Regional Anatomy II_Week 1_SP23.pdf

Week 1 Neck muscles and triangles Head and neck venous drainage Neck Borders ● Extends from base of cranium and inferior border of mandible to superior thoracic aperture. (Clavicle, manubrium, T1 vertebrae) ● Two triangles ○ ○ Anterior - extends from anterior midline to anterior border of SCM...

Week 1 Neck muscles and triangles Head and neck venous drainage Neck Borders ● Extends from base of cranium and inferior border of mandible to superior thoracic aperture. (Clavicle, manubrium, T1 vertebrae) ● Two triangles ○ ○ Anterior - extends from anterior midline to anterior border of SCM Posterior - extends from posterior border of SCM to anterior border of trapezius Musculature of the Neck ● Muscle groups of the anterior neck ○ ○ ○ ○ ○ Superficial muscles Infrahyoid muscles Suprahyoid muscles Lateral vertebral muscles Anterior vertebral muscles Superficial Muscles ● ● Platysma Sternocleidomastoid Platysma ● ● ● ● ● Thin muscle embedded in superficial fascia of neck Origin - deep fascia that covers upper parts of pectoralis major and deltoid muscles Insertion - fibers pass superficial to clavicle and run superiorly over side of neck. Some fibers insert into lower border of body of mandible while others fibers enter face and blend with muscles of lower lip and angle of mouth. Nerve supply - cervical branch of facial nerve Actions: ○ ○ ○ Tenses skin of neck Helps depress the mandible Draws down lower lip and angle of mouth Sternocleidomastoid ● ● ● ● Origin - anterior surface of manubrium of sternum (sternal head) and superior surface of medial third of clavicle (clavicular head) Insertion - 2 heads of origin join to then pass superiorly, posteriorly, and laterally to insert on to the mastoid process and lateral part of superior nuchal line Nerve supply - accessory nerve (motor) and branches from ventral rami of C2 and C3 spinal nerves (proprioceptive) Divides anterolateral part of neck into anterior and posterior triangles. Sternocleidomastoid Actions ● Unilateral contraction: ○ ○ ● Bilateral contraction: ○ ○ ● Lateral flexion of head and neck to same side of contracting muscle Rotation of head and neck to opposite side of contracting muscle Draw head forward Flexion of head and neck against resistance (rising from supine position) Can act as an accessory muscle of inspiration Deep Anterior and Lateral Neck Muscles ● ● ● ● Infrahyoid muscles Suprahyoid muscles Anterior vertebral muscles Lateral vertebral muscles Infrahyoid Muscles ● Thin, strap-like muscles that depress the hyoid and stabilizes larynx for phonation and swallowing ○ ○ ○ ○ Sternohyoid Omohyoid Thyrohyoid Sternothyroid Sternohyoid ● ● ● ● Origin - posterior surfaces of manubrium of sternum and sternal end of clavicle Insertion - body of hyoid Nerve supply - ansa cervicalis (ventral rami of C1 - C3) Action - depresses hyoid bone Omohyoid ● ● ● ● ● Inferior and superior bellies connected by an intermediate tendon Inferior belly attaches to superior border of scapula, just medial to suprascapular notch and crosses the lower part of posterior triangle of neck to end in intermediate tendon. Superior belly begins at intermediate tendon and ascends almost vertically in anterior triangle of neck attaching to the body of hyoid. Nerve supply - ansa cervicalis (ventral rami of C1 - C3) Action - depresses hyoid bone Thyrohyoid ● ● ● ● ● Upward continuation of sternothyroid Origin - oblique line of thyroid cartilage Insertion - into greater horn and body of hyoid Nerve supply - C1 fibers via hypoglossal nerve Action - depresses hyoid bone or elevates larynx Sternothyroid ● ● ● ● ● Located deep to sternohyoid Origin - posterior surface of manubrium of sternum Insertion - oblique line of thyroid cartilage Nerve supply - ansa cervicalis (ventral rami of C1 - C3) Action - depresses larynx Suprahyoid Muscles ● Elevate hyoid and depresses