7 Pharynx

STUDYAIMS

At the end of your study, you should be able to:

Know the general anatomyof the pharynx

Describe the anatomyof the nasopharynx

Describe the anatomyof the oropharynx

Describe the anatomyof the laryngopharynx

Know the muscles of the pharynx

Know the vascular supplyand lymphatic drainage of the pharynx

Understand the innervation of the pharynx

Outline the process of swallowing

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GUIDE

Head and Neck-Pharynx

Pharynx

[Plate 63, Pharynx: Median Section]

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[Plate 66, Pharynx: Opened Posterior View]

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The pharynxis a muscular tube, which is deficient anteriorlyas a result of the openings nasal and oral cavities and larynx-as revealed when the posterior wall is removed.

Muscular tube

Posterior to nasal and oral cavities

Continuous with both esophagus and larynx

Anterior to superior sixcervical vertebrae and prevertebral muscles and fascia

Retropharyngeal space = potential space between pharynxand prevertebral fascia

Divided into three parts: Nasopharynx, Oropharynx, and Laryngopharynx

Nasopharynx

Posterior to nose and above soft palate

Lined with ciliated epithelia

Boundaries

Anteriorly: continuous with nasal cavities via choanae

Roof and posterior wall: bodyof sphenoid and base of occipital bone

Laterally: superior constrictor muscle

Contains openings of auditory(Eustachian) tubes (from middle ear)

Salpingopharyngeal fold

Extends inferiorlyfrom medial end of auditorytube

Covers salpingopharyngeus muscle-opens tube during swallowing

Ridge over opening = torus tubarius

Pharyngeal recess

Slit-like projection

Posterior to torus

Contains abundant lymphoid tissue

Incomplete ring in superior part of pharynx

Aggregates in certain areas = tonsils

Lymphoid tissue in mucus membrane of roof and posterior wall = adenoids

Lymphoid tissue near opening of auditorytube = tubal tonsil

Oropharynx

From soft palate to superior ends of epiglottis

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Boundaries

Anteriorly: oropharyngeal opening posterior one third tongue epiglottis

Laterally: palatoglossal and palatopharyngeal arches (containing palatoglossus and palatopharyngeus muscles)

Superiorly: soft palate

Posteriorly: superior and middle constrictor muscles

Contains palatine tonsils

Found in cleft between palatoglossal and palatopharyngeal arches

Tonsil lies on tonsillar bed = superior constrictor muscle and pharyngobasilar fascia

Epiglottis

United to tongue bymedian and lateral glossoepiglottic folds

Depression between medial and lateral folds = epiglottic valleculae Laryngopharynx

From superior border of epiglottis to inferior border of cricoid cartilage

Lined with stratified squamous epithelium

Boundaries

Inferiorly: continuous with esophagus

Superiorly: continuous with oropharynx

Anteriorly: larynx

Posteriorly: middle and inferior constrictor muscles deep: Bodies of C4-C6 vertebrae

Laterally: middle and inferior constrictor muscles

Piriform recesses

Small depressions on either side of laryngeal inlet

Separated from inlet byaryepiglottic folds

Bounded mediallybythyroid cartilage and thyrohyoid membrane

Muscles of Pharynx

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Wall of pharynxis unique

Composed of outer circular and inner longitudinal layers of muscles

External circular layer consists of three constrictor muscles: pharyngeal constrictors

Inner longitudinal layer consists of three paired muscles

Pharyngeal constrictors = three muscles

Superior, middle, and inferior constrictor muscles form a muscular sleeve

Have strong internal facial lining: pharyngobasilar fascia

Contract involuntarilyin sequence = peristalsis

All supplied bypharyngeal plexus of nerves

Inner longitudinal layer = three muscles

Elevate larynx

Shorten pharynx

Act during swallowing and speaking

Stylopharyngeus

Palatopharyngeus

Salpingopharyngeus

Gaps between constrictors

Areas where structures can enter and leave pharynx

Between superior constructor and skull

Levator veli palatini

Auditorytube

Ascending palatine artery

Between superior and middle constructor

Stylopharyngeus muscle

Glossopharyngeal nerve

Stylohyoid ligament

Between middle and inferior constrictor

Internal laryngeal nerve

Superior laryngeal arteryand vein

Below inferior constructor

Recurrent laryngeal nerve

Inferior laryngeal artery

Arterial supply

Tonsillar artery(from facial) to tonsil

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Branches from

Ascending pharyngeal

Lingual

Ascending and descending palatine

Venous drainage

External palatine vein → pharyngeal plexus

Pharyngeal venous plexus → internal jugular vein

Lymphatic drainage

General drainage to deep cervical nodes

From tonsillar tissue to nodes near angle of mandible and tonsillar (jugulodigastric) node

Innervation

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From pharyngeal plexus (motor and almost all sensory)

Motor

From pharyngeal plexus via vagus nerve from cranial root of accessorynerve (cranial nerve [CN] XI)

To all muscles of pharynxexcept stylopharyngeus (CN V2)

Branches from external and recurrent branches of vagus

To inferior constrictor

Sensory

Mainlyfrom glossopharyngeal nerve (CN IX) via plexus

Also

Maxillarynerve (CN V2) to anterior and superior nasopharynx

Tonsillar nerves from branches of glossopharyngeal and vagus (CN X)

Swallowing (deglutition)

Occurs in three stages 1 = voluntary

Food is in the mouth, breathing occurs through the nasopharynx

Food is chewed (masticated) and mixed with saliva to produce a bolus

Bolus of food is compressed against hard palate

Palatoglossal folds relax

Muscles of tongue and soft palate push bolus into oropharynx

Cycle lasts 1 to 2 seconds 2 = involuntary

Reflexive, mediated via glossopharyngeal nerve

Nasopharynxis closed off bytension and elevation of the soft palate

Prevents refluxof food/fluids into the nose

Mediated bytensor veli palatine and levator veli palatine muscles

Suprahyoid muscles and longitudinal pharyngeal muscles contract

Elevate larynx

Close epiglottis

Propel bolus 3 = involuntary

Food propelled through the pharynxbyperistalsis (sequential contraction of all three constrictors) On reaching the distal end of pharynx, high pressure causes relaxation of terminal part of inferior constrictor

Called cricopharyngeus muscle

Serves as superior esophageal sphincter

Food enters the oesophagus

As bolus passes pressure drops, the sphincter closes Larynxand epiglottis return to normal positions

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