Lecture 3 - The Neck Region PDF

INTRODUCTION • Many important structures are contained within the area of the neck. • The neck connects the head and the trunk, and therefore, many vital structures cross this region. INTRODUCTION • The bony landmarks that form the superior limit of the neck region are: – The inferior margin of th...

INTRODUCTION • Many important structures are contained within the area of the neck. • The neck connects the head and the trunk, and therefore, many vital structures cross this region. INTRODUCTION • The bony landmarks that form the superior limit of the neck region are: – The inferior margin of the mandible – The mastoid process of the temporal bone – The external occipital protuberance • The lower limit is formed by: – The superior thoracic aperture – The clavicles INTRODUCTION • The skin of the neck is thin, and pliable. • The subcutaneous tissue contains nerves and superficial vessels which are covered by a flat muscle that ascends on the face from the anterior aspect of the neck (platysma muscle). SURFACE ANATOMY • • • • External Occipital Protuberance Spinous Process of the Axis (C-2) Spinous Process of C-7 (neck flexed) Laryngeal prominence: “Adam’s apple”: thyroid cartilage (larynx)located at C-4/C-5 • Hyoid Bone: superior to the thyroid cartilage, located at C-3 in the median plane, inferior to the chin SURFACE ANATOMY • Transverse Process of the Atlas: deep palpation; inferior to the mastoid process, rotate head slowly • Cricoid Cartilage: inferior to the thyroid cartilage, at the level of C6 • Tracheal rings: inferior part of the neck • Jugular (suprasternal) notch • Sternocleidomastoid muscle: clavicular and sternal heads, anterior and posterior borders SURFACE ANATOMY • Supraclavicular Fossa: triangular depression located posterior to the clavicular head of the SCM. Pressure point for the subclavian artery • Edges of the trapezius muscle: shrug the shoulders SUPERFICIAL MUSCLES OF THE NECK REGION • PLATYSMA – Wide, thin muscle located in the superficial fascia. It covers the superior part of the anterior cervical triangle and the anteroinferior part of the posterior cervical triangle. • O-fascia and skin over the pectoralis major and deltoid muscles • I-inferior border of the mandible and skin of the lower face • N-cervical branch of CNVII • F-muscle of facial expression • STERNOCLEIDOMASTOID – Key landmark in the neck. Runs superolaterally from the clavicle and sternum to the mastoid process. • O-Sternal Head: round tendon attaching to the manubrium of the sternum lateral to the jugular notch. Clavicular Head: Superior surface of the medial 1/3 of the clavicle. • I-Lateral surface of the mastoid process of the temporal bone and superior nuchal line of the occipital bone. • N-spinal roots of CNXI, and branches of C2 and C3. • F-tilt the head to the lateral side and superiorly turn it to the opposite side. When both muscles act together, they flex the neck. SUPERFICIAL MUSCLES OF THE NECK REGION • TRAPEZIUS: • O- superior nuchal line, ligamentum nuchae and spinous processes of C7, T1-T12. • I- Lateral 1/3 of the clavicle, acromion process, and spine of the scapula. • N- Accessory spinal nerve (CN XI) and cervical plexus (C3, C4). • F- Its upper portion elevates and rotates the scapula upwards in arm elevation. Its lower portion depresses and rotates the scapula downwards. – Adducts the scapula, tilts the chin, draws back acromion, rotates the scapula. CERVICALTRIANGLES The lateral aspects of the neck are divided into two distinct triangles: • ANTERIOR • POSTERIOR POSTERIOR CERVICAL TRIANGLE • BOUNDARIES • Anterior: posterior border of SCM • Posterior: anterior border of trapezius • Inferior: clavicle • Base is the clavicle, and apex is the superior nuchal line • Note: The occipital artery passes over the apex of the triangle before it ascends over the posterior aspect of the head. • ROOF is covered by the deep fascia. Superficial to it, one can find the superficial fascia, platysma, superficial veins, cutaneous nerves and skin. • FLOOR (from superior to inferior) • • • • • Splenius capitus muscle Levator scapulae muscle Scalenus posterior muscle Scalenus medius muscle Scalenus anterior muscle POSTERIOR CERVICAL TRIANGLE • The posterior cervical triangle is subdivided into two triangles by the inferior belly of the omohyoid muscle: – Occipital triangle – Supraclavicular, omoclavicular or subclavian triangle POSTERIOR CERVICAL TRIANGLE - Contents • VEINS: – External Jugular Vein= Posterior division of the Retromandibular + Posterior auricular veins • It crosses the SCM, pierces the deep fascia and it drains into the subclavian. It drains the face, scalp and exterior of the cranium • Tributaries: – Posterior/anterior external jugular veins – Suprascapular vein – Transcervical vein NOTE: The retromandibular vein is formed inside the parotid gland by the union of superficial temporal v + maxillary v. – Subclavian = main venous vessel of the UE. It lies posterior to the clavicle • ARTERIES: – Third portion of the subclavian – Transverse cervical (thyrocervical trunk) – Superficial cervical (transverse cervical) – Suprascapular (thyrocervical trunk) – Occipital (ECA) POSTERIOR CERVICAL TRIANGLE - Contents • NERVES: – CN XI: It divides the posterior triangle into a superior and inferior portions. It runs between the SCM and trapezius, and supplies motor fibers to both muscles. – The brachial plexus (between the scalene anterior and medius) – The cervical plexus • LYMPHATICS: – Anterior cervical LN – Superficial cervical LN CERVICAL PLEXUS • It is a network of nerves formed by the communication of the ventral rami of C1, C2, C3, and C4. • The plexus is located deep to the internal jugular vein and SCM. CERVICAL PLEXUS: Sensory Branches 1. 2. 3. Lesser Occipital Nerve (C2): supplies the skin over the lateral side of the occipital region. Great Auricular Nerve (C2-C3): accompanies the external jugular vein, and supplies the skin over the angle of the mandible. Transverse Cervical Cutaneous Nerve (colli)(C2-C3): supplies the skin over the anterior triangle of the neck. 4. Supraclavicular Nerve (C3-C4):It divides into three branches: 1. Medial 2. Intermediate (middle) 3. Lateral This nerve supplies the skin over the anterior aspect of the chest and shoulder. The medial and lateral supraclavicular nerves supply the sternoclavicular and acromioclavicular joints, respectively. CERVICAL PLEXUS - Branches Which branch of the cervical plexus travels with the external jugular vein? A. Greater auricular nerve B. Transverse cervical nerve C. Lesser occipital nerve D. Lateral supraclavicular nerve E. Spinal accessory nerve The lateral supraclavicular nerve supplies the sternoclavicular joint with sensory innervation. A. True B. False CERVICAL PLEXUS: Muscular Branches 5. The phrenic Nerve (C3-C4-C5): Important muscular branch of the cervical plexus. 6. The other muscular component of the plexus is the ansa cervicalis. This is a “loop” that arises from the cervical plexus and supplies the infrahyoid muscles of the neck. It’s embedded in the carotid sheath (embedded in the fascia), but it’s not a content of the sheath. ANTERIOR CERVICAL TRIANGLE • BOUNDARIES: – Anterior: median line of the neck – Posterior: anterior border of the SCM – Superior: inferior border of the mandible The apex of the triangle is at the jugular notch and its base is superior formed by the inferior border of the mandible and an imaginary line drawn from the angle of the mandible to the mastoid process. • CONTENTS: – The anterior cervical triangle contains muscles, veins, arteries, nerves, LN, and viscera. ANTERIOR CERVICAL TRIANGLE: Muscles • The hyoid bone is held in place by muscles that are attached to the mandible, skull, thyroid cartilage, sternum (manubrium), and the scapula. • These muscles are referred to as the hyoid muscles and are primarily responsible for steadying or moving the hyoid bone and larynx. • For descriptive purposes, they are divided into: • Suprahyoid muscles • Infrahyoid muscles SUPRAHYOID MUSCLES • These muscles are located superior to the hyoid bone, and they connect it (hyoid bone) to the skull. 1. Mylohyoid muscles: form the floor of the mouth. Nerve to the mylohyoid (CN V). 2. Geniohyoid muscles: they reinforce the floor of the mouth. Supplied by CN XII. 3. Stylohyoid muscles: innervated by CN VII. SUPRAHYOID MUSCLES 4. Digastric muscles: strap-like muscles that have two bellies: anterior and posterior that descend toward the hyoid bone. The two bellies are joined by a common central tendon: intermediate tendon, that is connected to the body of the hyoid bone. • • The anterior belly originates from the fossa of the mandible, and the posterior belly originates from the mastoid process. They both insert by a common tendon in the greater horn of the hyoid bone. The nerve supply to the anterior belly is the nerve to the mylohyoid muscle (CN V), and the posterior belly is supplied CN VII. INFRAHYOID MUSCLES • These are called “strap muscles” because of their ribbon-like appearance. • They are located inferior to the hyoid bone. • They anchor and depress the hyoid bone and the larynx during swallowing and speaking. INFRAHYOID MUSCLES 1. Sternohyoid muscle: supplied by the ansa cervicalis (C1, C2, C3). 2. Sternothyroid muscle: supplied by the ansa cervicalis. 