Back Muscles

The human back comprises many small and large muscles that provide structural support and flexibility, allowing for various movements of the spinal column and the whole torso. This group includes some of the major muscles essential for moving the body. All muscles located from the base of the skull, across the shoulders, and down to the top of the hips are considered back muscles.

Name, Location, and Anatomy of the Muscles of the Back

All the muscles in the back are paired, with most of them comprising groups of multiple smaller muscular slips or fascicles that contribute to the stability, flexibility, and intricate movements of the spinal column to bring about the movements of the head, neck, and body trunk.

While it is difficult to count the exact number, the human back muscles can be divided into 3 groups or layers based on their location and functions in the region — (1) superficial or extrinsic, (2) intermediate, and (3) deep or intrinsic.

Find out about all the muscle groups within these three layers:

Name	Location	Origin	Insertion	Action	Innervation
1. Superficial or Extrinsic Muscles (5) Have attachments on the shoulder and arm bones, which is why they are often considered to be upper limb muscles.
Trapezius	Upper back and neck, spanning from the base of the skull to the middle back and out to the shoulders	The medial third of the superior nuchal line and external occipital protuberance of the occipital bone, the nuchal ligament, and the spinous processes of the C7 to T12 vertebrae	Back of the clavicle’s lateral one-third and the acromion and spine of the scapula or shoulder blades	Elevating, retracting, and rotating the scapula while also assisting in extending the neck and bending it to the sides (when the scapula remains fixed)	Ventral rami of C3-C4 spinal nerves and the accessory nerve
Latissimus dorsi	Lower back and side, stretching from the lower spine up to the armpits	The inferior angle of the scapula, the spinous processes of T7-T12 vertebrae, the 9th to 12th ribs, and the posterior surface of the  iliac crest	The bicipital groove of the humerus bone	Internally rotating, extending, and adducting the arms and helping with the movement of the ribs during respiration	Thoracodorsal nerves arising from C6-C8 spinal nerves
Rhomboids (2)
— Rhomboid major	In the upper back, between the scapulae or shoulder blades	The spinous processes of T2-T5 vertebrae	The medial border of the scapula	Retracting the scapula and rotating it downwards at its joint with the thorax	Dorsal scapular nerves rising from the C4-C5 spinal nerves
— Rhomboid minor	Just above the rhomboid major, between the shoulder blades	The spinous processes of C7 and T1 vertebrae, and the nuchal ligament	Same as rhomboid major	Same as rhomboid major	Same as rhomboid major
Levator scapulae	Along the side of the neck, connecting to the upper part of the shoulder blades	The Transverse processes of C1-C4 vertebrae	The medial border of the scapula, on the superior surface	Elevating the scapula and assisting in tilting the neck	Dorsal scapular nerve of C5 and C3-C4 cervical nerves
2. Intermediate Muscles (2) Have attachments on the ribs and help in moving the thoracic cage. They are usually included in the chest muscle group.
Serratus posterior (2)
— Serratus posterior inferior	Lower back, just above the lumbar region, beneath the latissimus dorsi	The spinous processes of T11-L2 vertebrae	Lower borders of 9th-12th ribs	Depressing the lower 3-4 ribs when breathing out	T9-T11 intercostal and the subcostal nerves
— Serratus posterior superior	Upper back, deep to the shoulder blades, closer to the spine	The nuchal ligament and spinous processes of the C7-T3 vertebrae	Upper borders of 2nd-5th ribs	Elevating the upper ribs when breathing in	T2-T5 Intercostal nerves
3. Deep or intrinsic Muscles (12) Have attachments on the spinal column and play a vital role in moving the back and torso. Some sources consider this to be the only group of true back muscles. All these muscles originate from points inferior to where they are inserted.
Superficial Intrinsic Layer or Spinotransversales (2)
Splenius (2)
— Splenius capitis	Back of the neck, extending up to the base of the skull	Spinous processes of C7-T3 vertebra and the nuchal ligament	The occipital bone and temporal bone (mastoid process)	Straightening, rotating, and laterally flexing the head and neck	Dorsal rami of C2-C3 spinal nerves
— Splenius cervicis	Upper back and neck, below the splenius capitis, running down into the cervical vertebrae	Spinous processes of T3-T6 vertebrae	Transverse processes of C1-C3 vertebrae	Same as splenius capitis	Dorsal rami of the lower cervical nerves (C3 and lower)
