The pharynx, soft palate, and larynx

The pharynx is a muscular tube beginning behind the posterior nasal apertures and extending down to the cricoid cartilage in the neck where it becomes continuous below with the oesophagus. The pharynx is incomplete anteriorly where the nasal and oral cavities and laryngeal entrance open into it. The pharynx can thus be divided for descriptive purposes into three regions. Identify the three regions and their landmarks in Figure 28.1 : • The nasopharynx behind the posterior nasal apertures, extending down to the soft palate; • The oropharynx posterior to the oral cavity, extending from the soft palate to the tip of the epiglottis; • The laryngopharynx posterior to the laryngeal entrance between the epiglottis and level of the cricoid cartilage. Air enters the nasopharynx and passes through the oropharynx to enter the larynx at the laryngopharynx. Food and drink enter the oropharynx from the mouth, then travel through the laryngopharynx to the oesophagus and stomach. The pharynx is thus part of both the gastrointestinal and respiratory tracts. Essentially, food and air cross each other’s paths in the laryngopharynx. This anatomical arrangement requires precise control of swallowing to ensure that food and drink enter the oesophagus and not the larynx. As you can see in Figure 28.1 , the larynx, the last part of the upper respiratory tract, is situated superficially in the midline of the neck in front of the pharynx and is only covered anteriorly by skin, fascia, and the infrahyoid muscles. The laryngeal opening is just behind and below the root of the tongue. The walls of the larynx are reinforced by cartilage like the lower respiratory tract. However, instead of simple cartilage rings or plates in the walls attached to each other by fibrous tissue, the elaborately shaped laryngeal cartilages articulate with each other through synovial joints and can be moved with precision by the laryngeal muscles. The vocal folds stretch anteroposteriorly across the larynx; they can be brought together to close the larynx and protect the lower respiratory tract or tensed to produce noise, the phonation component of speech.