Muscles of The Back

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Muscles of The Back

Every one of us is well familiar with the division of muscles of the back. According to medical science, these muscles are divided into 3 different groups. Superficial, Intermediate, & deep.

Sr. No Muscles of The Back Type Description
1 Superficial Muscles of Back The superficial muscles of the back are associated with the movements of our shoulder.
2 Intermediate Muscles of Back Intermediate muscles of the back linked with the movement of our thoracic cage.
3 Deep Muscles of Back Deep Muscles of the back associated with the movements of vertebral column.

According to their development in the back, they are called the intrinsic muscles & extrinsic muscles. The deep muscles of our back develop embryologically and hence called intrinsic whereas the superficial & intermediate muscles do not develop and that’s why it is called extrinsic muscles. Let’s talk about these muscles one by one!

Superficial Muscles of The Back

The Superficial muscles of back lie under the skin & superficial fascia. These muscles start from the vertebral column and directly attached to the shoulder bones which are

  1. Clavicle.
  2. Scapula.
  3. Humerus.

That is why all of these muscles are strongly linked with the movement of the upper limb.

The superficial muscles group comprises of following muscles

  1. Trapezius
  2. Latissimus Dorsi.
  3. Levator Scapulae
  4. Rhomboids.

The latissimus & Trapezius lie superficially with the trapezius covering the levator scapulae & rhomboids. Let’s have a brief discussion on above mentioned muscles of back!

Trapezius Muscle of Back

It is called trapezius muscle because it its trapezius shape. These muscles are flat, triangular, and flat muscles. Among all the muscles of the back Trapezius is the most superficial muscle.

Attachments The Trapezius Muscles starts from the SkullLigamentum NuchaeSpinous Processes of C7-T12 The fibers of Trapezius muscles attached to ClavicleAcromionScapula Spine
Innervation Receiving the messages or moto innervation is from the accessory nerves. From c3 & c4 spinal nerves the Trapezius muscles also receives fibers.
Actions During the abduction of our arm the upper fibers of it rotates and elevates the scapula. The middle fibers actually retract the scapula while the lower one pulls the scapula inferiorly.

Latissimus Dorsi

The latissimus dorsi muscles without any doubt covers a great area of back it originally starts from the lower part of our back.

Attachments Latissimus Dorsi as mentioned above has wide origin from Spinous processes of T6-T12Iliac Crest.Thoracolumbar Fascia. Inferior 3 ribs. The fibers of Latissimus Dorsi converges into the tendons of our back which directly attached to the intertubercular sulcus of the humerus.
Innervation Thoracodorsal nerve.
Actions Rotates the upper limb of back.

Levator Scapulae

The Lavator is a kind of small strap type muscles which starts from the neck & went down through the scapula.

Attachments Starts from the transverse processes of the C1-C4 spine & went down to the medial border of scapula.
Innervation Dorsal Scapular Nerve.
Actions Perform the functionality of Scapula Elevation.  

Rhomboids

If you are a medical student then you might be familiar with the types of Rhomboids. If yes then its good but if not then I must feel to describe both types of Rhomboids one by one.

There are 2 types of Rhomboids.

  1. Major Rhomboids.
  2. Minor Rhomboids.

Let’s explore both of them one by one.

Major Rhomboids

Attachments Starts from the Spinal Processes of T2-T5 and directly attaches to the border (medial) of Scapula between the inferior angle and scapula spine.
Innervation Dorsal Scapular Nerve.
Actions Rotates & Retracts the Scapula.   

Minor Rhomboid

Attachments Starts from the Spinal processes of the C7-T1 spine & went down to the medial border of scapula at spine of scapula.
Innervation Dorsal Scapular Nerve.
Actions Perform the functionality of Scapula Elevation.  

Intermediate Muscles of The Back

The intermediate muscles of the back are divided into the 2 types of muscles

  1. Serratus Posterior Superior.
  2. Serratus Posterior Inferior.

The intermediate muscles of the back begin from the vertebral column and pass through the ribcage. The main functionality of muscles is to help elevating & depressing the ribs.  These muscles also have a minor function in respiratory.

Serratus Posterior Superior

The Serratus Posterior Superior muscles of the back are bit think and rectangular in shape. It exists deep to the rhomboid muscles located on the upper back portion.

Attachments These muscles start from the lower part of Ligamentum Nuchae.CervicalThoracic Spines from C7 to T3. The fibers of these muscles having direction inferolateral and attached through the ribs 2 to 5.
Innervation Intercostal Nerves.
Actions Assist to Elevates the Rib 2 to 5.   

Serratus Posterior Inferior

As compared to the Serratus Posterior Superior Inferior muscles are quite broad and strong. It exists under the latissimus dorsi which is the part of Superficial Muscles of the back.

Attachments Starts from the Thoracic & Lumber Spines (T11 to L3) The fibers of the muscles pass in superolateral direction and attached to the ribs 9 to 12.
Innervation Intercostal Nerves.
Actions Assist to Elevates the Rib 9 to 12.   

