Pharyngeal and Oral Anatomy

Introduction

 

This page looks at the anatomy of the pharynx and then that of the oral cavity. There is a separate page for laryngeal anatomy.

The Pharynx

 

The pharynx is a fibro-muscular tube extending from the skull base to the oesophagus. It has three distinct regions: the nasopharynx, the oropharynx and the laryngopharynx. Each of these has the cervical spine as its posterior relation and each has a defect in its anterior face.

 

The nasopharynx opens into the nasal cavity, the oropharynx into the oral cavity, and the laryngopharynx into the larynx.

 

 

 

 

 

 

 

N - nasopharynx: from skull base to soft palate, nasal cavity opens into it anteriorly at the choana

O - oropharynx: from soft palate to hyoid bone, oral cavity opens into it anteriorly at the faucial pillars

H - hypopharynx: from hyoid down to cricopharyngeus (around C5-6), the larynx opens into it anteriorly

 

The pharynx is made of three tubular muscles and a number of longitudinal muscles. These are listed in the table together with their innervating motor cranial nerve.

 

Sensation in the pharynx is mediated by the IX and X cranial nerves. Note that the superior constrictor is the muscle of the nasopharynx and oropharynx.

 

The nasopharynx

 

This opens anteriorly into the nasal cavity. Posteriorly lies the upper cervical spine (C1 and C2). Superiorly is the sphenoid bone. Laterally lies the upper reaches of the parapharyngeal space.

 

The nasopharynx houses the adenoid, a part of Waldeyer’s ring of lymphoid tissue. It is a midline structure that regresses in adolescence. The Eustachian tubes open where the lateral nasal wall meats the nasopharynx.

 

The oropharynx

 

The oropharynx lies between the nasopharynx and hypopharynx. In vertical extent the oropharynx lies between the soft palate and the hyoid bone. Anteriorly it communicates with the oral cavity via the palatal arches (fauces) between which lie the palatine tonsils. The tonsils themselves are a part of the oropharynx as is the tongue base. The cervical spine lies posteriorly and laterally lie the parapharyngeal spaces.

 

The laryngopharynx (aka hypopharynx)

 

The lowest part of the pharynx this is joined below to the oesophagus. Posteriorly is the cervical spine, laterally the parapharyngeal spaces (carotid sheath and thyroid lobe below) and anteriorly it opens into the larynx. The hypopharynx is described in three parts: the post cricoid area, the piriform sinus, and the posterior pharyngeal wall.

Longitudinal

  • Stylopharyngeus (IX)

  • Palatopharyngeus (X)

  • Salpingopharyngeus (X)

Tubular

  • Superior constrictor (X)

  • Middle constrictor (X)

  • Inferior constrictor (X) [thyropharyngeus and cricopharyngeus]

The oral cavity

 

The main areas to discuss in this area are;

  • The palate

  • The tongue & salivary ducts  

  • The teeth

The Palate

The palate is a colloquial term that described the partition between the nasal and oral cavity. It can be split anatomically into the hard and soft palate as shown on the diagram below.

The hard palate

 

The hard palate is named as such due to the presence of a bone. It is in fact made up of three bones: the palatine process of the maxilla and the paired palatine bones, which fuse during development. The bone is covered by a mucosal layer, respiratory superiorly and oral inferiorly, in continuation with the cavity in which the area lies.

 

The image opposite shows two main structures to be aware of: the palatine raphae and rugae.

The sensory innervation of the palate is provided by the trigeminal nerve Vvia the nasopalatine, greater and lesser palatine nerves respectively.

The hard palate provides a structural barrier between the oral and nasal cavities, allowing a partial vacuum to be formed to facilitate feeding.

The formation of phonetic sounds in speech also heavily rely on the hard palate, which is best highlighted by the hyponasal speech in defects of the palate. (click to here to learn more). 

The soft palate

 

The soft palate is a completely muscular posterior extension of the hard palate via an aponeurotic line. Its borders are the same as the hard palate however its posterior border hangs freely as the uvula.

Similar to the hard palate, the soft palate is important in aiding speech, for example in the pronunciation velar consonants such as [k], [g] and [ŋ].

During swallowing, the soft palate rises to prevent nasal regurgitation. This has a protective and a functional role.

 

 

Soft palate muscles​

It is impossible to talk about the soft palate without discussing the musculature of the soft palate.

There are 5 muscles of the soft palate, these can be broadly split into superior and inferior muscles.

 

Superior group

 

1. Tensor veli palatini

 

- Tenses the soft palate

- Opens the eustachian tube

 

2. Levator veli palatini

 

- Elevates the soft palate above neutral position

- The muscle in action when you “Say Ah”

 

These muscles cannot be visualised clinically.

Inferior group

 

3. Muscularis uvulae - uvula (Yellow)

 

- Function not fully understood

 

4. Palatoglossus (Blue)

 

- Depresses the soft palate

- Moves arch to midline

 

5. Palatopharyngeus (Purple)

 

- Depresses the soft palate

- Moves arch to midline

 

Tonsils (red)

 

 

Superior group

Inferior group

Roll over the image to reveal the corresponding muscles.

These muscles make up the appearance of the oropharynx. The motor innervation of these muscles is supplied by the vagus nerve. The tensor veli palatini is the one exception which gains its innervation from the trigeminal nerve.  

The clinical relevance behind the knowledge of these muscles is essential for tonsillectomy, which dissects the tonsils from the inferior palatine muscles.

 

The Teeth

 

Only a basic knowledge of teeth is required for practical medicine unless you plan on delving into the world of oral and maxillofacial surgery.

 

An adult human has 32 teeth which can be described by their location in a grid (shown below)

Taking the upper right canine tooth as in example using this format this can be described as the upper right 3 or documented as the (UR3) or

Dental pathology often results in the teeth become tender to percussion (TTP). The most sensitive investigation for exposing this pathology is an OPT or OPG (orthopantomogram), as shown below.

The tongue and salivary ducts

 

Underneath the tongue lies two structures important submandibular or Wharton's ducts. These drain the submandibular glands. It is sometimes possible to palpate calculi in these ducts in Sialolithiasis.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The floor of the tongue can be an area where infection can track via salivary gland infections or a dental abscess. This presents clinically with a raised floor of mouth which is a clinical sign of a potential airway at risk! 

 

 

Another important salivary duct is seen in Stensen's duct (the parotid duct), this opens opposite the upper second molar tooth.

For more salivary anatomy see the page on salivary gland disease.

Wharton's ducts

Lingual frenulum