Neck Muscles PDF

Neck – Part 2 Dr. David Hopper ANTERIOR TRIANGLE of the NECK BORDERS: Anterior: anterior median line Posterior: Sternocleidomastoid muscle Superior: inferior border of the mandible Apex: jugular notch Roof: subcutaneous fascia & platysma m. Floor: pharynx, larynx and thyroid gland covered by pret...

Neck – Part 2 Dr. David Hopper ANTERIOR TRIANGLE of the NECK BORDERS: Anterior: anterior median line Posterior: Sternocleidomastoid muscle Superior: inferior border of the mandible Apex: jugular notch Roof: subcutaneous fascia & platysma m. Floor: pharynx, larynx and thyroid gland covered by pretracheal fascia. SUPRAHYOID MUSCLES - 4 MYLOHYOID M. 0: Mylohyoid line of the mandible I: Median raphe and hyoid bone N: Nerve to the mylohyoid (V3) -this nerve also innervates anterior belly of digastric. F: Raises floor of oral cavity, draws hyoid forward. DIGASTRIC M. (anterior and posterior bellies) 0: Mastoid process I: Anteromedial aspect of mandible (digastric fossa) N: Posterior belly - Facial nerve (CN VII); Anterior belly - CN V3, specifically nerve to the mylohyoid muscle. F: Stabilizes, raises, anterior movement (anterior belly), and posterior movement (posterior belly) of the hyoid bone. The digastric has an intermediate tendon. This tendon divides the digastric muscle into an anterior and posterior belly. It also has a fibrous sling holding it to the hyoid bone SUPRAHYOID MUSCLES GENIOHYOID M. 0: I: N: F: Genial tubercle of mandible Hyoid bone C1, nerve to geniohyoid (runs with hypoglossal n. - CN XII) Raises hyoid bone. STYLOHYOID M. (this muscle is very closely related to the posterior belly of the digastric muscle ) 0: I: N: F: Styloid process Hyoid bone CN VII (facial nerve ) Moves hyoid posterosuperiorly. N.B. Before inserting onto the hyoid bone, the stylohyoid splits and wraps around the intermediate tendon of the digastric. NOTE: 1. The suprahyoid muscles function to raise the hyo-laryngeal complex during swallowing and also during vocalization. 2. These muscles (especially the mylohyoid, geniohyoid and anterior belly of the digastric) assist in depression of the mandible (i.e., jaw opening). Digastric Geniohyoid Mylohoid Stylohoid INFRAHYOID MUSCLES -4 THYROHYOID M. 0: oblique line of thyroid cartilage I: Hyoid bone N: Nerve to the thyrohyoid, C1 (ran with Hypoglossal N.) F: Lowers hyoid bone or raises thyroid cartilage or stabilizes both structures during vocalization STERNOHYOID M. 0: Posterior aspect of manubrium of sternum I: Hyoid bone N: Ansa cervicalis (C1-C3) F: Lowers hyoid bone or stabilizes hyoid during vocalization and depression of the mandible. STERNOTHYROID M. 0: Manubrium (posterior to sternohyoid) I: Oblique line of thyroid cartilage. N: Ansa cervicalis (C1-C3) F: Lowers thyroid cartilage or stabilizes same during vocalization and depression of the mandible. INFRAHYOID MUSCLES OMOHYOID M. (superior and inferior bellies) 0: I: N: F: Superior border of scapula (near scapular notch) Hyoid bone (junction of body and greater horn) Ansa cervicalis (C1-C3) Superior belly lowers hyoid bone or may stabilize hyoid from below N.B. The omohyoid has an intermediate tendon which is held to the clavicle by a fibrous sling. This divides the omohyoid into a superior and inferior belly. This is similar to the digastric muscle which has 2 bellies, an intermediate tendon, and a fibrous sling holding it to the hyoid. NOTE: 1. The infrahyoid muscles function to lower either the hyoid or thyroid cartilages or to stabilize them during vocalization and jaw opening. The thyrohyoid muscle may also help to raise the thyroid cartilage. 2. All of these muscles (including both bellies of the omohyoid) are innervated by the cervical plexus (ansa cervicalis), except the thyrohyoid, which is innervated by the nerve to the thyrohyoid from C1. Infrahyoid Muscles Hyoid Muscles involved in swallowing, speech, and depression of the mandible (with lateral pterygoid M.) Specific actions: 1. Swallowing: ■ ■ ■ 2. Jaw opening (depression of mandible): ■ ■ 3. Infrahyoids ! relaxed. Suprahyoids ! contracted w/ jaw elevators. The result is raising of the hyolaryngeal complex, and the floor of the mouth moves as well. Infra/suprahyoids are contracted stabilizing the hyoid bone. Result is that this provides a base of action to assist in opening of the jaw; the suprahyoids act mainly on the jaw. Vocalization: ■ ■ Supra & infrahyoids alternate