Neck Anatomy PDF

TRIANGLES OF THE NECK – part 1 Dr. David Hopper Surface Anatomy Synonyms for neck: cervix, collum, nucha Important landmarks of the neck: Hyoid bone- level of inferior mandible and C3. Not articulating with any other bones. Held by 4 supra-muscles and 4 infra-muscles and ligaments. Laryngeal prom...

TRIANGLES OF THE NECK – part 1 Dr. David Hopper Surface Anatomy Synonyms for neck: cervix, collum, nucha Important landmarks of the neck: Hyoid bone- level of inferior mandible and C3. Not articulating with any other bones. Held by 4 supra-muscles and 4 infra-muscles and ligaments. Laryngeal prominence - Midline elevation created by the thyroid cartilage. Thyroid notch - Depression on superior border of laryngeal prominence. Suprasternal (jugular) notch - Groove located upon superior border of manubrium between two clavicular heads. Supraclavicular fossa - Depression located lateral to clavicular origin of sternocleidomastoid m., posterior to middle third of clavicle, and anteromedial to clavicular insertion of trapezius m. -This fossa may serves as a pressure point to decrease bleeding of the upper extremity. Surface Anatomy Thyroid notch Supraclavicular fossa Skeletal & Cartilaginous Structures Cricoid cartilage Fascial Layers of the Neck Skin of neck - Loose; overlies platysma m. Superficial fascia – loose connective tissue, including the: -Platysma muscle - Superficial muscle originating from clavipectoral fascia, coursing superiorly over neck, inserting along with several muscles of facial expression into skin around the chin and mouth. -Innervated by the cervical branch of the facial nerve. Investing layer of dense connective tissue – a “sleeve” binding all structures in the neck.**Splits to encompass SCM and Trapezius muscles. Infrahyoid fascia – covering supra & infrahyoid muscles (strap muscles). Pretracheal fascia – viscera covered with a layer of fascia including the thyroid & parathyroid glands, trachea & esophagus. Carotid Sheath - carotid a. & v., vagus n. Prevertebral (deep cervical) fascia – covering vertebral musculature. Fascial Layers of the Neck The neck is divided into Anterior and Posterior triangles Posterior Triangle Boundaries Anterior - Sternocleidomastoid muscle Posterior - Trapezius muscle Inferior (base) - Clavicle Roof – Skin, superficial fascia and platysma (only covers lower portion of the triangle), Investing Fascia covering SCM & Trapezius muscles. Floor – Prevertebral (deep) fascia covering Splenius Capitis, Levator Scapulae, and the Scalene muscles. Roof- Platysma External Jugular Vein -The jugular veins carry blood from the head to the superior vena cava, which empties into the heart. -The external jugular vein is closest to the skin and can sometimes be seen as a rope-like bulge on the side of the neck. -Bulging of the external jugular vein is known as jugular vein distention. -The height of the bulge measured from the top of the clavicle is an indirect indicator of the central venous pressure, the pressure in the right atrium. -Jugular vein distention is affected by the position of the body. -If the height is greater than 3 to 4 centimeters when measured supine with head elevated 45 degrees, this may signal vascular or heart disease. Venous Drainage in the Neck • External Jugular Vein (superficial to SCM) drains into the Subclavian vein • Internal Jugular Vein (deep to SCM) joins the subclavian vein to form the Brachiocephalic Vein (bilaterally) The internal jugular vein is much larger and deeper than the external jugular vein • The right and left brachiocephalic veins join to form the Superior vena cava which, in turn, empties into the right atrium of the heart • The Retromandibular vein splits into anterior and posterior branches, the anterior branch joins with facial vein to from the Common facial vein which then drains into the internal jugular vein • Posterior retromandibular vein drains into the external jugular vein • Anterior jugular veins also drain into the external jugular vein External Vs. Internal Jugular Veins Venous Drainage of Head and Neck External jugular Vein Internal Jugular Vein Superior Vena Cava Posterior triangle of the neck Sternocleidomastoid (SCM) muscle: O: Sternal Head: anterior surface of the manubrium (sternum). Clavicular Head: superior surface of medial 1/3rd of clavicle. I: Lateral surface of mastoid process; lateral half of superior nuchal line. N: Spinal root of Accessory (CN XI). F: Laterally flexes neck to same side and rotates head toward opposite side (and somewhat superiorly). Acting together, these muscles flex the neck so chin is thrust forward. Trapezius muscle: O: Medial third of superior nuchal line, external occipital protuberance, nuchal ligament, spinous processes of C7-T12 vertebra, lumbar and sacral spinous processes. I: Lateral third of clavicle, acromion, and spine of the scapula. N: Spinal root of Accessory (CN XI; Motor); C2-C3 (pain, proprioception). F: Elevate, retract, adduct and rotate scapula; Superior fibers: elevate pectoral girdle, maintain level of shoulders against gravity or resistance -Patients frequently have tight upper trapezius, weak inhibited mid and lower trapezius