--- module: 080-02 language: en chapter: 80 title: "Head, Neck, Cranial Nerves, Pharynx, and Larynx Anatomy" module_title: "Neck triangles, fascia, pharynx, larynx, thyroid, and deep spaces" source_sha256: c732e0651021fad60e16b025b33945445b305c00e398c89bbce1a41c20688ada --- # Neck, pharynx, larynx, thyroid, and deep spaces ## Triangles and fascia ### Sternocleidomastoid divides anterior and posterior triangles #### Anterior: submental, submandibular, carotid, muscular #### Posterior: divided by inferior omohyoid ### Investing layer encloses sternocleidomastoid, trapezius ### Pretracheal fascia: thyroid, trachea, oesophagus ### Prevertebral fascia extends as axillary sheath ### Carotid sheath: carotid, internal jugular, vagus #### Sympathetic trunk behind, in prevertebral fascia ### Retropharyngeal and danger spaces #### Infection descends to mediastinum ## Muscles and cervical roots ### Sternocleidomastoid turns face contralaterally ### Accessory nerve supplies sternocleidomastoid, trapezius ### Suprahyoids elevate hyoid or depress mandible ### Infrahyoids stabilise and depress hyoid #### Ansa cervicalis C1 to C3 ### Mylohyoid, anterior digastric: mandibular nerve ### Posterior digastric, stylohyoid: facial nerve ### Plexus and subclavian artery between scalenes #### Subclavian vein anterior to anterior scalene #### Phrenic nerve descends on anterior scalene ## Pharynx and swallowing ### Skull base to cricoid near C6 ### Constrictors propel, longitudinal muscles elevate ### Vagus supplies most muscles #### Stylopharyngeus glossopharyngeal ### Sensation: maxillary, glossopharyngeal, vagus by region ### Swallowing sequence #### Palate closes, hyoid and larynx elevate #### Vocal folds close, upper sphincter relaxes #### Protection needs timing and sensation ### Piriform recess traps foreign bodies #### Removal can injure internal laryngeal nerve ## Laryngeal skeleton ### C3 to C6, suspended from hyoid ### Cricoid complete ring, narrow in children ### Cricothyroid joint tilt changes fold tension ### Cricoarytenoid joint positions vocal process ### Internal laryngeal nerve pierces thyrohyoid membrane ### Cricothyroid membrane: emergency airway access ## Laryngeal muscles and nerves ### Posterior cricoarytenoid: only major abductor ### Lateral cricoarytenoid and arytenoids adduct ### Cricothyroid lengthens and tenses folds ### Recurrent nerve supplies all but cricothyroid #### Sensation below folds ### Internal superior laryngeal: sensation above folds ### Left recurrent loops under aortic arch #### Longer course exposed to mediastinal disease ### Unilateral palsy: dysphonia, paramedian fold ### Bilateral injury threatens airway ### External branch injury impairs pitch ## Thyroid, parathyroids, and trachea ### Isthmus anterior to second to fourth rings ### Pretracheal sheath links gland to larynx #### Thyroid moves with swallowing ### Superior thyroid artery near external laryngeal nerve ### Inferior thyroid artery varies with recurrent nerve ### Inferior parathyroids vary from thymic descent #### Ectopic glands from jaw to mediastinum ### Tracheostomy: cricoid, isthmus, vessels, pleura ## Oesophagus and major vessels ### Oesophagus begins at cricopharyngeus near C6 ### Killian region: weak site for diverticulum ### Carotid bifurcation near upper thyroid cartilage #### Carotid sinus senses pressure #### Carotid body senses blood gases ### Internal carotid has no neck branches ### Internal jugular joins subclavian behind joint ### Open neck veins can entrain air ## Deep neck infection and airway ### Mylohyoid divides submandibular space #### Bilateral cellulitis elevates tongue ### Submandibular duct crossed by lingual nerve ### Stones favour long ascending submandibular duct ### Parotid: nerve, vein, artery from superficial #### Secretomotor via otic ganglion ### Peritonsillar infection causes trismus ### Parapharyngeal space near carotid sheath ### Danger signs: stridor, drooling, secretions #### Plan airway before manipulation ## Clinical synthesis ### Longitudinal conduits crossed by mobile structures ### Know the expanding space and route to airway