Throat anatomy: the nasopharynx, oropharynx, laryngopharynx and larynx

In everyday language the throat is the pharynx and larynx together: a ring-like muscular tube that is the passageway for air, food and liquid. It connects the mouth and nose to the windpipe, the lungs and the oesophagus, and it also helps to form speech. (Children's Hospital of Philadelphia: Throat Anatomy and Physiology.)

The pharynx is a muscular tube that connects the oral and nasal cavities to the larynx and the oesophagus. It runs from the base of the skull to the inferior border of the cricoid cartilage, at the level of C6. (TeachMeAnatomy: The Pharynx.)

Kenhub gives the length of the pharynx as 12 to 14 cm. The pharynx begins in the head behind the nasal cavity, runs down behind the mouth and merges with the larynx and oesophagus. (Kenhub: Pharynx.)

Cleveland Clinic describes the pharynx, which it also calls the throat, as a muscular tube in the middle of the neck, below the base of the skull and above the oesophagus and larynx, and gives a shorter length of about 4 inches (about 10 cm). The sources do not say exactly where they measure from, so treat the length as roughly 10 to 14 cm. (Cleveland Clinic: Pharynx.)

The muscles, vessels and organs around the throat in the neck. Neck anatomy.

The pharynx has three parts. The nasopharynx, at the top, is used only for breathing and speech. The oropharynx and the laryngopharynx below it carry both air and food. (OpenStax Anatomy and Physiology 2e, 23.3: The Mouth, Pharynx, and Esophagus.)

Radiopaedia sets the boundaries as follows. The nasopharynx lies behind the choanae of the nose, from the vault of the pharynx down to the soft palate. The oropharynx lies behind the base of the tongue and below the soft palate, with the palatoglossal and palatopharyngeal arches at its sides. The laryngopharynx, also called the hypopharynx, lies below the upper border of the epiglottis and above the cricoid cartilage, and opens in front into the larynx. (Radiopaedia: Pharynx.)

The pharyngeal wall has an incomplete outer layer of circular muscle and an inner layer of longitudinal muscle. Inside the muscles lies a sheet of connective tissue, the pharyngobasilar fascia, which is lined by mucous membrane. (National University of Singapore, Department of Anatomy: HN32 The Pharynx.)

The nasopharynx is the top part of the throat, behind the nose. In front are the choanae and the back edge of the nasal septum (vomer). Its roof, the vault, is formed by the clivus and the floor of the sphenoid sinus, and its back wall lies in front of the first and second cervical vertebrae. Below, it reaches the junction of the hard and soft palates, and the upper surface of the soft palate forms its moving floor. (Radiopaedia: Nasopharynx.)

The opening of the auditory (Eustachian) tube sits in the middle of each side wall. Behind it the cartilage of the tube raises a ridge, the torus tubarius, and behind that is a pocket called the fossa of Rosenmüller (lateral pharyngeal recess). Lymphoid tissue around the tube opening forms the tubal tonsil, and the adenoid lies in the roof. (Radiopaedia: Nasopharynx.)

The nasopharynx conditions the air we breathe in and is lined by ciliated pseudostratified columnar epithelium with goblet cells. The adenoids (pharyngeal tonsil) sit in its upper back part. They enlarge between about 3 and 8 years of age and then shrink. (TeachMeAnatomy: The Pharynx.)

The auditory tube connects the middle ear to the nasopharynx. It equalises the air pressure on the two sides of the eardrum and drains secretions from the middle ear. Tensor veli palatini does most of the work of opening it, helped by levator veli palatini and salpingopharyngeus. (TeachMeAnatomy: The Eustachian Tube.)

During swallowing the soft palate and uvula swing upwards like a pendulum to close off the nasopharynx, so food cannot enter the nose. (OpenStax Anatomy and Physiology 2e, 22.1: Organs and Structures of the Respiratory System.)

The nasal cavity that opens into the nasopharynx through the choanae. Nose anatomy.

