Anatomy of the pharynx and esophagus

The cervical viscera are composed of three layers based on their main functions.

The most superficial layer is the endocrine layer which contains the thyroid and parathyroid glands, then there’s the respiratory layer which contains the larynx and the trachea, and finally, the deepest layer is the alimentary layer which contains the pharynx and the esophagus.

So, let’s start with the pharynx which also has a respiratory function because it conducts air to the larynx, from where it passes through the trachea and into the lungs.

The pharynx extends from the cranial base to the inferior border of the cricoid cartilage anteriorly and the inferior border of the C6 vertebra posteriorly.

It’s located posterior to the nasal and oral cavities and it extends inferiorly past the larynx, where it continues with the esophagus.

Now, the pharyngeal wall consists of three layers: the buccopharyngeal fascia is the most external layer, covering the pharynx and, inferiorly, it’s continuous with the pretracheal fascia.

Then, there is a muscular layer which has an outer circular part and an inner longitudinal part, and the innermost mucous membrane which has a thick submucosa that contributes to the pharyngobasilar fascia.

Moreover, the posterior wall of the pharynx lies against the prevertebral layer of the deep cervical fascia.

The interior of the pharynx is divided into three parts: the nasopharynx which is located posterior to the nose and superior to the soft palate, the oropharynx which is located posterior to the mouth, and the laryngopharynx which is located posterior to the larynx.

The nasopharynx is the posterior extension of the nasal cavities and communicates with the nose through two paired openings called choanae, which are separated by the posterior end of the nasal septum.