MUSCLES OF THE BACK

  MUSCLES OF THE BACK

There are six pairs of large muscles in the back in addition to those that form the posterior abdominal wall.

The arrangement of these muscles is the same on each side of the vertebral column.

They are

1.       Trapezius

2.       Teres major

3.       Psoas

4.       Latissimus dorsi

5.       Quadratus lumborum

6.       Sacrospinalis.

1. TRAPEZIUS .

This muscle covers the shoulder and the back of the neck. The upper attachment is to the occipital protuberance, the medial attachment is to the transverse processes of the cervical and thoracic vertebrae and the lateral attachment is to  the clavicle and to the spinous and acromion processes of the scapula.

It pulls the head backwards,squares the shoulders and controls the movements of the scapula when the shoulder joint is in use.

2         TERES MAJOR .

This originates from the inferior angle of the scapula and is inserted into the humerus just below the shoulder joint.

It extends , adducts and medially rotates the arm.

1.       PSOAS MUSCLE

This arises from the transverse processes and bodies of the lumbar vertebrae.

It passes across the flat part of the ilium and behind the inguinal ligament to be inserted into the femur.

Together with the iliacus it flexues the hip joint.

2.       LATISSIMUS DORSI

This arises from the posterior part of the iliac crest and the spinous processes of the lumbar and lower thoracic vertebrae.

It passes upwards across the back then under the arm to be inserted into the bicipital groove of the humerus.

It adducts,medially rotates and extends the arm.

3.       QUADRATUS LUMBORUM

This muscle originates from the iliac crest then it passé upwards,parallel and close to the vertebral column and it is inserted into the 12^th rib .

Together the two muscles fix the lower rib during respiration and cause extension of the vertebral column (being backwards).

If one muscle contracts it causes lateral flexion of the lumbar region of the vertebral column.

4.       SACROSPINALIS (ERECTOR SPINAE).

This is a group of muscles lying between the spinous and transverse processes of the vertebrae.

They originate from the sacrum and are finally inserted into the occipital bone.

Their contraction causes extension of the vertebral column.