The Neck Anatomy PDF

9. The Neck A: Bones of the Neck Cervical Vertebrae Typical cervical vertebrae (C3-C6) have: o Small vertebral body § Concave superiorly and convex inferiorly o Large and triangular vertebral foramen o...

9. The Neck A: Bones of the Neck Cervical Vertebrae Typical cervical vertebrae (C3-C6) have: o Small vertebral body § Concave superiorly and convex inferiorly o Large and triangular vertebral foramen o Transverse foramina in the transverse processes § Where vertebral arteries run towards the head o Superior facets of articular processes directed superoposteriorly o Inferior facets of articular processes directed inferoposteriorly o Short spinous processes Atlas (C1): o Ring-like and kidney shaped o Lacks a spinous process and body o Consists of 2 lateral masses connected by anterior and posterior arches o Concave superior articular facets receive the occipital condyles Axis (C2): o A peg-like dens projects superiorly from its body (odontoid process) Vertebra prominens (C7): o Has a long spinous process that is not bifid o Has large transverse processes but small transverse foramina Hyoid Lies anteriorly at the level of C3 between mandible and thyroid cartilage Has no articulations with any other bone Suspended from the styloid process of temporal bones by the stylohyoid ligaments Firmly bound to the thyroid cartilage Axis (C2 vertebra) 1 Zaid Ganie  B: Cervical Fascia Superficial Cervical Fascia Superficial Cervical Fascia Layer of fatty connective tissue lying between the dermis of the skin and the investing layer of the deep cervical fascia Thinner than superficial fascia in other regions of the body, especially anteriorly Contents: o Cutaneous nerves, blood and lymphatic vessels o Superficial lymph nodes o Variable amounts of fat o Platysma Cutaneous and superficial muscles of the neck Muscle Origin Insertion Innervation Main action Inferior border of mandible. Deep fascia covering Cervical branch Draws corners of mouth inferiorly Platysma Skin and subcutaneous tissue. superior parts of deltoid of facial nerve Tenses skin of the neck and pectoralis major Lateral surface of mastoid process Sternal head: anterior Motor: spinal Unilateral contraction: of temporal bone. surface of manubrium of accessory n. Tilts head to the same side. Lateral half of superior nuchal sternum. Pain and Bilateral contraction: Extends neck at SCM ligament. Clavicular head: superior proprioception: atlantooccipital joint. surface of medial third of C3 & C4 Brings chin to manubrium. clavicle. Thrusts chin forward while head is kept at the same level. Medial third of superior nuchal line. Lateral third of clavicle. Motor: spinal Descending part elevates scapulae. External occipital protuberance. Acromion and spine of accessory n. Ascending part depresses scapulae. Trapezius Nuchal ligament. scapula. Pain and All parts retract scapulae. Spinous processes of C7-T12 proprioception: Ascending and descending rotate vertebrae. C3 & C4 glenoid cavities superiorly. Deep Cervical Fascia 2 Layers of deep fascia: Relevance of the deep cervical fasciae: Investing Natural cleavage planes allowing tissues to be Pretracheal separated during surgery Prevertebral Limit the spread of abscesses resulting from infection Carotid Allows structures in the neck to move freely over one another without difficulty Investing layer: Most superficial layer of deep fascia Surrounds the entire neck deep to the skin and subcutaneous tissue At the 4 corners of the neck, it splits into superficial and deep layers to enclose the trapezius and sternocleidomastoid muscles o These muscles are both innervated by accessory nerve (CN XII) Superior attachments Inferior attachments o Superior nuchal lines of occipital bone o Manubrium of sternum o Mastoid processes of temporal bones o Clavicles o Zygomatic arches o Acromions and spines of scapulae o Inferior border of mandible o Hyoid bone o Spinous processes of cervical vertebrae Contents: o Sternocleidomastoid o Trapezius o Submandibular gland o Parotid gland (forms its fibrous capsule) Continuous with the periosteum of C7 spinous process and with the nuchal ligament Splits into 2 above the manubrium to enclose sternocleidomastoid o One layer attaches to the anterior and the other to the posterior surface of the manubrium o Suprasternal space- lies between these layers and encloses § Anterior jugular veins § Jugular venous arch § Fat § Deep lymph nodes 1. Pretracheal layer: Limited to the anterior part of the neck Extent: o inferiorly from the hyoid to thorax where it blends with the pericardium Has 2 parts: o Thin muscular part § Encloses infrahyoid muscles o Visceral part § Encloses thyroid gland, trachea and oesophagus continuous posteriorly and superiorly with the buccopharyngeal fascia of the pharynx blends laterally with the carotid sheaths 2. Prevertebral layer: Forms a tubular sheath for the vertebral column and the muscles associated with it o Anteriorly- longus colli and longus capitis o Laterally- scalenes o Posteriorly- deep cervical muscles Extent: o Superiorly- attached to cranial base o Inferiorly- blends with the endothoracic fascia peripherally and fuses with the anterior longitudinal ligament centrally at the T3 vertebra o Laterally- continuous with the axillary sheath 3 3. Carotid layer: Extent: cranial base to root of the neck o Communicates with mediastinum and cranial base- pathways for spread of infection and extravasated blood Blends anteriorly with investing and pretracheal layers and posteriorly with the prevertebral