Spasm of the Sternocleidomastoid Muscle – Torticollis Torticollis, also known as wry neck or loxia,is a symptom defined by an abnormal asymmetrical head or neck position due to a variety of reasons. Torticollis is derived from the Latin words tortus for twisted and collum for neck Sternocleidomastoid (SCM) and upper trapezius trigger points – whiplash, anterior head carriage, poor biomechanics, etc. Trigger points can refer to the ear, neck, chin, vertex, forehead, eye, occiput, temple, shoulder, etc Cervical Plexus C1-C4 Ventral Rami Erb’s Point Erb's point – An area halfway along the posterior border of the SCM muscle where the sensory portion of the cervical plexus emerges Lesser occipital: From ventral rami of C2 and sometimes 3; Cutaneous to mastoid process Great auricular: From ventral rami of C2-3; Cutaneous to area around ear Transverse cervical: From ventral rami of C2-3; Cutaneous nerve to throat Supraclavicular: From ventral rami of C3-4; Splits into three branches - anterior, middle and posterior (also called medial, intermediate and lateral); Cutaneous to area over clavicle Also emerging from Erb’s Point Accessory (cranial nerve XI): From medulla oblongata; Motor to sternocleidomastoid and trapezius Erb's point Erb’s Point Floor of the Posterior Triangles 1. 5. 2. 4. 3. Posterior triangle2 sub-triangles divided by inferior belly of omohyoid Occipital triangle - Upper triangle, larger; Boundaries - sternocleidomastoid, trapezius, inferior belly of omohyoid. Supraclavicular triangle - Lower triangle, smaller; Boundaries - sternocleidomastoid, clavicle, inferior belly of omohyoid. Scalene Muscles Anterior scalene: 0: anterior tubercles of transverse processes C3-6 I: scalene tubercle of 1st rib (of Lisfranc) N: C4-6 F: elevate 1st rib (forced inspiration), flex and laterally flex neck Middle scalene - largest and longest: 0: posterior tubercles of transverse processes C2-7 I: upper surface of 1st rib N: C3-8 F: elevate 1st rib (forced inspiration), lateral flex neck Posterior scalene: 0: posterior tubercles of transverse processes C4-6 I: upper surface of 2nd rib N: C5-7 F: elevate 2nd rib (forced inspiration), laterally flex neck Scalene Muscles Scalenes – trigger points check for neck dysfunction and improper breathing since the scalenes are accessory breathing muscles attaching to the first and second ribs If scalenes become tight enough they can be a cause of “thoracic outlet syndrome” - Irritation of the brachial plexus and/or subclavian/axillary artery ***roots and trunks of brachial plexus and subclavian A. between the anterior and middle scalenes Scalene Muscles Contents of the Occipital Triangle Upper portion of brachial plexus (Roots & Trunks) Cervical Plexus Sensory portion - The sensory portion of the cervical plexus is more superficially placed than the motor portion and is located directly posterior to the sternocleidomastoid m. The sensory branches are: 1. Lesser occipital n. - C2 (C3) - To mastoid region and superior ear. 2. Great Auricular n. - C2, C3 - To the ear. 3. Transverse cervical n. - C2, C3 - To the neck. 4. Supraclavicular n. - C3, C4 - Medial, intermediate, and lateral branches to skin above the clavicle and deltoid m. Motor portion - The motor portion of the cervical plexus lies deep to the sensory portion and much of it can be found in the anterior -carotid triangle. The motor portion makes up the Ansa Cervicalis. The two limbs (roots) of the ansa cervicalis are: 1. C1 ventral ramus - provides separate motor innervation to the thyrohyoid and geniohyoid muscles and also forms the Superior Root Of The Ansa Cervicalis (descendens hypoglossi). 2.C2 and C3 rami - combine to form the Inferior Root Of The Ansa Cervicalis (descendens cervicalis). The ansa cervicalis is deep to the SCM and superficial to the carotid sheath Cervical Plexus Cervical Plexus – Sensory Portion Motor Portion of Cervical Plexus – Ansa Cervicalis, ventral rami branches to prevertebral cervical muscles, contribution to the Phrenic nerve (other is from Brachial plexus) Ansa Cervicalis The ventral ramus of C1 runs along with the hypoglossal nerve. The fibers of C1 give several branches which leave CN XII (blue boxes) 1. Superior root of the ansa cervicalis (descendens hypoglossi). participates in the ansa cervicalis 2. Nerve to the thyrohyoid which innervates the muscle of the same name 3. Nerve to the geniohyoid continues with the hypoglossal n. as it exits the carotid triangle, and innervates the muscle of the name Branches from the ventral ramus of C2 and C3 join together to form the Inferior root of ansa cervicalis (descendens cervicalis). Together the superior and inferior roots combine to form the ansa cervicalis. The ansa cervicalis gives off many branches which provide motor innervation to the infrahyoid (strap) mm. (i.e. both bellies of the omohyoid, sternohyoid, sternothyroid; red boxes). Phrenic nerve - part of the cervical plexus and brachial plexus. It arises from the ventral rami (anterior primary divisions) of C3, C4, and C5 with C4 providing the most significant contribution. The phrenic nerve provides motor innervation to the diaphragm (green box). Cervical Plexus