The annular cartilage is the only complete cartilaginous ring of the larynx and also its main supporting structure. It has an anterior arch similar to a normal tracheal ring and a much wider posterior plate or cricoid blade (Figure 3). The blade has a vertical crest in its midline and two lateral fossae, places of introduction of the posterior cricoarytenoid muscles, which are the main abductors of the vocal cords. The paired arytenoid cartilage lies at the upper edge of the posterior cricoid plate (Figure 3) and articulates at the cricoarytenoid joints in the lateral portion of the cricoid lamina. The vocal cords are posterior attached to the vocal processes of the arytenoid cartilage and anterior to the thyroid cartilage. The tracheal bifurcation is the point at which the trachea divides into two main or main bronchi and is continuous with them. In the thorax, the trachea is shifted slightly to the right at this point by the left aortic arch. This is at the level of the sternal angle – the lower edge of the fourth thoracic vertebra. Most venous flow from the bronchial arterial system empties into the pulmonary veins, although some may be emptied into the azygos and hemiazygos systems (16). Lymphatic drainage is carried out through the subcarinary and lower paratracheal lymph node chains. Along the entire length of the trachea is an extensive submucosal plexus fed by intercartilaginous arteries, each of which enters the soft tissue space between the tracheal rings and extends anteriorly (Figure 10). When they reach the midline, these arteries sink deeper and end in submucosal capillary plexuses. The tracheal cartilage receives its blood supply from these plexuses, while the membranous trachea is vascularized by secondary branches of the primary esophageal arteries.

There are several known anatomical variations in the tracheobronchial system, but their true incidence is unknown due to their primarily asymptomatic nature. However, detecting these variations may be important when performing certain procedures, such as bronchoscopy, endotracheal intubation or positioning lung isolation devices (17). The innervation of the trachea originates from tracheal palate from the thoracic sympathetic chain and the inferior ganglion of the vagus nerve. This innervation is responsible for tracheobronchial muscle tone (bronchoconstriction or bronchodilation), mucus production and vascular permeability. The afferent vague fibers are also responsible for sneezing and coughing reflex. The lowest part of the trachea, the bifurcation, is called the hull. It is located slightly to the right of the midline at the level of the fourth or fifth posterior thoracic vertebra and the anterior sternomanubrial junction. The lower thyroid vessels and their tracheoesophageal branches supply blood to the proximal trachea, while the bronchial arteries vascularize the distal trachea, carina, and main bronchi (Figure 9) (10-12). The trachea is also fed by small branches from the subclavian artery, the internal msimmaris artery and the unnamed artery. Once they reach the tracheoesophageal sulcus, the tracheoesophageal branches divide into primary tracheal and primary esophageal branches (Figure 10). The tracheal vessels enter the trachea through their lateral wall and branch above and below the width of several tracheal rings. Since most of the complications that occur after tracheal reconstruction are related to the disruption of vascular supply to the anastomosis, surgical surgeons must accurately understand not only the blood supply to the trachea, but also its segmental nature and longitudinal anastostatic connections.

In the preface to his “De Humani Corporis Fabrica”, Andreas Vesalius [1514-1564] wrote that anatomy should rightly be regarded as the solid foundation of the whole art of medicine. This observation is even more relevant to the art of respiratory surgery, where safe techniques largely depend on an optimal knowledge of normal anatomy and its variants. For example, surgeons performing subglottic or tracheal resections need to be aware of the special anatomical arrangements of these structures, as well as their blood supply and innervation, if they want to avoid incorrect operations or technical problems. In fact, the essential facts of anatomy must be known to ensure that each patient receives the best possible surgery for their respiratory disease. In anatomy, the keel is a cartilaginous ridge in the trachea that occurs between the division of the two main bronchi. [1] [2] A tracheal is generally described as a bronchus of the right upper lobe originating from the trachea, usually at the junction of the middle and distal thirds. Its prevalence ranges from 0.1% to 2% and is often associated with congenital heart defects such as tetralogy of Fallot or ventricular septal defects. The most serious clinical implication of a tracheabronchus is that a misplaced endotracheal tube can obscure its lumen, leading to secondary atelectasis, obstructive pneumonia or even respiratory failure (18, 19). If left undetected, accidental intubation directly into a tracheabronchus can also lead to respiratory failure. The tracheal lumen narrows slightly as it progresses towards Carina. The angle between the two main bronchi of the trunk varies from person to person and is usually larger in children than in adults (13).