layer Contents: o Common and internal carotid arteries o Internal jugular vein o Vagus nerve o Carotid sinus nerve o Sympathetic nerve fibers (carotid periarterial plexuses) o Deep cervical lymph nodes Retropharyngeal space: Potential space consisting of loose connective tissue Extent: o Superiorly- between the prevertebral layer (deep) and buccopharyngeal fascia (superficial) o Inferiorly- the buccopharyngeal fascia is continuous with the pretracheal layer Alar fascia: Subdivides the retropharyngeal space (into anterior and posterior) Attached along the midline of the buccopharyngeal fascia from the cranium to C7 vertebral level o Extends laterally and terminated in the carotid sheath Closed superiorly by the cranial base and on each side by the carotid layer Opens inferiorly into the mediastinum Allows movement of the pharynx, oesophagus, larynx and trachea Spread of infections in the neck: If the infection occurs: Between the investing layer and muscular part of pretracheal fascia o Infection will not spread to mediastinum Between the investing layer and the visceral part of the pretracheal fascia o Infection can spread to thoracic cavity anterior to mediastinum Posterior to the prevertebral layer: o Pus may perforate the prevertebral layer and enter retropharyngeal space § Bulge in the pharynx causes difficulty swallowing and speaking In the head o May spread posterior to oesophagus to posterior mediastinum o May spread anterior to the trachea to the anterior mediastinum In the retropharyngeal space o May spread to the superior mediastinum 4  C: Anterior Triangles of the Neck Muscles of the anterior cervical region (extrinsic muscles of the larynx) Muscle Origin Insertion Innervation Main action Suprahyoid Muscles Mylohyoid Mylohyoid line of mandible Mylohyoid raphe and body of n. to mylohyoid Elevates hyoid, floor of mouth hyoid from CN V3 and tongue Geniohyoid Inferior mental spine of mandible Pulls hyoid anterosuperiorly C1 via CN XII Shortens floor of mouth and Body of hyoid widens pharynx Stylohyoid Styloid process of temporal Stylohyoid n. Elevates and retraces hyoid- from CN VII elongates floor of mouth Digastric Anterior belly: digastric fossa of Intermediate tendon to body n. to mylohyoid Depresses mandible against mandible and greater horn of hyoid from CN V3 resistance Posterior belly: mastoid notch of Digastric br. of Elevates and steadies hyoid temporal bone CN VII during swallowing/speaking Infrahyoid Muscles Sternohyoid Manubrium of sternum and medial Body of hyoid C1-C3 by a br. of Depresses hyoid after end of clavicle ansa cervicalis elevation during swallowing Omohyoid Superior border of scapula near Inferior border of hyoid Depresses, retracts and suprascapular notch steadies hyoid Sternothyroid Posterior surface of manubrium Oblique line of thyroid C2 -C3 by a br. of Depresses hyoid and larynx cartilage ansa cervicalis Thyrohyoid Oblique line of thyroid cartilage Inferior border of body and C1 via CN XII Depresses hyoid and elevates greater horn of hyoid larynx 5  Boundaries Contents Submental Triangle Lateral: Anterior bellies of digastric Anterior jugular veins muscle Submental lymph nodes Inferior: Hyoid bone Apex: Mandible Floor: Mylohyoid muscle Submandibular Triangle Superior: Ramus of mandible Submandibular gland Inferior anterior and posterior: Submandibular lymph nodes o Anterior belly of digastric muscle Hypoglossal nerve (CN XII) o Posterior belly of digastric muscle Nerve to mylohyoid Floor Parts of facial artery and vein o Mylohyoid muscle o Hyoglossus muscle o Middle constrictor muscle of the pharynx Roof: Investing fascia Muscular Triangle Superior: Superior belly of omohyoid Infrahyoid muscles Inferior: Anterior border of SCM Thyroid and parathyroid glands Medial: Midline Recurrent laryngeal nerve Floor: pretracheal fascia Carotid Triangle Superior: posterior belly of digastric Common carotid artery muscle Internal and external carotid artery Inferior: superior belly of omohyoid Carotid sinus and carotid body Lateral: anterior border of SCM Internal jugular vein Floor Glossopharyngeal nerve o thyrohyoid muscle Vagus nerve o middle constrictor muscle of the Spinal accessory nerve pharynx Hypoglossal nerve o inferior constrictor muscle of the Superior root of ansa cervicalis pharynx Branches of cervical plexus Thyroid gland Larynx and pharynx Deep cervical lymph nodes 6  D: Posterior Triangle of the Neck Boundaries of the posterior triangle Anterior: Posterior border of SCM Posterior: Anterior border of trapezius Inferior: Middle ⅓ of the clavicle Apex: At superior attachments of SCM and trapezius Roof: Investing fascia Floor: Prevertebral fascia and muscles o Splenius capitis, levator scapulae and middle, posterior and anterior scalene Divisions (divided by inferior belly of omohyoid) Occipital triangle Omoclavicular triangle Occipital Triangle Superficial contents Cutaneous branches of cervical plexus (C1-4) o Great auricular nerve o Lesser occipital nerve o Supraclavicular nerve o Transverse cervical nerve External jugular vein Superficial branch of transverse cervical artery Superficial cervical lymph nodes Deep contents Spinal accessory nerve (CN XI) Phrenic nerve Trunks and roots of brachial plexus Occipital artery Thyrocervical truck (1st part of subclavian a.) o Suprascapular artery o Transverse cervical trunk o Dorsal scapular artery o Ascending cervical artery o Inferior thyroid artery Omoclavicular Triangle Superficial contents Inferior part of external jugular vein Superficial cervical lymph nodes Deep