00.1+HA+Hafez+Notes+Neck+Anatomy.pdf

Hafez, HA, Neck Anatomy 2023-24 Neck Bones Cervical Vertebrae Atlas Vertebral Foramen Anterior Arch Anterior Tubercle Fovea dentis (fovea for the Dens) Posterior Arch Posterior Tubercle Groove for the Vertebral a. Lateral Mass Transverse Foramen Transverse Process Superior Articular Surface Inferio...

Hafez, HA, Neck Anatomy 2023-24 Neck Bones Cervical Vertebrae Atlas Vertebral Foramen Anterior Arch Anterior Tubercle Fovea dentis (fovea for the Dens) Posterior Arch Posterior Tubercle Groove for the Vertebral a. Lateral Mass Transverse Foramen Transverse Process Superior Articular Surface Inferior Articular Facets Axis Vertebral Body Superior Articular Facets Inferior Articular surface Vertebral Foramen Vertebral Arch 1 Hafez, HA, Neck Anatomy 2023-24 Laminae Pedicles Spinous Process Transverse Process Transverse Foramen Dens (odontoid process) Inferior Articular Process Inferior Articular Facet Typical Cervical Vertebrae Vertebral Body Superior articular surface Inferior articular surface Superior vertebral notch Inferior vertebral notch Vertebral Foramen Vertebral Arch Lamina Pedicle Spinous Process Transverse Process Transverse Foramen Anterior Tubercle Posterior Tubercle 2 Hafez, HA, Neck Anatomy 2023-24 Superior Articular Process Superior Articular Facet Inferior Articular Process Inferior Articular Facet Joints of the Cervical vertebral column Joints between articular processes Zygapophyseal joints Between the inferior articular process of the more superior vertebra and superior articular process of the more inferior vertebra Intervertebral symphysis, between bodies of the adjacent vertebrae Bodies of the adjacent vertebrae are joined by an intervertebral disc Two parts Anulus fibrosus Concentric lamellae of fibrocartilage forming the circumference of the IV disc Nucleus pulposus Inner gelatinous core Atlanto-occipital joint The articulations are between the superior articular surfaces of the atlas and the occipital condyles “Yes” joint Permit flexion and extension Sideway tilt of the head Ligaments 3 Hafez, HA, Neck Anatomy 2023-24 Anterior and posterior atlanto-occipital membranes Reinforces the joint capsule Atlanto-axial joint Two (right and left) lateral atlanto-axial joints between the inferior articular facets of C1 and the superior articular facets of C2 Gliding motion One median atlanto-axial joint between the dens of C2 and the anterior arch of the atlas Pivot joint “No” joint 4 Hafez, HA, Neck Anatomy 2023-24 Hyoid bone Hyoid Bone Lies in the anterior part of the neck at the level of the C3–C4 vertebrae, between the mandible and the thyroid cartilage. Site for muscle attachment Suspended by muscles; does not articulate with any other bone. Suspended from the styloid processes of the temporal bones by the stylohyoid ligaments The hyoid consists of Body – lies anteriorly greater horns lesser horns Spinal nerves A nerve is a collection of axons (nerve fibers) outside the CNS. Peripheral nerves include: Cranial nerves Spinal nerves A spinal nerve consists of two roots; a dorsal (posterior) and a ventral (anterior) root An anterior (ventral) nerve root, consisting of motor (efferent) fibers passing from nerve cell bodies in the anterior (ventral) horn of the spinal cord gray matter to effector organs located peripherally. A posterior (dorsal) nerve root, consisting of sensory (afferent) fibers from cell bodies in the spinal (sensory) or posterior (dorsal) root ganglion that extend peripherally to sensory endings and centrally to the posterior horn of spinal cord gray matter. The posterior and anterior nerve roots unite, at about the level of the intervertebral foramen, to form a spinal nerve (mixed, sensory and motor), which immediately divides into two rami (branches): a posterior (dorsal) ramus and an anterior (ventral) ramus. As branches of the mixed spinal nerve, the posterior and anterior rami carry both motor and sensory fibers, as do all their subsequent branches. The relationship between nerves and skin and muscle is established during their initial development during somite period. 5 Hafez, HA, Neck Anatomy 2023-24 Muscles of the Neck Platysma: a superficial muscle of the neck located in the superficial fascia. It covers the anterior and lateral surfaces of the neck. Attachment 1: Fascia covering the superior parts of pectoralis major and deltoid muscles Attachment 2: Inferior border of the mandible and commissures of the mouth Action: Draw the mandible down. Draw commissures of the mouth inferiorly and widens it to form a frown. Innervation: Cervical branch of facial nerve Muscle Origin Insertion Actions Nerve Supply Trapezius External occipital protuberance Spine of the Elevate scapula scapula the Accessory n. Acromion the Superior nuchal line Ligamentum nuchae Retract scapula Lateral 1/3 of Depress the clavicle scapula Proprioceptive branches from C3 and C4 the Spinous process of C7 and T1 to T12 Sternocleidomastoid Manubrium Mastoid Unilaterally: Accessory n. process of the temporal bone Turns face to Proprioceptive branches from Medial 1/3 of contralateral C2 and C3 side the clavicle Superior Tilts head to nuchal line ipsilateral side Bilaterally: Flexes Head Table contents from Netter’s Head and Neck Anatomy for Dentistry 3rd ed. with modifications 6 Hafez, HA, Neck Anatomy 2023-24 Muscle Origin Insertion Stylohyoid Styloid process Body hyoid Mylohyoid of Nerve Supply the Elevates hyoid Retracts hyoid the Facial n. the Mylohyoid Mylohyoid of Elevates line of the opposite side at hyoid mandible the raphe Body hyoid Digastric (posterior and Mastoid anterior bellies connected by process a tendon attached to the hyoid) Geniohyoid Actions the Mandibular n. Elevates the the floor of the oral cavity of Digastric fossa Elevates of the mandible hyoid Facial n. (posterior belly) Depress retract mandible Chin (Inferior Body genial hyoid tubercle) of and the Mandibular (anterior belly) n. the Elevate hyoid the C1 ventral ramus, which follows the hypoglossal n. Move the hyoid and tongue anteriorly Table contents from Netter’s Head and Neck Anatomy for Dentistry 3rd ed. with modifications Muscle Origin Insertion Actions Omohyoid (superior and Superior border Body inferior bellies connected by of the scapula hyoid a tendon) of the Depresses the hyoid Sternohyoid Manubrium Body hyoid of the Depresses the hyoid Sternothyroid Manubrium Thyroid cartilage Thyrohyoid Thyroid cartilage Greater horn of Depresses the hyoid the hyoid Nerve Supply Ansa cervicalis Depresses the larynx C1 ventral ramus, which follows the hypoglossal n. Table contents from Netter’s Head and Neck Anatomy for Dentistry 3rd ed. with modifications 7 Hafez, HA, Neck Anatomy 