Second Order: Back

Trapezius

Action: Elevate, Superiorly Rotate, Retract, and Depress Scapula
Origin (M.I.P): Medially attached to occipital bone, ligamentum nuchae, and spinous process of C7- T12
Insertion (L.S.D): Laterally attached to Clavical, Acromion Process, and Spine of Scapula
Innervation: Accessory Nerve

Levator scapulae

Action: Elevates and Inferiorly rotates Scapula

Origin (MIP): Inferiorly attaches to the superior part of the medial border of scapula

Insertion (LSD): Superiorly attaches to the transverse process of the C1-C4 vertrebrae

Innervation: Cervical nerves (C3-C4) and dorsal scapular nerve (C5)

Rhomboid major

Action: Elevates, retracts, and inferiorly rotates scapula

Origin (MIP): Medially attaches to the spinous processes of T2-T5 vertebrae

Insertion (LSD): Laterally attaches to the medial border of the scapula from spine to inferior angle

Innervation: Dorsal Scapular Nerve

Subscapularis

Action: Medially rotates arm

Origin (MIP):Subscapular fossa of scapula

Insertion (LSD): Lesser tubercle of humerus

Innervation: Upper and lower subscapular nerves (C5–C6)

Supraspinatus

Action: Abducts arm

Origin (MIP): Supraspinous fossa of scapula

Insertion (LSD): Greater tubercle of humerus

Innervation:Suprascapular nerve (C5–C6)

Latissimus dorsi

Action: Agonist of arm extension; adducts arm; medially rotates arm (“swimmer’s muscle”)

Origin (MIP): Spinous processes of T7–T12 vertebrae; ribs 8–12; iliac crest; thoracolumbar fascia

Insertion (LSD): Intertubercular sulcus of humerus

Innervation: Thoracodorsal nerve (C6–C8)

Longissimus group

Action: Bilateral action: Extends vertebral column; maintains posture Unilateral action: Laterally flexes vertebral column

Origin (MIP):Tendon from posterior part of iliac crest, posterior sacrum, and lumbar spinous processes

Insertion (LSD): Mastoid process of temporal bone and transverse processes of cervical and thoracic vertebrae

Innervation: Cervical and thoracic spinal nerves

Rotatores

Action: Bilateral action: Extends vertebral column Unilateral action: Rotates vertebral column toward the opposite side

Origin (MIP): Transverse process of immediately inferior vertebra

Insertion (LSD): Spinous process of each vertebra

Innervation: Cervical, thoracic, and lumbar spinal nerves

Splenius capitis and cervicis

Action: Unilateral action: Turns head to same side Bilateral action: Extends neck

Origin (MIP): Ligamentum nuchae

Insertion (LSD): Occipital bone and mastoid process of temporal bone

Innervation: Cervical spinal nerves

Interspinales

Action: Extends vertebral column

Origin (MIP): Spinous processes of more inferior vertebra

Insertion (LSD): Spinous process of each vertebra

Innervation: Cervical, thoracic, and lumbar spinal nerves

Gluteus maximus

Action: Extends thigh; laterally rotates thigh

Origin (MIP): Iliac crest, sacrum, coccyx

Insertion (LSD): Iliotibial tract of fascia lata; linea aspera and gluteal tuberosity of femur

Innervation: Inferior gluteal nerve (L5–S2)

Gluteus medius

Action: Abducts thigh; medially rotates thigh

Origin (MIP): Posterior iliac crest; lateral surface between posterior and anterior gluteal lines

Insertion (LSD): Greater trochanter of femur

Innervation: Superior gluteal nerve (L4–S1)

Superior gemellus

Action: Laterally rotates thigh

Origin (MIP): Ischial spine and tuberosity

Insertion (LSD): Obturator internus tendon

Innervation: Nerve to obturator internus (L5–S1)

Piriformis

Action: Laterally rotates thigh

Origin (MIP): Anterolateral surface of sacrum

Insertion (LSD): Greater trochanter

Innervation: Nerve to piriformis (S1–S2)

Quadratus femoris

Action: Laterally rotates thigh

Origin (MIP): Lateral border of ischial tuberosity

Insertion (LSD): Intertrochanteric crest of femur

Innervation: Nerve to quadratus femoris (L5–S1)

Obliquus capitis superior

Action: Turns head to same side

Origin (MIP):Transverse process of atlas

Insertion (LSD):Inferior nuchal line of occipital bone

Innervation: Suboccipital nerve (posterior ramus of 1st cervical spinal nerve)

Rectus capitis posterior major

Action: Extends neck

Origin (MIP): Spinous process of axis

Insertion (LSD): Inferior nuchal line of occipital bone

Innervation: Suboccipital nerve (posterior ramus of 1st cervical spinal nerve)