contents 3rd part of subclavian artery and vein Suprascapular artery, vein and nerve Phrenic nerve Supraclavicular lymph nodes Trunks of brachial plexus 7  E: Prevertebral Muscles Muscle Innervation Main action Anterior vertebral muscles Longus colli Anterior rami of C2-C6 Flexes neck with rotation contralaterally if unilateral contraction Longus capitis Anterior rami of C1-C3 Rectus capitis anterior C1-C2 Flex head Anterior scalene C4-C6 Lateral vertebral muscles Rectus capitis lateralis C1-C2 Flexes and stabilises head Splenius capitis Posterior rami of middle cervical spinal nn. Lateral flexion and rotation of head on the same side Extends head and neck Levator scapulae Dorsal scapular n. (C5) & C3-C4 Downward rotation of scapula Middle scalene Anterior rami of cervical spinal nn. Flexes neck laterally Posterior scalene Anterior rami of C7-C8 F: Suboccipital Triangle Boundaries of the root of the neck: Inferior- superior thoracic aperture Lateral- 1st pair of ribs and their costal cartilages Anterior- manubrium of the sternum Posterior- T1 vertebra Boundaries Superomedial- rectus capitis posterior major Superolateral- obliquus capitis superior Inferior- obliquus capitis inferior Floor- posterior atlantooccipital membrane and posterior arch of C1 vertebra Roof- semispinalis capitis Contents Vertebral artery Suboccipital nerve 8  G: Arteries of the Neck Carotid Arterial System Medial view of right carotid artery Carotid arterial system At the level of the superior border of the thyroid cartilage, the common carotid divides into the internal and external carotid arteries. Carotid sinus: o A dilation of the proximal part of the internal carotid artery o Innervated mostly by the glossopharyngeal n. via the carotid sinus n., but also the vagus n. o Baroreceptor that reacts to changes in arterial blood pressure Carotid body: o Small reddish-brown ovoid mass lying in a septum on the medial side of the bifurcation o Innervated mainly by the carotid sinus n. and vagus n. o Chemoreceptor that monitors the levels of oxygen in the blood § Initiates a reflex that increases the rate and depth of respiration, cardiac rate and blood pressure Internal carotid artery Direct continuation of the common carotid a. superior to the origin of the external carotid a. Enters the cranium through carotid canal in the petrous part of the temporal bone External carotid artery Branch Direction Distribution Superior thyroid Anterior Thyroid gland, infrahyoid muscles and SCM and larynx Ascending pharyngeal Medial Pharynx, prevertebral muscles, middle ear and cranial meninges Lingual Anterior Tongue Facial Anterior Palatine tonsils, soft palate, pterygoid, mylohyoid, and digastric muscles, the submandibular gland, and all of the face Occipital Posterior Posterior scalp Posterior auricular Posterior Adjacent muscles, parotid gland, facial nerve, structures in the temporal bone, auricle and scalp Maxillary (Terminal branch) Superficial temporal (Terminal branch) Branches of external carotid artery: Some Anatomists Like Freaking Out Poor Medical Students 9  Subclavian Artery Course: o Arch superolaterally, reaching an apex as they pass posterior to anterior scalene muscles o As the descend, they lie posterior to the middle of the clavicles The parts of the subclavian artery are described relative to the anterior scalene o 1st part- medial to anterior scalene o 2nd part- posterior to anterior scalene o 3rd part- lateral to anterior scalene Branch Distribution Vertebral artery Medulla, spinal cord, cerebellum, deep muscles of the neck, dura mater of PCF Internal thoracic First 6 intercostal spaces 1 Suprascapular May arise independently. Supplies muscles on the posterior aspect of scapula Ascending cervical Lateral muscles of the upper neck and spinal branches into the intervertebral foramina Thyrocervical trunk Inferior thyroid Larynx, trachea, oesophagus, thyroid and parathyroid glands and adjacent muscles Transverse cervical Bifurcates into superficial cervical and dorsal scapular*. Supplies rhomboids, levator scapulae, trapezius and trunks of the brachial plexus 2 Costocervical trunk Superior intercostal First two intercostal spaces Deep cervical Posterior deep cervical muscles 3 Dorsal scapular* May arise from thyrocervical trunk. Participates in scapular arterial anastomosis Vertebral artery Cervical part o Ascends into the pyramidal space between the scalene and longus colli & capitis muscles Vertebral part o At the apex of the pyramidal space the artery passes deep to course through the foramina transversaria of vertebrae C1-C6 Suboccipital part o Courses in a groove on the posterior arch of the atlas and through the suboccipital triangle before entering the cranium through foramen magnum Cranial part o At the inferior border of pons, the right and left arteries join to form the basilar artery 10  H: Veins of the Neck Internal jugular vein: Commences at the jugular foramen in the posterior cranial fossa as the direct continuation of the sigmoid sinus Superior bulb- dilation at its origin Inferior bulb- dilation at the inferior end that has a bicuspid valve to prevent backflow into the vein Branches: o Occipital vein o Facial vein o Lingual vein o Superior laryngeal vein o Superior thyroid vein o Middle thyroid vein o Pharyngeal vein External jugular vein: (superficial to deep fascia) Begins near the angle of the mandible Posterior division of the retromandibular vein unites with posterior auricular vein Crosses the SCM obliquely and pierces investing fascia at the posterior border