Extrinsic (do not belong to back itself); Produce/control LIMB movements; includes:

• Trapezius
• Latissimus Dorsi
• Levator Scapulae
• Rhomboids

Extrinsic (not part of back itself); Produce respiratory movement; Includes:

1. Serratus Posterior Superior: lies deep to rhomboids and extends downward from spines of vertebral column to Ribs 2-5.

2. Serratus Posterior Inferior: lies deep to latissimus dorsi and extends upward from lower thoracic/upper lumbar spine to lower 4 ribs (9-12)

Originates from back; produces vertebral column movement and maintains posture; 3 layers:

1. Superficial Intrinsic: most superficial of deep m's;

• Splenius Capitis
• Splenius Cervicis

2. Erector Spinae: intermediate intrinsic layer;

• Iliocostalis
• Longissimus
• Spinalis

3. Transversospinal Group: Deepest intrinsic layer;

• Semispinalis (5-7 vertebrae)
• Multifidus (2-4 vertebrae)
• Rotator longus/brevis (1-2 vertebrae)

Deep muscles of back: superficial intrinsic;

O: Ligamentum nuchae, spinous processes of vertebrae C7-T6

I: Mastoid process of temporal and nuchal line of occipital, transverse processes of C1-C4

N: Dorsal Rami of cervical spinal nerves

A: Bilaterally extends, or laterally rotates/flexes head to same side

Deep Muscles of the Back: Intermediate Intrinsic; extends pelvis-skull; lateral to medial (I love spaghetti):

• Iliocostalis
• Longissimus
• Spinalis

3 layers arranged in 3 longitudinal, parallel columns; bilaterally maintains errect posture; unilaterally flexes vertebral column to same side

Deep back muscle: intermediate intrinsic (erector spinae);

O: Iliac crests (lumborum); inferior 6 ribs (thoracis); and ribs 3-6 (cervicis)

I: Angles of ribs (lumborum and thoracis), transverse processes of cervical vertebrae C6-C4 (cervicis)

N: Dorsal Rami of spinal nerves

A: Bilaterally extends vertebral column; ipsolaterally bends vertebral column to same side (lateral flexion)

Deep back muscle: intermediate intrinsic (erector spinae);

O: Transverse processes of lumbar to cervical vertebrae

I: Transverse processes of thoracic through cervical vertebrae and to ribs superior to origin; capitis inserts into mastoid processes of temporal bone

N: Dorsal Rami of spinal nerves

A: Extends vertebral column (thoracic and cervical vertebrae together); acting on one side= bend laterally; capitis extends head and turns face toward same side

Deep back muscle: Intermediate intrinsic (erector spinae);

has 3 parts also: thoracics, cervices, and capitis;

O: Spines of lumbar and thoracic lower vertebrae

I: Spines of upper thoracic and cervical vertebrae

N: Dorsal Rami of spinal nerves

A: Extends vertebral column (and possibly head)

Deep muscles of the back; Deepest layer; 3 muscles:

• Semispinalis
• Multifidus
• Rotatores

All extend from inferior lateral to superior medially from transverse processes to spinous processes

Deep back muscle: Deep intrinsic layer (Transversospinal group); spans to 6 vertebrae above;

O: Transverse processes of C7-T12

I: Occipital bone (capitis); spinous processes of cerical (cervicis) and thoracic vertebrae T1-T4 (thoracis)

N: Dorsal Rami of spinal nerves

A: Bilaterally extends head and spine; unilaterally rotates head and neck to opposite side

Deep back muscle: Deep intrinsic layer (Transversospinal group); spans to 4 vertebrae above;

O: Posterior sacrum, L1-5 mamillary processes, T1-12 transverse processes, C4-7 articular processes

I: Spinous Processes (4 above)

N: Dorsal Rami of spinal nerves

A: Bilaterally extends spine; unilaterally rotates spine to opposite side

Deep back muscle: Deep intrinsic layer (Transversospinal group); spans to 1-2 vertebrae above;

O: Transverse Processes

I: Spinous processes (1-2 above)

N: Dorsal Rami of spinal nerves

A: Bilaterally extends spine; unilaterally rotates spine to opposite side

Really not a back muscle; forms part of abdominal wall;

O: Iliac crest and iliolumbar fascia

I: Transverse processes of upper lumbar vertebrae and lower margin of 12th rib

N: Ventral Rami

A: Bilaterally extends spine and fix 12th rib; unilaterally flexes trunk to same side (lateral flexion)

Vertical band-like muscle; paired (separated by linea alba); covered anteriorly & posteriorly by rectus sheath;

O: Pubic crest & symphysis

I: Xiphoid process and costal cartilages of ribs 5-7

N: Intercostal nerves

A: Flexes lumbar region of vertebral column (trunk); compresses abdomen (increase intraabdominal pressure)

Flat, horizontal muscle; most superficial of 3 horizontal m's; fibers run down and inward;

O: Lower 8 ribs

I: Linea alba

N: Intercostal nerves

A: Aids rectus abdominis in flexing and rotating spine (to opposite side) and compressing abdomen

Flat, horizontal muscle; most intermediate of 3 horizontal m's; Upper fibers run superiorly, middle fibers run horizontally, lower fibers run inferiorly;

O: Lumbodorsal fascia, iliac crest, and inguinal ligament

I: Linea alba, pubic crest, & last 3 ribs

N: Intercostal nerves

A: Flexes and rotates spine/trunk to same side; compresses abdomen

Flat, horizontal muscle; deepest layer of 3 horizontal m's; Fibers run horizontally

O: Inguinal ligament, lumbodorsal fascia, cartilages of last 6 ribs, iliac crest

I: Linea alba, pubic crest

N: Intercostal nerves

A: Compresses abdomen