mandible ○ ○ ○ Digastric Stylohyoid Mylohyoid Digastric ● ● ● ● ● ● Consists of posterior and anterior bellies connected by an intermediate tendon Posterior belly attaches to digastric (mastoid) notch (medial to mastoid process) & becomes continuous with intermediate tendon. Intermediate tendon pierces stylohyoid and runs in fibrous sling connected to body and greater horn of hyoid to become continuous with anterior belly Anterior belly attaches to digastric fossa of mandible Nerve supply - posterior belly via facial nerve; anterior belly via nerve to mylohyoid (branch of inferior alveolar nerve, from V3) Actions - depresses mandible and elevates hyoid bone Stylohyoid ● ● ● ● ● Origin - Styloid process Insertion - into hyoid bone at junction of body and greater horn It is pierced near its insertion by intermediate tendon of digastric Nerve supply - facial nerve Action - elevates hyoid bone Mylohyoid ● ● ● ● ● ● Lies deep to anterior belly of digastric 2 mylohyoid muscles form muscular floor of oral cavity Origin - mylohyoid line of mandible Insertion - Most posterior fibers attach to body of hyoid bone. The rest of fibers terminate in midline raphe extending from mandible to hyoid Nerve supply - nerve to mylohyoid Actions - elevates floor of mouth and tongue during swallowing, elevates hyoid bone, depresses mandible Lateral Vertebral Muscles ● Lateral flexion of the neck and elevation of the 1st and 2nd ribs ○ ○ ○ Scalenus anterior Scalenus medius Scalenus posterior Scalenus Anterior ● ● ● Origin - transverse processes of C3 to C6 vertebrae Insertion - superior surface & medial border of 1st rib Relations: ○ ○ Anterior to scalenus anterior - subclavian vein, phrenic nerve, superficial (transverse) cervical and suprascapular arteries (branches of thyrocervical trunk), and terminal part of thoracic duct (on left side) Posterior to scalenus anterior - brachial plexus and subclavian artery (pass through interscalene triangle & is bounded by scalenus anterior, scalenus medius, and 1st rib) Scalenus Medius ● ● ● Largest and longest of scalene muscles Origin - transverse processes of C2 to C7 vertebrae Insertion - superior surface of 1st rib Scalenus Posterior ● ● ● Smallest of scalene muscles Origin - transverse processes of C4 to C6 vertebrae Insertion - outer surface of 2nd rib Anterolateral Neck ● What triangles are located here? ● What divides them? Anterior Triangle of the Neck Boundaries: ● ● ● Anterior - midline of the neck Posterior - anterior border of the sternocleidomastoid Superior - inferior border of body of mandible Subdivisions: ● ● ● ● Submandibular (digastric) triangle Carotid triangle Muscular triangle Submental triangle Submandibular Triangle Boundaries: ● ● ● ● Anterior - anterior belly of digastric Posterior - posterior belly of digastric and stylohyoid Superiorly - inferior border of body of mandible Floor - mylohyoid and hyoglossus muscles Contents ● ● ● ● ● Submandibular gland (superficial part) Facial vessels (a. and v.) Submandibular lymph nodes Hypoglossal nerve Mylohyoid nerve and vessels (a. and v.) Carotid Triangle Boundaries: ● ● ● Anterior and superior - posterior belly of digastric Anterior and inferior - superior belly of omohyoid Posterior - anterior border of sternocleidomastoid Contents ● ● ● ● Arteries - common carotid, initial segments of external and internal carotid, some branches of external carotid Veins - internal jugular and some of its tributaries Nerves - vagus, accessory, hypoglossal, ansa cervicalis, internal and external laryngeal Deep cervical lymph nodes Muscular Triangle Boundaries: ● ● ● Anterior - anterior midline of neck Posterior and superior superior belly of omohyoid Posterior and inferior anterior border of sternocleidomastoid Contents ● ● Sternohyoid and sternothyroid muscles Viscera of neck (e.g.: thyroid and parathyroid glands, larynx, trachea) Submental Triangle