Pharynx (Throat)

What Is the Pharynx?

The pharynx is the muscular tube at the back of the nose and mouth, better known as the throat, that carries air down to the larynx and food down to the esophagus. It is a semicircular, funnel-shaped fibromuscular tube that is open at the front, where it faces the nasal cavity, the mouth and the larynx, and closed at the back. The word comes from the Greek for throat and is pronounced "FAIR-inks"; the plural is pharynges.

The pharynx is one of the few places where the respiratory and digestive systems share a single pathway. Air from the nose crosses it on its way to the larynx, while food and drink from the mouth cross it on their way to the esophagus. A set of quick, automatic movements during swallowing keeps the two traffic streams apart.

Explained simply

Picture the pharynx as a crossroads behind the mouth. The road from the nose and the road from the mouth both enter it from the front, and two roads leave at the bottom: the windpipe in front for air and the food pipe behind for food. Every time you swallow, the crossroads briefly turns into a one-way street so food goes down the right road.

Where Is the Pharynx Located?

The pharynx is located behind the nasal cavity, the mouth and the larynx, in front of the neck vertebrae, extending from the base of the skull down to the lower border of the cricoid cartilage at about the level of the sixth cervical vertebra (C6). Below that point it continues as the esophagus.

Borders of the pharynx

• Above: the base of the skull, formed by the body of the sphenoid bone and the base of the occipital bone.
• Below: the lower edge of the cricoid cartilage, where the pharynx becomes the esophagus.
• In front: the nasal cavity, the oral cavity and the larynx, which open into it.
• Behind: the cervical vertebrae and the deep neck muscles, separated by a thin, slippery space that lets the pharynx slide up and down during swallowing.
• On each side: the large blood vessels and nerves of the neck, including the carotid arteries and the internal jugular veins.

What does the pharynx connect?

The pharynx has seven openings: the two choanae leading from the nasal cavity, the two Eustachian tubes leading to the middle ears, the opening from the mouth, the inlet of the larynx and the opening into the esophagus. These connections make it the meeting point of the airway, the food passage and the ears.

What Are the Three Parts of the Pharynx?

The three parts of the pharynx are the nasopharynx behind the nose, the oropharynx behind the mouth and the laryngopharynx behind the larynx. They follow one another from top to bottom without any wall between them.

Nasopharynx

The nasopharynx is the uppermost section, lying between the skull base and the soft palate behind the nasal cavity. It carries only air, holds the adenoids (pharyngeal tonsil) on its back wall and roof, and receives the openings of the Eustachian tubes on its side walls. During swallowing the soft palate rises to seal it off.

Oropharynx

The oropharynx lies behind the mouth and the base of the tongue, from the soft palate down to the level of the epiglottis. It carries both air and food. The palatine tonsils sit in its side walls between two folds called the palatoglossal and palatopharyngeal arches, and the lingual tonsil covers the back of the tongue. Between the base of the tongue and the epiglottis lie two small pockets called the valleculae.

Laryngopharynx

The laryngopharynx, also called the hypopharynx, is the lowest section, running from the epiglottis down to the lower edge of the cricoid cartilage. Here the passage splits: the inlet of the larynx opens in front, and the pharynx continues behind as the esophagus. On each side of the laryngeal inlet lies a deep gutter, the piriform recess (piriform fossa), which guides swallowed food around the airway.

The tonsils of the throat

The adenoids, the small tubal tonsils near the Eustachian tube openings, the palatine tonsils and the lingual tonsil form a ring of lymphoid tissue around the upper throat, often called Waldeyer's ring. This ring stands guard at the entrance to both the airway and the digestive tract.

What Is the Pharynx Made Of?

The pharynx is made of four main layers: an inner mucous membrane, a fibrous layer called the pharyngobasilar fascia, a muscular layer of skeletal muscle arranged in an outer circular and an inner longitudinal layer, and a thin outer covering of connective tissue (buccopharyngeal fascia).

Lining and histology

The nasopharynx is lined partly by ciliated pseudostratified columnar epithelium with goblet cells, the same respiratory lining found in the nose. The oropharynx and laryngopharynx are lined by nonkeratinized stratified squamous epithelium, a tougher, many-layered lining that resists the rubbing of swallowed food. Mucous glands in the submucosa keep the surface moist, and lymphoid tissue lies under the lining throughout.