Receives the cervicodorsal, suprascapular and anterior jugular veins Terminates in the subclavian vein Subclavian vein Passes anterior to the anterior scalene muscle and phrenic nerve Unites at the medial border of anterior scalene with internal jugular vein to form brachiocephalic vein Anterior Jugular vein Arises near the hyoid from confluence of the superficial submandibular veins Superior to the manubrium they unite across the midline to form the jugular venous arch in the suprasternal space 11  I: Nerves of the Neck Cervical Plexus Lies anteromedial to levator scapulae and middle scalene muscles and deep to SCM Superficial branches are sensory (cutaneous) and pass posteriorly o Emerge around the middle of the posterior border of SCM at the nerve point of the neck Deep branches are motor and pass anteromedially Branch Origin Distribution Cutaneous Lesser occipital Anterior ramus of C2 Skin of the neck and scalp posterosuperior to the auricle Greater auricular Anterior rami of C2&C3 Skin over the parotid gland, mastoid process and auricle Transverse cervical Anterior rami of C2&C3 Divides into superior and inferior branches to supply skin of anterior cervical region Supraclavicular nerves Anterior rami of C3&C4 Skin over the shoulder Motor Anterior ramus of C1 Geniohyoid and thyrohyoid Ansa cervicalis via CN XII Anterior rami of C1-C3 Omohyoid, sternohyoid and sternothyroid Phrenic Anterior rami of C3-C5 Runs posterior to subclavian v. and anterior to internal thoracic a. and enters thorax (Chiefly C4) Cranial Nerves in the Neck Nerve Course Branches Carotid branch- carotid body and sinus Leaves cranium through jugular foramen and follows stylopharyngeus. Branches to stylopharyngeus Glossopharyngeal Passes between superior and middle pharyngeal constrictors to reach Nerve to palatine tonsil oropharynx and tongue Branches to posterior third of tongue Pharyngeal branches Tympanic n. ® lesser petrosal n. Auricular branch Leaves cranium through jugular foramen and enters carotid sheath. Pharyngeal plexus Vagus Continues to root of the neck to enter thorax through superior thoracic Cervical cardiac branches aperture Superior laryngeal nerve Recurrent laryngeal nerves Emerges as rootlets from C1-C5 and ascends through the foramen Spinal accessory magnum. It briefly joins the vagus nerve and separates as it leaves Branches to trapezius and SCM the jugular foramen. It descends along the internal carotid a. Branches to all extrinsic and intrinsic Leaves cranium through hypoglossal canal where it is joined by muscles of the tongue besides Hypoglossal superior root of ansa cervicalis. It passes medial to angle of mandible palatoglossus and between mylohyoid and hyoglossus to reach the tongue Carries C1 fibres to geniohyoid and thyrohyoid 12  J: Thyroid and Salivary Glands Thyroid and Parathyroid Glands Thyroid Gland: Location Lies deep to the sternothyroid and sternohyoid muscles Located anteriorly in the neck at the level of C5-T1 vertebrae Anteriorly- o Loose sheath formed by pretracheal fascia o Sternohyoid and sternothyroid Posteriorly- cricoid cartilage and upper 2-3 tracheal rings Posterolateral- carotid sheaths and their contents Structure Consists primarily of right and left lobes anterolateral to the larynx and trachea A thin isthmus unites the lobes over the trachea anterior to 2nd and 3rd tracheal rings Surrounds by a thin fibrous capsule which sends septa deeply into the gland Function Endocrine gland- ductless gland that secretes directly into the blood Secretes o Thyroid hormone § Acts on whole body except itself, the uterus and spleen § Controls metabolic rate o Calcitonin § Controls calcium metabolism Arterial supply Superior and inferior thyroid arteries lie between the fibrous capsule and loose fascial sheath Superior thyroid artery from external carotid artery: o Descends to superior poles of the gland, pierces pretracheal layer o Supplies anterosuperior aspect Inferior thyroid artery from thyrocervical trunk of subclavian artery: o Run superomedially posterior to carotid sheaths o Supplies posteroinferior aspect Thyroid ima artery o In 10% of people o Small unpaired artery ascending on the anterior surface of trachea to supply the gland 13  Venous Drainage Thyroid venous plexus on the anterior surface is formed by 3 veins: o Superior thyroid veins § Accompany the superior thyroid veins § Drain the superior poles o Middle thyroid veins § Run parallel to the inferior thyroid arteries § Drain the middle lobes o Inferior thyroid veins § Run independently § Drain the inferior poles Superior and middle thyroid veins drain into the internal jugular veins Inferior thyroid vein drains into the brachiocephalic vein posterior to manubrium Lymphatic Drainage Lymphatic vessels run in the interlobular connective tissue Communicate with a capsular network of lymphatic vessels Superiorly o Prelaryngeal lymph nodes drain into superior deep cervical lymph nodes Inferiorly o Pretracheal and paratracheal lymph nodes drain into inferior deep cervical nodes Laterally o Vessels located along the superior thyroid veins pass directly into the inferior deep cervical lymph nodes Some vessels drain into brachiocephalic nodes or thoracic duct Innervation Sympathetic o Superior middle and inferior cervical ganglia via § Cardiac periarterial plexus § Superior thyroid periarterial plexus § Inferior thyroid periarterial plexus Parasympathetic o Superior and recurrent laryngeal nerves from vagus nerve All fibres are vasomotor o They constrict blood vessels NB: Secretion