Only unpaired neck triangle Boundaries: ● ● ● Lateral - anterior bellies of digastric muscles Inferior - body of hyoid Floor - mylohyoid muscles Posterior Triangle of the Neck Boundaries: ● ● ● ● Apex - union of the sternocleidomastoid and the trapezius muscles at the superior nuchal line of the occipital bone Anterior - posterior border of the sternocleidomastoid Posterior - anterior border of the trapezius Inferior - middle ⅓ of the clavicle Subdivisions: ● ● Occipital Supraclavicular Posterior Triangle ● Floor consists of splenius capitis, levator scapulae, scalenus posterior, and scalenus medius (all covered by prevertebral layer of deep cervical fascia) ○ ● A small part of scalenus anterior may be present, but it is usually hidden by sternocleidomastoid Inferior belly of omohyoid crosses inferior part of posterior triangle & divides posterior triangle into occipital triangle (above it) and supraclavicular (omoclavicular or subclavian) triangle (below it) Contents ● ● ● ● ● Arteries - subclavian artery (3rd part), superficial (transverse) cervical artery, suprascapular artery, dorsal scapular artery, occipital artery Veins - external jugular vein and its tributaries, subclavian vein (occasionally) Nerves - brachial plexus and branches arising from its roots and trunks, accessory nerve, branches of cervical plexus Some cervical lymph nodes (along course of accessory nerve and superficial/transverse cervical vessels) Inferior belly of omohyoid muscle Head and Neck Venous System Superficial neck veins ● ● External jugular vein Internal jugular vein External Jugular Vein Begins posterior to angle of mandible by union of posterior auricular vein and posterior branch of retromandibular vein ● ● Posterior auricular vein drains scalp posterior and superior to auricle Retromandibular vein formed within parotid gland by union of superficial temporal and maxillary veins. At lower end of gland it divides into anterior and posterior branches. The anterior branch joins facial vein posterior branch joins posterior auricular vein to form external jugular vein. External Jugular Vein ● ● EJV descends obliquely, superficial to sternocleidomastoid, toward middle of clavicle pierces investing layer of deep cervical fascia to drains into subclavian vein Tributaries - transverse cervical, suprascapular, and anterior jugular veins Anterior Jugular Vein Begins in submental region by union of several small veins ● ● Descends close to anterior midline superior to jugular (suprasternal) notch of sternum it turns laterally and passes posterior (deep) to sternocleidomastoid which then drains into external jugular vein. Right and left anterior jugular veins are usually joined across midline by jugular venous arch Internal Jugular Vein Deep drainage of the IJV collects most venous blood from the head and neck ● ● ● ● Begins in jugular foramen, as a continuation of sigmoid sinus which ends posterior to corresponding sternoclavicular joint by joining subclavian vein to form brachiocephalic vein. Lies within carotid sheath, lateral to internal carotid artery (in upper neck), and lateral to common carotid artery (in lower neck) Deep cervical lymph nodes lie alongside internal jugular vein Upper and lower ends of IJV are dilated (superior and inferior bulbs) Internal Jugular Vein Tributaries: • Inferior petrosal sinus leaves cranial cavity via jugular foramen and drains into superior bulb • Lingual vein(s) • Pharyngeal veins • Facial vein • Superior and middle thyroid veins • Occipital vein (sometimes) Subclavian Vein ● ● ● ● Begins at lateral border of 1st rib as a continuation of the axillary vein Passes over 1st rib, anterior and slightly inferior to subclavian artery (separated by scalenus anterior muscle) Ends posterior to sternoclavicular joint by joining IJV to form brachiocephalic vein Has only one constant tributary ■ External jugular vein