The middle lobe, the smallest lobe of the right lung, is wedge-shaped, and includes the part of the anterior border and the anterior part of the base of the lung. The human left lung, unlike the right, contains no middle lobe. However, the term lingula is used to denote a projection of the upper lobe of the left lung that serves as the homologue. Some sources define the lingula as a distinct lobe. The Right Lung is divided into superior (upper), middle, and inferior (lower) lobes by horizontal and oblique fissures. The horizontal fissure separates the superior from middle lobes. The oblique fissure separates the inferior lobe from the superior and middle lobes. Middle lobe can be divided into two parts as lateral and and medial.