The lungs are located within the thorax, within the thoracic cavity and within the pleura. They occupy about 3/4 of the thoracic cavity, with the rest occupied by the heart and the mediastinum. The right lung occupies almost the entire right hemi thorax and the left is displaced by the heart and occupies a lesser amount of space.
The lungs are divided into upper and lower lobes which is somewhat of a conceptual misnomer since the lower lobes creep up posteriorly to almost the apex of the lungs and the upper lobes (together with the lingula and middle lobe) on the other hand reach more inferiorly in the anterior location. The lobes may have just as well been called the posterior lobes and the anterior lobes but because the upper lobes reach the most superior position in the chest and the lower lobes the most inferior and diaphragmatic parts, they were reasonably labeled upper and lower.
| Lobar Position |
| This cross section through the heart shows all the lobes of the lungs with upper lobes taking an anterior location while the lower lobes are posterior. Courtesy Ashley Davidoff MD. 32160d.800 |
The segments are named according to their position, and include the apical anterior and posterior segments in the upper lobes, the lateral and medial components of the RML, the superior and inferior of the lingula, and the superior (apical) lateral medial anterior and posterior basal segments. Note that all the names relate to the position of the segments. There is a move to give these segment numbers – but it seems far easier to understand the spatial positioning by naming the segments according to their position.
The middle lobe has a very intimate relation to the right heart border (RA), while the lingula has a similar relationship with the left ventricle. This has relevance in the evaluation of infiltrates on the CXR since disease in the RML will cause silhouetting of the right heart border (RA), while an infiltrate in the lingula will silhouette the left heart border. On the lateral examination since both of these are anterior segments they will be seen as anterior infiltrates. Hence the position of infiltrates as seen on the CXR can be accurately localized to segments by looking at the relationship to the heart in the P-A and whether the infiltrate is anterior or posterior on the lateral CXR.
Applied Anatomy
| Situs Inversus |
| This unfortunate baby has situs inversus associated with complex congenital heart disease. The baby’s right lung had the morphology of a left lung in that it had two lobes rather than three. The left lung had the morphology of the right having 3 lobes. This inversion of the position of the organs is called situs inversus. Complex congenital heart disease is noted with dextrocardia and a white tubular graft is noted in the upper chest from recent surgery. The liver is mainly on the left side, and the stomach on the right. Courtesy Ashley Davidoff MD. 10850 |
Situs inversus has a wide variation of clinical presentations. Some patients with situs inversus may live a completely normal life without ever being aware of the condition. At the other extreme, such as in the case above, the aberrant morphology, particularly related to the heart, can be life threatening.
| Situs Inversus of the Lungs |
| This is an unusual case of a patient with dextrocardia and chronic sinusitis. When you review the bronchogram, a study previously performed to outline the bronchi, you will note that the bronchus on the right side looks more like a left bronchus being long and thin with a relatively obtuse angle off the carina, while the bronchus on the left side looks more like a right bronchus being short and fat with a relatively acute angle off the carina. Thus there is situs inversus of the lungs and tracheobronchial tree.. Courtesy Ashley Davidoff MD. 06248 |
| Situs Inversus and Sinusistis |
| In the same patient note the total opacification of the left maxillary sinus and air fluid level in the right maxillary sinus characteristic of acute sinusitis. This patient has a syndrome called Kartagener’s syndrome (aka immotile cilia syndrome) where ciliary motility is diminished, resulting in suboptimal defense mechanisms in the bronchial and sinus epithelia, causing sinusitis and bronchiectasis, and decreased sperm motility resulting in sterility. Courtesy Ashley Davidoff MD. 06247 |
| Herniated Lung |
| In this patient rib fractures resulted in a focal defect in the right lower lung field and resulting herniation of the lung. This is seen in the cross sectional images in a and b, in the coronal reformat in c, and in the volume rendering image in d.
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Anatomy of the Structures Surrounding the Lungs – Neighbours
The lungs are completely surrounded by the pleura, a variety of muscles and the bony thoracic cage. The heart and other structures of the mediastinum form the medial relations of the lungs.
Within the mediastinum lies the heart and pericardium, the trachea and main stem bronchi, esophagus, thoracic duct, lymph nodes, and both phrenic and vagus nerves. The mediastinum is situated anterior to the sternum and ventral to the spinal column, nestled between the pleural sacs of the right and left lungs. Superiorly it reaches the level of the fourth thoracic vertebrae and rests upon the diaphragm inferiorly. Below the diaphragm lie the liver, gall bladder, and spleen.
Surrounding the lungs are the thoracic muscles and the diaphragm itself. These are the muscles related to respiration. Their operation alters the pressure within the thorax. When the thorax expands the pressure decreases, allowing air from the trachea into the lungs. When it contracts, the lungs compress and air leaves the lungs. When the diaphragm contracts it flattens and sinks as much as 7-10 cm below its normal level at rest. As the muscles relax the thorax returns to normal pressure and air from the lungs is released. This is known as abdominal respiration and accounts for approximately 70% of respiration in a resting body.
| Relations |
| This is an autopsy specimen of a heart and lungs from a young patient with congenital heart disease who died following surgery. The image is taken from above showing the trachea and the two-mainstem bronchi before the bronchi enter the lungs. Note the pink color of the lungs of this young patient, the surgical shunt from aorta to right pulmonary artery, the ductus from aorta to left pulmonary artery and the presence of bilateral hyparterial bronchi suggesting bilateral left sidedness and the polysplenia syndrome.
Courtesy Ashley Davidoff MD 07236
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| Orientation of Lower Lobe Veins and Arteries |
| 34764 heart cardiac pulmonary arteries anatomy venous drainage pulmonary veins left atrium relationship to esophagus LA coronary sinus A-V groove normal anatomy Davidoff MD |