2023-24 Muscle Origin Insertion Actions Nerve Supply Anterior scalene Transverse Scalene tubercle on Elevates 1st rib Ventral rami processes (anterior the 1st rib of C4 to C6 tubercle) of C3 to C6 Lateral flexion of the neck Middle scalene Transverse 1st rib processes (posterior tubercle) of C2 to C7 Posterior scalene Transverse 2nd rib processes (posterior tubercle) of C5 to C7 Lateral flexion of Ventral rami the neck of C5 to C8 Ventral rami of C6 to C8 Table contents from Netter’s Head and Neck Anatomy for Dentistry 3rd ed. with modifications 8 Hafez, HA, Neck Anatomy 2023-24 Fascia of the Neck Fascia Includes the Superficial fascia (contains the platysma m.), and Deep fascia Deep Fascia Deep to the superficial fascia. It includes Deep investing fascia: surrounds all structures of the neck and envelops the trapezius and sternocleidomastoid muscles. It forms the roof of the posterior triangle. The deep investing fascia is pierced by cutaneous branches of the cervical plexus; the lesser occipital, great auricular, transverse cervical, and supraclavicular nerves; and the external and anterior jugular veins. Pretracheal fascia: surrounds the viscera of the neck (trachea, esophagus and thyroid gland). Anteriorly, it encloses the infrahyoid muscles. The pretracheal fascia begins superiorly at the hyoid bone and ends inferiorly in the upper thoracic cavity. Posterior to the pharynx, the pretracheal layer is referred to as the buccopharyngeal fascia and separates the pharynx from the prevertebral layer. The buccopharyngeal fascia begins superiorly at the base of the skull and merges with fascia covering the esophagus that then continues inferiorly into the thoracic cavity. The pretracheal space is between the fascia covering the posterior surface of the infrahyoid muscles and the pretracheal fascia (covering the anterior surface of the trachea and the thyroid gland). The pretracheal space passes between the neck and the anterior part of the superior mediastinum. Prevertebral fascia: surrounds the vertebral column and the deep muscles associated with it. These muscles include the longus coli, longus capitis, the anterior, middle, and posterior scalene muscles, and the deep muscles of the back. The phrenic nerve and brachial plexus emerge within the prevertebral fascia. The prevertebral fascia is specialized in two areas; anteriorly and in forming the axillary sheath: Anteriorly, the prevertebral fascia splits into two layers, the anterior wall of the split is referred to as the alar fascia. The danger space is the space between the prevertebral fascia and the alar fascia. 9 Hafez, HA, Neck Anatomy 2023-24 The retropharyngeal space is a longitudinal fascial space between the superior part of the prevertebral fascia (alar fascia) and the buccopharyngeal fascia. The retropharyngeal space contains loose connective tissue, and is closed superiorly by the cranial base and on each side by the carotid sheath. The alar fascia separates the retropharyngeal space from the danger space. The alar fascia and the buccopharyngeal fascia fuse around C6 or T1-4 (variable). The retropharyngeal face and the danger space are potential spaces. They are real spaces when, for example fluid accumulates within. The danger space provides an opportunity for the spread of infection from the neck to the mediastinum. The axillary sheath is an anterolateral extension of the prevertebral fascia from the anterior and middle scalene muscles to surround the brachial plexus and subclavian artery as these structures pass into the axilla. The prevertebral fascia forms the floor of the posterior triangle of the neck. Carotid sheaths: surround the contents of the carotid sheath on both sides neck. It is a column of fascia that surrounds the common carotid artery, the internal carotid artery, the internal jugular vein, and the vagus nerve. It receives contributions from the deep investing, prevertebral, and pretracheal fascia. Arteries of the Neck Arteries of the neck include branches of: Common carotid arteries and Subclavian arteries Common carotid arteries The right common carotid artery originates from the brachiocephalic trunk The left common carotid artery is a direct branch of the arch of the aorta Both right and left common carotid arteries ascend contained within the carotid sheath. In the carotid triangle and near the superior edge of the thyroid cartilage each common carotid artery divides into its two terminal branches—the external and internal carotid arteries The carotid body is a collection of chemoreceptors in the area of the bifurcation and is responsible for detecting changes in blood chemistry, primarily oxygen content. It is innervated by branches from both the glossopharyngeal and vagus nerves. 10 Hafez, HA, Neck Anatomy 2023-24 The carotid sinus is a dilation at the base of the internal carotid artery. It contains baroreceptors that monitor changes in blood pressure and is innervated by a branch of the glossopharyngeal nerve. Internal Carotid artery The internal carotid artery ascends toward the base of the skull. It gives off no branches in the neck and enters the cranial cavity through the carotid canal in the petrous part of the temporal bone. We will discuss in detail with the arterial circle of the brain. External Carotid artery The superior thyroid artery Arises from the anterior surface near or at the bifurcation Descend to supply the superior pole of the thyroid gland Give rise to the superior laryngeal artery; this artery accompanies the superior laryngeal nerve and pierces the thyrohyoid membrane to enter the larynx The lingual artery Arises from the anterior surface of the external carotid artery just above the superior thyroid artery at the level of the hyoid bone Passes deep to the hypoglossal nerve Passes between the middle pharyngeal constrictor and hyoglossus muscles The facial artery Arises from the anterior surface of the external carotid just above the lingual a. Passes deep to the stylohyoid and posterior belly of the digastric muscles Continues deep to the submandibular gland Emerges anterior to the masseter muscle to enter the face The ascending pharyngeal artery The second and smallest branch Arises from the posterior aspect of the external carotid artery Ascends between the internal carotid artery and the pharynx. 