Deep Muscles of the Back: Anatomy, Layers, and Functions

Name: Deep Back Muscles (Division, Origin, Insertion, Function)
Uploaded: 2026-01-11T16:51:32.490310+00:00
Channel: Taim Talks Med
Description: Deep Muscles of the Back: Anatomy, Layers, and Functions Overview The back’s musculature is divided into superficial and deep groups.

Taim Talks Med

Jan 11, 2026

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4 min read

YouTube video ID: amSlQ7S5orQ

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Overview

The back’s musculature is divided into superficial and deep groups. Superficial muscles (trapezius, latissimus dorsi, rhomboids, levator scapulae, serratus posterior superior & inferior) lie closest to the skin. Removing these three superficial layers reveals the deep back muscles, which are organized into three anatomical layers based on depth and orientation.

Deep Back Muscles – Layer Classification

Layer	Position (relative to bone)	Main Muscle Groups
1st (most superficial of the deep group)	Just beneath the superficial muscles	Spinospinal system (spinalis) and Spinotransverse system (splenius, longissimus, iliocostalis)
2nd	Intermediate depth	Transversospinal system (rotatores, multifidi, semispinalis)
3rd (deepest)	Closest to the vertebrae	Suboccipital muscles and System of short muscles (interspinales, intertransversarii)

1. Suboccipital Muscles (3rd Layer – Neck Region)

Rectus Capitis Posterior Minor – Origin: posterior tubercle of atlas; Insertion: occipital bone below inferior nuchal line.
Rectus Capitis Posterior Major – Origin: spinous process of axis; Insertion: inferior nuchal line of occipital bone.
Obliquus Capitis Superior – Origin: transverse process of atlas; Insertion: inferior nuchal line of occipital bone.
Obliquus Capitis Inferior – Origin: spinous process of axis; Insertion: transverse process of atlas. These four tiny muscles stabilize the atlanto‑occipital joint and assist in head extension and rotation.

2. System of Short Muscles (3rd Layer – Along the Spine)

Interspinales – Located between adjacent spinous processes; most prominent in cervical and lumbar regions; origin: spinous process of the lower vertebra, insertion: spinous process of the upper vertebra.
Intertransversarii – Situated between transverse processes; most developed in the cervical region; origin: transverse process of the lower vertebra, insertion: transverse process of the upper vertebra. These muscles connect neighboring vertebrae, providing fine‑tuned segmental stability.

3. Transversospinal System (2nd Layer)

Rotatores

Long fibers – Origin: transverse process of a vertebra; insertion: spinous process of the vertebra two levels above (skips one).
Short fibers – Origin: transverse process; insertion: spinous process of the immediately superior vertebra (considered part of the 3rd layer).

Multifidi

Short fibers – Origin: transverse process; insertion: spinous process of the vertebra two levels above.
Long fibers – Origin: transverse process; insertion: spinous process of the vertebra three levels above. Predominantly located laterally to the spinous processes, especially in the lumbar region.

Semispinalis (three parts)

Semispinalis Thoracis – Origin: transverse processes T6‑T12; Insertion: spinous processes C6‑T4.
Semispinalis Cervicis – Origin: transverse processes T1‑T6; Insertion: spinous processes C2‑C5.
Semispinalis Capitis – Origin: transverse processes C4‑T6; Insertion: occipital bone between the inferior and superior nuchal lines. These muscles are relatively large and span multiple spinal segments, contributing to powerful extension and contralateral rotation.

4. Spinospinal System (1st Layer – Most Superficial Deep Muscles)

Spinalis Cervicis – Origin: spinous processes C6‑T2; Insertion: spinous processes C2‑C4.
Spinalis Thoracis – Origin: spinous processes T10‑L3; Insertion: spinous processes T1‑T8. These muscles run directly along the vertebral column and reinforce the erector spinae group.

5. Spinotransverse System (1st Layer)

Longissimus (three parts)

Longissimus Thoracis – Origin: dorsal surface of sacrum, iliac crest, and spinous processes T11‑L5; Insertion: transverse processes T1‑T12 and the costal angles of ribs 2‑12 (variations exist).
Longissimus Cervicis – Origin: transverse processes T1‑T6; Insertion: transverse processes C2‑C5.
Longissimus Capitis – Origin: transverse processes C4‑T4; Insertion: mastoid process of the temporal bone.

Splenius (two parts)

Splenius Capitis – Origin: spinous processes C3‑T3; Insertion: mastoid process.
Splenius Cervicis – Origin: spinous processes T3‑T6; Insertion: transverse processes C1‑C2.

