Chapter 145: Airway and Pulmonary Anatomy

INTRODUCTION

The term “airway” refers to the nasal and oral cavities, pharynx, larynx, trachea, and principal bronchi.

NASAL CAVITY

The nasal cavities are divided by the nasal septum. The roof of the nasal cavity is the cribriform plate. The lateral wall is the origin of the turbinates. Openings in the lateral wall communicate with paranasal sinuses. The greater and lesser palatine nerves innervate the turbinates and most of the nasal septum, and the anterior ethmoid nerve. The ethmoid nerve provides sensation to the nares and the anterior third of the nasal septum. The palatine nerves arise from the sphenopalatine ganglion.

ORAL CAVITY

The roof of the mouth consists of the hard palate anteriorly and the soft palate posteriorly. The tongue makes up most of the mouth floor. Temporomandibular joint (TMJ) rotation initiates mouth opening, followed by sliding of mandibular condyles within the TMJ.

PHARYNX

The pharynx is a fibromuscular tube that extends from the base of the skull to the lower border of the cricoid cartilage. The oropharynx is innervated by branches of the vagus, facial, and glossopharyngeal nerves. The glossopharyngeal nerve gives sensory innervation to the posterior third of the tongue, vallecula, anterior surface of the epiglottis, walls of the pharynx, and tonsils.

LARYNX

As seen in Figure 145-1, the larynx consists of nine cartilages: three single (thyroid, cricoid, and epiglottic) and three paired (arytenoid, corniculate, and cuneiform). Together, these house the vocal cords. The thyroid cartilage helps to protect the vocal cords. The intrinsic and extrinsic muscles of the larynx control the laryngeal structures. The superior laryngeal nerve and the recurrent laryngeal nerve, both branches of the vagus nerve, innervate the larynx. The recurrent laryngeal nerves supply all the intrinsic muscles of the larynx except the cricothyroid muscle. The superior laryngeal nerve provides sensory innervation to the base of the tongue, epiglottis, aryepiglottic folds, and the arytenoids, as well as motor innervation to the cricothyroid muscle. The cricothyroid membrane is located anteriorly between the thyroid and cricoid cartilages, directly subcutaneous to the skin. Any needle punctures or incisions made to this membrane should be made in the inferior third because the superior cricothyroid arteries course through the upper two-thirds.

In adults, the trachea is approximately 15 cm with 17-18 C-shaped cartilages supporting its structure anteriorly, and a membranous portion overlying the esophagus posteriorly, the trachealis muscle. The first tracheal ring is anterior to the C6 vertebra. The trachea ends at the carina, at the level of the T5 vertebra, where it bifurcates into ...