from the gland is hormonally regulated by pituitary gland (no secretomotor fibres to this gland) Recurrent laryngeal nerves: Arise from vagus nerve in the inferior part of the neck Right recurrent loops inferior to right subclavian a. at T1-T2 Left recurrent loops inferior to aortic arch at T4-T5 Both ascend superiorly to the posteromedial aspect of the thyroid gland 14 Parathyroid glands: Location and structure: o Small flattened, oval glands o Lie external to the thyroid capsule on the medial half of the posterior surface of each lobe of the thyroid gland within the pretracheal fascia o Superior parathyroid glands § Less variable in position § 1 cm superior to piercing of inferior thyroid a. § Level of inferior border of cricoid cartilage o Inferior parathyroid glands § Variable in position § 1 cm inferior to piercing of inferior thyroid a. Function: o Secretes Parathormone (PTH) § Regulates calcium and phosphorus metabolism § Targets the skeleton, kidneys and intestines Arterial supply: o Primarily supplied by inferior thyroid a. o May also be supplied by § Superior thyroid a. § Thyroid ima a. § Laryngeal a. § Tracheal. § Oesophageal a. Venous drainage: o Parathyroid veins § Drain into thyroid venous plexus Lymphatic drainage o Run along thyroid vessels deep cervical lymph nodes and paratracheal lymph nodes Innervation o Vasomotor fibres from thyroid branches of the cervical ganglia o No secretomotor fibres- the gland is hormonally regulated Salivary Glands Saliva is secreted by the parotid, submandibular and sublingual glands and the mucous glands of the oral cavity Functions of saliva: o Keeps the mucosa moist o Lubricates food during mastication o Begins the digestion of starches o Prevents tooth decay Accessory salivary glands are scattered over the palate, lips, cheeks and tongue 15  Submandibular glands: Lies along the body of the mandible Submandibular duct: o 5cm long o Arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscles o As it runs anteriorly, the lingual nerve loops underneath o Opens by 1 or 3 orifices on a small sublingual papilla beside the base of the frenulum of the tongue Arterial supply: o Submental arteries Venous drainage: o Submental veins Lymphatic drainage: o Jugulo-omohyoid lymph nodes of the deep cervical lymph nodes Innervation: Presynaptic parasympathetic secretomotor fibres of facial n. ® chorda tympani ® lingual n. ® Submandibular ganglion ® gland Postsynaptic sympathetic vasoconstrictive fibres from superior cervical ganglion Sublingual glands: Smallest and most deeply situated and almond-shaped Lie in the floor of the mouth between the mandible and the genioglossus The glands from each side unite to form a horseshoe-shaped mass around the connective tissue core of the frenulum of the tongue Numerous small sublingual ducts open on the floor of the mouth along the sublingual folds Arterial supply: o Sublingual a. (from lingual a.) and submental a. (from facial a.) Innervation: o Accompany submandibular gland innervation Parotid glands: Location: o Lies in parotid region o Superior: zygomatic arch o Posterior: ear and anterior border of SCM o Medial: ramus of mandible o Anterior: medial border of masseter o Inferior: angle of mandible Content of parotid region: o Parotid gland and duct o Parotid plexus of facial nerve o External carotid artery o Retromandibular vein o Masseter muscle Structure: o Largest of the salivary glands o Enclosed within a tough fascial capsule o Has an irregular shape since it is wedged between the ramus of the mandible and the mastoid process Parotid duct: o Passes horizontally from anterior edge of the gland o At anterior border of masseter, it turns medially to pierce buccinator o Enters the oral cavity through a small orifice opposite the 2nd maxillary molar tooth Blood supply: o Posterior auricular artery from external carotid o Superficial temporal artery from external carotid 16  Venous drainage: o Retromandibular vein Embedded within the parotid gland: o Parotid plexus of the facial nerve o Retromandibular vein o External carotid artery Innervation: Presynaptic parasympathetic secretomotor fibres of glossopharyngeal n. ® otic ganglion sensory fibres of auriculotemporal n. (from CN V3) (via auriculotemporal n.) Sympathetic cervical ganglia ® sympathetic vasomotor fibres of external carotid plexus ® parotid gland Sensory fibres of great auricular n. 17  K: Pharynx and Cervical Oesophagus Pharynx Superior expanded part of the oesophagus posterior to the nasal and oral cavities Extent: o Superior- cranial base o Inferior- inferior border of cricoid cartilage at the level of C6 vertebra o Anterior- nasal cavity, oral cavity and larynx o Posterior- buccopharyngeal fascia Widest opposite hyoid (5 cm) and narrowest at junction with oesophagus (1.5 cm) flat posterior wall lies against the prevertebral layer of deep cervical fascia divided into 3 parts o Nasopharynx- posterior to the nose and superior to the soft palate o Oropharynx- posterior to mouth o Laryngopharynx- posterior to the larynx Nasopharynx Has a respiratory function Posterior extension of the nasal cavities Borders: o Anterior- choana and soft palate o Posterior- basilar part of the occipital bone and C1 vertebra o Roof- body of sphenoid Features: o Tonsils (aggregates of lymphoid tissue) § Pharyngeal (adenoid) tonsil- in the mucosa of the roof and posterior wall of the nasopharynx § Tubal tonsils- in the submucosa of the pharynx near the nasopharyngeal opening o Opening of the pharyngotympanic tube o Salpingopharyngeal fold § Extends inferiorly from the medial end of the pharyngotympanic tube § Vertical fold of the mucosa § Covers the salpingopharyngeus muscle o Torus tubarius § Superior to the opening of the pharyngotympanic tube o Pharyngeal recess § Posterior to the torus tubarius and salpingopharyngeal fold § Extends laterally and posteriorly o Ridge of levator veli palatini 18 Oropharynx Has a digestive function Boundaries: o Superior- soft palate and uvula o Inferior- base of the tongue and superior border of epiglottis o Lateral- palatopharyngeal and palatoglossal arches o Posterior- pharyngobasilar fascia over palatopharyngeus, superior constrictor and body of C2 Contents: o Palatine tonsils § On each side of the oropharynx in the tonsillar bed between the palatine arches (palatopharyngeal and palatoglossal arches) o Tonsillar bed § Formed by the superior pharyngeal constrictor and the thin, fibrous sheet of pharyngobasilar fascia Fascia blends with the periosteum of the cranial base o Lingual tonsils § On the posterior third of the tongue Pharyngeal lymphatic (Waldeyer’s) ring 1 pharyngeal tonsil 2 tubal tonsils 2 palatine tonsils 1 lingual tonsil 2 lateral bands 19 Laryngopharynx Lies posterior to the larynx Boundaries: o Superior- superior border of the epiglottis and pharyngoepiglottic folds o Inferior- inferior border of the cricoid cartilage o Anterior- larynx o Posterior- pharyngobasilar fascia, middle and inferior constrictor muscles and C4- C6 vertebrae o Lateral- pharyngobasilar fascia and middle and inferior constrictor muscles Features: o Laryngeal inlet § Communication between the laryngopharynx and the larynx on the anterior wall o Piriform fossa (recess) § Small depression of the laryngopharyngeal cavity on either side of the laryngeal inlet § Laterally bounded by the medial surfaces of the thyroid cartilage and the thyroid membrane § Branches of the internal and recurrent laryngeal nerves lie deep to its mucosa Vulnerable to injury when a foreign body lodges in the fossa o Aryepiglottic fold § Separates the piriform fossa from the laryngeal inlet Pharyngeal muscles: Arranged with longitudinal muscles internally and circular muscles externally Circular muscles are the pharyngeal constrictors Internal longitudinal muscles elevate the larynx and shorten the pharynx during swallowing/speaking Fascial lining: o Strong internal pharyngobasilar fascia o Thin external buccopharyngeal fascia (blends with the pretracheal layer of deep cervical fascia) Constrictors contract involuntarily for sequential contraction 20  External layer- pharyngeal constrictors Muscle Origin Insertion Innervation Main Action Superior Pterygoid hamulus Pharyngeal tubercle on Pharyngeal br. of vagus n. Pterygomandibular raphe basilar part of occipital pharyngeal plexus Adjacent part of mandible bone Middle stylohyoid ligament Pharyngeal br. of vagus n. Constrict walls of greater and lesser horns pharyngeal plexus pharynx during of hyoid Pharyngeal raphe br. of external and swallowing Inferior Oblique line of thyroid recurrent laryngeal nn. of cartilage vagus n. Side of cricoid cartilage Internal layer- longitudinal muscles Muscle Innervation Main Action Palatopharyngeus Pharyngeal br. of vagus n. Salpingopharyngeus pharyngeal plexus Elevate (shorten and widen) pharynx and larynx during swallowing and speaking Stylopharyngeus Glossopharyngeal n. 21 Gaps in the pharyngeal constrictor muscles: Gap Contents Levator veli palatini 1. Between superior pharyngeal constrictor and cranium Pharyngotympanic tube Ascending palatine artery Stylopharyngeus 2. Between superior and middle pharyngeal constrictors Glossopharyngeal nerve (CN IX) Stylohyoid ligament 3. Between middle and inferior pharyngeal constrictors Internal laryngeal nerve Superior laryngeal artery and vein 4. Inferior to the inferior pharyngeal constrictor Recurrent laryngeal nerve Inferior laryngeal artery and vein Arteries of the pharynx tonsillar branch of facial a. Ascending & descending palatine a. From external carotid a. o Lingual a. o Superior thyroid a. o Ascending pharyngeal a. Inferior thyroid a. from subclavian a. Veins of the pharynx Inferior part: o External palatine v. to pharyngeal venous plexus to pterygoid venous plexus o Thyroid vv. to IJV Nerves of the pharynx Derives from pharyngeal nerve plexus Motor fibres o From vagus n. to all muscles of pharynx and soft palate except tensor veli palatini and stylopharyngeus o From glossopharyngeal n. to stylopharyngeus o From mandibular n. to tensor veli palatini Sympathetic vasomotor fibres o From superior cervical ganglion to blood vessels Sensory fibres o From glossopharyngeal n. to all parts of the pharynx o From maxillary nerve to mucosa of anterior and superior nasopharynx Cervical Oesophagus Muscular tube connecting the pharynx to the stomach Begins at the pharyngo-oesophageal junction o Narrowest part of the oesophagus o Cricopharyngeal part of the inferior pharyngeal constrictor acts as a sphincter First third is voluntary, middle is mixed, last third is involuntary Cervical oesophagus- part of the voluntary upper third o Begins immediately posterior to the inferior border of the cricoid cartilage § Level of C6 vertebra o Inclines slightly to the left as it descends into the superior mediastinum § Enters through superior thoracic aperture and becomes thoracic oesophagus Slit-like lumen when empty Lumen expands for food bolus which elicits reflex peristalsis in the inferior two thirds 22 Relations Anterior- o Trachea (attached by loose connective tissue) o