Download TSM33 - Neck and Pharynx

TSM33: NECK AND PHARYNX
16/10/08
LEARNING OUTCOMES
Describe the basic anatomy of the neck and pharynx
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The anterior neck can be divided into two regions:
o Anterior triangle – between the two sternocleidomastoid muscles down to the sternum
o Posterior triangle – between sternocleidomastoid and trapezius (little clinical significance)
The pharynx can be divided into three regions:
o Nasopharynx – from the posterior nares to the soft palate
o Oropharynx – from the soft palate to the superior margin of the epiglottis
o Laryngopharynx – from the superior margin of the epiglottis to the oesophagus
Describe the clinical anatomy of the neck
CERVICAL FASCIA AND COMPARTMENTS
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The neck contains unique sheets of cervical fascia arranged in various fascial layers:
o Superficial fascia – surrounds anterior neck; innervated by facial nerve (CNVII)
o Deep fascia – surrounds rest of the neck; several different layers:
 Investing layer – surrounds all structures within the neck
 Carotid sheaths – laterally; surround the neurovascular components
 Pre-tracheal layer – ventrally; surrounds the viscera
 Pre-vertebral layer – dorsally; surrounds the vertebrae and associated muscles
These fascia enclose four distinct longitudinal compartments within the neck:
o Vascular – two bilaterally; covered by carotid sheath
 Contain the internal jugular vein, common carotid artery and vagus nerve
o Visceral – ventrally; covered by pre-tracheal fascia
 Contains the pharynx, larynx, trachea, oesophagus and thyroid gland
o Vertebral – dorsally; covered by pre-vertebral fascia
 Contains the vertebral column and associated deep muscles
MUSCLES
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There are two important sets of muscles in the neck – the suprahyoid and infrahyoid (strap)
Supra-hyoid – includes mylo- and geniohyoid (see TSM31 - Mouth and Tongue)
o Digastric – two ‘bellies’; both insert around a looped tendon on the medial hyoid
 Anterior belly arises from the mandible; innervated by nerve to mylohyoid (of V3)
 Posterior belly arises from the mastoid process; innervated by facial nerve (CNVII)
o Stylohyoid – arises from the base of the styloid process and inserts onto the lateral hyoid
 Innervated by the facial nerve (CNVII)
o Generally these muscles depress the mandible or raise the hyoid depending which is fixed
Infra-hyoid – strap muscles; all innervated by C1-C3 via ansa cervicalis
o Omohyoid – most superficial, from the scapula to the lateral hyoid; crosses the carotid sheath
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Sternohyoid – long thin muscle, from the sternum to the hyoid
Thyrohyoid – deeper muscle, from the inferior margin of the thyroid cartilage to the hyoid
Sternothyroid – deepest, from the medial sternum to the inferior thyroid cartilage
These muscles either depress the hyoid or fix the hyoid so that the supra-hyoids can act
BRANCHES OF THE EXTERNAL CAROTID ARTERY
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The common carotid artery ascends the neck bifurcating at the superior margin of thyroid cartilage
o The internal carotid artery gives off no branches in the neck and ascends to the skull
The external carotid artery gives off numerous branches as it ascends the neck:
o Superior thyroid – descends from the bifurcation to supply the superior thyroid
o Ascending pharyngeal – small posterior branch supplying (around) the pharynx
o Lingual – anterior branch to the tongue with the lingual nerve and submandibular duct
o Facial – supplies the front of the face, soft palate, submandibular glands
o Occipital – posterior branch, ascends to supply the posterior scalp
o Posterior auricular – small branch supplying (around) the ear and parotid glands
The external carotid artery terminates in the parotid gland bifurcating into two terminal branches:
o Superficial temporal – supplies the parotid gland, lateral face and temple region
o Maxillary – larger branch, supplies numerous structures around the maxilla and mandible
Describe the clinical anatomy of the pharynx
CONSTRICTOR MUSCLES
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The pharynx is a muscular semicircular tube that extends from the base of the skull to the oesophagus
Three overlapping constrictor muscles with internal mucous linings make up the pharyngeal walls:
o Superior constrictor – from the pterygomandibular raphe to the pharyngeal tubercle
o Middle constrictor – from the hyoid bone
o Inferior constrictor – from the thyroid cartilage
These muscles are effectively suspended from the base of the skull at the pharyngeal tubercle
o They are all continuous posteriorly and meet along the pharyngeal raphe
o They are all innervated by branches of the vagus nerve (CNX)
o Anteriorly they are paired with lateral openings between them
o In swallowing they contract in a supero-inferior sequence to propel food to the oesophagus
LONGITUDINAL MUSCLES
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Along with the constrictors there are three longitudinal muscles that contribute to the laryngeal wall:
o Stylopharyngeus – from the styloid process; innervated by the glossopharyngeal nerve (CNIX)
o Salpingopharyngeus – from the auditory tube; innervated by the vagus nerve (CNX)
o Palatopharyngeus – from the palatine aponeurosis; innervated by the vagus nerve (CNX)
These muscles all act to elevate the pharynx - salpingopharyngeus also facilitates pressure
equalisation between the oropharynx and middle ear