The outer circular muscle layer

The circular layer is made of three pharyngeal constrictor muscles shaped like incomplete rings that are open at the front. They overlap from below like three cups stacked inside one another, and all of them meet at the back in a midline seam, the pharyngeal raphe.

• Superior constrictor: the highest and thinnest, lining the upper pharynx around the nasopharynx and oropharynx.
• Middle constrictor: a fan-shaped muscle attached to the hyoid bone, around the oropharynx.
• Inferior constrictor: the thickest, around the laryngopharynx. Its upper part, the thyropharyngeus, has oblique fibers attached to the thyroid cartilage; its lower part, the cricopharyngeus, has horizontal fibers attached to the cricoid cartilage and works as the upper esophageal sphincter.

The inner longitudinal muscle layer

Three paired longitudinal muscles run downward inside the constrictors. The stylopharyngeus comes from the styloid process of the temporal bone, the palatopharyngeus from the palate, and the salpingopharyngeus from the cartilage of the Eustachian tube. Together they shorten and widen the pharynx and pull the larynx upward during swallowing.

Blood supply and nerves

Arterial blood comes from branches of the external carotid artery: the ascending pharyngeal artery, the lingual artery, the facial artery (through its ascending palatine and tonsillar branches) and the maxillary artery, with the thyroid arteries helping to supply the lowest part. Veins form a pharyngeal venous plexus that drains into the internal jugular vein. Most muscles are supplied by the vagus nerve through the pharyngeal plexus; the stylopharyngeus alone is supplied by the glossopharyngeal nerve, which also carries most sensation from the oropharynx.

What Does the Pharynx Do?

The pharynx carries air from the nose and mouth to the larynx, moves food and liquid from the mouth into the esophagus, shapes the sound of the voice, balances air pressure in the middle ears and helps defend the body against inhaled and swallowed germs. Because it links the nasal cavity with the larynx and the mouth with the esophagus, it is a working part of both the respiratory and digestive systems.

Function of the pharynx in the respiratory system

In breathing, the pharynx is the passage that lets inhaled air move from the nasal cavity to the larynx, then the trachea and the lungs. Because the nasopharynx and oropharynx are joined through the opening behind the soft palate (the pharyngeal isthmus), we can breathe through the nose, through the mouth or through both. The nasopharynx continues the warming, moistening and filtering of air begun in the nose and paranasal sinuses. These jobs are part of the wider respiratory system functions.

Function of the pharynx in the digestive system

In digestion, the pharynx receives each mouthful pushed back by the tongue and squeezes it down into the esophagus. The circular constrictor muscles contract one after another from top to bottom, driving the food through the tube, while the longitudinal muscles widen the pharynx and lift the larynx out of the way.

Other functions

• Speech: the pharynx works with the larynx, tongue, palate and lips to produce speech sounds and acts as a resonating chamber; changing its shape helps form different vowels and gives each voice its tone.
• Hearing and ear pressure: the Eustachian tubes connect the nasopharynx to the middle ears and open during swallowing and yawning to equalize the air pressure on the eardrum.
• Immune defense: the tonsils and adenoids sample germs entering through the nose and mouth and start immune responses against them.
• Protection: the gag reflex, triggered by touching the back of the throat, helps stop large objects from being swallowed or inhaled.

How Does the Pharynx Work During Breathing and Swallowing?

During breathing, muscles in the throat wall hold the pharynx open so air can flow freely to the larynx; during swallowing, a fast reflex briefly closes off the nose and the airway so that food passes only into the esophagus. The switch between these two modes happens in about a second, many times a day.

Keeping the airway open

Unlike the trachea, most of the pharynx has no rigid framework of bone or cartilage, so it can narrow or collapse when its muscles relax. Muscles such as the genioglossus, which pulls the tongue forward, act as dilators that keep the oropharynx open with every breath. During sleep these muscles relax, which is why the throat can partly close and cause snoring.

