The Anatomic Demarcation of the Lungs
Until recently, the discourse concerning the anatomical demarcation of lungs was seemingly not an essential subject and very little was understood about lungs (Shields, 1992). However, with the current development of endoscopic as well as radiographic techniques together with pulmonary surgery advancement, detailed study regarding the anatomy of lungs has become a necessity in medical world (Shields, 1992).
According to gross anatomy, lungs are divided into two, left and right. The left lung is accorded two lobes which are the lower (inferior) and the upper (superior) lobes, whereas the right lung has got 3 lobes of lower, middle and upper (Moghissi et al., 1992). The left lung encompasses one fissure (oblique) that demarcates the lower from the upper lobe. The right lung as well has the oblique fissure that divides the lower and upper portion. Besides, there is horizontal fissure that divides the upper portion of the right lung into middle and upper lobes. The right lower lobe is located below the oblique fissure and comprises of the entire lower portion of the right lung (Moghissi et al., 1992).
Figure: Five Lung Lobes
Oblique is the major fissure in both lungs and horizontal is a minor fissure demarcating the upper and the middle lobes of the right lung. In humans, oblique fissure of the right lung always starts at the posterior end of the fifth rib and runs downward to itinerary of sixth rib ending at the diaphragm near the sixth costochondral junction. The horizontal fissure commences in the midaxillary region at sixth rib anterior to the costochondral junction of the fourth rib. On the left lung, oblique fissure begins at the posterior end of between 3rd and 5th rib and prolongs downward to the seventh costochondral junction (Shields, 1992).
That said, the left upper lobe (LUL) is situated at the anterior side of the chest. This lobe is divided into five major bronchopulmonary segments which include apical, posterior, anterior, superior lingular and inferior lingular segments. The left lower lobe (LLL) is situated at the posterior side of the chest and is also divided into 5 bronchopulmonary segments that include superior, cardiac, anterior basal, posterior basal and lateral basal (Shields, 1992).
Besides, the right upper lobe of the lung is situated at the anterior side of the chest and it’s sometimes referred to as RUL. Unlike the left upper lobe, this one is divided into 3 major bronchopulmonary segments, which comprise apical, anterior and posterior segments. The only middle lobe of the lungs (RML) never extends to posterior surface of the chest thus can be examined from the anterior side. It comprises of 2 bronchopulmonary segments of lateral and medial segments. The right lower or inferior lobe of the lung, which sometimes referred to as RLL is primarily situated toward the posterior side of the thoracic wall. It has 5 bronchopulmonary segments, which include apical, anterior basal, medial basal, posterior basal and lateral basal (Shields, 1992).
Each and every segment of bronchopulmonary is supplied with dissimilar blood vessels and segmental bronchus. Therefore, in cases of damage or infection of one segment, other segments within the same lobe may possibly not be damaged. Each bronchopulmonary segments is made up of about 130, 000 lung lobules, measuring approximately 3.5mm in diameter and encompass a number of alveoli (minute sac-like structures or regions that allow gaseous exchange) (Moghissi et al., 1992).
Moghissi, K., Thorpe, J., & Ciulli, F. (1992). Thoracic & Cardiac Surgery. Amsterdam; Elsevier
Shields, T. (1992). General Thoracic Surgery. Philadelphia; Wilkins & Lippincott