Muscles of the back consist of extrinsic and intrinsic groups:

•    the extrinsic muscles -move the upper limbs and the ribs

•    the intrinsic muscles -maintain posture and move the vertebral column

•    movements include flexion (anterior bending), extension, lateral

flexion, and rotation.

The muscles of the back are organised as follows:

• Extrinsic muscles are involved in the Upper Limb (UL) and thoracic wall movement and are innervated by the anterior rami.

a)Superficial group - is related to and involved in movement of the UL.

b)Intermediate group - is related to the thoracic wall and serve as a respiratory function.

• Intrinsic muscles: are deep in position and innervated by the posterior rami. Support and move the vertebral column and head

TRAPEZIUS

• The Motor innervation of the trapezius muscle is accessory nerve.

• The Origin of the trapezius is from Sup nuchal line, ext. occipital protuberance, Ligamentum nuchae, spinous processes of Cervical 7 to Thoracic12

•The insertion of the trapezius muscle is Lateral 1/3 of the clavicle, acromion and spine of the scapula

•The function of the trapezius muscle is to Assist in rotating the scapula during abduction of the humerus, Upper fibres elevate, middle fibres retract the scapula, and lower fibers depress scapula.

LATISSIMUS DORSI

•Latissimus dorsi Is large, flat and triangular at lower portion of the back and ends in a tendon that attaches to the humerus.

• Latissimus dorsi's Motor innervation  is the thoracodorsal nerve.

•  the Latissimus dorsi originates from Spinous processes of Thoracic 7 to Lumbar 5, sacrum, iliac crest, ribs X to XII

•The  Insertion of the Latissimus dorsi is Floor of the intertubercular sulcus of humerus

• the function of the Latissimus dorsi Is to Extend, adduct, medially rotate the humerus, holds the inferior angle of scapula in place

LEVATOR SCAPULA

-levator scapula Is a slender muscle that descends from the transverse processes of the cervical vertebrae to upper portion of the medial border of the scapula.

-Motor innervation of the levator scapula is dorsal scapular nerve, C3-C4 ant rami

-The  function of  the levator scapula is to Elevate the scapula.

Rhomboid minor

-Rhomboid minor arises from ligamentum nuchae, spinous processes of CVII

Rhomboid minor attaches to medial scapula border.

-Rhomboid major arises from Thoracic two to Thoracic 5 spinous processes

Rhomboid major attaches to medial scapula border below rhomboid minor.

-Motor innervation of the Rhomboid minor and major is dorsal scapular nerve

-The function of the Rhomboid muscles is to work together to retract the scapula to the vertebral column.

•   The muscles in the intermediate group are two flat muscular sheets that lie in the superior and inferior aspects of the back.

•   The fibres from Serratus posterior superior and inferior pass outwards from the vertebral column to attach to the ribs. Referred to as the respiratory group.

•    Serratus posterior superior is deep to the rhomboid muscles.Their Fibres descend from vertebral column.

•  Serratus posterior inferior is deep to Lattisimus dorsi.Their Fibres ascend from vertebral column.

Motor innervation of the Serratus posterior superior is ant rami of T2-T5

Motor Innervation of Serratus posterior inferior is ant rami of T9-T12

Function of the   Serratus posterior superior is to Elevate ribs 2-5

Function of Serratus posterior inferior is to depresses ribs 9-12

DEEP GROUP OF MUSCLES include:

1)SUPERFICIAL LAYER: Extensors & rotators of the head and neck, which are

2)INTERMEDIATE LAYER- Extensors & rotators of the vertebral column- which is erector spinae

3)DEEP LAYER-TRANSVERSOSPINALES MUSCLE GROUP:  which are semispinalis, multifidus, rotatores

-Innervation to the deep muscles is by posterior rami of spinal nerves.

•   splenius capitus and cervicis muscles run from the spinous processes and ligamentum nuchae vertically upwards and laterally

•    Splenius capitus: Is supplied by Posterior primary rami of middle cervical nerves

-Splenius capitus Originates from the  Lower ½ Lig. Nuchae, spinous processes of Cervical 7 to Thoracic 4

-The splenius capitus Insertion is the Mastoid process, skull

•   Splenius cervicis is supplied by the Posterior rami of lower cervical nerves

-The splenius cervicis Originates from the Spinous process of Thoracic 3 to Thoracic 6

-The splenius cervicis Inserts to the Transverse process of cervical 1 to cervical 3

-The function of the both splenius cervicis and capitus is to Extend the neck.

-The function of the individual splenius muscle is to rotate the head to one

side

ERECTOR SPINAE

•The Erector spinae is covered by thoracolumbar fascia and serratus post. Inf, rhomboids, splenius muscles.

•The outermost/laterally placed column of muscles of erector spinae is iliocostalis

•The middle/intermediate column of the erector spinae is the longissimus, Largest of

the subdivisions of erector spinae