The Neck

1. The Neck Head & Neck Unit – Lecture 11 د. حيدر جليل الأعسم

2. The Neck It is the region of the body that lies between lower borders of the mandible (superiorly) and suprasternal notch and upper border of clavicle (inferiorly). Posteriorly, the neck extends from the superior nuchal line to intervertebral disc between C7 & T1 vertebrae. Compartments of the Neck: Visceral compartment:is anterior and contains parts of digestive system (pharynx &esophagus) and respiratory systems (larynx & trachea), and several endocrine glands; Vertebral compartment: is posterior and contains cervical vertebrae covered posteriorly by a large mass of extensor muscles and anteriorly a smaller group of flexor muscles. Two Vascular compartments which are lateral and contain the vertically running carotid arteries, internal jugular veins, vagus nerve, and deep cervical lymph nodes.

3. Sternocleidomastoid Muscle It is the Key Muscle of the Neck It divides the neck into anterior and posterior triangles. Its anterior border covers carotid arteries, internal jugular vein, and deep cervical lymph nodes; it also overlaps thyroid gland. It is covered superficially by skin, fascia, platysmamuscleand external jugular vein. Deep surface of posterior border is related to cervical plexus of nerves, phrenic nerve, and upper part of brachial plexus. Origin:Manubrium sterni (sternal head) and medial third of clavicle (clavicular head) Insertion:Mastoid process of temporal bone and occipital bone Action:Two muscles acting together flex neck draw head forward; one muscle rotates face to opposite side. Nerve Supply: Spinal part of accessory nerve and anterior rami of C2 & C3.

4. Neck Superficial structures 1. Skin of the Neck: Natural cleavage lines are horizontal around the neck 2. Superficial Cervical Fascia: thin layer enclosing other structures of the neck platysma muscle, cutaneous nerves, superficial veins & superficial lymph nodes 3. Platysmais a thin muscular sheet embedded in superficial fascia. 4. Deep Cervical Fascia: It is deep to superficial layer and is condensed in certain areas to form well-defined fibrous sheets. 5. Cutaneous Nerves of the neck: Posterior rami of cervical nerves C2 to C5. Anterior rami of cervical nerves C2 to C4. 6. Superficial Veins of the neck: A. External Jugular Vein B. Anterior Jugular Veins 7. Superficial Lymph Nodes: lie along external jugular vein superficial to sternocleidomastoid muscle.

5. Cutaneous Nerves of the neck Posterior rami of cervical: C2 to C5 supply skin overlying back of the neck and back of the scalp as high as the vertex. Greater occipital nerve: is a branch of the posterior ramus of the 2nd cervical nerve. Anterior rami of cervical: Nerves C2 to C4: supply front & sides of neck & form cervical plexus from which different branches emerges around the posterior border of sternocleidomastoid: 1. Lesser occipital nerve (C2) 2. Great auricular nerve (C2 & C3) 3. Transverse cutaneous nerve (C2 & C3) 4. Supraclavicular nerves (C3 & C4)

6. Superficial Veins of the neck External Jugular Vein It begins behind angle of mandible by union of posterior auricular vein& posterior division of Retromandibular vein. It descends obliquely across sternocleidomastoid and just above clavicle, pierces deep fascia and drains into Subclavian vein. Anterior Jugular Veins: begin just below chin (by union of several small veins) and runs downword close to the midline. The two sides united by a transverse trunk (jugular arch) just above suprasternal notch. The vein then turns sharply laterally and passes deep to sternocleidomastoid muscle to drain into external jugular vein.

7. Muscular Triangles of the Neck Sternocleidomastoid divides the neck into: Anterior Triangle: bounded above by body of mandible, posteriorly by anterior border of sternocleidomastoid, and anteriorly by midline. The Superficial neck muscles in anterior triangle of neck are divided into suprahyoid & infrahyoid muscles. Anterior triangle is further subdivided by superficial muscles into carotid, submandibular, submental & muscular triangle. Posterior Triangle: is bounded posteriorly by trapezius muscle, anteriorly by posterior border of sternocleidomastoid & inferiorly by middle 1/3 of clavicle. Posterior triangle is further subdivided by inferior belly of omohyoid into a large occipital triangle above & a small supraclavicular triangle below.