Intrinsic Deep Muscles of the Back

There is nothing wrong to say that deep muscles of the back are very much developed & went through the sacrum to the skull base. These muscles are very much associated with the movement of our spine and actually control the postures.

Deep Fascia plays crucial role in the organization of these muscles because they are fully covered with it.

The deep back muscles are officially divided into 3 different layers.

  1. Superficial Deep Back Muscles Layer.
  2. Intermediate Deep Back Muscles Layers.
  3. Deep Back Muscles layer.

We going to have a deep insight to all of above mentioned one by one.

Superficial Deep Back Muscles

You might be familiar with another name of Superficial muscles of deep back yes, it isspinotransversales. This group comprised of 2 type of muscles

  1. Splenius capitis
  2. Splenius Cervicis.

Both of these types of muscles help the movement of neck and head.

Splenius Capitis

Attachments These types of muscles start from the lower side of Ligamentum Nuchae. Spinous Processes C7 to T3/4 Vertebrate. The fibers went through and attached to the mastoid process & occipital bone of human skull. 
Innervation Posterior Rami of Spinal Nerves C3 & C4. 
Actions Assist to rotate head to the side.   

Splenius Cervicis

Attachments Splenius Cervicis starts from the T3 to T6 vertebae. The fibers of these muscles ascend and attached to the processes C1 to C3/4.
Innervation Posterior Rami of Spinal Nerves C3 & C4. 
Actions Assist to rotate head to the side.   

Intermediate Intrinsic Back Muscles

The intermediate intrinsic muscles of the back officially divided into 3 following types of muscles.

  1. Iliocostalis.
  2. Longissimus.
  3. Spinalis.

Al together these back muscles combined to form a column which is called the erector spinae.

The erector spinae are located at the posterolaterally to column between the costal angle of ribs and vertebral spinous processes.

All the above mentioned three muscles of the intermediate intrinsic back muscles are further divided into their superior attachments.

Iliocostalis

These muscles are situated within the erector spinae. These muscles are attached with the ribs and further divided into following 3 parts – lumborum, thoracis, & cervicis.

Attachments Originates from the origin of tendinous and directly attached to the cervical transverse processes and costal angle of the ribs.
Innervation Posterior Rami of spinal nerves.
Actions Helps in laterally flex to the vertebral column by acting unilaterally. Also helps to extend the vertebral column & head when act as bilaterally.

Longissimus

These muscles are located between the spinalis & iliocostalis. It is the largest one.

Attachments Originates from the  common tendinous & directly attached to the lower ribs of C2 to T12 processes and also with the mastoid process of the human skull. 
Innervation Posterior Rami of spinal nerves.
Actions Helps in laterally flex to the vertebral column by acting unilaterally. Also helps to extend the vertebral column & head when act as bilaterally.

Spinalis

Attachments Originates from the origin of tendinous and directly attached to the C2, T1 to T8 processes and also occipital bone of skull.
Innervation Posterior Rami of spinal nerves.
Actions Helps in laterally flex to the vertebral column by acting unilaterally. Also helps to extend the vertebral column & head when act as bilaterally.

Deep Intrinsic Back Muscles

Deep intrinsic muscles of the back are situated under the erector spinae and also called the transversospinales. Deep Intrinsic Back muscles are short but strong.

Here are the major types of muscles in Deep Intrinsic Back Muscles.

  1. Semispinalis.
  2. Multifidus
  3. Rotatores.

Semispinalis

The Semispinalis is one of the most superficial deep back muscles. Just like the other muscles it is also divided by its attachments into the following 3 types.

  1. Thoracic.
  2. Cervicis.
  3. Capitis.
Attachments Starts from the T Process of C4 to T10. The fibers of these muscles go up to the 4 to 6 vertebral segments and attaching to the C2 to T4 and occipital bone of human skull.
Innervation Posterior Rami of spinal nerves.
Actions Assist in rotation of vertebral column and head.

Multifidus

The multifidus muscles of the back just located under the semispinalis muscles. These muscles developed best in the lumbar area of back.

Attachments Multifidus has wide origin these originates from the Sacrum. Posterior iliac Spine. Tendinous Origin of Erector Spinae. T1 to T3C4 to C7 The fibers go up to 2 to 4 vertebral segments.
Innervation Posterior Rami of spinal nerves.
Actions Stabilize the Vertebral Column.

Rotatores

Thoracic region consists most of the rotatores.

Attachments The rotatores starts from the transverse processes. The fibres of these muscles go right up and directly attached to the lamina & spinous processes of superior vertebrae.
Innervation Posterior Rami of spinal nerves.
Actions Stabilize the Vertebral Column.

Minor Deep Intrinsic Muscles

Attachments Starts from the C7 to T11 and directly attached to the rib. Assist to elevate the ribs.
Innervation Posterior Rami of spinal nerves.
Actions Stabilize the Vertebral Column.

You can get more information about muscles: we have shared links below. Follow links to get more information.

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Upper Back Muscles
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