Muscular System: Muscles of the Neck and Superficial Thorax

muscles of the neck

-primarily originate on axial skeleton and travel superiorly

-allow for head and neck movements: head occurs at atlanto-occipital joint, neck allows movement at C2-C7

-movements include flexion, extension, lateral flexion, and rotation

-sternocleidomastoid, scalenes, splenius

sternocleidomastoid

-two-headed muscle on anterolateral aspect

-delineates borders of anterior and posterior triangles of the neck

-origin: manubrium of sternum, medial clavicle

-insertion: mastoid process of temporal bone

-action: head/neck flexion, lateral flexion, contralateral rotation

-innervation: CN II (accessory), C2-C3

scalene muscles- overview

-anterior, middle, posterior

-synergist of sternocleidomastoid

-lateral aspect of the neck, deep to SCM

anterior scalene

-origin: transverse processes of C3-C6

-insertion: 1st rib

-action: neck flexion, lateral flexion, elevate ribs 1, 2 (breathing)

-innervation: ventral rami C3-C8

middle scalene

-origin: transverse processes of C2-C7

-insertion: 1st rib

-action: neck flexion, lateral flexion, elevate ribs 1-2 (breathing)

-innervation: ventral rami C3-C8

posterior scalene

-origin: transverse processes of C5-C7

-insertion: 2nd rib

-action: neck flexion, lateral flexion, elevate ribs 1-2 (breathing)

-innervation: ventral rami C3-C8

splenius- overview

-splenius capitis and cervicis

-deep to trapezius

-antagonist to SCM and scalenes, works with SCM for lateral flexion

splenius capitis

-origin: spinous processes C7-T6, nuchal ligament

-insertion: mastoid process, superior nuchal line

-action: head/neck extension, neck lateral flexion and ipsilateral rotation

-innervation: dorsal rami C3-C4

splenius cervicis

-origin: spinous processes C7-T6, nuchal ligament

-insertion: transverse processes of C1-C4

-action: neck extension, neck lateral flexion and ipsilateral rotation

-innervation: dorsal rami C5-C6

superficial muscles of the thorax

-primarily run from ribs or vertebral column to pectoral girdle

-provide movement of the scapula including elevation/depression, protraction/retraction, and upward/downward rotation

-anterior: pectoralis minor, serratus anterior, subclavius

-posterior: levator scapulae, trapezius, rhomboids (major + minor)

pectoralis minor

-deep to pectoralis major

-origin: anterior surface of ribs 3-5

-insertion: coracoid process of scapula

-action: depression and protraction of scapula, elevates ribs

-innervation: medial pectoral nerve, C8-T1

brachial plexus

C5-T1

serratus anterior

-deep and inferior to pectoral muscles

-forms medial wall of axilla

-origin: muscle slips on ribs 1-8

-insertion: anterior medial border of scapula

-action: protraction of scapula (PM), upward rotation

-innervation: long thoracic nerve C5-C7

subclavius

-small cylindrical muscle

-origin: costal cartilage of rib 1

-insertion: groove on inferior surface of clavicle

-action: depress pectoral girdle, stabilizer

-innervation: nerve to the subclavius- C5

trapezius

-most superficial

-broad, triangular muscle

-upper, middle, and lower portions

-origin: external occipital protuberance, nuchal ligament, spinal processes of C7-C12

-insertion: acromion, spine of scapula, lateral 1/3 clavicle

-action: upper: elevate, middle: retraction: lower: depression. upward rotation

-innervation: CN 11 (accessory), C3-C4

levator scapulae

-deep to upper trapezius

-origin: transverse processes C1-C4

-insertion: medial border of scapula, near superior angle

-action: elevation of scapula, retraction, downward rotation

-innervation: dorsal scapular nerve C4-C5, C3-C4

rhomboids- overview

-major and minor

-rectangular muscles, deep to trapezius, inferior to levator scapulae

rhomboid major

-origin: spinous processes T2-T5

-insertion: medial border of scapula, inferior to the spine

-action: retraction, elevate, downward rotation

-insertion: dorsal scapular nerve C4-C5

rhomboid minor

-origin: spinous processes C7-T1

-insertion: medial border of scapula, at level or superior to spine

-action: retraction, elevate, downward rotation

-insertion: dorsal scapular nerve C4-C5

muscles that flex the neck

sternocleidomastoid, scalenes

muscles that flex the head

sternocleidomastoid

muscles that extend the neck

splenius cervicis and capitis

muscles that extend the head

splenius capitis

muscles that rotate the head/neck

-sternocleidomastoid --contralateral

-splenius capitis and cervicis (only neck) --ipsilateral

muscles that laterally flex the head/neck

-sternocleidomastoid

-splenius capitis and cervicis (only neck)

-scalenes

muscles that elevate the scapula

upper trapezius, levator scapulae, rhomboids

muscles that depress the scapula

lower trapezius, pectoralis minor, subclavius (whole PG)

muscles that protract the scapula

pectoralis minor, serratus anterior

muscles that retract the scapula

middle trapezius, levator scapulae, rhomboid major and minor

muscles that upward rotate the scapula

trapezius, serratus anterior

muscles that downward rotate the scapula

levator scapulae, rhomboids