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Back muscles anatomy

By Edited Sep 17, 2016 0 0

Overview of the back muscles anatomy

Back Muscles Anatomy
The back muscle anatomy consist of muscles that support as well as move different parts of the body like the pelvis, the spine the shoulder and the head.

These muscles are divided into two major groups:

  • The superficial (extrinsic) muscles.
  • The deep (intrinsic) muscles.

 

The superficial muscles

Superficial muscles - Back muscles anatomy

These muscles connect the upper limb with the vertebral Colum or inevitably to the trunk, these are:

§  Trapezius.

§  Rhomboid major and minor.

§  Levator scapulae.

§  Latissimus dorsi.

While Serratus posterior superior and inferior form the intermediate layer of muscles, passing from the vertebral spines to the ribs; the two muscles slope in opposite directions and are muscles of respiration.

Trapezius muscle - Anatomy back muscle

Trapezius muscle: originates from the external occipital protuberance, superior nuchal line (medially), nuchal ligament, spinous processes and their supraspinous ligaments from C7 to T12. It then inserts to the acromium and posterior lateral 1/3 of the clavicle. Its action is to elevate and steady the scapular, rotates the scapular forward to raise the arm above the head and also retracting the scapular, bracing back the shoulder.

Latissimus dorsi - Anatomy fo the back muscles
Latissimus dorsi: originates thoracolumbar fascia that starts from T7 to L5, slops up the iliac crest and ends at the superior iliac spine. It inserts on the flow of the intertubercular grove of the humerus and functions to adduct the humerus; medially rotate the humerus and downward rotation of the scapular.

Lavator scapulae - Anatomy of back muscle
Lavator scapulae: originates from spinous processes of C1 to C4 and inserts at the medial aspect of superior border of the scapular. It elevates the scapular.

Rhomboideus major - Anatomy of the muscle of the back
Rhomboideus major: origin is tendinous fibers of supraspinous ligament of T2 to T5 and inserts at medial border of the scapular inferior to the spine. It adducts and downwardly moves the scapular. 

Rhomboidus minor - Muscle of the back anatomy
Rhomboidus minor: Originates from the lower ligamentum nuchae and spines of C7 to T1, it inserts at the medial border of the scapular superior to the spine. It retracts the scapular bracing the arm backwards.

The deep muscles

Deep muscles - Anatomy back muscles

These are a complex group of muscles extending from the pelvis to the skull. It includes the following: splenius capitis, splenius cervicis, extensor spinae, iliocostalis, longissimus, spinalis, multifidus, rotators, semi-spinalis, interspinalis, and inter-transverse muscles

Splenius capitis - Muscle of the back anatomy
Splenius capitis: originates from the edge of lower half of ligamentum nuchae and supraspinous ligament of T1 toT3. The muscle passes upwards and laterally under cover of sternocleidomastoid to attach to the mastoid process and below the lower 1/3 of superior nuchal line. It extends the head.

Splenus cervicis - Anatomy back muscle
Splenus cervicis: ascends from the spinous processes of T3 to T6 to the posterior tubercles of the transverse processes of C2 to C4. It extends the neck.

Note: the iliocostalis, longissimus and spinalis muscles have a common origin which is – the tendon of erector spinae muscle at the sacrum and iliac crest.

 

Iliocostalis muscle - Anatomy of the back muscle
Iliocostalis muscle: It extends and also laterally flexes the vertebral column keeping the body in a vertical position. It further divides into three branches: the ilioostalis lumber, which inserts by a flattened tendon to inferior border of lower ninth to twelfth ribs; iliocostalis thoracis which inserts to the thoracic region of forth to eighth rib and iliocostalis cervicis which attaches to transverse processes of C2 to C3 and to the edges of third to sixth rib.

Longissimus muscle

It lies medially from iliocostalis muscle and is divided into three groups.