11 Hafez, HA, Neck Anatomy 2023-24 The occipital artery Arises from the posterior surface of the external carotid artery, near the level of origin of the facial artery, Passes upward and posteriorly deep to the posterior belly of the digastric muscle Emerges on the posterior aspect of the scalp The posterior auricular artery Arises from the posterior surface of the external carotid artery Passes upward and posteriorly to the ear The superficial temporal artery is one of the terminal branches of external carotid a. Appears as an upward continuation of the external carotid artery Passes anterior to the ear Gives rise to the transverse facial artery The maxillary artery is the larger of the two terminal branches of the external carotid artery Arises posterior to the neck of the mandible, it passes through the parotid gland, continues medial to the neck of the mandible and into the infratemporal fossa, and continues through this area into the pterygopalatine fossa. Subclavian Arteries The right subclavian artery arises from the brachiocephalic trunk. The left subclavian artery arises from the arch of the aorta The subclavian arteries arch superior and lateral and pass posterior to the anterior scalene muscles (versus the subclavian veins, which pass anterior to the anterior scalene muscles). Then they descend posterior to the middle of the clavicle. Each subclavian artery changes name to axillary once passing through the lateral margin of the first rib. 12 Hafez, HA, Neck Anatomy 2023-24 Three parts of each subclavian artery are described relative to the anterior scalene muscle: The first part is medial to the anterior scalene muscle Vertebral artery, internal thoracic artery, and thyrocervical trunk The second part is posterior to it Costocervical trunk The third part is lateral to it Dorsal scapular Vertebral Artery Arises from the first part of the subclavian artery. Passes deeply to course through the transverse foramina of C6-C1. In 5% of people, the left vertebral artery arises from the arch of the aorta. The vertebral artery courses in a groove on the posterior arch of the atlas before it enters the cranial cavity through the foramen magnum. The internal carotid and vertebral arteries supply the brain and contribute to the arterial circle of the brain. The vertebral arteries supply the posterior part of the brain. Details will be covered with blood supply to the brain; stay tuned!. Internal thoracic artery Arises from the antero-inferior aspect of the subclavian artery and passes inferomedially into the thorax. Will be covered in the thorax Thyrocervical trunk Arises from the anterosuperior aspect of the first part of the subclavian artery, near the medial border of the anterior scalene muscle. Has variable branches, inferior thyroid, transverse cervical, suprascapular, ascending cervical (may arise from inferior thyroid) 13 Hafez, HA, Neck Anatomy 2023-24 The largest and most important branch of the thyrocervical trunk is the inferior thyroid artery, the primary visceral artery of the neck, supplying the larynx, trachea, esophagus, and thyroid and parathyroid glands, as well as adjacent muscles. The transverse cervical artery crosses the root of the neck superior to the clavicle and deep to the omohyoid and supplies the trapezius. The suprascapular artery passes lateral and posterior. It passes over the transverse scapular ligament in the suprascapular notch to supply supraspinatus and infraspinatus. The ascending cervical artery sends muscular branches to the lateral muscles of the upper neck. Costocervical trunk Arises from the posterior aspect of the second part of the subclavian artery (posterior to the anterior scalene on the right side and usually just medial to this muscle on the left side). The trunk passes posterosuperiorly and divides into the Supreme intercostal: supplies the first two intercostal spaces Deep cervical: supplies the posterior deep cervical muscles Dorsal Scapular artery Passes between the superior and middle trunks of the brachial plexus Supplies muscles of the scapular region including rhomboid minor, rhomboid major and levator scapulae. It contribute to scapular anastomoses It may arise from the transverse cervical artery Veins of the Neck Internal Jugular vein Collects blood from the skull, brain, superficial face, and parts of the neck. Begins as a dilated continuation of the sigmoid sinus (one of the dural venous sinus). This initial dilated part is referred to as the superior bulb of jugular vein and receives another dural venous sinus (the inferior petrosal sinus) soon after it is formed. It exits the skull through the jugular foramen together with the glossopharyngeal, vagus, and accessory nerves, and enters the carotid sheath. 14 Hafez, HA, Neck Anatomy 2023-24 Within the carotid sheath: the internal jugular vein is lateral, the common carotid is medial, the vagus nerve is in between and posterior. The internal jugular veins join with the subclavian veins to form the right and left brachiocephalic veins. Tributaries: Inferior petrosal sinus, and the facial, lingual, pharyngeal, occipital, superior thyroid, and middle thyroid veins. The point of union of the internal jugular vein and subclavian vein is referred to as the venous angle. PS: the venous angle is the site where the thoracic duct (left side) and the right lymphatic trunk (right side) drain lymph collected throughout the body into the venous circulation. External Jugular Vein Formed at the angle of the mandible by the union of the posterior division of the retromandibular vein and posterior auricular vein. It drains most of the scalp and side of the face. Once formed, the external jugular vein passes straight down the neck in the superficial fascia and is superficial to the sternocleidomastoid muscle throughout its course. The external jugular vein crosses the sternocleidomastoid muscle obliquely, deep to the platysma. Just superior to the clavicle, it pierces the deep investing fascia of the neck inferiorly at the posterior border of the sternocleidomastoid muscle. It terminates in the subclavian vein. The posterior auricular vein drains the scalp behind and above the ear. The retromandibular vein is formed when the superficial temporal and maxillary veins join in the substance of the parotid gland and it descends to the angle of mandible, where it divides into an anterior and a posterior division. The posterior division joins the posterior auricular vein to form the external jugular vein, and the anterior division joins the facial vein to form the common facial vein, which passes deep and becomes a tributary to the internal jugular vein. Anterior Jugular Vein The smallest and most variable of jugular veins. Formed near the hyoid bone by the confluence of the submandibular veins. Descends superficially between the midline and the anterior border of the sternocleidomastoid muscle. 