LP2 muscles of the back

Action origin insertion

Trapezius upper

Action:

• Superior fibers: elevation of scapula; superior rotation of scapula

Origin:

• Occipital bone 

• Nuchal ligament

Insertion:

• Clavicle

Action origin insertion

Trapezius middle

Action:

• Middle fibers: retraction (adduction) of scapula

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Origin:

• C7 and upper thoracic v

Insertion:

• Scapula

Action origin insertion

Trapezius lower

Action:

• Inferior fibers: depression of scapula

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Origin:

• Spinous processes of T1-12 vertebrae

Insertion:

• Scapula

Action origin insertion

Latissimus dorsi

Action:

• Adduction of arm

• Extension of arm

• Medial rotation of arm

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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

Rhomboid major

Action:

• Retraction (adduction) of scapula

• Elevation of scapula

Origin:

• Spinous processes of T2-5 vertebrae

Insertion:

• Medial border of scapula

Action origin insertion

Rhomboid minor

Action:

• Retraction (adduction) of scapula

• Elevation of scapula

Origin:

• Spinous processes of C7-T1 vertebrae

Insertion:

• Medial border 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 LumborumAction:

• Lateral flexion of trunk (single)

• Extension of trunk (paired)

• Fix/depress rib 12