The configuration of the cartilage on the hull is also quite variable. The anterior anatomical relationships of the trachea are those with the thyroid gland in the neck and the large intrathoracic mediastinal vessels. In the neck, the thyroid gland and the thyroid isthmus are located in front of the trachea at the level of the second or third tracheal ring, while in the mediastinum, large vessels pass through the trachea at different levels (Figure 8). The unnamed artery passes through the middle trachea obliquely from its place of origin in the aortic arch, and the right and left innominatus veins are located in front of the unnamed artery. In young women, the unnamed artery is often located at a higher point at the base of the neck and may therefore be in contact with tracheal mastosis in the neck. This particular anatomical arrangement can sometimes lead to catastrophic postoperative tracheovascular fistulas. The superior vena cava is located at the front and right of the trachea. Posteriorly, the membranous trachea is in contact with the esophagus on the left and the vertebral bodies on the right.

The trachea is a membranous cartilaginous tube that is continuous with the larynx at the level of the annular cartilage (Figure 6). Its upper part is located at the level of the sixth or seventh cervical vertebra of the neck, while its lower end is at the level of the fourth or fifth thoracic vertebra of the chest. In adults, tracheal length ranges from 10 to 13 cm (longer in men than in women), with about 5 cm above the suprasternal notch. The trachea is only one part of the respiratory system. Learn the anatomy of all remaining organs easily and efficiently with Kenhub`s respiratory system quiz and tagged diagrams! In tracheomalacia, tracheal cartilage becomes exceptionally soft. As a result, they cannot keep the trachea open and it continually collapses during inhalation and leakage. The affected area may extend over only a few cartilages or affect the entire trachea. Such diffuse involvement occurs during Williams-Campbell syndrome. As a birth defect, tracheomalacia manifests itself in early childhood. He has signs and symptoms of shortness of breath such as dyspnea, cough, stridor, wheezing and tachypnea. If the tracheal collapse is severe, it can even manifest as respiratory arrest (apnea).

In such cases, a tracheal tube or airway stents are used to bypass the obstruction and keep the trachea open. Tracheostomies and continuous nighttime ventilation may also be required. The trachea has a horseshoe-shaped anterior part of 18−22 cartilaginous rings (2 rings per cm of trachea) and a posterior membranous part (Figure 7). Between the anterior rings, the non-cartilaginous tissue is elastic and allows the trachea to lengthen or shorten during breathing. In younger people, the trachea is slightly more elastic and elastic, while in older people it is stiffer or sometimes even ossified, an important consideration in tracheal resections. The most common anatomy of the bronchial artery is a right artery emerging from an intercostal artery and two left arteries of distinct origin. The insert (below) shows the three most common bronchial artery arrangements. The trachea and bronchi together form the tracheobronchial tree. The thoracic part divides into the main right and left bronchi at the tracheal bifurcation. The tracheal bifurcation shelters a cartilaginous ridge oriented towards the sagittal called the keel.

Venous drainage from the larynx is carried out through the upper and lower laryngeal veins, which eventually flow through the thyroid veins into the internal cervical veins. The lymphatic vessels of the glottis flow into the deep cervical lymph nodes, while those of the subglottic airways flow into the internal jugular, prelaryngeal and upper paratracheal nodes. Tracheomalacia is a birth defect that affects the development of tracheal cartilage rings. When bronchial cartilage is affected, the condition is called bronchomalacia.