Superior lobe of left lung

At a glance

English

Superior lobe of left lung

Latin (TA2)

Lobus superior pulmonis sinistri

System

Respiratory

Region

Thorax

Side

Single, on the midline

About the superior lobe of left lung

The left lung has only two lobes, upper and lower, divided by a single oblique fissure. The superior lobe lies in front of and above that fissure. It includes the apex, which climbs above the first rib to the base of the neck, and most of the front of the lung. Because the left lung gives room to the heart, its front border is cut away in a deep cardiac notch, and below this notch a thin, tongue-shaped extension of the upper lobe, the lingula, curls forward over the heart. The lingula is the left counterpart of the right middle lobe.

The mediastinal surface of the upper lobe is marked by the structures it rests on. A deep cardiac impression lodges the left ventricle, larger and deeper than the matching hollow on the right lung. Above the hilum a curved groove carries the aortic arch, a groove from the arch runs up to the apex for the left subclavian artery, and a shallower groove in front lodges the left brachiocephalic vein.

Air enters through the left superior lobar bronchus. Its upper division gives an apicoposterior and an anterior segmental bronchus; its lower, lingular division gives superior and inferior lingular bronchi. The lobe therefore has four bronchopulmonary segments, each with its own airway and artery, which allows a single segment or the lingula alone to be removed when necessary. Branches of the left pulmonary artery supply it and the left superior pulmonary vein drains it.

The lingula is prone to the same problems as the right middle lobe, and disease in it blurs the left heart border on a frontal X-ray. Collapse of the whole upper lobe draws it forwards against the chest wall and gives a hazy veil over the upper left chest. As on the right, the apical segments are favoured by tuberculosis, and an apical tumour can involve the nerves at the root of the neck.

Function and supply

Function

Exchanges gases between inspired air and the blood in the upper and front part of the left lung.

Nerve supply

Pulmonary plexus (vagal and sympathetic fibres), with visceral sensory fibres carrying stretch and cough reflexes.

Blood supply

Upper-lobe branches of the left pulmonary artery for gas exchange and left bronchial arteries from the aorta for the tissue; drained by the left superior pulmonary vein.