The oropharynx is the part of the throat you see at the back of an open mouth. It lies between the soft palate and the upper border of the epiglottis. It contains the back third of the tongue, the lingual tonsil, the palatine tonsils in their tonsillar fossae between the palatoglossal and palatopharyngeal arches, and the superior constrictor muscle in its wall. (TeachMeAnatomy: The Pharynx.)

Radiopaedia lists its subsites as the base of the tongue with the lingual tonsils, the tonsils with their fossae and pillars, the underside of the soft palate and uvula, and the side and back walls. Its lower limit is the level of the hyoid bone or the tip of the epiglottis, and it includes the valleculae and the oropharyngeal isthmus between the palatoglossal arches. (Radiopaedia: Oropharynx.)

The valleculae are a pair of small pockets in front of the epiglottis and behind the base of the tongue, one on each side of the median glosso-epiglottic fold. They play a part in the swallowing of solid food. (Radiopaedia: Vallecula.)

The fauces is the opening between the mouth and the oropharynx. As the oropharynx carries food as well as air, its lining changes from the pseudostratified ciliated epithelium of the nasopharynx to tougher stratified squamous epithelium. (OpenStax Anatomy and Physiology 2e, 22.1: Organs and Structures of the Respiratory System.)

The oral cavity, palate and uvula in front of the oropharynx. Mouth anatomy.

The laryngopharynx is the lowest part of the pharynx, behind the larynx. In front it opens into the larynx; below and behind it continues into the oesophagus. (OpenStax Anatomy and Physiology 2e, 22.1: Organs and Structures of the Respiratory System.)

It runs from the pharyngo-epiglottic folds at the level of the hyoid bone down to the lower edge of the cricoid cartilage at C6, where it becomes the cervical oesophagus. The inferior constrictor forms its back and side walls and the laryngeal cartilages its front wall. Radiologists divide it into three subsites: the piriform sinuses, the postcricoid region and the posterior wall. (Radiopaedia: Hypopharynx.)

The piriform fossa (piriform sinus or recess) is a pear-shaped pocket on each side of the laryngeal inlet. It is bounded medially by the aryepiglottic fold and the arytenoid and cricoid cartilages, and laterally by the thyroid cartilage and the thyrohyoid membrane. The internal laryngeal nerve runs just under the lining of its front wall. (Radiopaedia: Pyriform sinus.)

Foreign bodies such as fish bones can lodge in the piriform fossa and cause pain. (National University of Singapore, Department of Anatomy: HN32 The Pharynx.)

Waldeyer's ring is a ring of lymphoid tissue in the pharynx: one pharyngeal tonsil (adenoid) in the roof of the nasopharynx, two tubal tonsils around the auditory tube openings, two palatine tonsils in the oropharynx and one lingual tonsil on the back third of the tongue. The tonsils are mucosa-associated lymphoid tissue and are a first line of defence against microbes entering through the nose and mouth. (TeachMeAnatomy: The Tonsils and Adenoids (Waldeyer's Ring).)

Each palatine tonsil lies in the tonsillar bed on the side wall of the oropharynx, between the palatoglossal arch in front and the palatopharyngeal arch behind. Its outer surface has a fibrous capsule separated from the superior constrictor by loose connective tissue. Its main artery is the tonsillar branch of the facial artery, and it drains to the jugulodigastric and upper deep cervical lymph nodes. (TeachMeAnatomy: The Tonsils and Adenoids (Waldeyer's Ring).)

The palatine tonsils, adenoid and lingual tonsil in detail. Tonsils.

The pharynx has six paired muscles. Three constrictors (superior, middle and inferior) form the outer circular layer; three longitudinal muscles (palatopharyngeus, salpingopharyngeus and stylopharyngeus) form the inner layer. The constrictors are lined on their inner side by the pharyngobasilar fascia and contract in sequence, like a wave of peristalsis, during swallowing. (Kenhub: Muscles of the pharynx.)

The constrictors contract from top to bottom to push food down. The inferior constrictor has two parts: thyropharyngeus, which arises from the thyroid cartilage, and cricopharyngeus, which arises from the cricoid cartilage. The longitudinal muscles shorten and widen the pharynx and raise the larynx. (TeachMeAnatomy: The Pharynx.)

