The Pharynx, Larynx, and Trachea
The neck is covered by the subcutaneous tissue of the neck, or superficial fascia, just under the skin. Beneath that layer you’ll find the pharynx, larynx, and trachea. These anatomical structures help you breathe and speak.
The pharynx is the region posterior to the nasal cavity, oral cavity, and larynx that extends from the base of the skull inferiorly until it becomes continuous with the esophagus.
The pharyngeal muscles include an external layer: the superior, middle, and inferior constrictor muscles. They constrict the pharynx to force food toward the esophagus when swallowing. Under this layer lies another layer of muscles: the palatopharyngeus, stylopharyngeus, and salpingopharyngeus. They elevate the larynx and shorten the pharynx when you speak and when you swallow.
The pharynx is divided into three regions:
Nasopharynx: The nose opens into the nasopharynx via openings called choanae. It contains pharyngeal tonsils, which are collections of lymphoid tissue. The auditory tube, or pharyngotympanic tube, opens into the nasopharynx. It’s accompanied by the salpingopharyngeal fold, which is a fold of mucous membrane.
Oropharynx: The oropharynx begins where the oral cavity ends. The base of the tongue forms the floor, and the palatoglossal and palatopharyngeal arches form the lateral walls. The palatoglossal arch is a fold of mucosa that runs from the soft palate to the tongue. The palatopharyngeal arch is a fold of mucosa posterior to the palatoglossal arch that attaches from the soft palate to the pharyngeal wall. Palatine tonsils are found in the tonsilar sinuses between the arches. The soft palate forms the roof.
Laryngopharynx: The laryngopharynx lies behind the larynx. Its walls are formed by the thyroid cartilage and the middle and inferior pharyngeal constrictor muscles. The piriform fossa is a depression in the mucous membrane on each side of the inlet.
Blood flow to the pharynx is supplied by the tonsillar artery and branches of the maxillary and lingual arteries. The maxillary nerve, glossopharyngeal nerve, and vagus nerve provide nerve supply. Lympthatic fluids drain into the deep cervical nodes.
The larynx, commonly called the voice box, is the organ that contains the vocal folds that allow your voice to be heard. It lies at the levels of the 4th, 5th, and 6th cervical vertebrae.
The framework of the larynx is made up of cartilage held together by membranes and ligaments:
Thyroid cartilage: The thyroid cartilage is the largest structure in the larynx. It is made up of two pieces of hyaline cartilage that meet in the front and middle to form the laryngeal prominence, or Adam’s apple. The posterior portion of the cartilage forms two horns, the superior horn and the inferior horn.
Cricoid cartilage: The cricoid cartilage is ring shaped and is the only complete ring in the entire airway. The posterior portion is taller than the anterior part of the ring. It sits below the thyroid cartilage.
Arytenoid cartilages: Two arytenoid cartilages are small, pyramid-shaped cartilages that sit atop the cricoid cartilage at the back of the larynx. Each has the following parts:
An apex that articulates with the corniculate cartilage
A base that articulates with the cricoid cartilage
A vocal process attached to the vocal ligament
A muscular process that attaches to the posterior and lateral
Corniculate cartilages: Two small corniculate cartilages articulate with the arytenoid cartilage, and two small cuneiform cartilages are found in the aryepiglottic folds.
Epiglottis: The epiglottis is a piece of elastic cartilage covered with a mucous membrane. It’s found behind the tongue, and it attaches to the back of the thyroid cartilage.
Thyrohyoid membrane: The thyrohyoid membrane connects the thyroid cartilage to the hyoid bone. Part of it thickens to form the thyrohyoid ligament.
Cricotracheal ligament: The cricotracheal ligament runs between the cricoid cartilage and the first ring of the trachea.
Quadrangular membrane: The quadrangular membrane runs between the epiglottis and the arytenoid cartilages. Part of the inferior free edge forms the vestibular ligament, which is part of the vestibular folds.
Median cricothyroid ligament: The median cricothyroid ligament attach the cricoid cartilage to the thyroid cartilage.
The vocal folds (or vocal cords) produce the sounds you make when talking, singing, or shouting. Each fold is made up of a vocal ligament and vocalis muscles.
Vocal folds produce the tones that come from the larynx. The gap between them is called the rima glottidis.
The shape of the rima glottidis changes depending on what the vocal folds are doing. The rima is narrow during normal breathing, but it’s much wider during forced respiration. When you speak, the folds are close together and form a slit.