Pharynx

Pharynx
Head and neck
Pharynx
Latin	(Greek: Pharynx)
Gray's	subject #244 1141
Artery	pharyngeal branches of ascending pharyngeal artery, ascending palatine, descending palatine, pharyngeal branches of inferior thyroid
Vein	pharyngeal plexus
Nerve	pharyngeal plexus, maxillary nerve, mandibular nerve
MeSH	Pharynx

The pharynx (plural: pharynges) is an organ found in animals, including humans. It is part of the digestive system and also the respiratory system. The pharynx is also part of the conducting zone of the respiratory system which is made up of the nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles; their function is to filter, warm, and moisten air and conduct it into the lungs.^{[citation needed]}

In humans it makes up the part of the throat situated immediately posterior to the nasal cavity, posterior to the mouth and superior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx (epipharynx), the oropharynx (mesopharynx), and the laryngopharynx (hypopharynx). The pharynx is part of the digestive system and also the respiratory system; it is also important in vocalization.

Etymology

The word pharynx (pronounced /ˈfærɪŋks/^[1][2]) is derived from the Greek phárynx, meaning "throat". Its plural form is pharynges /fəˈrɪndʒiːz/ or pharynxes /ˈfærɪŋksəz/, and its adjective form is pharyngeal (/ˌfærɪnˈdʒiːəl/ or /fəˈrɪndʒiəl/).

Structure

Nasopharynx

The higher or most cephalad portion of the pharynx. It extends from the base of the skull to the upper surface of the soft palate.^[3] It includes the space between the internal nares and the soft palate and lies above/superior to the oral cavity. The pharyngeal tonsils, more commonly referred to as the adenoids, are lymphoid tissue structures located in the posterior wall of the nasopharynx.

The nasopharynx, oropharynx, and laryngopharynx or larynx can be seen clearly in this sagittal section of the head and neck.

Polyps or mucus can obstruct the nasopharynx, as can congestion due to an upper respiratory infection. The Eustachian tubes, which connect the middle ear to the pharynx, open into the nasopharynx. The opening and closing of the Eustachian tubes serves to equalize the barometric pressure in the middle ear with that of the ambient atmosphere.

The anterior aspect of the nasopharynx communicates through the choanae with the nasal cavities. On its lateral walls are the pharyngeal ostia of the auditory tube, somewhat triangular in shape, and bounded behind by a firm prominence, the torus tubarius or cushion, caused by the medial end of the cartilage of the tube that elevates the mucous membrane. Two folds arise from the cartilaginous opening:

• the salpingopharyngeal fold, a vertical fold of mucous membrane extending from the inferior part of the torus and containing the salpingopharyngeus muscle
• the salpingopalatine fold, a smaller fold extending from the superior part of the torus to the palate and containing the levator veli palatini muscle. The tensor veli palatini is lateral to the levator and does not contribute the fold, since the origin is deep to the cartilaginous opening.

Behind the ostium of the auditory tube is a deep recess, the pharyngeal recess (also referred to as the fossa of Rosenmüller). On the posterior wall is a prominence, best marked in childhood, produced by a mass of lymphoid tissue, which is known as the pharyngeal tonsil. Superior to the pharyngeal tonsil, in the midline, an irregular flask-shaped depression of the mucous membrane sometimes extends up as far as the basilar process of the occipital bone; it is known as the pharyngeal bursa.

Oropharynx

The oropharynx or mesopharynx lies behind the oral cavity, extending from the uvula to the level of the hyoid bone. It opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the Palatoglossal arch and the Palatopharyngeal arch, is the palatine tonsil. The anterior wall consists of the base of the tongue and the epiglottic vallecula; the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars; the superior wall consists of the inferior surface of the soft palate and the uvula. Because both food and air pass through the pharynx, a flap of connective tissue called the epiglottis closes over the glottis when food is swallowed to prevent aspiration.The oropharynx is lined by non keratinised squamous stratified epithelium.