Intermediate Intrinsic Layer or the Erector Spinae Group (3)
Spinalis	Thin, long muscle along the spine, running from the middle back up through the midline to the base of the skull	Spinous processes of C7-T1 and T11-L2 vertebrae, and the nuchal ligament	Spinous processes of C2-C4 and T1-T8	Bending the upper back and trunk to the sides and extending the back, neck, and trunk	Dorsal rami of corresponding spinal nerves
Longissimus	Runs along the sides of the spine from the lower back to the neck.	Transverse processes of C4-T5 and L1-L5 vertebrae and the ilium and sacrum  bones	Transverse processes of cervical, thoracic, and lumbar vertebrae, and the mastoid process of temporal bone	Bending the head and trunk to the sides, straightening the back and neck, and bending them backward	Same as Spinalis
Iliocostalis	Outermost back muscle along the ribs, from the hips and lower back to the upper back.	Angles of the 3rd-12th ribs and lateral sacral and iliac crests	Transverse processes of C4-C7 and L1-L4 vertebrae and the angles of all the ribs	Straightening the beck and back, and bending sideways	Same as Spinalis
Deep Intrinsic Layer or Transversospinales (5)
Semispinalis (3)
— Semispinalis Capitis	Upper back and neck, just beneath the skull and alongside the spine	Articular processes of C4-C7, and transverse processes of C7-T6 vertebrae	On the occipital bone, between the superior and inferior nuchal lines	Straightening, bending, and rotating the head and neck	Dorsal rami of C1-C5 spinal nerves
— Semispinalis Cervicis	Neck and upper back, running between the vertebrae of the cervical spine.	Transverse processes of T1-T6 vertebrae	Spinous processes of C2-C5 vertebrae	Same as the semispinalis capitis	Dorsal rami of the lower cervical nerves (usually C3-C6)
— Semispinalis Thoracis	Middle and upper back, along the spine	Transverse processes of T6-T10 vertebrae	Spinous processes of C6-T4 vertebrae	Straightening and rotating  the head and trunk, as well as bending them sideways and arching backward	Dorsal rami of corresponding cervical and thoracic nerves
Multifidus	Runs along the entire length of the spine, from the lower back to the neck	Superior articular processes of C4-C7, transverse processes of all thoracic vertebrae, mammillary processes of all lumbar vertebrae, and the back of sacrum and ilium bones	Spinous processes of vertebrae located 2 to 5 segments above the point of origin of each fascicle	Stabilizing the spine and assisting other muscles in extending, bending, and rotating it	Dorsal rami of corresponding spinal nerves
Rotatores	Along the spine from the neck to the lower back, but most prominent in the thoracic region	Transverse processes of all vertebrae (most prominent in the thoracic region)	Spinous process and laminae of vertebrae located 1-2 segments above the origin of each fascicle	Stabilizing the spinal column and helping with straightening and rotating the thoracic spine region	Dorsal rami of corresponding spinal nerves, mainly the thoracic nerves
Deepest Intrinsic Layer or Segmental Muscles (2*)
Interspinales	Tiny muscles located between the vertebrae, running along the entire spine, but most developed in the cervical and lumbar regions	Spinous processes of C3-L5 vertebrae	Spinous processes of C2-L4 vertebrae	Stabilizing the spinal column	Dorsal rami of corresponding spinal nerves
Intertransversarii	Along the spine, on the side of the vertebrae; most prominent in the cervical and lumbar regions	Transverse processes of cervical and lumbar vertebrae and accessory processes of lumbar vertebrae	Transverse and mammillary processes (in the cervical region) of the vertebrae inferior to the point of origin	Same as interspinales	Ventral and dorsal rami of corresponding spinal nerves

*Note that the levatores costarum, originating from the transverse processes of C7-T11 and inserted into all 12 ribs, is sometimes considered to belong to the deepest intrinsic layer. However, it is more appropriate to classify them as thoracic wall muscles based on their primary role in elevating the ribs during respiration.

The deep and deepest intrinsic muscles play a role in proprioception, which means helping the body sense its position and movement, allowing for adjustments and stability during various activities. They contribute significantly to the coordination of movements between the arms and legs in relation to the trunk.

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