Back Muscle's A/P

Trapezius - Upper (Superior)

Origin:

• Occipital bone (superior nuchal line)

• Nuchal ligament

Insertion:

• Clavicle (lateral)

Action:

• Superior fibers: elevation of scapula; superior rotation of scapula (glenoid cavity directed superiorly)

Trapezius - Middle

Origin:

• C7 and upper thoracic v

Insertion:

• Scapula (spine and acromion)

Action:

• Middle fibers: retraction (adduction) of scapula

Trapezius - Lower (inferior)

Origin:

• Spinous processes of T1-12 vertebrae

Insertion:

• Scapula (base of spine)

Action:

• Inferior fibers: depression of scapula

Latissimus Dorsi

Origin:

• Sacral and lumbar spines via thoracolumbar fascia

• Ilium (iliac crest) 

• Ribs (lower four)

• Spinous processes of T6-12 vertebrae

• Scapula (inferior angle)

Insertion:

• Intertubecular sulcus of the humerus

Action:

• Adduction of arm

• Extension of arm

• Medial rotation of arm

Rhomboid Major

Origin:

• Spinous processes of T2-5 vertebrae

Insertion:

• Medial border of scapula

Action:

• Retraction (adduction) of scapula

• Elevation of scapula

Rhomboid Minor

Origin:

• Spinous processes of C7-T1 vertebrae

Insertion:

• Medial border of scapula

Action:

• Retraction (adduction) of scapula

• Elevation of scapula

Iliocostalis (Erector Spinae)

Action:

•  lateral flexion of vertebral column (single)

• extension of vertebral column (paired)

• Depression of ribs

Longissimus (Erector Spinae)

Action:

•  lateral flexion of vertebral column (single)

• extension of vertebral column (paired)

• Depression of ribs

Spinalis (Erector Spinae)

Action:

•  lateral flexion of vertebral column (single)

• extension of vertebral column (paired)

• Depression of ribs

Quadratus Lumborum

Action:

• Lateral flexion of trunk (single)

• Extension of trunk (paired)

• Fix/depress rib 12