Lungs and Plèvres are located in the thoracic cavity. The upper opening is located at the first rib and the upper edge of the thorax. The lower opening of the thorax is wide, closed by the diaphragm muscle. This thoracic cavity is divided in two by the mediastinum, the largest of which is the heart in the anterior mediastinum. The mediastinum separates the two right and left hemithorax where the right and left lungs are located. The pulmonary apex exceeds the level of the first rib and is located in the supraclavicular hollow.
The right and left lungs are not symmetrical:
the right about 700g;
the left about 600g.
In women, in general, the thoracic cavity is less bulky.
Normal appearance: smooth, pink and more and more gray over time.
They each have three sides:
– Peripheral: molded on the bony thorax, this is the costal side ;
– Internal: mediastinal surface molded on the elements of the mediastinum ;
– Lower: diaphragmatic side ;
The heart overflows on the left, hence certain differences in morphology.
2. Right lung
Each lung has a global pyramidal arrangement, the top is at the top, the face is at the bottom.
Costal side: two fissures which separate it into three pulmonary lobes: upper, middle, lower.
– Upper lobe, medium: almost horizontal fissure called small fissure
– Middle and lower lobes: oblique or large fissure
There are few reliefs, the most visible being that of the first rib.
Its layout is the same, it is pyramidal.
The diaphragmatic side is molded on the dome, which explains why it is more concave than the other sides of the lung. There is also the hilum of the right lung. The hilum has the shape of a racket with a large upper part. This hilum is circumscribed by a relief: the line of reflection of the pleura. The hilum forms a hollow where the two right lobar bronchi penetrate, because the right main bronchus divides a little before the hilum. Anteriorly, the branches of division of the artery follow the bronchial division. The two right pulmonary veins go to the left atrium: there is an upper right and a lower right pulmonary vein.
There are also bronchial arteries and bronchial veins which are nutrients.
The imprint of the heart is not very marked on the right lung, but that of the azygos vein, which drains blood from the wall of the thorax, and which rises along the right flank of the spine, is more marked. Around the hilum, there is the imprint of the arch of the superior vena cava.
3. Left Lung
Same general arrangement: pyramidal. The anterior edge has an incision: the cardiac incision. The left lung has only one fissure, therefore two lobes: upper and lower.
The left pulmonary hilum has the same arrangement as the right hilum. There is a relief which surrounds this hilum: line of reflection of the visceral sheet of the pleura. The two sheets meet at the bottom to form the triangular ligament of the lung located under the hilum. It is a means of fixing the lung by its mediastinal surface. The hilum consists of:
– the left main bronchus which divides later
– a left pulmonary artery
– two left pulmonary veins go towards the left atrium to bring back the blood rich in Oxygen
– nutrients: bronchial arteries plus veins and there are bronchial nerves.
4. Bronchial and Pulmonary Segmentation
First main bronchi then lobar bronchi: three lobar bronchi on the right, two on the left.
Then the segmental bronchi, each lung has ten segments, then sub-segmental which give the last division: the bronchioles: it is the element which penetrates into the lobule, functional unit of the lung, it is the place, where make gas exchanges. The pulmonary artery follows this bronchial segmentation and there is an arteriole in each lobule.
It has the shape of a pyramid with a summit oriented towards the hilum. Each lobule corresponds to a bronchiole which branches out in the pulmonary lobule to come into contact with the alveoli. Each alveoli corresponds to a small branching of the arteriole which follows the bronchial segmentation, this is how the air enters and leaves the alveoli. In the alveolus hematosis is carried out: gas exchange, the blood leaves towards the periphery of the lobule by small venules which travel to regroup at the periphery of the lobules, then to the top to constitute the pulmonary vein in the hilum which transports the blood enriched in O2 to the left atrium then the left ventricle then, then, to the large circulation.
Upper lobe: three segments: apex or apical segment, below back, the dorsal segment, and in front of it the ventral segment.
Medium lobe: two segments:
– the postero-external segment or lateral segment,
– the antero-internal segment or medial segment.
Lower lobe: five segments. At the top of the lower lobe, apical segment of the lower lobe or Nelson segment, under it, in contact with the heart, the para-cardiac segment, it is not visible on an external view, and, in the lower part, the three segments of the base , front to back: baso-ventral, baso-lateral, baso-dorsal.
From the right primitive bronchus, we have:
– upper lobar bronchus, short common trunk which gives the apical bronchi of the upper, dorsal and ventral lobe
– medium bronchus, generally shorter. It quickly divides into lateral and medial segmental bronchi.
– lower lobar bronchus: it quickly gives the apical bronchus, and in depth, gives the bronchus of the para-cardiac segment and then divides for the base segments into baso-ventral, baso-lateral and baso-dorsal.
The upper lobe has five segments: the apical segment, the dorsal segment of the upper lobe, the ventral segment, a cranial segment, and a caudal segment.
The lower lobe with five segments: an apical segment of the lower lobe, a para-cardiac segment, and the three segments: baso-lateral, baso-ventral and baso-dorsal.
From the left primitive bronchus, we have:
– the upper lobar bronchus, which gives three bronchi for the apical, dorsal and ventral segments; and, two bronchi for the cranial and caudal segments
– the lower lobar bronchus, which gives the bronchus of the apical segment of the lower lobe, and a common trunk, the ventro-para cardiac trunk which is divided into segmental para cardiac and baso-ventral bronchi, and it has in addition two bronchi for the baso-lateral and baso-dorsal segments.
5.1. Anatomical description
Serous membrane formed by two sheets:
– parietal lining the wall of the thorax and the mediastinum: at the level of the apex, the pleura is raised and maintained by costo-pleural and vertebro-pleural ligaments, hence the formation of a pleural dome;
– visceral lining the lungs, in contact with it, and up to its line of reflection at the level of the hilum. He engages in pulmonary fissures;
The parietal pleura forms dead ends:
– on each side of the heart: mediastino-diaphragmatic dead ends
– at the level of the last ribs: the lung does not descend into the acute costo-diaphragmatic angle.
You should know that: pleural effusions. There are three, if there is blood, it is a hemothorax, if it is gas, then it is a pneumothorax, and if it is a liquid purulent, it’s pleurisy.
The parietal sheet lines the wall and the organs of the mediastinum. The two right and left parietal sheets can sometimes unite.
– either behind the sternum, we then speak of pleural symphysis;
– either behind the esophagus, we then speak of an inter-azygo-esophageal and aortico-esophageal cul-de-sac, or else Morosow’s interpleural ligament.
5.2. Pleural line projections
Anterior: in relation to the skeleton of the sternum, the pleural domes extend beyond the clavicle into the supraclavicular hollow. The anterior pleural line is located behind the sternum. At the level of the fourth costal cartilage, it deviates from the midline with an imprint of the heart on the left.
Posterior: in relation to the spine, it is covered by the pleura, the pleura departs at the level of the costo-diaphragmatic dead end and follows the insertion of the diaphragm: the line of reflection of the pleura is about 3 cm of the midline. The pleura crosses the end of the twelfth rib 6 cm from the midline.
Copyright photo: By An officer or employee of the United States Government, as described at File: Illu bronchi lungs.jpg, with modifications by User: Adrian J. Hunter – Based on File: Illu bronchi lungs.jpg which is public domain as described at that file’s description page., Public domain,