The HACEK organisms (Haemophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella) are part of the normal oropharyngeal flora, which grow slowly, prefer a carbon dioxide-enriched atmosphere, and share an enhanced capacity to produce endocardial infections, especially in young children.^[4] Fusobacterium is a pathogen.^[5]

Laryngopharynx

The hypopharynx or laryngopharynx or (Latin: pars laryngea pharyngis) is the caudal part of the pharynx; it is the part of the throat that connects to the esophagus. It lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory (larynx) and digestive (esophagus) pathways. At that point, the laryngopharynx is continuous with the esophagus posteriorly. The esophagus conducts food and fluids to the stomach; air enters the larynx anteriorly. During swallowing, food has the "right of way", and air passage temporarily stops. Corresponding roughly to the area located between the 4th and 6th cervical vertebrae, the superior boundary of the laryngopharynx is at the level of the hyoid bone. The laryngopharynx includes three major sites: the pyriform sinus, postcricoid area, and the posterior pharyngeal wall. Like the oropharynx above it, the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium. It is innervated by the pharyngeal plexus.

It can be divided into three sub-sites:

1. piriform sinus
2. postcricoid area
3. posterior pharyngeal wall

The vascular supply to the hypopharynx includes the Superior Thyroid Artery, the Lingual Artery and the Ascending Pharyngeal Artery. The primary neural supply is from both the vagus and glossopharyngeal nerves. The vagus nerve provides a branch termed "Arnolds Nerve" which also supplies the external auditory canal, thus hypophayrngeal cancer can result in referred otalgia. This nerve is also responsible for the ear-cough reflex in which stimulation of the ear canal results in a person coughing.

Other animals

As in humans other animals also have pharynxes. It is part of the digestive system and also the respiratory system.

• 

  Everted pharynx of Alitta virens (also known as Nereis virens), lateral view

• 

  Pharynx of the turbellarian Prorhynchus fontinalis

• 

  Longitudinal section through the roundworm Caenorhabditis elegans showing the position of the pharynx in the animal body.

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  Microscopic cross section through the pharynx of a larva from an unknown lamprey species.

Pharyngeal jaws

Pharyngeal jaws are a "second set" of jaws contained within an animal's pharynx, distinct from the primary (oral) jaws. Pharyngeal jaws have been studied in moray eels. When the moray bites prey, it first bites normally with its oral jaws, capturing the prey. Immediately thereafter, the pharyngeal jaws are brought forward and bite down on the prey to grip it; they then retract, pulling the prey down the eel's esophagus, allowing it to be swallowed. ^[6]

An illustration of the pharyngeal jaws of a moray eel.

Additional images

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  Conducting passages

• 

  Organs of the digestive system

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  Nose and nasal

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  Coronal section of right ear, showing auditory tube and levator veli palatini muscle.

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  The entrance to the larynx, viewed from behind

• 

  The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind.

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  Acute catarrhal pharyngitis. The oropharynx is swollen and red

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  Deep dissection of human larynx, pharynx and tongue seen from behind

• 

  Deep dissection of human larynx, pharynx and tongue seen from behind

See also

This article uses anatomical terminology; for an overview, see anatomical terminology.

• Nasopharyngeal carcinoma
• Pharyngeal consonant
• Pharyngeal (disambiguation)
• Pharyngitis
• Saccopharynx, a genus of deep sea eel-like fishes with large mouths, distensible stomachs and long scaleless bodies
• Tonsil
• Uvula

References

This article incorporates text from a public domain edition of Gray's Anatomy.

General

• Stedman's/LWW 1551471
• Human Anatomy and Physiology Elaine N. Marieb and Katja Hoehn, Seventh Edition.
• TNM Classification of Malignant Tumours Sobin LH & Wittekind Ch (eds)Sixth edition UICC 2002 ISBN 0-471-22288-7

External links

Look up pharynx in Wiktionary, the free dictionary.

Wikimedia Commons has media related to Pharynx.

• 31:st-1401 at the SUNY Downstate Medical Center
• 31:st-1403 at the SUNY Downstate Medical Center
• 31:st-1406 at the SUNY Downstate Medical Center