15 Hafez, HA, Neck Anatomy 2023-24 Inferiorly, each anterior jugular vein pierces the investing layer of cervical fascia to enter the subclavian vein. Occasionally, the anterior jugular vein may enter the external jugular vein immediately before the external jugular vein enters the subclavian vein. Often, the right and left anterior jugular veins communicate with each other, being connected by a jugular venous arch in the area of the suprasternal notch. Lymphatics of the Neck Superficial structures drain into the superficial cervical lymph nodes (along the course of the external jugular vein). Into deep cervical lymph nodes The main group of deep cervical lymph nodes forms a chain along the internal jugular vein, mostly under the sternocleidomastoid muscle. Lymph from these nodes drain into inferior deep cervical lymph nodes, then drains into the supraclavicular group of nodes, which accompany the transverse cervical artery. 16 Hafez, HA, Neck Anatomy 2023-24 Nerves of the Neck Nerves of the neck include cranial and spinal nerves. Cranial nerve VII (Facial) Cranial nerve IX (Glossopharyngeal) Cranial nerve X (Vagus) Cranial nerve XI (Accessory) Cranial nerve XII (Hypoglossal) Cervical sympathetic trunk Cervical plexus Phrenic nerve Brachial plexus Facial Nerve After it exits the skull through the stylomastoid foramen, the facial nerve innervates the following structures in the neck, Posterior belly of the digastric m. Stylohyoid m. Platysma m. (cervical branch) Glossopharyngeal Nerve After it exits the skull through the jugular foramen, it lies deep to the styloid process and associated muscles. It curves around the lateral border of the stylopharyngeus muscle. The glossopharyngeal nerve innervates the following structures in the neck, Stylopharyngeus muscle Carotid body and sinus Sensory branches to the pharynx through the pharyngeal plexus Vagus Nerve It exists the skull through the jugular foramen with the glossopharyngeal and accessory nerves. 17 Hafez, HA, Neck Anatomy 2023-24 It descends in the carotid sheath along with the internal jugular vein, and the common carotid artery. The vagus nerve innervates the following structures in the neck, Contribute to pharyngeal plexus (motor branches) A branch to the carotid body Larynx through the superior laryngeal and inferior laryngeal nerves The vagus nerves give rise to the recurrent laryngeal nerves in the thorax, but they ascend in the groove between the trachea and esophagus to reach the larynx. They will be discussed with the larynx. Their origin will be discussed in the thorax. To be continued!! Accessory Nerve It exists the skull through the jugular foramen with the glossopharyngeal and vagus nerves. It begins its descent medial to the internal jugular vein, emerging from between the internal jugular vein and internal carotid artery to cross the lateral surface of the internal jugular vein as it passes downward and backward to disappear either into or beneath the anterior border of the sternocleidomastoid muscle. The accessory nerve supplies the sternocleidomastoid muscle before entering the lateral cervical region. It passes postero-inferiorly, within or deep investing fascia, running on the levator scapulae from which it is separated by the prevertebral fascia. The accessory nerve then disappears deep to the anterior border of the trapezius. The accessory nerve supplies motor branches to trapezius and sternocleidomastoid muscles. Hypoglossal nerve The hypoglossal nerve exits the skull through the hypoglossal canal. To be continued with the head!! Cervical sympathetic trunk Brief introduction: The autonomic nervous system is characterized by the presence of two neurons that synapse in sequence. Those two neurons (preganglionic and postganglionic) link the CNS to the structures innervated. One neuron (preganglionic) cell body is located in the central nervous system and sends its myelinated axon out as part of the peripheral nervous system. These preganglionic axons synapse with the second neuron (postganglionic), and the non-myelinated axons 18 Hafez, HA, Neck Anatomy 2023-24 of these postganglionic neurons end on cardiac muscle, smooth muscle cells, or gland cells. The postganglionic neuronal cell bodies are located in ganglia. Ganglia, where the synapse takes place, are located close to the vertebral column in the case of the sympathetic NS. The sympathetic nervous system is called the thoracolumbar division or outflow. White rami communicantes (presynaptic neuronal axons) originate from the spinal cord lateral horn, travel in the ventral primary rami of spinal nerves, and connect to ganglia located in the sympathetic trunk. From T1 to L2, there is a ganglion that corresponds to each spinal cord segment. If they synapse in the ganglia, they may return back to connect to the ventral primary rami. Preganglionic (presynaptic) neurons that do not synapse in the thoracic sympathetic trunk and ascend to the cervical region end in one of the three ganglia that connected to form the cervical sympathetic trunk; the superior cervical ganglion, middle cervical ganglion, inferior cervical ganglion. Cervical sympathetic trunk: The cervical sympathetic trunks lie anterolateral to the vertebral column and extend superiorly to the level of the C1 vertebra or cranial base. The cervical sympathetic trunks receive no white rami communicantes from the cervical region of the spinal cord. The cervical sympathetic trunks include three cervical sympathetic ganglia: superior, middle, and inferior. These ganglia receive presynaptic fibers conveyed to the trunk by superior thoracic white rami communicantes, which ascend through the sympathetic trunk to the ganglia. After synapsing with the postsynaptic neuron in the cervical sympathetic ganglia, postsynaptic neurons send fibers to the following structures: 1. Cervical spinal nerves via gray rami communicantes 2. Thoracic viscera via cardiopulmonary plexus 3. Head and viscera of the neck via branches of arteries (accompanies arteries as sympathetic periarterial nerve plexuses, especially the vertebral and internal and external carotid arteries. The superior cervical ganglion lies at the level of the C1 and C2 vertebrae. It is the sole sympathetic supply (vessels and sweat glands) to the head via perivascular plexuses. Postsynaptic fibers from the superior cervical ganglia pass to a. Ventral rami of C1-C4 spinal nerves b. Internal carotid sympathetic plexus and enter the cranial cavity 19 Hafez, HA, Neck Anatomy 2023-24 c. External carotid artery branches d. Cardiac branches The middle cervical ganglion, is sometimes absent. When present, it lies on the anterior aspect of the inferior thyroid artery at the level of the cricoid cartilage and the transverse process of C6 vertebra. Postsynaptic fibers from the middle cervical ganglion pass to a. Ventral rami of the C5 and C6 spinal nerves b. Cardiac branches