BIOL 413: Muscle Sheet One

Superficial back, trunk, and shoulder muscles

trapezius origin

superior nuchal line, external occipital protuberance, ligamentum nuchae, C7-T12 spinous processes

trapezius insertion

lateral 1/3 of clavicle, acromion, spine of scapula

trapezius action

assists in rotating scapula during abduction of humerus above horizontal. upper fibers elevate, middle fibers adduct, lower fibers depress scapula.

trapezius innervation

accessory nerve XI (motor), C3 and C4 (proprioception)

latissimus dorsi origin

spinous processes of T7-L5 and sacrum, iliac crest, ribs 10-12

latissimus dorsi insertion

floor of intertubercular sulcus of humerus

latisimmus dorsi action

extends (backwards), adducts, and medially rotates humerus

latissimus dorsi innervation

thoracodorsal nerve: C6-C8 (motor)

levator scapulae origin

transverse processes of C1-C4

levator scapulae insertion

upper portion of medial border of scapula

levator scapulae action

elevates scapula

levator scapulae innervation

C3 to C4, dorsal scapular nerve: C4, C5 (motor)

rhomboid major origin

spinous processes T2-T5

rhomboid major insertion

medial border of scapula (between spine and inferior angle)

rhomboid major action

retracts and elevates scapula

rhomboid major innervation

dorsal scapular nerve: C4, C5 (motor)

rhomboid minor origin

lower portion of ligamentum nuchae, spinous processes C7-T1

rhomboid minor insertion

medial border of scapula at spine of scapula

rhomboid minor action

retracts and elevates scapula

rhomboid minor innervation

dorsal scapular nerve: C4, C5 (motor)

pectoralis major origin

medial half of clavicle and anterior surface of sternum, first seven costal cartilages, aponeurosis of external oblique

pectoralis major insertion

lateral lip of intertubercular sulcus of humerus

pectoralis major action

adduction, medial rotation, and flexion of humerus at shoulder joint

pectoralis major innervation

medial and lateral pectoral nerves (motor)

pectoralis minor origin

anterior surfaces of 3-5 ribs and deep fascia overlying related intercostal spaces

pectoralis minor insertion

coracoid process of scapula

pectoralis minor action

depresses tip of shoulder, protracts scapula

pectoralis minor innervation

medial pectoral nerves (motor)

deltoid origin

inferior edge of the crest of the spine of the scapula, lateral margin of acromion, anterior border of lateral 1/3 of clavicle

deltoid insertion

deltoid tuberosity of humerus

deltoid action

major abductor of arm. clavicular fibers assist in flexing arm (forward), posterior fibers assist in extending the arm (backward)

deltoid innervation

axillary nerve: C5, C6 (motor and sensory)

serratus anterior origin

lateral surfaces of upper 8-9 ribs and deep fascia overlying related intercostal spaces

serratus anterior insertion

costal (inner) surface of medial border of scapula

serratus anterior action

protraction and rotation of scapula, keeps medial border and inferior angle of scapula opposed to thoracic role

serratus anterior innervation

long thoracic nerve: C5, C6, C7 (motor)

splenius capitis origin

lower half of ligamentum nuchae, spinous processes C7-T4

splenius capitis insertion

mastoid process, skull below lateral 1/3 of superior nuchal line

splenius capitis action

individually: draw and rotate head to one side (turning face)

together: draw head back and extending neck

splenius capitis innervation

posterior rami middle cervical nerves (mixed motor and sensory)

semispinalis capitis innervation

greater occipital nerve: C2 (sensory), upper cervical spine nerves like C3 (mixed motor and sensory)

semispinalis capitis origin

transverse processes of T1-T6/7 and C7, articular processes of C4-C6

semispinalis capitis insertion

medial area between superior and inferior nuchal lines of occipital bone

semispinalis capitis action

individually: pulls head posteriorly and turns it, causing chin to move superiorly and turn toward side of contracting muscle

together: pulls head posteriorly

erector spinae (general) origins

spinous processes of lower vertebrae/iliac crest, angles of ribs (3-6, lower six), transverse processes of upper 4-5 thoracic vertebrae, articular processes of lower 3-4 cervical vertebrae, spinous processes of thoracic vertebrae

erector spinae (general) insertions

posterior margin of mastoid process, angles of upper and lower ribs, transverse processes of C4-C6 and all thoracic vertebrae, spinous processes of C2 and T1-T8

erector spinae (general) actions

primary extensors of vertebral column and head

unilaterally: turn head or vertebral column laterally

bilaterally: straighten back, pull head posteriorly

erector spinae (general) innervation

posterior rami of spinal nerves (mixed motor and sensory)