Iliocostalis (three parts)

Iliocostalis Lumborum – Origin: thoracolumbar fascia, iliac crest, dorsal sacrum; Insertion: lower six ribs.
Iliocostalis Thoracis – Origin: lower six ribs; Insertion: upper six ribs.
Iliocostalis Cervicis – Origin: upper six ribs; Insertion: transverse processes C4‑C6. These muscles form the bulk of the erector spinae, extending the vertebral column and laterally flexing the spine.

Common Features of All Deep Back Muscles

Origin & Insertion – Almost every deep back muscle originates and inserts on vertebral elements (spinous, transverse processes, or vertebral bodies).
Primary Function – Extension of the vertebral column, providing spinal stability, maintaining posture, and preserving the natural spinal curves.

Functional Significance

Stability – By anchoring adjacent vertebrae, these muscles prevent excessive motion and protect intervertebral discs.
Posture – Continuous low‑level activity maintains upright posture and the lumbar lordosis.
Movement – Coordinated activation produces extension, rotation, and lateral flexion of the trunk and neck.

Overall, the deep back musculature works as an integrated system, with each layer contributing specific mechanical advantages while sharing the core role of spinal support and extension.

The deep back muscles are organized into three depth‑based layers—suboccipital and short muscles (deepest), the transversospinal group (intermediate), and the spinospinal/spinotransverse group (most superficial). Despite their varied names and locations, they all originate and insert on vertebrae and collectively provide extension, stability, and postural control of the spine.

