<Ul> <Li> Superior </Li> <Li> Anterior </Li> <Li> Posterior </Li> <Li> Medial </Li> <Li> Lateral </Li> </Ul> <Ul> <Li> Superior </Li> <Li> Inferior </Li> </Ul> <P> The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung . The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments . Each bronchopulmonary segment has its own (segmental) bronchus and arterial supply . Segments for the left and right lung are shown in the table . The segmental anatomy is useful clinically for localising disease processes in the lungs . A segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue . </P> <P> The right lung has both more lobes and segments than the left . It is divided into three lobes, an upper, middle, and a lower, by two fissures, one oblique and one horizontal . The upper, horizontal fissure, separates the upper from the middle lobe . It begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced backward to the hilum . </P>

Airways that supply one lobe of a lung are called