Recurrent laryngeal nerves (in tracheo-oesophageal groove) Posterior- cervical vertebrae Lateral- o Right and left lobes of thyroid gland o Carotid sheath and its contents o Thoracic duct on the left Inferior- o Cervical pleura at the root o Thoracic duct Arteries Branches of the inferior thyroid aa. o Gives off ascending and descending branches that anastomose and cross the midline Veins Inferior thyroid vv. Nerves Somatic motor and sensory to upper half and autonomic and visceral sensory to lower half somatic fibres via branches from the recurrent laryngeal nerves vasomotor fibres from the cervical sympathetic trunks via the plexus around the inferior thyroid artery 23  L: Larynx Composed of 9 cartilages connected by ligaments and membranes and contains vocal folds Located in the anterior neck at the level of the bodies of C3-C6 vertebrae Connects the inferior part of the pharynx with the trachea Functions: o Valve routing air and food § Upward and forward movements facilitate the closing of the laryngeal inlet and opening of the oesophagus o Voice production § Vocal ligament and intrinsic muscles o Airway patency § Serves as the sphincter of the lower respiratory tract Laryngeal Skeleton Consists of 3 single cartilages (thyroid, cricoid and epiglottic), 3 paired cartilages (arytenoid, corniculate and cuneiform), extrinsic and intrinsic membranes Single cartilages: 1. Thyroid cartilage o Largest of the cartilages o Superior border lies opposite C4 vertebra o Laminae: § Two plate-like regions of the inferior 2/3 of the cartilage that fuse anteriorly in the median plane to form the laryngeal prominence (Adam’s apple) o Superior thyroid notch: § V-shape superior to the laryngeal prominence where the laminae diverge o Inferior thyroid notch: § Shallow indentation in the middle of the inferior border of the cartilage o Superior and inferior horns: § Superior and inferior projections of the posterior border of each lamina o Median thyroid ligament: § Thick part in the median part of the thyrohyoid membrane o Lateral thyrohyoid ligaments: § Thick parts in the lateral parts of the thyrohyoid membrane o Cricothyroid joints: § Articulation between the inferior horns of the thyroid cartilage and the lateral surfaces of the cricoid cartilage § Movements- rotation and gliding of the thyroid cartilage ® change in length of vocal folds 24 2. Cricoid cartilage o Smaller than thyroid cartilage but thicker and stronger o Cricoid is the only complete ring of cartilage to encircle any part of the airway o Lamina: § Posterior part of cricoid § Depressions for attachment of posterior cricoarytenoids § Vertical ridge for attachment to oesophagus o Arch: § Anterior part of cricoid o Median cricothyroid ligament: § Attachment of the cricoid to the inferior margin of the thyroid cartilage 3. Epiglottis o Consists of elastic cartilage for flexibility o Heart-shaped and covered with mucous membrane o Located posterior to the root of the tongue and the hyoid and anterior to the laryngeal inlet o Forms the superior part of the anterior wall and the superior margin of the inlet o Has a broad, free superior end o Stalk of the epiglottis: § Attached to the angle formed by the thyroid laminae Extrinsic laryngeal membranes: 1. Thyrohyoid membrane: o Attachment of the superior border and the superior horns of the thyroid cartilage to the hyoid 2. Hyo-epiglottic ligament: o Attaches to the anterior surface of the epiglottic cartilage to the hyoid 3. Thyro-epiglottic ligament: o Attaches the stalk of epiglottis to the angle formed by the laminae of the thyroid cartilage 4. Crico-tracheal ligament: § Attachment of the cricoid to the first tracheal ring 25  Paired cartilages: 1. Arytenoid o Paired, 3-sided pyramidal cartilages o Articulate with the lateral parts of the superior border of the cricoid cartilage lamina o Apex superiorly, vocal process anteriorly and muscular process laterally o Apex- bears the corniculate cartilage and attaches to aryepiglottic fold o Vocal process- provides the posterior attachment for the vocal ligament o Muscular process- lever to which the posterior and lateral cricoarytenoid muscles are attached o Cricoarytenoid joints: § Located between the bases of the arytenoid cartilages and the superolateral surfaces of the lamina of the cricoid cartilage § Permit the arytenoid cartilages to slide toward or away from one another to tilt anteriorly and posteriorly to rotate 2. Corniculate o Appears as a small nodule in the posterior part of the aryepiglottic fold o Attaches to the apex of the arytenoid cartilage 3. Cuneiform o Appears as a small nodule in the posterior part of the aryepiglottic fold o Does not directly attach to other cartilages Intrinsic laryngeal membranes Fibroelastic membrane of the larynx Composed of 2 parts: 1. Conus elasticus (cricovocal membrane) Inferior attachment o Arch of the cricoid cartilage Superior attachments o Anterior- thyroid cartilage o Posterior- vocal processes of arytenoids Vocal ligament- thickened medial part of membrane under the vocal fold Median cricothyroid ligament- anterior thickening in the midline of the membrane 2. Quadrangular membrane Runs between the lateral margin of the epiglottis and the anterolateral surface of the arytenoid cartilage Attached to the corniculate cartilage Vestibular ligament- thickened free lower margin under the vestibular fold o Attached posteriorly to the anterolateral surface of the arytenoid o Attached anteriorly to the thyroid angle just superior to the vocal ligament 26 Cavity of the larynx