contractions and relaxation. Actions are dependent upon the sounds you are making. ANTERIOR TRIANGLE – further subdivided into 4 triangles by Digastric m. and omohyoid m. Submandibular triangle (digastric triangle) Submental triangle Carotid triangle Muscular triangle Digastric/Submandibular Triangle • Bounded by the lower edge of the mandible and the anterior and posterior bellies of the digastric muscle • Floor is formed by mylohyoid and hyoglossus muscles • Anterior part contains submandibular salivary gland • Facial vein and submandibular lymph nodes are superficial to submandibular gland • Facial artery is deep to submandibular gland • Hypoglossal nerve runs deep to the gland (on it’s way to the tongue) Submandibular Triangle Submental Triangle • Formed by the left and right anterior bellies of the digastric muscles, and hyoid bone (only 1 submental triangle) • Floor is formed by mylohyoid muscle • Contains submental lymph nodes and small veins that unite to form the anterior jugular vein Muscular Triangle • Boundaries are midline, hyoid, superior belly of omohyoid M., and lower anterior border of the SCM M. • Contains most of the infrahyoid muscles (not inferior belly of omohyoid M.), lower part of the larynx, upper trachea, thyroid and parathyroid glands Thyroid Gland Has two lobes, a right and a left, which are united in the midline by the isthmus. Pyramidal lobe is the remnant of the embryological thyroglossal duct. The superior and inferior thyroid arteries provide the blood supply Thyroid Hormone is involved in cellular metabolism and calcitonin hormone in calcium homeostasis PARATHYROID GLANDS The PARATHYROID GLANDS, four in number (two on each side), are located on the posterior aspect of the thyroid gland. They secrete parathyroid hormone, a small protein that takes part in the control of calcium and phosphorus homeostasis Regulating calcium levels in the body within a very narrow range Without this hormone (and these glands), the nervous and muscular systems could not function properly Carotid Triangle • Boundaries Superior belly of the omohyoid muscle inferiorly Posterior belly of the digastric muscle superiorly Sternocleidomastoid muscle posteriorly Floor is formed by portions of thyrohyoid, hyoglossus and middle and inferior constrictor muscles of the pharynx • Contents Common carotid artery dividing into internal and external carotid Numerous branches of external carotid artery Internal jugular vein and its tributaries Hypoglossal nerve Accessory and vagus nerves Part of the chain of deep cervical nodes Carotid Sheath • The Carotid Sheath contains- Internal Jugular Vein, Common Carotid Artery, Internal Carotid Artery, and Vagus Nerve • Ansa cervicalis is superficial to the sheath, Sympathetic chain is deep to the sheath The carotid triangle contains the superior portion of the common carotid artery, large part of the internal carotid artery, the external carotid artery and many of its branches The Carotid Triangle contains arteries which originate from the arch of the aorta. The aortic arch has three large branches: 1. Brachiocephalic trunk (innominate artery); The brachiocephalic trunk divides into the right common carotid a. and the right subclavian a. 2. Left Common Carotid artery. 3. Left Subclavian artery. Common Carotid Artery • • • • • • • • • • • Supply most of the head and neck Left common carotid –from the aortic arch Right common carotid –branch of brachiocephalic trunk Carotid hemostasis may be used in an emergency by compression of the common carotid artery at the level of cricoid cartilage Carotid bifurcation at the level of superior edge of thyroid cartilage Two receptors at the carotid bifurcation provide feedback to the vasomotor and respiratory centers of the brain: carotid sinus and carotid body The body is a highly vascular area between internal and external carotid arteries just above the bifurcation Chemoreceptor, sensitive to levels of oxygen, carbon dioxide and pH of the blood The carotid sinus is a fusiform dilation of common carotid artery • Baroreceptor to monitor blood pressure Sensory innervation from carotid body and sinus is Glossopharyngeal N. Motor is Vagus and other nerves that control muscles of respiration Internal Carotid Artery • Ascends to the carotid canal in the base of the skull without giving off branches in the neck • Styloid process and its associated muscles interpose between the internal and external carotid arteries • Ophthalmic branch supplies the forehead and anastomoses with facial and superficial temporal A. External Carotid Artery • Supplies most of the face and visceral neck • Gives off eight major branches: 1.Superior thyroid artery –anteriorly, gives rise to Superior laryngeal artery 2.Ascending pharyngeal artery –arises close to bifurcation, medially* 3.Lingual artery –anteriorly 4.Facial artery –anteriorly 5.Occipital artery –posteriorly, “pinned” down by Hypoglossal N.