3. Thyrohyoid muscle: responsible for closing the laryngeal opening during swallowing and preventing food from entering the larynx. Innervated by C1 fibers via CN XII. 4. Omohyoid muscle: it has two bellies joined by an intermediate tendon. The inferior attachment is the superior border of the scapula, and the superior attachment is the inferior aspect of the hyoid bone. Supplied by the ansa cervicalis. SUBDIVISIONS OF THE ANTERIOR CERVICAL TRIANGLE • 1. 2. 3. 4. The superior belly of the omohyoid and digastric muscles divide the anterior cervical triangle into four (4) smaller triangular regions: Digastric triangle (submandibular) Submental triangle (suprahyoid) Carotid triangle Muscular triangle 1 2 3 4 CAROTID SHEATH • It is part of the deep cervical fascia that surrounds the following structures: 1. 2. 3. 4. 5. Internal Jugular Vein Deep Cervical LN’s Vagus nerve Common Carotid Artery Internal Carotid Artery Note: These structures are contained within the sheath. The ansa cervicalis is embedded in it. CAROTID ARTERY • It is the main artery of the head and neck. • The RCC artery begins at the bifurcation of the brachiocephalic trunk, posterior to the right sternoclavicular joint. • The LCC artery arises from the aortic arch and ascends into the neck posterior to the left sternoclavicular joint. • Each carotid artery ascends within the carotid sheath to the level of the thyroid cartilage, where it terminates by dividing into the internal and external carotid arteries. CAROTID ARTERY • The external carotid arteries supply the skull, face, and neck. The internal carotid arteries supply the structures within the skull. • The common carotid and internal carotid arteries have no branches in the neck. EXTERNAL CAROTID ARTERY • BRANCHES: 1. 2. 3. 4. 5. 6. 7. 8. Superior Thyroid artery Ascending Pharyngeal artery Lingual artery Facial artery At the apex of the Occipital artery posterior cervical triangle Posterior Auricular artery Superficial Temporal artery (end artery) Maxillary artery (end artery) THE CAROTID SINUS • It is a small dilation of the proximal part of the ICA. • It is a blood-pressure-regulating area innervated by the glossopharyngeal nerve (CN IX). • It is also supplied by the vagus nerve (CN X) and sympathetic division of the autonomic nervous system. • It responds to changes in arterial blood pressure. • It is a baroreceptor that responds to increases in arterial blood pressure by slowing the heart rate via the vagus nerve. THE CAROTID BODY • It is a small ovoid mass of tissue located at the bifurcation of the common carotid arteries, in close relation with the carotid sinus. • This is a chemoreceptor that responds to changes in the chemical composition of the blood. • It responds to either increases of CO2 or H+ = decrease pH; or decreases in O2 or increases in pH leading to an increase in respiration. • Innervated by the carotid sinus nerve (branch from the CN IX), but also by CN X and the sympathetic. CERVICAL VISCERA • The cervical viscera are organized in three layers: 1. Superficial Endocrine Layer: 1. Thymus 2. Thyroid gland 3. Parathyroid gland 2. Middle Respiratory Layer: 1. Larynx 2. Trachea 3. Deep Alimentary Layer: 1. Pharynx 2. Esophagus Superficial Layer • Superior attachment – zygomatic arch • Inferior attachment – thorax, axilla. • Like subcutaneous tissue. • The platysma and muscles of facial expression are ensheathed within it. Superficial Layer of the Deep Cervical Fascia • Completely surrounds the neck. • Arises from spinous processes. • Superior border – nuchal line, skull base, zygoma, mandible. • Inferior border – chest and axilla. • Splits at mandible and covers the masseter laterally and the medial surface of the medial pterygoid. • Envelopes – SCM – Trapezius – Submandibular gland – Parotid gland • Forms floor of submandibular space Middle Layer of the Deep Cervical Fascia • Visceral Division – Superior border • Anterior – hyoid and thyroid cartilage • Posterior – skull base – Inferior border – continuous with fibrous pericardium in the upper mediastinum. – Buccopharyngeal fascia • Name for portion that covers the pharyngeal constrictors and buccinator. – Envelopes • • • • • Thyroid Trachea Esophagus Pharynx Larynx • Muscular Division – Superior border – hyoid and thyroid cartilage – Inferior border – sternum, clavicle and scapula – Envelopes infrahyoid strap muscles Deep Layer of Deep Cervical Fascia • Arises from spinous processes and ligamentum nuchae. • Splits into two layers at the transverse processes: – Alar layer • Superior border – skull base • Inferior border – upper mediastinum at T1-T2 – Prevertebral layer • • • • Superior border – skull base Inferior border – coccyx Envelopes vertebral bodies and deep muscles of the neck. Extends laterally as the axillary sheath.