c. Peri-arterial plexuses to the thyroid gland. The inferior cervical ganglion Postsynaptic fibers from the inferior cervical ganglion pass to a. Ventral rami of the C7 and C8 spinal nerves (roots of the brachial plexus) b. Cardiac branches c. The sympathetic peri-arterial nerve plexus around the vertebral artery into the cranial cavity. In approximately 80% of people, the inferior cervical ganglion fuses with the first thoracic ganglion to form the large cervicothoracic ganglion (stellate ganglion). This star-shaped ganglion lies anterior to the transverse process of the C7 vertebra, just superior to the neck of the 1st rib on each side and posterior to the origin of the vertebral artery. Cervical Plexus The anterior rami of C1–C4 make up the roots of the cervical plexus. The cervical plexus lies anteromedial to the levator scapulae and middle scalene muscles and deep to the sternocleidomastoid muscle. Branches of the cervical plexus include: Cutaneous branches pass posteriorly Motor branches pass anteromedially. Motor branches include the roots of the phrenic nerve and the ansa cervicalis. 20 Hafez, HA, Neck Anatomy 2023-24 Ansa Cervicalis (motor) The superior root of the ansa cervicalis, conveying fibers from spinal nerves C1 and C2. The inferior root of the ansa cervicalis arises from a loop between spinal nerves C2 and C3. The superior and inferior roots of the ansa cervicalis unite, forming the ansa cervicalis, consisting of fibers from the C1–C3 spinal nerves. The ansa cervicalis and sternohyoid). supply the infrahyoid muscles (omohyoid, sternothyroid, The thyrohyoid muscle receives C1 fibers, which join then descend independently from the hypoglossal nerve, distal to the superior root of the ansa cervicalis (nerve to thyrohyoid). Fibers from C1 also supply the geniohyoid muscle. Cutaneous branches of the cervical plexus Emerge around the middle of the posterior border of the sternocleidomastoid muscle, often called the nerve point of the neck (Erb’s point) These branches supply the skin of the neck, superolateral thoracic wall, and scalp between the auricle and the external occipital protuberance. Cutaneous branches of cervical plexus include: Lesser occipital nerve Great auricular nerve Transverse cervical nerve Supraclavicular nerves Lesser occipital nerve (C2 and C3): supplies the skin of the neck and scalp posterosuperior to the auricle Great auricular nerve (C2 and C3): ascends vertically across the sternocleidomastoid muscle to the inferior pole of the parotid gland, where it supplies the skin over the mastoid process, and inferior to the auricle. Transverse cervical nerve (C2 and C3): passes anteriorly and horizontally across the sternocleidomastoid muscle deep to the external jugular vein and platysma to supply the skin covering the anterior cervical region. 21 Hafez, HA, Neck Anatomy 2023-24 Supraclavicular nerves (C3 and C4): emerge as a common trunk under cover of the sternocleidomastoid muscle, sending small branches to the skin of the neck that cross the clavicle and supply the skin over the shoulder Phrenic nerve The phrenic nerves originate from the C3, C4, C5. The phrenic nerves contain motor, sensory, and sympathetic nerve fibers (from the cervical sympathetic ganglia). The sole motor supply to the diaphragm as well as sensation to its central part. Each phrenic nerve forms at the superior part of the lateral border of the anterior scalene muscle, at the level of the superior border of the thyroid cartilage. Deep to the prevertebral fascia, it descends obliquely with the internal jugular vein across the anterior scalene and then runs deep to the transverse cervical and suprascapular arteries. The phrenic nerve crosses anterior to the subclavian artery and posterior to the subclavian vein. Roots of Brachial Plexus The roots of the brachial plexus (anterior rami of C5–C8 and T1) appear between the anterior and the middle scalene muscles. The five rami unite to form the three trunks of the brachial plexus, which descend inferolaterally through the lateral cervical region. The plexus then passes between the 1st rib, clavicle, and superior border of the scapula to enter the axilla, providing innervation for most of the upper extremity. 22 Hafez, HA, Neck Anatomy 2023-24 Larynx The larynx is the organ of voice production (the “voice box”) composed of cartilages connected by membranes and ligaments. Muscles of the larynx move the laryngeal cartilages in such a way to produce sound and maintain the patency of the airway. The larynx is located in the anterior neck at the level of the bodies of C3–C6 vertebrae. The laryngeal skeleton includes the thyroid, cricoid, epiglottic, and arytenoid cartilages. The arytenoid cartilage is the only paired cartilage among these main cartilages. There are two paired small corniculate and cuneiform cartilages which bring the total to nine laryngeal cartilages The thyroid cartilage is the largest of the cartilages; its superior border lies opposite the C4 vertebra. Thyroid laminae fuse anteriorly to form the laryngeal prominence (“Adam’s apple”); is well marked in men but seldom visible in women. Superior to this prominence, the laminae diverge to form a V-shaped superior thyroid notch. The less distinct inferior thyroid notch is a shallow indentation in the middle of the inferior border of the cartilage. The posterior border of each lamina projects superiorly as the superior cornu and inferiorly as the inferior cornu. The superior border and superior horns attach to the hyoid by the thyrohyoid membrane. The thick median part of this membrane is the median thyrohyoid ligament; its lateral parts are the lateral thyrohyoid ligaments. The inferior horns articulate with the cricoid cartilage at the cricothyroid joints. The arytenoid cartilages are paired, three-sided pyramidal cartilages that articulate with the superior border of the cricoid cartilage lamina forming the cricoarytenoid joints. Each cartilage has an apex superiorly, a vocal process anteriorly, and a large muscular process that projects laterally from its base. The apex bears the corniculate cartilage and attaches to the aryepiglottic fold. The vocal process provides attachment for the vocal ligament. The muscular process serves as an attachment site for the posterior and lateral cricoarytenoid muscles. The vocal ligaments extend from the junction of the laminae of the thyroid cartilage anteriorly to the vocal process of the arytenoid cartilage posteriorly. When covered by mucosa the vocal ligament is referred to as the vocal fold. The opening (space) between the vocal folds is the rima glottidis. The lateral cricothyroid ligaments and the median cricothyroid ligament span between the thyroid and cricoid cartilages anteriorly. 