Muscles of the Neck and Vertebral Column: Head Movements and Trunk Extension

Sternocleidomastoid

- Anterolateral Neck Muscles - 2-headed muscle located deep to platysma on anterolateral surface of neck - Flexes and laterally rotates head

Splenius

- Anterolateral neck muscles - Broad bipartite superficial muscle extending from upper thoracic vertebrae to skull - Extend or hyperextend head

Scalenes

- Anterolateral neck muscles - More later than anterior on neck; deep to platysma and sternocleidomastoid - Elevate first 2 ribs (aid in respiration); flex and rotate neck

2 functional groups

- Anterolateral neck muscles: move head - Intrinsic muscles of the back: extend trunk and maintain posture

Splenius (Intrinsic Muscles of the Back)

- Broad bipartite superficial muscle extending from upper thoracic vertebrae to skull; capitis portion covers and holds down deeper neck muscles - Extend or hyperextend head

Semispinalis

- Composite muscle forming part of deep layer of intrinsic back muscles; extends from thoracic region to head - Extends vertebral column and head and rotates them to opposite side

Quadratus lumborum

- Fleshy muscle forming part of posterior abdominal wall - Laterally flexes vertebral column when acting separately; when together, lumber spine extends and 12th rib is fixed; maintains upright posture

Longissimus

- Intermediate tripartite muscle group of erector spinae; extend by many muscle slips from lumbar region to skull - Extend and laterally flex vertebral column; capitis extends head and turns the face toward the same side

Erector Spinae

- Intrinsic muscle of the back - Prime mover of back extension

Iliocostalis

- Most lateral muscle group of erector spinae muscles; extend from pelvis to neck - Extend and laterally flex the vertebral column; maintains posture

Spinalis

- Most medial muscle column of erector spinae; cervicis usually rudimentary and poorly defined - Extends vertebral column