Spine and Trunk Muscles (1B)

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Rectus Abdominis

A: FLEX the vertebral column

O: Pubic crest, pubic symphysis

I: Cartilage of 5th, 6th, and 7th ribs and xiphoid process

External Oblique Abdominal

A: Unilaterally:

laterally FLEX vertebral column to the same side

ROTATE vertebral column to the opposite side

Bilaterally:

FLEX the vertebral column

O: external surfaces of 5th to 12th ribs

I: Anterior part of the iliac crest, rectus sheath to linea alba

Internal Oblique Abdominal

A: Unilaterally:

Laterally flex vertebral column to the same side

Rotate vertebral column to the same side

Bilaterally:

flex the vertebral column

O: lateral inguinal ligament, iliac crest, and thoracolumbar fascia

I: Internal surface of lower three ribs, rectus sheath to linea alba

Transverse Abdominis

A: Compress abdominal contents

O: Lateral inguinal ligament, iliac crest, thoracolumbar fascia, and internal surface of lower 6 ribs

I: Rectus sheath to linea alba

Erector Spinae Group

A: Unilaterally: laterally flex vertebral column to the same side

bilaterally: extend the vertebral column

O: common tendon (thoracolumbar fascia) that attaches to the posterior surface of sacrum, iliac crest, spinous processes of the lumbar, and last 2 thoracic vertebrae

I: Various attachments at the posterior ribs, spinous and transverse processes of thoracic and cervical vertebrae, and mastoid process of temporal bone

Quadratus Lumborum

A: Unilaterally: laterally flex the vertebral column to the same side

bilaterally: fix the last rib during forced inhalation and exhalation

assist to extend the vertebral column

O: posterior iliac crest

I: last rib and transverse processes of 1st through 4th lumbar vertebrae

Sternocleidomastoid

A: Unilaterally:

laterally flex the head and neck to the same side

rotate the head and neck to the opposite side

Bilaterally:

flex the neck

O: Sternal head: top of manubrium

clavicular head: medial one-third of the clavicle

I: Mastoid process of temporal bone and the lateral portion of superior nuchal line of occiput

Splenius Capitis

A: Unilaterally:

Rotate the head and neck to the same side

laterally flex the head and neck to the same side

Bilaterally:

extend the head and neck

O: Inferior one half of ligamentum nuchae and spinous processes of C7 to T4

I: Mastoid process and lateral portion of superior nuchal line

Splenius Cervicis

A: Unilaterally:

Rotate the head and neck to the same side

laterally flex the head and neck to the same side

Bilaterally:

extend the head and neck

O: Spinous processes of T3 to T6

I: transverse processes of C1 to C3

Trapezius (Upper)

A: Unilaterally:

laterally flex the head and neck to the same side

rotate the head and neck to the opposite side

O: External occipital protuberance, medial portion of superior nuchal line of the occiput, ligamentum nuchae, and spinous processes of C7 through T12

I: Lateral one third of clavicle, acromion, and spine of the scapula

Trapezius (Middle & Lower)

A:
O: External occipital protuberance, medial portion of superior nuchal line of the occiput, ligamentum nuchae, and spinous processes of C7 through T12
I: Lateral one third of clavicle, acromion, and spine of the scapula

Levator Scapula

A:

Laterally flex the head and neck

rotate the head and neck to the same side

BILATERALLY

Extend the head and neck

O: Transverse processes of 1st to 4th cervical vertebrae

I: medial border of scapula, between superior angle and superior portion of spine of scapula