23 Hafez, HA, Neck Anatomy 2023-24 The conus elasticus extends between the vocal ligaments superiorly and the median cricothyroid membrane inferiorly. It includes the vocal ligament and lateral cricothyroid membrane. The vestibular ligaments extend between the thyroid and arytenoid cartilages and form the superior boundary of the laryngeal ventricle. When covered by mucosa the vestibular ligaments are referred to as the vestibular folds. These folds lie superior to the vocal fold and extend from the thyroid cartilage to the arytenoid cartilage. The vestibular folds play little or no part in voice production; they are protective in function. The aryepiglottic ligament, which is covered with mucosa to form the aryepiglottic fold, extends from the arytenoid and epiglottic cartilages. The quadrangular membrane extends between the epiglottis and arytenoid. It extends from the aryepiglottic ligament superiorly to the vestibular ligament inferiorly. The epiglottic cartilage, consisting of elastic cartilage, and situated posterior to the root of the tongue and the hyoid and anterior to the laryngeal inlet. Its broad superior end of the epiglottis is free. Its tapered inferior end, the stalk of the epiglottis, is attached to the angle formed by the thyroid laminae by the thyro-epiglottic ligament. The hyo-epiglottic ligament attaches the anterior surface of the epiglottic cartilage to the hyoid. The corniculate and cuneiform cartilages appear as small nodules in the posterior part of the aryepiglottic folds. The corniculate cartilages attach to the apices of the arytenoid cartilages; the cuneiform cartilages do not directly attach to other cartilages. The cricoid cartilage is shaped like a signet ring with its band (arch) facing anteriorly. The lamina faces posteriorly. The cricoid cartilage is the only complete ring of cartilage. It attaches to the inferior margin of the thyroid cartilage by the cricothyroid ligaments and to the first tracheal ring by the cricotracheal ligament. Where the larynx is closest to the skin and most accessible, the median cricothyroid ligament may be felt as a soft spot during palpation inferior to the thyroid cartilage. Joints of the larynx The inferior horns of thyroid cartilage articulate with the cricoid cartilage at the cricothyroid joints. It is a synovial joint. The main movements at these joints are rotation and gliding of the thyroid cartilage, which result in changes in the length of the vocal folds. 24 Hafez, HA, Neck Anatomy 2023-24 The crico-arytenoid joints, located between the bases of the arytenoid cartilages and the superolateral surfaces of the lamina of the cricoid cartilage, permit rotation and gliding of the arytenoid cartilages. These movements are important in approximating, tensing, and relaxing the vocal folds. Adduction (getting closer) or abduction (getting away) of the vocal folds close, or open, respectively the rima glottidis. Compartments of the Larynx The laryngeal cavity extends from the laryngeal inlet (aditus) to the level of the inferior border of the cricoid cartilage. Superiorly, the larynx communicates with the laryngopharynx at the laryngeal inlet. Inferiorly, the laryngeal cavity is continuous with the cavity of the trachea. The laryngeal cavity includes the Laryngeal aditus (inlet) Laryngeal vestibule: between the laryngeal inlet and the vestibular folds The middle part of the laryngeal cavity: the central cavity (airway) between the vestibular and vocal folds laryngeal ventricle (saccule): recesses extending laterally from the middle part of the laryngeal cavity between vestibular and vocal folds. Rima glottidis is the space between the vocal cords. The glottis includes the focal folds and vocal processes and the space in between, the rima glottidis. This is the part controlled by muscular activities, and changes result in sound production and modulation. The infraglottic cavity: the cavity of the larynx inferior to the glottis. It is contained in the cricoid cartilage. It is continuous with the lumen of the trachea The vocal folds control sound production. It projects into the laryngeal cavity. Each vocal fold contains a vocal ligament. The vocalis muscle is contained within the vocal fold. The vocal folds are the source of the sounds (tone) that come from the larynx. These folds produce audible vibrations when their free margins are closely (but not tightly) apposed during phonation and air is forcibly expired intermittently. The vocal folds also serve as the main inspiratory sphincter of the larynx when they are tightly closed. Complete adduction of the folds forms an effective sphincter that prevents the entry of air. The glottis (the vocal apparatus of the larynx) includes the vocal folds and processes, together with the rima glottidis. The shape of the rima glottidis varies according to the position of the vocal folds. During ordinary breathing, the rima is narrow and wedgeshaped; during forced respiration, it is wide and trapezoidal in shape. The rima glottidis is slit-like when the vocal folds are closely approximated during phonation. Variation in 25 Hafez, HA, Neck Anatomy 2023-24 the tension and length of the vocal folds, in the width of the rima glottidis, and in the intensity of the expiratory effort produces changes in the pitch of the voice. The muscles of the larynx include extrinsic and intrinsic muscles. The extrinsic muscles of the larynx are the supra and infrahyoid muscles, covered above, remember! Intrinsic muscles of the larynx Intrinsic laryngeal muscles They alter the length and tension of the vocal folds and the size and shape of the rima glottidis. Muscle Origin Arch of Cricothyroid cartilage Thyroarytenoid Insertion Innervation Main Action(s) Inferior margin External branch cricoid and inferior of superior Stretches and tenses horn of thyroid laryngeal nerve vocal ligament cartilage (from vagus) Thyroid cartilage Arytenoid Relaxes vocal ligament Vocalis (part Vocal process of Ipsilateral of thyroarytenoid vocal ligament arytenoid Posterior cricoarytenoid Posterior surface of lamina of Muscular cricoid cartilage process Lateral cricoarytenoid Arch of cartilage arytenoid cricoid cartilage Relaxes vocal ligament Inferior laryngeal Abducts vocal folds nerve (recurrent (widen rima glottidis) of laryngeal nerve), from vagus Adducts vocal folds (narrow rima glottidis) Transverse Contralateral One arytenoid and oblique arytenoid cartilage arytenoids cartilage narrow rima glottidis Table contents from Moore’s clinically oriented anatomy with modifications Thyroepiglottic and aryepiglottic muscles help close the laryngeal aditus. Notes about muscles: 26 Hafez, HA, Neck