Variants and anomalies of the respiratory organs, pleura and mediastinum

External nose. The number of nasal cartilages varies, often their number is less than usual. In 20% of cases, the right and left vomeronasal cartilages are present in the back of the nasal septum. The size and shape of the nose, the configuration of the nostrils are very variable.

Nasal cavity. Often near the anterior nasal spine in the mucous membrane there is a blind canal - the vomeronasal (Jacobson's) organ. This organ is directed upward and backward, rudimentary, and is a homologue of the Jacobson's organ of vertebrates. Behind and below the opening of the Jacobson's organ there is sometimes an opening leading to the blindly closed incisive (Stenon's) duct. It is located in the incisive canal and is a rudimentary formation. In 70% of cases, the nasal septum is deviated to the right or left. The prominence of the nasal turbinates and the depth of the nasal passages vary. Often behind the semilunar cleft there is an additional opening connecting the maxillary sinus with the middle nasal passage.

Larynx. The laryngeal cartilages vary in the degree of calcification in different people (elderly and old). The configuration and size of the cartilages have significant individual differences. The upper horns of the thyroid cartilage are often absent, a unilateral or bilateral opening with a diameter of 1-6 mm is found in its plate. The cricoid cartilage sometimes has an additional tubercle located on the lower edge of its arch (marginal denticle), granular cartilages can be absent, double or increase in size. Sometimes the cricothyroid joints of the larynx are absent. Mobility in the laryngeal joints is variable, their ligaments are expressed to varying degrees. The muscles of the larynx are the most variable. In 10% there is a thyrotracheal muscle, in 10% - a cricotracheal muscle and in 3% - an unpaired transverse thyroid muscle. Very rarely, the lateral epiglottothyroid muscle and the muscle that lifts the thyroid gland are found. In 20% of cases, the cricoepiglottic muscle is present, in 9% - the muscle that lowers the arytenoid cartilages. Frequently (about 16%), additional bundles of the thyroarytenoid muscle are found. In 22%, the lateral thyroarytenoid muscle is absent. In the anterior half of the laryngeal ventricle, on one or both sides, there may be a small notch - the laryngeal appendix, which has a variable shape and size.

Trachea. The length and width of the trachea, the number of cartilages in its walls (from 12 to 22) are variable. The shape of the cartilages often has individual characteristics. The trachea may be divided into 3 main bronchi (tracheal trifurcation), sometimes congenital tracheal fistulas and communications with the esophagus are observed. Rarely, there is a thyrotracheal bursa between the isthmus of the thyroid gland and the trachea. Rarely, a similar bursa is located between the aorta and the trachea (aortotracheal bursa).

Lungs. The lungs vary in shape and size. Often there are additional lobes of the right and left lungs (up to 6 lobes per lung). Sometimes the tops of the lungs receive independent bronchi that extend from the main bronchi. Very rarely, in the presence of diaphragm defects, displacement of additional lobes into the abdominal cavity is possible. The degree of development of intrapulmonary connective tissue, the number of acini and their components vary individually.

Pleura. The depth and severity of the pleural sinuses vary individually. Adhesions often form in the pleural cavity between the parietal and visceral pleura. In 7% of cases, the right and left mediastinal pleura in the anterior mediastinum are closed for some distance behind the sternum, forming the mesocardium.

Mediastinum. Sometimes the mediastinum is narrow or unusually wide, which is related to the configuration of the chest. The topography of the organs of the chest and abdominal cavities can be sharply changed, even to the opposite of their normal position (complete or partial).