A bronchopulmonary segment is a portion of lung supplied by a specific tertiary bronchus (also called a segmental bronchus) and arteries. These arteries branch from the pulmonary and bronchial arteries, and run together through the center of the segment. Veins and lymphatic vessels drain along the edges of the segment. The segments are separated from each other by layers of connective tissue. Each bronchopulmonary segment is a discrete anatomical and functional unit, and this separation means that a bronchopulmonary segment can be surgically removed without affecting the function of the others.