8. Suprahyoid Muscles They are 4 suprahyoid muscles in submental and submandibular triangles. They pass from hyoid bone to skull or mandible and raise the hyoid. 1. Stylohyoid:arises from base of styloid process and passes anteroinferiorly to attach to lateral area of the body of hyoid bone. During swallowing it pulls hyoid bone posterosuperiorly and is innervated by facial n. 2. Digastric: has two bellies connected by a tendon, which attaches to the body of hyoid bone: Posterior bellyarises from mastoid notch on medial side of mastoid process of temporal bone; Anterior bellyarises from digastric fossa on lower inside of mandible. Action:When mandible is fixed, it raises hyoid bone; and when hyoid bone is fixed, it lowers the mandible. Innervation: posterior belly by the facial nerve, whereas anterior belly is by trigeminal nerve. 3. Mylohyoid: Floor of the mouth 4. Geniohyoid: Floor of the mouth

9. Infrahyoid Muscles They are 4 infrahyoid muscles in the muscular triangles. Because of their appearance, they are sometimes referred to as the 'strap muscles'. 1. Sternohyoid: is a long, thin muscle originating from posterior aspect of sternoclavicular joint and adjacent manubrium and inserted onto body of hyoid bone. It depresses the hyoid & innervated by ansa cervicalis. 3. Omohyoid: is lateral to sternohyoid muscle and consists of two bellies with an intermediate tendon that is attached to clavicle by fascial sling. It depresses and fixes hyoid bone. It is innervated by the ansa cervicalis. Inferior belly: begins on superior border of scapula, medial to suprascapular notch, and passes forward and upward across the posterior triangle ending at the intermediate tendon; Superior belly: begins at intermediate tendon & attached to body of hyoid.

10. Infrahyoid Muscles They are 4 infrahyoid muscles in the muscular triangles. Because of their appearance, they are sometimes referred to as the 'strap muscles'. 3. Thyrohyoid: It is deep to superior parts of omohyoid and sternohyoid. Originating at oblique line on lamina of thyroid cartilage it passes upwards to insert into greater horn and adjacent aspect of body of hyoid. It depresses hyoid, but when hyoid is fixed it raises the larynx. It is innervated by C1 fibers through hypoglossal nerve. 4. Sternothyroid: It lies beneath sternohyoid, and in continuity with thyrohyoid. It arises from posterior surface of the manubrium of sternum and passes upwards to attach to oblique line on lamina of thyroid cartilage. Sternohyoid muscle draws the larynx (thyroid cartilage) downward and is innervated by ansa cervicalis.

11. Subdivisions of Anterior Triangle

12. Carotid System Common carotid arteries: Right common carotid: from brachiocephalic trunk - right sternoclavicular joint. (neck only?) Left common carotid: direct branch of aortic arch - left sternoclavicular joint. (thorax & neck) Both arteries ascend through neck lateral to Trachea & esophagus and behind anterior border of sternocleidomastoid (within a fascial compartment (Carotid Sheath). its course is closely related to internal jugular vein & vagus nerve. Near superior edge of thyroid cartilage, it divides into external & internal carotid arteries. Relations of the Common Carotid Artery Anterolaterally:Skin, Fascia, Sternocleidomastoid, Sternohyoid, Sternothyroid & Superior Belly of Omohyoid. Posteriorly: Transverse processes of lower four cervical vertebrae, Prevertebral muscles & sympathetic trunk. Medially:Larynx, Pharynx and below trachea & esophagus. The lobe of the thyroid gland also lies medially. Laterally:Internal jugular vein & posterolaterally the vagus nerve.

13. Carotid System Carotid Sinus: It is dilation at bifurcation of common carotid artery and beginning of internal carotid artery. It contains receptors that monitor changes in blood pressure (paro-receptor)and are innervated by a branch of the glossopharyngeal nerve. A rise in blood pressure causes slowing of heart rate and vasodilatation of arterioles. Carotid Body: It is a small structure that contains accumulation of chemical receptors and lies posterior to bifurcation of common carotid artery. It issensitive to high CO2 & low O2 contents in blood. It causes a rise in blood pressure & heart rate & an increase in respiratory movements.

14. Internal Carotid Arteries It is a terminal branch of common carotid artery & supplies brain, eye, forehead &part of nose. It ascends in neck within carotid sheath (with internal jugular vein & vagus nerve). It passes deep to parotid salivary gland. Internal carotid artery gives off no branches in the neck. Relations of Internal Carotid Artery in Neck: Anterolaterally:Below digastric: skin, fascia, anterior border of sternocleidomastoid and hypoglossal nerve. Above digastric: stylohyoid, stylopharyngeus, glossopharyngeal nerve, pharyngeal branch of vagus nerve, parotid gland and external carotid artery. Posteriorly: Sympathetic trunk, Longus Capitis & Transverse processes of upper 3 cervical vertebrae. Medially:Pharyngeal wall & Superior laryngeal nerve. Laterally: Internal jugular vein & Vagus nerve.

