Pharynx - Anatomy & Physiology

Introduction

Developing Head - Copyright RVC

The pharynx is part of both the respiratory and digestive system. Both systems have entrances to the pharynx but they are separated from each other by the soft palate. During exercise or during respiratory distress, the mouth can be used as an additional opening of the respiratory system and then the oropharynx also becomes an air-way.

The pharynx can be split into different regions- the oropharynx, laryngeal pharynx (sometimes referred to as the oesophageal pharynx) and the nasopharynx.

Nasopharynx Anatomy - Copyright RVC

Structure and Function

Opening of the larynx is on the floor of the pharynx

Caudal and dorsal to the laryngeal opening is the opening into the oesophagus

In the dorsal region of the nasopharynx there are paired openings into the Auditory (Eustacian) Tubes

The lining of the middle ear cavity and auditory tube is continuous with that of the nasopharynx

Located between the base of the skull and the first two cervical vertebrae dorsally

larynx ventrally

Mandible, pterygoid muscles and hyoid apparatus laterally

Walls contain striated muscle

Pharynx Labelled - Copyright C.Clarkson and T.F.Fletcher University of Minnesota

During swallowing the soft palate is raised which divides the pharynx into dorsal and ventral sections
- Laterally, two pairs of palatopharyngeal arches are present from the soft palate to the oesophagus
- The dorsal compartment is the nasopharynx
- The rostral compartment is the oropharynx

The laryngeal pharynx is separated from the oropharynx by the epiglottis

Tonsils are present on the lateral walls of the oropharynx
- Covered by flaps of mucosa
- Partially visible in the open mouth

The pharynx plays an important role in deglutition

Soft palate dividing the oropharynx and the nasopharynx - Copyright RVC

Musculature

Muscles that constrict

Run dorsally to roof of pharynx

Rostral constrictor muscles are the hyopharyngeous, pterygopharyngeous and the palatopharyngeous muscles
- Originate from the pterygoid region of the skull and the aponeurosis of the soft palate
- Shorten the pharynx

Middle constictor muscle is the thyopharyngeous muscle
- Origniates from the hyoid bone

Caudal constictor muscles are the cricopharyngeous muscle
- Originates from the thyroid cartilage of the larynx

Muscles that dilate

Enclose pharynx laterally and dorsally

Dilator muscle is the stylopharyngeous muscle

Originates from the hyoid apparatus

Widens the rostral pharynx

Muscles that shorten

The pterygopharyngeal muscle and palatopharyngeal muscle shorten the pharynx

Enclose pharynx laterally and dorsally

Muscles that close the Pharyngeal Arch

The palatopharyngeous muscle also closes the pharyngeal arch

Innervation

Pharyngeal muscles arise from arch 4

Pharyngeal branch of the vagus nerve (CN X) from the cranial root of the accessory nerve (CN XI)

Stylopharyngeous muscle comes from arch 3 and is innervated by the accessory nerve (CN XI)
Glossopharyngeal nerve (CN IX) supplies taste to the pharynx