Like the trachea and lungs, the larynx is derived from the foregut (endoderm). However, the endodermal tissues are reinforced by mesodermal derivatives from the fourth and sixth branchial arches, which give rise to the muscular and cartilaginous elements of the larynx. Reflecting the pattern of foregut development, the larynx is at one point obliterated by epithelial proliferation, which subsequently recanalizes. Failure of this developmental step leads to laryngeal atresia, which constitutes a neonatal airway emergency [1].

Laryngomalacia is the most common congenital malformation of the larynx. It is thought to represent a delay in the development of the laryngeal cartilages, which are found to be weak and pliable. During inspiration the cartilages collapse due to the negative intraluminal pressure, causing various degrees of airway obstruction. Fortunately, the degree of obstruction is not overly severe, and watchful waiting is recommended for most cases. This pathology usually resolves within the first 2 years of life. However, severe cases may require tracheostomy or laryngoplasty [2]. In the adult, laryngomalacia may occur from prolonged intubation, as well as from long-standing massive thyroid goiters.

The larynx does not articulate with any fixed bony structures; rather, it is suspended by ligaments from the hyoid bone, which is in turn suspended from the base of the skull. This lack of firm attachment allows the larynx to move cephalad in order to protect the airway during swallowing. Furthermore, the movement of the larynx changes the dimensions of the supraglottic resonant chamber, contributing to changes in voice pitch [3].

The thyroid gland is caudal in relation to the thyroid cartilage; only the superior thyroid poles and pyramidal lobe of the gland make contact with the cartilage. The thyroid isthmus covers the 2nd and 3rd tracheal rings. This anatomical position puts the thyroid out of the surgical field of cricothyroidotomy for emergency airway. It is often necessary to divide the thyroid isthmus during the course of a tracheostomy (Fig. 4.1).

Tracheoinnominate fistulas are an infrequent but lethal complication of tracheostomies. The chief risk factors are a low-lying tracheostomy, hyperinflated cuff, neck or chest deformity, and prolonged presence of this form of airway.

The anatomical substrate is the proximity between the anterior wall of the trachea and the posterior wall of the innominate artery. Fistulization occurs through a decubitus mechanism and herald bleeding is present in up to 50 % of cases. This makes careful evaluation of bleeding from a tracheostomy site mandatory. Bronchoscopy is the modality of choice [4] (Fig. 4.2).

Emergency management consists of hyperinflation of the tracheostomy cuff to tamponade the bleeding and digital pressure over the tracheostomy. Bronchoscopy is useful in clearing the airway of blood. Manipulation of the tracheostomy tube or exchange of the airway is contraindicated, as it may precipitate massive hemorrhage.

Classically, surgical repair consisted of median sternotomy with resection of the innominate artery without vascular reconstruction [4, 5]. More recently, endovascular stent grafting and coiling have emerged as useful treatment modalities [6, 7] (Fig. 4.3).

Although acute epiglottitis has become less common since the widespread use of Haemophilus influenzae vaccines, it should still be considered in the workup of children with acute respiratory distress. It is noteworthy that in this scenario attempts to examine the larynx may lead to worsening of the obstruction. Hence, the recommended diagnostic test is a lateral neck X-ray, which shows a thickened epiglottis. Intubation is then carried out bronchoscopically under general anesthesia [8].

The neonatal larynx is located more cranially than that of the adult; this protects it from trauma, but makes it less accessible for surgical access. It is funnel shaped and much narrower than that of the adult. This determines that comparable increases in epithelial thickness due to edema result in a proportionally greater loss of cross-sectional area in the newborn and young child. Due to its small diameter and shape, the neonatal larynx provides a seal around cuffless endotracheal tubes, allowing the delivery of PEEP without an inflatable cuff. Unfortunately, this tight fit makes it more prone to pressure necrosis leading to the development of subglottic stenosis [9].

The false vocal cords (also named vestibular folds) are folds of pseudostratified epithelium with a core of connective tissue and glands. They lie cephalad to the true vocal cords. Traditionally, the false vocal cords were considered to be rather passive structures, contributing mainly to the lubrication of the larynx through their mucus glands. More recently, this view has been modified to an active role during phonation, airway protection, and the Valsalva maneuver [10].

The muscles of the larynx are divided into intrinsic and extrinsic, based on whether they begin and end on the larynx or beyond it. The intrinsic muscles are responsible for the movements of the vocal cords as well as that of the laryngeal cartilages. The extrinsic muscles elevate or depress the larynx as a whole. The epithelium of the edge of the vocal cords lacks lymphatics, which makes metastatic spread of early malignancies unlikely and allows limited resections. However, lateral to this edge there are lymphatic networks that could allow the spread of malignancy [11].