouette of the lower head and the thorax of a human.

The thoracic cavity is shown bounded by yellow ribs (in cross-section) with intercostal muscles between the ribs. Inside the ribs is the thoracic cavity in pale blue. At the base of the thoracic cavity is the diaphragm, coloured purple, and displayed as an inverted U-shape, with the abdominal cavity below.

Two lungs, coloured pink are on the right and left sides of the thoracic cavity; the lungs are covered with pleurae, shown as a white layer covering the lungs. The lobes of the lung are shown on the right lung.

The mouth and nasal cavities proceed to the pharynx in the neck; this leads to the oesophagus, all coloured pink. From the top of the oesophagus proceeds the trachea (coloured yellow) with darker yellow cartilage rings stiffening and supporting it; at the top of the trachea is shown the box-like larynx in pale yellow. The trachea branches to lead to two bronchi, one leading into each of the right and left lungs. The left bronchus is traced into the left lung, showing extensive branching into ramifying bronchioles, stiffened with cartilage.

The heart is shown in dark red between the base of the lungs; the trunks of major arteries are shown proceeding from the heart.

 1.1.2 Lower respiratory tract