Anatomy 2023-24 The posterior crico-arytenoid is the only abductor of the vocal folds. This is the basis for understanding laryngeal hemiplegia or hoarseness! The cricothyroid muscle is the only intrinsic laryngeal muscle that is innervated by the superior laryngeal nerve. All other muscles are innervated by the recurrent laryngeal nerve (inferior laryngeal nerve). Adductors and abductors: These muscles move the vocal folds to open and close the rima glottidis. The principal adductors are the lateral crico-arytenoid muscles, which pull the muscular processes anteriorly, rotating the arytenoid cartilages so that their vocal processes swing medially. When this action is combined with that of the transverse and oblique arytenoid muscles, which pull the arytenoid cartilages together, air pushed through the rima glottidis causes vibrations of the vocal ligaments (phonation). The sole abductors are the posterior crico-arytenoid muscles, which pull the muscular processes posteriorly, rotating the vocal processes laterally and thus widening the rima glottidis. Sphincters: The combined actions of most of the muscles of the laryngeal inlet result in a sphincteric action that closes the laryngeal inlet as a protective mechanism during swallowing. Tensors: The principal tensors are the cricothyroid muscles, which tilt or pull the thyroid cartilage anteriorly and inferiorly toward the arch of the cricoid cartilage. This elongate and tighten the vocal ligaments, raising the pitch of the voice. Relaxers: The principal muscles in this group are the thyro-arytenoid muscles, which pull the arytenoid cartilages anteriorly, thereby relaxing the vocal ligaments to lower the pitch of the voice. The vocalis muscles lie within the vocal folds. Blood supply of the larynx Arteries 1. Superior laryngeal artery A branch of the superior thyroid artery (a branch of the external carotid a.) Accompanies the internal branch of the superior laryngeal nerve through the thyrohyoid membrane and branches to supply the internal surface of the larynx. 2. Inferior laryngeal artery A branch of the inferior thyroid artery (a branch of thyrocervical trunk) Accompanies the inferior laryngeal nerve (the recurrent laryngeal nerve once in larynx) and supplies the mucous membrane and muscles in the inferior part of the larynx. 3. Cricothyroid artery, a small branch of the superior thyroid artery, supplies the cricothyroid muscle. 27 Hafez, HA, Neck Anatomy 2023-24 Veins 1. Superior laryngeal vein usually Joins the superior thyroid vein and through it drains into the internal jugular vein. 2. Inferior laryngeal vein Joins the inferior thyroid vein or the venous plexus of veins on the anterior aspect of the trachea, which empties into the left brachiocephalic vein The laryngeal lymphatic vessels superior to the vocal folds accompany the superior laryngeal artery through the thyrohyoid membrane and drain into the superior deep cervical lymph nodes. The lymphatic vessels inferior to the vocal folds drain into the pretracheal or paratracheal lymph nodes, which drain into the inferior deep cervical lymph nodes. Innervation of the Larynx 1. Superior laryngeal nerve Arises from the vagus at the superior end of the carotid triangle. Divides into two terminal branches within the carotid sheath: a. Internal branch, Internal laryngeal nerve. It is sensory and autonomic to the superior half of the larynx superior to the vocal folds b. External branch, External laryngeal nerve. It is motor to the cricothyroid muscle. The internal laryngeal nerve, the larger of the terminal branches of the superior laryngeal nerve, pierces the thyrohyoid membrane with the superior laryngeal artery, supplying sensory fibers and autonomic supply to the superior half of the larynx superior to the vocal folds. The external laryngeal nerve, the smaller terminal branch of the superior laryngeal nerve. It supplies the cricothyroid muscle. 28 Hafez, HA, Neck Anatomy 2023-24 2. Inferior laryngeal nerve The continuation of the recurrent laryngeal nerve. It enters the larynx by passing deep to the inferior border of the inferior pharyngeal constrictor and medial to the lamina of the thyroid cartilage. Accompany the inferior laryngeal artery into the larynx. It supplies all the intrinsic muscles except the cricothyroid muscle. Provides sensory fibers to the laryngeal mucosa below the vocal folds Esophagus The esophagus is part of the gastrointestinal system and has only a short course in the lower neck. It begins at the C6 level, where it is continuous with the pharynx above and courses inferiorly to pass through the thoracic inlet. It lies directly anterior to the vertebral column Trachea The trachea is part of the lower airway and, like the esophagus, begins at the C6 level where it is continuous with the larynx above. The trachea lies directly anterior to the esophagus and passes inferiorly in the midline to enter the thorax. Thyroid and Parathyroid glands The thyroid and parathyroid glands are endocrine glands positioned anteriorly in the neck. The thyroid gland is a large, unpaired gland, whereas the parathyroid glands, usually four in number, are small and are on the posterior surface of the thyroid gland. Thyroid Gland Located anteriorly in the neck below and lateral to the thyroid cartilage. It consists of two lateral lobes connected with an isthmus that crosses the anterior surfaces of the second and third tracheal cartilages. Lying deep to the sternohyoid, sternothyroid, and omohyoid muscles, the thyroid gland is in the visceral compartment of the neck. This compartment also includes the pharynx, trachea, and esophagus and is surrounded by the pretracheal fascia. 29 Hafez, HA, Neck Anatomy 2023-24 The thyroid gland arises as a median outgrowth from the floor of the pharynx near the base of the tongue. The foramen cecum of the tongue indicates the site of origin and the thyroglossal duct marks the path of migration of the thyroid gland to its final adult location. The thyroglossal duct usually disappears early in development, but remnants may persist as a cyst or as a connection to the foramen cecum. A pyramidal lobe could be present as a functional thyroid gland extending upward from the gland along the path of the thyroglossal duct. A functional thyroid gland could be associated with the tongue (a lingual thyroid), anywhere along the path of migration of the thyroid gland. Arteries of Thyroid Gland Two major arteries supply the thyroid gland. 1. Superior thyroid artery The first branch of the external carotid artery. It descends, passing along the lateral margin of the thyrohyoid muscle, to reach the superior pole of the lateral lobe of the gland where it divides into anterior and posterior glandular branches anteriorly and posteriorly, respectively. The posterior glandular branch anastomoses with the inferior thyroid artery. 