Between and around the constrictors are four gaps in the pharyngeal wall where muscles, nerves and vessels enter. Stylopharyngeus and the glossopharyngeal nerve pass between the superior and middle constrictors, and the internal laryngeal nerve passes between the middle and inferior constrictors. (Kenhub: Muscles of the pharynx.)

The larynx sits in the front of the neck in the midline, in front of the oesophagus, at the level of the third to sixth cervical vertebrae. It is continuous with the oropharynx above and the trachea below. Its skeleton is nine cartilages: the unpaired cricoid, thyroid and epiglottis and the paired arytenoid, corniculate and cuneiform cartilages. It conducts air, protects the airway and produces the voice. (Kenhub: Larynx.)

The epiglottis is a leaf-shaped cartilage that projects up into the pharynx above the laryngeal inlet. When you swallow, the larynx moves up and forward and the epiglottis swings down over the inlet, closing the airway and keeping food out. (Kenhub: Larynx.)

The larynx, or voice box, contains the vocal cords and forms the upper opening into the windpipe. (Children's Hospital of Philadelphia: Throat Anatomy and Physiology.)

The laryngeal cartilages, vocal folds and intrinsic muscles in detail. Larynx anatomy.

The trachea begins at the lower margin of the cricoid cartilage, at C6. It is usually 10 to 13 cm long and is held open by 15 to 20 D-shaped rings of cartilage. The oesophagus lies directly behind it. (Radiopaedia: Trachea.)

The cervical oesophagus starts at the lower border of the cricoid cartilage (C5 to C6) at the upper oesophageal sphincter, which is formed by cricopharyngeus. This is the narrowest point of the oesophagus. The oesophagus lies behind the trachea, with the recurrent laryngeal nerves in the groove between them, and is about 22 to 24 cm long. (Radiopaedia: Oesophagus.)

The windpipe from the cricoid cartilage to the carina. Trachea.

Swallowing (deglutition) has three phases. In the voluntary phase, the tongue pushes the bolus up and back against the palate into the oropharynx. In the pharyngeal phase, receptors in the oropharynx signal the swallowing centre in the medulla oblongata; the soft palate and uvula close off the nasopharynx, the larynx is pulled up and the epiglottis folds over the glottis, breathing stops briefly, the constrictors move the bolus down and the upper oesophageal sphincter relaxes. In the oesophageal phase, peristalsis carries the bolus to the stomach. (OpenStax Anatomy and Physiology 2e, 23.3: The Mouth, Pharynx, and Esophagus.)

OpenStax gives a swallow of solid or semisolid food about 4 to 8 seconds, and very soft food or liquids about 1 second. (OpenStax Anatomy and Physiology 2e, 23.3: The Mouth, Pharynx, and Esophagus.)

Kenhub notes that swallowing coordinates 22 muscle groups in the mouth, pharynx and oesophagus. The vagus nerve (CN X) is the main nerve involved, helped by the trigeminal, facial, glossopharyngeal, accessory and hypoglossal nerves. If the epiglottis does not seal the airway, food or liquid can enter it, causing choking, voice changes and shortness of breath. (Kenhub: Stages of swallowing.)

The food pipe from the throat to the stomach, with its sphincters. Oesophagus (esophagus).

The vagus nerve (CN X) supplies almost all the pharyngeal muscles; stylopharyngeus, supplied by the glossopharyngeal nerve (CN IX), is the exception. The pharyngeal plexus on the middle constrictor carries pharyngeal branches of CN IX and CN X, branches of the external laryngeal nerve and sympathetic fibres from the superior cervical ganglion. (TeachMeAnatomy: The Pharynx.)

Sensation from most of the pharynx is carried by the glossopharyngeal nerve. The exceptions are the upper nasopharynx, supplied by a pharyngeal branch of the maxillary nerve (V2), the valleculae, supplied by the internal laryngeal nerve, and the rest of the laryngopharynx, which Radiopaedia assigns to the recurrent laryngeal nerve. Lymph from the pharynx drains mostly to the retropharyngeal nodes. (Radiopaedia: Pharynx.)