Longissimus thoracic - Muscle of back anatomy
Longissimus thoracic: It is the largest of all muscles originating from elector spine. It attaches to second to fifth rib.

Longissimu cervicis - Anatomy of back muscle
Longissimu cervicis: Lies medially to longissimus thoracic and inserts to the transvers processes of C1 to C2.

Longissimus capitus - Muscle of the back anatomy
Longissimus capitus: Lies between longissimus cervicis and semispinalis capitis. It inserts at the posterior margin of mastoid process. It extends the head and turns the face towards the same side as the muscle.

Spinalis muscle - Back muscle anatomy
Spinalis muscle: It resides most medially. It extends the vertebral column, maintains a medial erect position of the body and stabilizes the vertebral column. It also further divides into three groups of fibers. The spinalis thoracis, which inserts at the spinous processes of lower thoracic and most lumber vertebrae; spinalis cervicis, which inserts at spinous processes of C2 to C4 and spinalis capitis which attaches between the superior and inferior nuchal lines.

Transverso-spinalis muscles

Transverso-spinalis muscles - Back muscle anatomy

The transversospinalis muscular group consists of the following: semispinalis thoracis, rotators thoracis, multifidus, semispinalis cervicis, rotators cervicis, semispinalis capitis and rotators capitis.

They run obliquely upwards and medially from the transverse processes to adjacent, and sometimes more adjacent, spinous processes.

Semi-spinalis muscles:

Semi-spinalis thoracis - Anatomy back muscle
Semi-spinalis thoracis and cervicis extend the thoracic an cervical regions of the vertebral column, and then towards the opposite side well as semi-spinalis  capitis extends the head, and  turns the face slightly towards the opposite side.

Semi-spinalis thoracis originate from transverse processes of T6 toT12 and inserts at spinous processes of upper thoracic and most lumber vertebrae.

Semi-spinalis cervicis - Anatomy of back muscle
Semi-spinalis cervicis originates from the transvers processes of T1 to T5 and inserts at the spinous processes of C2 to C5.

Semi-spinalis capitis - Muscle of the back anatomy
Semi-spinalis capitis originates from the transvers processes of T1 to T6 inserts between the superior and inferior nuchal lines of occipital bone.

Multifidus muscle:

Multifidus muscle - Anatomy of the muscle of the back

Origin: 

Cervical region. Articular processes of lower cervical vertebrae.

Thoracic region: transverse processes of all thoracic vertebrae.

Lumber region: Have three portions; the lower portion from the dorsal sacrum, the deep surface from the tendonous part of erector spine and the last portion from mammillary process of lumber vertebra.

Insertion:  Spinous process of all vertebrae from C2 to L5.

Action: Bilaterally extends vertebrae column, controls lateral flexion to side opposite contraction and unilaterally rotates vertebral bodies to opposite side.

Rotators: They lie deep to multifidus and are fully developed only in the thoracic region. All rotators originate from transverse process of one vertebrae skip one vertebrae and insert to the spinous process of the above vertebra.

Rotators can also be categorized as short rotators and long rotators, the former attach close vertebrae and the later to the far apart vertebrae.

Segmental muscles

Segmental muscles - Muscle anatomy of the back

These are most deep muscles of the back. There are two segmental muscles:

Interspinalis muscles: These lie between spinous processes and they extend through the vertebral column.

Intertransversal muscles: These originate from the posterior and anterior tubercle of transverse processes and insert at the thoracic and lumber lateral aspect of the transverse and mammillary processes.

Lavatory costae longus: Originates from the transverse processes of cervical and thoracic vertebrae and insert at the ribs below them. They elevate the ribs.

Suboccipital muscles - Anatomy of the back muscles
Suboccipital muscles: They are four- obliqus capitis inferior, obliqus capitis superior, rectus capitis posterior minor and rectus capitis posterior major.

All muscles that make up the back muscle anatomy receive their blood supply from the branches of the axillary artery and are innervated by the posterior rami of spinal nerves.

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