2. Inferior Thyroid artery A branch of the thyrocervical trunk, which arises from the first part of the subclavian. It ascends along the medial edge of the anterior scalene muscle, passes posteriorly to the carotid sheath, and reaches the inferior pole of the lateral lobe of the thyroid gland. At the thyroid gland, the inferior thyroid artery divides into an inferior branch (anastomoses with the posterior branch of the superior thyroid artery), and an ascending branch which supplies the parathyroid glands. Occasionally, a small thyroid ima artery arises from the brachiocephalic trunk or the arch of the aorta and ascends on the anterior surface of the trachea to supply the thyroid gland. After branching from the vagus nerve and looping around the subclavian artery on the right and the arch of the aorta on the left, the recurrent laryngeal nerves ascend in a groove between the trachea and esophagus. They pass deep to the posteromedial surface of the lateral lobes of the thyroid gland and enter the larynx by passing deep to the lower margin of the inferior constrictor of the pharynx. 30 Hafez, HA, Neck Anatomy 2023-24 Together with branches of the inferior thyroid arteries, the recurrent laryngeal nerves pass through the cricotracheal ligament. These relationships need to be considered when surgically removing or manipulating the thyroid gland!! Laryngeal hemiplegia!!!! Venous drainage of the thyroid gland Three veins drain the thyroid gland: 1. Superior thyroid vein primarily drains the area supplied by the superior thyroid artery. 2. Middle thyroid veins 3. Inferior thyroid veins The superior and middle thyroid veins drain into the internal jugular vein, and the inferior thyroid veins empty into the right and left brachiocephalic veins, respectively. Lymphatic drainage of the thyroid gland is to nodes beside the trachea (paratracheal nodes) and to deep cervical nodes inferior to the omohyoid muscle along the internal jugular vein. Parathyroid glands The parathyroid glands are two pairs of small, ovoid, yellowish structures on the deep surface of the lateral lobes of the thyroid gland. They are designated as the superior and inferior parathyroid glands. However, their position is quite variable and they may be anywhere from the carotid bifurcation superiorly to the mediastinum inferiorly. Derived from the third (the inferior parathyroid glands) and fourth (the superior parathyroid glands) pharyngeal pouches, these paired structures migrate to their final adult positions and are named accordingly. The arteries supplying the parathyroid glands are the inferior thyroid arteries, although the superior thyroid arteries may contribute to the supply of the superior parathyroid glands. The venous and lymphatic drainage follows that described for the thyroid gland. Lymphatics of the neck Superficial structures drain into the superficial cervical lymph nodes, which are located along the course of the external jugular vein. Lymph from these nodes, like lymph from all of the head and neck, drains into inferior deep cervical lymph nodes, then drains into the supraclavicular group of nodes, which accompany the cervicodorsal trunk. 31 Hafez, HA, Neck Anatomy 2023-24 The main group of deep cervical lymph nodes forms a chain along the internal jugular vein, mostly under the sternocleidomastoid muscle. Other deep cervical nodes include the prelaryngeal, pretracheal, paratracheal, and retropharyngeal nodes. Efferent lymphatic vessels from the deep cervical nodes join to form the jugular lymphatic trunks, which usually join the thoracic duct on the left side and enter the junction of the internal jugular and subclavian veins (right venous angle) directly or via a short right lymphatic duct on the right. 32 Hafez, HA, Neck Anatomy 2023-24 Triangles of the Neck The neck is divided by the sternocleidomastoid muscles into an anterior triangle and posterior triangle. The posterior triangle: Borders: Posterior border of the sternocleidomastoid Middle third of the clavicle Anterior border of the trapezius Roof: skin, then, superficial fascia with platysma, then, deep investing fascia Floor: prevertebral fascia (covering semispinalis capitis, splenius capitis, levator scapulae, scalene muscles) Divided by inferior belly of omohyoid muscle into: Occipital triangle Omoclavicular triangle The anterior triangle: Borders: Anterior border of the sternocleidomastoid Inferior border of the mandible Midline of the neck Divided into: Submental triangle Submandibular triangle Carotid triangle Muscular triangle The following table shows the boundaries of the constructed triangles of the neck and their contents. 33 Hafez, HA, Neck Anatomy 2023-24 Subdivision Boundaries Contents Posterior Triangle Occipital triangle Omoclavicular triangle Posterior border of the sternocleidomastoid Middle third of the clavicle Cutaneous branches of cervical plexus Accessory nerve Roots, trunks of brachial plexus Phrenic nerve Anterior border of the trapezius External Jugular vein 3rd part of subclavian artery Dorsal scapular artery and vein Suprascapular artery & vein Transverse cervical artery& vein Anterior triangle Submental triangle (unpaired) Right and left anterior Submental lymph nodes bellies of right and left Tributaries forming the anterior jugular vein digastric muscles Body of hyoid bone Mylohyoid m. forms the floor of the triangle Submandibular Inferior border of triangle mandible (paired) Anterior and posterior (Digastric bellies of the digastric Triangle) muscle Submandibular gland Submandibular lymph nodes Hypoglossal nerve Mylohyoid nerve facial artery and vein Lingual artery and vein Carotid triangle Posterior belly (paired) digastric muscle of Common carotid artery; external and internal carotid arteries 34 Hafez, HA, Neck Anatomy 2023-24 Subdivision Boundaries Superior belly omohyoid muscle Contents of Tributaries to the common facial vein Cervical branch of the facial nerve Anterior border of Superior thyroid; ascending pharyngeal; sternocleidomastoid lingual, facial, and occipital arteries muscle Internal jugular vein Vagus nerve Accessory nerve Hypoglossal nerve Superior and inferior roots of ansa cervicalis Ansa cervicalis Sympathetic trunk Muscular triangle (paired) Midline of neck Superior belly omohyoid muscle of Sternohyoid, omohyoid, sternothyroid, and thyrohyoid muscles Thyroid and parathyroid glands Anterior border of Pharynx, larynx, trachea, esophagus sternocleidomastoid Lymph nodes muscle Table is from Moore’s clinically oriented anatomy with modifications 35