Superior aperture: o Laryngeal inlet o Opens into the anterior aspect of the pharynx below the posterior tongue o Boundaries: § Anteriorly- mucosa covering the superior margin of the epiglottis § Laterally- aryepiglottic folds § Posteriorly- interarytenoid notch in the midline Inferior aperture: o Continuous with the trachea o Completely encircled by the cricoid cartilage o Always open (unlike superior aperture which can be closed by the epiglottis) Regions of the cavity: 1. Vestibule o Upper chamber o Between the laryngeal inlet and the vestibular folds (membrane enclosing vestibular ligaments) 2. Middle part o Between the vestibular folds above and vocal folds (membrane enclosing vocal ligaments) below 3. Infraglottic space o Inferior chamber o Between the vocal folds and inferior aperture Laryngeal ventricles and saccules: o Mucosa of the middle cavity bulges laterally o Between the vestibular and vocal ligaments o Laryngeal ventricle- trough shaped space produced by mucosal bulging o Laryngeal saccule- tubular extension of each ventricle § Projects antero-superiorly between vestibular fold and thyroid cartilage § Contains numerous mucous glands to lubricate the vocal folds Rima vestibuli: o Triangular opening between the adjacent vestibular folds o Apex is anterior and base is formed by posterior wall of laryngeal cavity Rima glottidis: o Inferior to the rima vestibuli and narrower o Triangular opening between the adjacent vocal folds o Base of the triangle is formed by interarytenoid fold (mucosa covering interarytenoid notch) Both rima glottidis and rima vestibuli can be opened and closed by movement of cartilages 27  Intrinsic Laryngeal Muscles Adjust the tension in the vocal ligaments to open and close the rima glottidis Control the inner dimensions of the vestibule and close the rima vestibuli Facilitate closing of the laryngeal inlet Muscle Origin Insertion Main Action Innervation Cricothyroid Anterolateral part of Oblique part- inferior horn Forward and downward External br. of superior arch of cricoid of thyroid cartilage rotation of thyroid cartilage laryngeal n. from vagus Straight part- inferior at cricothyroid joint n. margin of thyroid cartilage Tenses vocal ligament Posterior crico-arytenoid Posterior surface of Vocal process of arytenoid Abduction and external lamina of cricoid rotation of arytenoid (opens rima glottidis) Lateral crico-arytenoid Superior surface of Vocal process of arytenoid Internal rotation of arytenoid arch of cricoid (closes rima glottidis) Transverse arytenoid Posterior surface of Posterior surface of Adduction of arytenoids Recurrent laryngeal br. arytenoid opposite arytenoid of vagus n. Oblique arytenoid Muscular process of Apex of opposite arytenoid Sphincter of laryngeal inlet arytenoid Aryepiglottic part- extends into aryepiglottic fold Thyroarytenoid Thyroid angle and Anterolateral part of Sphincter of vestibule and cricothyroid ligament arytenoid laryngeal inlet Lateral margin of epiglottis Relaxes vocal ligament vocalis Vocal process of Ipsilateral vocal ligament Adjusts tension (minutely) in arytenoid Thyroid angle vocal folds Abductors- posterior crico-arytenoids Adductors- lateral crico-arytenoids, transverse and oblique arytenoids Sphinters- adductors and aryepiglottic part of oblique arytenoids Tensors- cricothyroid muscles Relaxers- thyroarytenoid muscles NB: vocalis is medial to thyroarytenoid 28  Arteries of the larynx Superior laryngeal artery o Branch of superior thyroid artery o Pierces thyrohyoid membrane o Supplies superior internal surface of larynx o Accompanied by superior laryngeal nerve Inferior laryngeal artery o Branch of inferior thyroid artery o Accompanied by recurrent laryngeal nerve o Supplies inferior internal surface of larynx Veins of the larynx Superior laryngeal vein o To superior thyroid v. to IJV Inferior laryngeal vein o To inferior thyroid v. to left brachiocephalic v. Lymphatic drainage Above vocal folds: o Superior deep cervical lymph nodes Below vocal folds: o Pretracheal or paratracheal lymph nodes to inferior deep cervical lymph nodes Innervation Vagus nerve Superior laryngeal Recurrent laryngeal Internal laryngeal External laryngeal Inferior laryngeal Sensory motor motor sensory and autonomic Anterior Posterior Cricothyroid Inferior pharyngeal constrictor Laryngeal mucosa above Posterior cricoarytenoid Laryngeal vocal folds Transverse and oblique mucosa arytenoids below vocal folds Lateral cricoarytenoid Thyro-arytenoid Vocalis Aryepiglottic part of oblique arytenoids Thyroepiglottic 29  M: Lymphatic Drainage of the Head and Neck Superficial tissues drain to superficial cervical lymph nodes o Located along the course of the external jugular vein Drains into the inferior deep cervical lymph nodes Drains into the supraclavicular group of nodes o Accompanies the cervicodorsal trunk The main group of deep cervical lymph nodes forms a chain along the IJV o Mostly behind SCM Efferent vessels from deep cervical lymph nodes join to form the jugular lymphatic trunks o Jugular lymphatic trunk joins the thoracic duct on the left side o Jugular lymphatic trunk enters the junction of the internal jugular and subclavian veins on the right Thoracic duct passes superiorly through the superior thoracic aperture along the left border of the oesophagus o Arches laterally in the root of the neck § posterior to carotid sheath § anterior to sympathetic trunk and vertebral and subclavian arteries o Enters the left brachiocephalic vein at the junction of the subclavian vein and IJV 30