15. External Carotid Arteries It is 2nd terminal branch of common carotid artery. It supplies structures in neck, face, scalp, tongue & maxilla. It terminates in substance of parotid gland behind neck of mandible by dividing into superficial temporal & maxillary aa. its pulsations can be felt near its origin. Relations of the External Carotid Artery: Anterolaterally: Lower level: Ant. border of sternocleidomastoid. Above this level: crossed by hypoglossal nerve, posterior belly of digastric muscle & stylohyoid. Within parotid gland: crossed by facial nerve. Posteriorly: Internal jugular vein lies first lateral & then posterior to it. Medially: pharynx & internal carotid artery. Structures passing between external & internal carotid arteries. glossopharyngeal nerve, pharyngeal branch of vagus & Stylopharyngeus.

16. Internal Jugular Vein It is continuation of sigmoid sinus receiving blood from brain, face & neck & it descends within carotid sheath initially posterior to ICA & then passes lateral to it & remain lateral to common carotid artery with vagus nerve posterior to it &partially between the 2 vessels. It joins subclavian vein behind medial end of clavicle to form brachiocephalic vein. Its course is closely related to deep cervical lymph nodes. It has dilatation at its upper end (superior bulb) & near its termination (inferior bulb). Relations of the Internal Jugular Vein Anterolaterally: Skin, fascia, sternocleidomastoid & parotid. Its lower part is covered by sternothyroid, sternohyoid & omohyoid muscles. Higher up, it is crossed by stylohyoid, posterior belly of digastric & spinal part of accessory nerve. Posteriorly: Transverse processes of cervical vertebrae, levator scapulae, scalenus medius, scalenus anterior, cervical plexus, phrenic nerve, thyrocervical trunk, vertebral vein & first part of subclavian artery. Medially: Above: internal carotid artery and 9th, 10th, 11th, and 12th cranial nerves. Below: common carotid artery and vagus nerve.

17. Nerves of Anterior Triangle of Neck These include: Cranial nerves : facial, glossopharyngeal, vagus, accessory, and hypoglossal nerves Peripheral nerves: Transverse cervical n. & upper & lower roots of ansacervicalis. • Glossopharyngeal nerve [IX]: Itdescends between internal carotid artery & internal jugular vein, then passes between internal & external carotid arteries, and curves around lateral border of stylopharyngeus muscle. At this point, it continues in an anterior direction, deep to hyoglossusmuscle and reaches base of tongue & palatine tonsil. 2. Hypoglossal nerve [XII]: It is medial to internal jugular vein & internal carotid artery immediately outside skull and then it passes outward between internal jugular vein & internal carotid artery . It supplies tongue but does not give off any branches as it passes through anterior triangle of the neck.

18. Nerves of Anterior Triangle of Neck These include: Cranial nerves : facial, glossopharyngeal, vagus, accessory, and hypoglossal nerves Peripheral nerves: Transverse cervical n. & upper & lower roots of ansa cervicalis. 3. Transverse cervical nerve: It is a branch of cervical plexus arising from anterior rami of cervical nerves C2- C3. It emerges from beneath posterior border of sternocleidomastoid (middle of the muscle). 4. Accessory nerve [XI]: It emerges between internal jugular vein & internal carotid artery. It passes then lateral to internal jugular vein to Disappear beneath anterior border of sternocleidomastoid. Accessory nerve gives off no branches through the anterior triangle of the neck.

19. Nerves of Anterior Triangle of Neck 5. Vagus nerve [X]: It is enclosed in carotid sheath behind internal jugular vein & internal carotid and common carotid arteries. Branches of vagus nerve include motor pharyngeal branch, carotid body branch, superior laryngeal nerve & possibly a cardiac branch. 6. Ansa cervicalis: It is a loop of nerve fibers from cervical nerves C1-C3 that innervate muscles of anterior triangle. It begins as branches from cervical nerve C1 joining hypoglossal nerve, then some of cervical nerve fibers leave it again and descend between internal jugular vein and internal carotid first, and then common carotid arteries. These nerve fibers forms Superior Root of Ansa Cervicalis: innervate superior belly of omohyoid and upper parts of sternohyoid & sternothyroid muscles. Inferior root of ansa cervicalis: is a nerve from C2 & C3. It innervate inferior belly of omohyoid, and lower parts of sternohyoid and sternothyroid.

