Final answer:
The human lungs are divided into lobes separated by fissures; the right lung comprises three lobes, while the left has two. Each lobe contains bronchopulmonary segments, supplied with air and blood through their respective tertiary bronchus and artery, and further divided into pulmonary lobules.
Step-by-step explanation:
Each lung within the human body is divided into sections known as lobes, which are separated by fissures. The right lung consists of the superior, middle, and inferior lobes. The left lung, slightly smaller due to the presence of the heart, has only the superior and inferior lobes. These lobes are separated by the oblique and horizontal fissures; the horizontal fissure is only present in the right lung.
Each lobe is made up of bronchopulmonary segments, receiving air from their own tertiary bronchus and blood from their own artery. If diseases affect these segments, they may be removed surgically with minimal impact on surrounding segments. Beneath the segmental level are pulmonary lobules, each supplied with air by a large bronchiole. An interlobular septum, made of connective tissue, demarcates these lobules.
The lungs are bordered at the base by the diaphragm, a dome-shaped muscle critical for breathing. The right lung is shorter and wider than the left, which has a cardiac notch to accommodate the heart. The apex is the uppermost part of each lung, while the base is at the bottom near the diaphragm. The costal surface abuts the ribs, and the mediastinal surface faces towards the midline of the body.