What happens when we swallow

1. The tongue pushes the chewed food, now called a bolus, back into the oropharynx; this step is voluntary.
2. Touching the back of the throat triggers the swallowing reflex, controlled by the brainstem, and breathing pauses for a moment.
3. The soft palate rises and presses against the back wall of the pharynx, sealing off the nasopharynx so food does not enter the nose.
4. The larynx is pulled up and forward, the vocal folds close, and the epiglottis tips back over the laryngeal inlet, so food is kept out of the airway.
5. The constrictor muscles contract in a wave from top to bottom, squeezing the bolus down past the epiglottis and around the piriform recesses.
6. The cricopharyngeus relaxes to open the upper esophageal sphincter, the bolus enters the esophagus, and the airway reopens for the next breath.

Pharynx vs Larynx vs Trachea: What Is the Difference?

The pharynx is the shared muscular throat behind the nose and mouth, the larynx is the cartilage voice box below and in front of it that opens only into the airway, and the trachea is the windpipe that continues down from the larynx to the lungs. Air passes through all three in that order, but food passes only through the pharynx.

The larynx sits in front of the laryngopharynx and is built of cartilages, including the thyroid and cricoid cartilages, that protect the airway and hold the vocal folds. The trachea, which belongs to the lower respiratory tract, is held open by C-shaped rings of hyaline cartilage. The pharynx, in contrast, depends on muscle rather than cartilage, which lets it squeeze food along but also lets it narrow when its muscles relax.

A fuller side-by-side comparison is on our larynx vs pharynx page.

How Does the Pharynx Develop and Change With Age?

The pharynx develops from the primitive pharynx, the upper end of the embryo's foregut, which is surrounded by a series of pharyngeal arches and pouches that shape the muscles, nerves and cavities of the throat. This shared origin explains its pattern of nerve supply.

Before birth

The muscles of the pharynx come from the third and fourth pharyngeal arches. The stylopharyngeus develops from the third arch and is therefore supplied by the nerve of that arch, the glossopharyngeal nerve, while the constrictors come from the fourth arch and are supplied by the vagus nerve. The first pharyngeal pouch forms the Eustachian tube and middle ear cavity, and the second pouch contributes to the palatine tonsils.

Infancy and childhood

In a newborn the larynx sits high in the neck, so the epiglottis nearly touches the soft palate. This arrangement lets a baby breathe through the nose while sucking and swallowing milk. During early childhood the larynx gradually descends and the oropharynx lengthens, which gives the adult throat more room for speech sounds but also makes the airway and food passage cross more sharply. The tonsils and adenoids grow during childhood and then shrink.

Older age

With age the pharyngeal muscles tend to lose some strength and the swallowing reflex becomes a little slower. Healthy older adults usually swallow safely, but these changes reduce reserve, and swallowing difficulty becomes more common after strokes and other neurological conditions.

Common Conditions That Affect the Pharynx

Pharynx conditions range from common infections to rare cancers, and most involve inflammation of the lining, the tonsils, or the muscles and nerves that control swallowing. Our respiratory diseases section covers airway conditions in more depth, and anyone with a lasting sore throat or swallowing problem should see a doctor.

• Pharyngitis: inflammation of the pharynx, causing swelling, redness, pain when swallowing, a scratchy feeling and sometimes white patches in the throat. Most cases are viral; some are bacterial, such as strep throat.
• Tonsillopharyngitis: a viral or bacterial infection of the tonsils and pharynx together, causing a sore throat and difficulty swallowing.
• Pharyngeal cancer: cancer of the nasopharynx, oropharynx or laryngopharynx. Possible signs include a lump in the throat or neck, bleeding, nasal blockage, ear and throat pain, trouble swallowing and hearing loss.
• Throat paralysis: weakness of the pharyngeal muscles caused by nerve damage, historically linked to infectious diseases such as diphtheria, rabies and polio, and today more often to strokes or other neurological conditions.
• Cobblestoning: bumpy streaks of lymphoid tissue on the back wall of the pharynx, often linked to allergic rhinitis and postnasal drip.
• Laryngopharyngeal reflux (LPR): stomach acid that travels up the esophagus into the throat, common in people with gastroesophageal reflux disease (GERD).
• Obstructive sleep apnea: repeated narrowing or collapse of the pharynx during sleep, which interrupts breathing and causes loud snoring.
• Pharyngeal pouch (Zenker's diverticulum): a pouch of lining that bulges out through a weak spot in the inferior constrictor above the cricopharyngeus, more common in older adults.