The internal branch of the superior laryngeal nerve, a branch of the vagus, gives sensation to the laryngopharynx and the upper larynx. (TeachMeAnatomy: The Vagus Nerve (CN X).)

The gag reflex tests these nerves: the glossopharyngeal nerve carries the sensory (afferent) limb from the oropharynx and the vagus nerve the motor (efferent) limb. An absent gag reflex suggests damage to CN IX. (TeachMeAnatomy: The Glossopharyngeal Nerve (CN IX).)

The arteries of the pharynx all come from the external carotid artery: the ascending pharyngeal artery and branches of the facial (including the tonsillar artery), lingual and maxillary arteries. The veins form a pharyngeal venous plexus that drains to the internal jugular vein. (Kenhub: Pharynx.)

The glossopharyngeal and vagus nerves that serve the throat. Cranial nerves.

A sore throat (pharyngitis) can come from tonsillitis, viral or bacterial infections such as flu or strep throat, allergies or mouth breathing. Cancers can arise in each part of the pharynx: nasopharyngeal, oropharyngeal and hypopharyngeal cancer. (Cleveland Clinic: Pharynx.)

Tonsillitis is usually viral; bacteria cause about a third of cases. A peritonsillar abscess (quinsy) is a collection of pus beside the tonsil, a complication of bacterial tonsillitis, and always needs drainage. (TeachMeAnatomy: The Tonsils and Adenoids (Waldeyer's Ring).)

Enlarged adenoids can block the openings of the auditory tubes and cause chronic otitis media with effusion (glue ear). (TeachMeAnatomy: The Pharynx.)

The fossa of Rosenmüller, the recess behind the torus tubarius, is the most common place for nasopharyngeal carcinoma to start. (Radiopaedia: Fossa of Rosenmüller.)

A pharyngeal pouch (Zenker diverticulum) is an outpouching of the back wall of the hypopharynx just above the upper oesophageal sphincter. It forms through Killian's dehiscence, a weak area between the thyropharyngeus and cricopharyngeus parts of the inferior constrictor. More than half of patients are 60 to 80 years old, and trapped food causes difficulty swallowing, regurgitation and bad breath. (Radiopaedia: Zenker diverticulum.)

In obstructive sleep apnoea the oropharynx collapses during sleep. Smoking, which swells the lining, and obesity, which adds fat around the airway, both make this more likely. (Kenhub: Muscles of the pharynx.)

Where the tonsils and pharynx drain, including the jugulodigastric node. Lymph nodes of the head and neck.

Cricoid cartilage

The cricoid cartilage is a complete signet-ring-shaped cartilage forming the lower part of the larynx.

Epiglottis

The epiglottis is a leaf-shaped elastic cartilage that covers the laryngeal inlet during swallowing.

Hyoid bone

A U-shaped bone in the neck.

Inferior pharyngeal constrictor

The lowest of the three constrictors of the pharynx.

Levator veli palatini

A muscle of the soft palate.

Middle pharyngeal constrictor

The middle of the three pharyngeal constrictors.

Palatine tonsil

The palatine tonsils are the two masses of lymphoid tissue at the back of the mouth, one on each side of the oropharynx. They are what most people mean by the tonsils.

Palatopharyngeus

A muscle of the soft palate and pharynx that forms the posterior pillar of the fauces.

Pharyngeal raphe

The pharyngeal raphe is a midline fibrous seam on the posterior wall of the pharynx.

Salpingopharyngeus

A thin muscle of the pharynx running from the pharyngotympanic tube.

Soft palate

The soft palate is the muscular back part of the roof of the mouth. Its free back edge carries the uvula.

Stylohyoid ligament

A fibrous band from the styloid process to the hyoid.

Stylopharyngeus

A slender pharyngeal muscle arising from the styloid process.

Superior pharyngeal constrictor

The uppermost of the three constrictors forming the pharyngeal wall.

Tensor veli palatini

A palatal muscle that tenses the soft palate.

Thyroid cartilage

The thyroid cartilage is the largest cartilage of the larynx, forming the laryngeal prominence.

Uvular muscle

A small paired muscle forming the core of the uvula.