* 6.Posterior auricular artery –posteriorly 7.Superficial temporal artery 8. Maxillary artery 7. 7a. 8. 6. 5. 4. 3. 2. 1. Internal Jugular Vein • Lies deep to the SCM, (external jugular vein is superficial and drains into the subclavian vein) • Formed by union of the inferior petrosal and sigmoid sinuses as it exits the skull through the jugular foramen together with glossopharyngeal, vagus and spinal accessory nerves • Descends through the neck in the carotid sheath • Receives facial veins, one or more lingual veins, superior and middle thyroid veins and veins from the pharyngeal venous plexus • Anastomoses with anterior and external jugular veins • Comes together with subclavian vein to form brachiocephalic vein • Brachiocephalic veins, R&L, join to form the superior vena cava Internal Jugular Vein • May be used for insertion of central venous lines: • In the root of the neck, lies anterior to the carotid artery and posterior to the sternocleidomastoid muscle • Does not have valves Lymphatics of the Neck Lymph from the face and anterior region of the neck drains by two pathways 1.Superficial cervical nodes parallel the external jugular vein Receive drainage mainly from occipital nodes, retro auricular nodes and parotid nodes, with some drainage from anterior cervical nodes 2.Deep cervical nodes parallel the internal jugular vein Receive drainage from superficial face and deep structures through submandibular, submental and jugulodigastric nodes Jugulodigastric node lies just below the posterior belly of digastric muscle; drains tonsillar region There is abundant anastomoses between various nodal regions and between superficial and deep cervical lymphatics The functions of lymphatics include: Drainage of tissue fluid, collection of lymph plasma from tissue spaces, and transport of lymph to the venous system typically via lymphatic vessels Absorption and transport of fat from the digestive system. Formation of a defense mechanism for the body. When foreign protein drains from an infected area, antibodies specific to the protein are produced by immunologically competent cells and/or lymphocytes and dispatched to the infected area (Nodes) Lymphatics of the Neck Deep cervical lymphatics in the root of the neck form jugular trunks 1.Right jugular trunk/lymphatic duct terminates at the junction of the internal jugular vein and the subclavian vein The right lymphatic duct drains the right head and neck, right upper extremity and right thorax 2.Left jugular trunk enters thoracic duct just before it enters the venous system at the junction of the internal jugular vein and subclavian vein The thoracic duct drains left head and neck, left trunk and upper extremity, entire abdomen and lower body All lymph must pass through at least one node before entering the venous system Nerves • Nerves in the triangles of the neck (can find X, XI, and XII in the carotid triangle) -Vagus -Accessory -Hypoglossal -Sympathetic Chain -Cervical Plexus -Phrenic -Brachial Plexus 39 Carotid Triangle • Vagus N (CN X): – Runs between the internal carotid and the internal jugular vein within the carotid sheath. – Gives several branches in the neck pharyngeal N. superior laryngeal N. –branches to internal and external laryngeal nerves cardiac plexus nerves recurrent laryngeal nerves – on the right loops behind subclavian A. and on the left loops behind the aortic arch • Spinal accessory N. (CN XI): – Enters the carotid triangle from behind the posterior belly of digastric and runs to the posterior aspect of the SCM. – Innervates SCM & trapezius. • Hypoglossal (CN XII): – Enters the carotid triangle from behind the posterior belly of digastric. – Then runs anterior, slightly inferior, exits triangle and “loops” into the floor of the mouth. • Cervical Sympathetic trunk (chain): – This is located behind the posterior wall of the carotid sheath. Primary structures visible here include the superior, middle and inferior cervical ganglia Sympathetic Chain There are usually three cervical sympathetic ganglia, although the number may vary. The three main ganglia are as follows: 1. Superior (C1-C4) - This very large ganglion supplies structures of the head via the internal carotid plexus and also supplies the superior cardiac nerves which participates in the cardiac plexus of nerves. 