Pharynx

Part 1

Pharynx

Is about 12 cm long

Extending from base of skull to the lower border of the cricoid cartilage

Opposite the sixth cervical vertebra where it is continuous with oesophagus

Divided in to 3 parts : nasopharynx,oropharynx and laryngopharynx

Nasopharynx

Behind the nasal cavity and above the soft palate.

Posterior nasal apertures open into it anterioly

Below it is continuous with oropharynx through pharyngeal isthmus

The nasopharynx is part of the upper respiratory tract and does not normally give passage to food or drink

Nasopharynx Auditory tube opens on the lateral wall of nasopharynx

This opening is bounded above and behind by the tubal elevation produced by underlying medial end of auditory tube

A collection of lymphoid tissue,the pharyngeal tonsil or adenoid is located beneath the mucous membrane

The tonsil may become enlarged in chronic infections of upper respiratory system leading to mouth breathing

Nasopharynx

The mucous membrane lining the nasopharynx is of the respiratory type,covered by ciliated cuboidal epithilium

Receives its sensory and secretomotor nerve supply through a branch of pterygopalatine gangilion

It resembles the mucous membrane lining the nose

Oropharynx Extends from soft palate to epiglottis

Oral cavity opens into oropharynx anteriorly through oropharngeal isthmus ,which is bounded on each side by a fold of mucous membrane ,the palatoglossal arch

The arch is produced by the underlying palatoglossus muscle

The lateral wall of oropharynx ,behind the palatoglossal arch presents a vertical ridge of mucous membrane ,the palatopharyngeal arch produced by palatopharyngeus muscle

Oropharynx Between palatoglossal and palatopharyngeal arches is a depression ,the tonsillar sinus.

The palatine tonsil ,a mass of lymphoid tissue, is situated beneath the mucous membrane lining the sinus

Laterally the tonsil is enclosed by a fibrous capsule

The tonsil is very variable in size and is frequently the site of infection which causes it to become enlarged and painful (tonsillitis)

The oropharynx is lined by stratified squamous epithilium, nerve supply is from pharyngeal plexus

Laryngopharynx Extends from epiglottis to the lower border of the cricoid cartilage

Laryngopharynx is lined by stratified squamous epithilium and innervated by vagus through the internal and recurrent laryngeal branches

On functional nasopharynx regarded as part of nasal cavity

Unlike oropharynx and laryngopharynx it is respiratory in function ,lined by respiratory mucosa which receives its sensory innervation from trigiminal nerve

Muscles of pharynx

Three paired of constrictor muscles , meet their fellows of opposite side in the posterior pharyngeal wall at the median pharyngeal ligament and raphe

Three other muscles,these are stylopharngeus ,salpinopharyngeus ,palatopharyngeus

Superior constrictorArises from lower two thirds of posterior border of the medial pterygoid plate (including hamulus) and from the posterior end of mylohyoid line on the medial surface of the mandible

Between hamulus and the mandible the fibres arise from the pterygomandibular raphe where they interdigitate with fibers of buccinator

Between the upper border of the muscle and the base of the skull is a gap through which the cartilaginous part of auditory tube and levator veli palatini muscle pass

The remainder of the gap is closed by pharyngobasilar fascia

Middle constrictor

Attached anteriorly to stylohyoid ligament, the lesser Cornu and upper border of greater Cornu of hyoid bone

The upper fibers diverge upwards,passing superficial to the lower part of superior constrictor

The lower fibers run horizontally passing deep to upper part of inferior constrictor

Inferior constrictor Consists of two parts (thyropharyngeus and cricopharyngeus)

Thyropharyngeus arises from oblique line on the lamina of the thyroid cartilage and inserted in to pharyngeal raphe

Cricopharyngeus attached anteriorly to the side of the arch of cricoid cartilage

It encircles the lower most part of pharynx

A weak area called killians dehiscence, is present between thyropharyngeus and cricopharyngeus giving rise to pharyngeal pouch

Salpinopharyngeus

Arises from the cartilage of auditory tube

It passes downwards beneath the pharyngeal mucous membrane and raised to form salpinopharyngeal fold and blends with constrictor muscle

Stylopharngeus muscle Arises from medial surfaces of styloid process

It passes between the internal and external carotid arteries

It crosses the lower border of superior constrictor muscle and continues downwards inside the middle constrictor , beneath the pharyngeal mucous membrane to be inserted into posterior border of thyroid cartilage and the side wall of the pharynx

Pharyngeal muscles , with exception of stylopharngeus are innervated by accessory nerve

Stylopharngeus is the only muscle derived from third pharyngeal arch and supplied by glossopharyngeal nerve