20. The Thyroid Gland One of the contents of Anterior Triangle

21. Thyroid Gland It is one of the endocrine glands and consists of right and left lobes connected by a narrow isthmus. It is a vascular organ surrounded by a sheath derived from pretracheal layer of deep fascia. The sheath attaches gland to Larynx & Trachea. Each lobe is pear shaped, with its apex being directed upward as far as oblique line on lamina of thyroid cartilage; its base is at level of 4th or 5th tracheal ring. Isthmus extends across the midline in front of 2nd, 3rd & 4th tracheal rings with sometimes a Pyramidal Lobe projecting upward. A fibrous or muscular band frequently connects pyramidal lobe to hyoid bone; if it is muscular, it is called Levator glandulae thyroideae.

22. Thyroid Gland Relations of the Lobes Anterolaterally: Sternothyroid, Sup. belly of omohyoid, Sternohyoid & sternocleidomastoid. Posterolaterally: Carotid sheath (common carotid artery), internal jugular vein & vagus. Medially:Larynx, Trachea, Pharynx &Esophagus Associated with these, are cricothyroid muscle and its nerve supply External laryngeal nerve. Finally, in a groove between esophagus & trachea is recurrent laryngeal nerve. Rounded posterior border of each lobe is related posteriorly to Superior and Inferior Parathyroid Glands and anastomosis between superior and inferior thyroid arteries. Relations of the Isthmus Anteriorly: Sternothyroid, sternohyoid, anterior jugular veins, fascia & skin. Posteriorly: 2nd, 3rd and 4th rings of trachea.

23. Arterial Supply of Thyroid Gland 1. Superior thyroid artery: a branch of external carotid artery that descends to upper pole of each lobe, accompanied by external laryngeal nerve. 2. Inferior thyroid artery: a branch of thyrocervical trunk that ascends behind the gland to level of cricoid cartilage. It then turns medially and downward to reach posterior border of the gland. The recurrent laryngeal nerve crosses either in front of or behind the artery, or it may pass between its branches. 3. Thyroidea ima: sometimes present and arise from brachiocephalic artery or arch of aorta. It ascends in front of trachea to isthmus.

24. Thyroid Gland Venous drainage of thyroid gland: Superior and Middle thyroid veins:drain into internal jugular vein. Inferior thyroid veins:anastomose with one another and drain into left brachiocephalic vein in the thorax. Lymph Drainage of thyroid gland: It drains mainly laterally into deep cervical lymph nodes. A few lymph vessels descend to paratracheal nodes. Nerve Supply of thyroid gland: Superior, middle, and inferior cervical sympathetic ganglia

25. Parathyroid Glands They are 4 endocrine glands with ovoid shape (6 mm long max.) closely related to posterior border of thyroid gland & lying within its fascial capsule. Superior parathyroid glands are more constant in position & lie at level of middle of posterior border of thyroid. Inferior parathyroid glands usually lie close to inferior poles of thyroid gland. Blood Supply of Parathyroid glands: Arterial supply: superior & inferior thyroid aa. Venous drainage: into superior, middle and inferior thyroid veins. Lymph Drainage: Deep cervical & paratracheal lymph nodes Nerve Supply: Superior or middle cervical sympathetic ganglia. Functions of the Parathyroid Glands: produce parathyroid hormone

26. Posterior Triangle of Neck

27. Posterior Triangle of the neck Posterior triangle of the neck is on lateral aspect of the neck in direct continuity with upper limb. Boundaries: Anteriorly: Sternocleidomastoid post. edge Posteriorly:by anterior edge of trapezius. Inferiorly (base):middle third of clavicle; Superiorly (apex):is occipital bone (post. to mastoid process between attachments of trapezius & sternocleidomastoid. Roof:investing layer of cervical fascia Floor: consist of (from superior to inferior) splenius capitis, levator scapulae, and posterior, middle & anterior scalene muscles covered by prevertebral layer of cervical fascia.

28. Contents of posterior triangle Vessels: • External jugular vein • Subclavian artery &its branches • Subclavian vein • Transverse cervical & suprascapularaa. Nerves: 1. Accessary nerve. 2. Branches of Cervical Plexus. 3. Components of brachial plexus. Accessory nerve: (in posterior triangle) It cross anterior triangle till reaching superior border of sternocleidomastoid muscle, then passes either deep to or through it to enter posterior triangle. It crosses posterior triangle in an oblique downward direction within investing layer of cervical fascia till reaching anterior border of trapezius muscle to supply it.

29. Report Cervical Plexus: • Roots (origins) • Branches • Distribution of branches & their destination • References موعد التسليم الاحد 16 – 12 - 2012

30. End of the Lecture GOOD LUCK