2. Middle (C5-C6) – (may be absent) - supplies the thyroid gland and the middle cardiac nerve which also participates in the cardiac plexus. This ganglion gives branches to run with the external carotid artery and its branches thereby effecting vasoconstriction. 3. Inferior (C7-C8) - frequently fuses with the first thoracic ganglion to form the very large stellate (cervicothoracic) ganglion. Some nerves from the inferior ganglion run to the heart while others participate in the formation of the vertebral plexus which surround the artery of that name Interruption of the sympathetic chain in the neck can result in the distinct condition known as Horner's Syndrome. Cervical Plexus • • • Sensory innervation Motor innervation Ansa cervicalis (C1-C3) innervates the strap (infrahyoid) muscles, C1 innervates the other infrahyoid muscle and one suprahyoid muscle (geniohyoid) • C3 and C4 contribute to the phrenic nerve which is motor to the diaphragm and runs on top of anterior scalene • Brachial plexus contributes C5 to the phrenic nerve Phrenic Nerve – C3, 4, 5 Brachial Plexus • The anterior primary divisions of the ventral rami of C5 – T1 are found between the scalenus anterior and the scalenus medius muscles • Subclavian artery also emerges from between the anterior and middle scalene muscles • The subclavian vein is anterior to the anterior scalene muscle (along with phrenic nerve • Roots (C5-T1 ventral rami), Trunks, Divisions, Lateral Cord – Lateral Pectoral, Musculocutaneous, Median Medial Cord – Medial Pectoral, Ulnar, Median, Medial Brachial, Medial Antebrachial Posterior Cord – Axillary, Radial, Upper Subscapular, Lower Subscapular, Thoracodorsal • Supraclavicular Branches – are off roots and/or divisions Dorsal Scapular (C5), rhomboids, levator scapulae M. Suprascapular (C5,6), supraspinatus, infraspinatus M. Long Thoracic (C5,6,7), serratus anterior M. N to Subclavius (C5,6), subclavius M. Brachial Plexus BRANCHES ROOT of the NECK The root of the neck or deep neck is the region in or near the superior thoracic aperture. The superior thoracic aperture is bounded posteriorly by the first thoracic vertebra, laterally by the first ribs, and anteriorly by the superior aspect of the sternum (manubrium). Important structures of this region include the following: 1. thoracic duct 2. vagus nerve 3. recurrent laryngeal nerve 4. phrenic nerve 5. brachial plexus 6. subclavian arteries and veins and their branches 7. common carotid arteries 8. sympathetic chain 9. the apices of the left and right lungs and their pleural coverings (cupulae) ** neck issues can be due to lung Recurrent Laryngeal Nerve – branch from the Vagus nerve that “returns” to go to the larynx. This nerve loops behind the aortic arch on the left and behind the subclavian artery on the right. The difference is due to the branchial arch development. Arteries of the Lateral Neck - Subclavian The Subclavian artery, as it relates to the anterior scalene muscle, can be “broken into” three segments. The first segment lies medial to the anterior scalene, the second segment runs posterior to the anterior scalene, and the third segment runs lateral to the anterior scalene and continues on as the axillary artery after crossing the first rib. Dorsal Scapular artery Subclavian Artery – VIT C and sometimes D 1st part Vertebral artery – to brain via transverse foramina & foramen magnum Internal Thoracic artery – posterior aspect of anterior chest wall Thyrocervical Trunk: Inferior Thyroid a. – thyroid and larynx. Transverse Cervical a. – scalene & post. Triangle mm., brachial plexus. Suprascapular a. – area above the scapula and rhomboids. Ascending Cervical a. – anterior scalene region 2nd part Costocervical Trunk: Supreme Intercostal a. – first and second intercostal spaces. Deep Cervical a. – prevertebral and deep neck structures. 3rd part aberrant forms of Dorsal Scapular Arteries in the Lateral Cervical Region t t V t T t C c I Deep Cervical Supreme Intercostal c