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Full Transcript YouTube

Hey What’s up. Meditay here and in this 
video, we’ll be covering the Deep muscles  
of the back. Alright. Generally, the muscles 
of the back consist of superficial muscles  
and deep muscles. The superficial muscles 
consist of the The trapezius and Latissimus,  
which are the 1st layer. The 2nd layer 
are the Rhomboid Major Minor and Levator  
Scapula, and the 3rd layer of muscles consists 
of the Serratus Posterior superior and inferior. 
And when you remove these three layers, you’ll 
finally get to the Deep muscles of the back. 
Now the deep muscles of the back are categorized 
based on their shape and structure and location. 
Generally, they consist of the Suboccipital 
Muscles, there’s the system of short muscles,  
the Transversospinal system, Spinospinal system 
and then there’s the spinotransverse system. 
The Suboccipital muscles consists of 4 muscles. 
These are the Rectus Capitis Posterior major and  
Minor. And there’s the Obliquus Capitis Superior 
and Inferior. The system of short muscles consists  
of the Interspinales and the Intertransversarii 
muscles. The muscles you see in front of you now,  
are considered the 3rd Layer of the 
deep back muscles, meaning they’re  
the deepest layer closest to the bone.
Then we have the Transversospinal System,  
which consists of the semispinalis, 
Multifidi and Rotatores. 
The rotatores muscles consist of short and 
long muscle fibers. The short muscle fibers  
of rotatores are considered a part of the 
3rd layer since they’re as close to the  
bones as the 3rd layer are. The long fibers of 
rotatores are considered a part of the 2nd layer,  
as the multifidi and semispinalis are.
Next we have the Spinospinal System,  
which consist of Spinalis, and the Spinotransverse 
System, which consist of Splenius, Longissimus and  
Iliocostalis. All of these are considered as the 
1st layer of the deep muscles of the back, or the  
most superficial ones. So these muscles are just 
below the superficial muscles of the back. Aight. 
Even though the deep back muscles 
are divided into system of muscles,  
they all share some common features. And that 
is that one; almost all the deep back muscles  
originate and insert at the vertebra. And two; All 
share the same function, which is extension of the  
vertebral column. So they provide stability of 
the vertebral column, and they help maintain our  
posture and the natural curve of the spine.
Let’s now cover all of these muscles,  
starting with the 3rd layer, 
which are closest to the bones. 
And we’ll start with these muscles 
you see here. Lets zoom in on them.  
The muscles you see here, are called; Suboccipital 
muscles, since.. well, they like sub occipitally,  
and they’re therefore also considered 
as a system of deep muscles of the neck. 
Ok. First, we have a muscle called 
the Rectus Capitis Posterior Minor,  
which originate at the Posterior tubercle 
of Atlas, and Insert at the Occipital bone  
below the inferior nuchal line. Then we 
have the Rectus Capitis Posterior Major,  
which originate from the spinous process 
of Axis, and insert at the inferior nuchal  
line of the occipital bone. So these are 
the Rectus Capitis Posterior muscles. 
Then we have the Oblique muscles of the head. 
The Obliqus capitis Superior, which oritinate  
at the transverse process of Atlas, and insert at 
the inferior nuchal line of the occipital bone. 
And the Obliquus Capitis Inferior, which 
originate at the spinous process of Axis,  
and insert at the Transverse Process of Atlas.
So that was the suboccipital muscles.  
Next, we have the muscles shown here between the 
vertebrae. They’re called the System of Short  
muscles. And the system of short muscles are a 
system connecting adjacent vertebra together. 
And they consist of the 
Interspinales, which are here. 
The interspinales are mostly developed in the 
Cervical and Lumbar region, but they’re also  
present in the thoracic region with less muscle 
fibers. The interspinales are located between  
the spinous processes. They originate from the 
spinous process of the vertebra below, and insert  
at the spinous process of the vertebra above.
The other muscle is called Intertransversarii,  
which are here. They’re mostly developed in 
the cervical region, and they lie between  
the transverse processes of the vertebra.
They originate from the transverse process  
of the vertebra below, and Insert at the 
transverse process of the vertebra above. 
So that was the 3rd layer of the deep back 
muscles. Awesome. Now let’s do the 2nd layer. 
Remember they’re the Transversospinal 
system. The transversospinal system are  
a system of muscle fibers that go from the 
transverse process of the lower vertebra  
to the spinous process of the upper vertebra. 
It kinda make sense when looking at the name. 
The first ones are the Rotatores muscles. The 
rotatores muscles are deep muscles located in  
the thoracic region, and they consist of long and 
short fibers. The long rotatores, which are here,  
originate from the transverse process of the 
vertebra below, and insert at the spinous process  
of 2 vertebra above. So it skips one vertebra.
The short Rotatores muscle however,  
these ones. Are generally considered as a 
part of the 3rd layer of deep back muscles,  
together with the suboccipital and the 
interspinales and intertransversarii as  
we looked at earlier. They originate at the 
transverse process of the vertebra below and  
insert at the spinous process of 1 vertebra above.
So that’s these ones. Then we have some slightly  
larger muscles, called multifidi. The multifidi 
muscles fill the space lateral to the spinous  
process. And they’re more distinctive at the 
lumbar region. The multifidi also consist of  
short and long fibers. The short multifidi 
muscles, go like this. They originate at  
the transverse process of the vertebra below and 
insert at the spinous process of 2 vertebra above. 
The Long multifidi muscles originate at the 
transverse process of the vertebra below  
and insert at the spinous process of 
3 vertebra above. So that’s generally  
how the multifidi muscles are arranged.
Next we have the Semispinalis, which are here. 
They consist of three parts. 
Let’s go through them. 
First, we have the Semispinalis Thoracis, which 
are here highlighted in green. They originate  
at the transverse Process of T6 through T12, 
and insert at the spinous process of C6 to T4 
Then there’s the Semispinalis 
Cervicis, which is here in yellow. 
This one originates from the transverse process of 
T1-T6, and insert at the Spinous Process of C2-C5. 
And the last part is the Semispinalis 
Capitis, which is here in purple.  
This one originates from the 
Transverse Process of C4 to T6,  
and insert at the Occipital Bone, between 
the inferior and superior nuchal line. 
So that was all the muscles of 
the Transversospinal system.  
The 2nd layer of the deep back muscles.
Now let’s finally do the 1st layer, which  
is the most superficial layer just underneath 
the superficial muscles of the back, The first  
ones are here. They’re called the Spinospinal 
System. Because they go from the spinous process  
of the lower vertebra to the spinous process 
of the upper vertebra. So surprisingly enough,  
these muscles are called Spinalis 
Muscles. And they’re made up of 2 muscles. 
One is in the cervical region, 
called Spinalis Cervicis.  
They originate from the spinous process of C6 to 
T2 and insert at the spinous process of C2 to C4. 
The other one is at the Thoracic 
region, called Spinalis Thoracis.  
It originates from the spinous process of T10 to 
L3 and insert at the spinous process of T1-T8. 
So that’s this one. Then there’s another large 
muscle that’s considered the 1st layer of the  
Deep back muscles. And they’re the Spinotransverse 
System, which are a system of fibers that go from  
the spinous process of the lower vertebra to the 
transverse process of the upper vertebra. And  
they’re called the Longissimus Muscles. There are 
3 parts. First there’s the Longissimus Thoracis,  
which originate from the dorsal 
surface of sacrum, as you see here.  
The Iliac Crest and the spinous process of T11 to 
L5. And they insert at the transverse process of  
T1 to T12, as well as the costal angle of the 2nd 
to 12th rib. Or some sources might say from the  
3rd to the 12th rib. These origin and insertion 
points really differ from source to source. 
Then there’s the Longissimus Cervicis. 
This one. It originates from the transverse  
process of T1-T6, and insert at 
the transverse process of C2-C5 
Then there’s the Longissimus 
Capitis, which is here in yellow. 
It originates from the transverse process of 
C4 to T4, and insert at the mastoid process.  
Then there’re some large muscles up here, 
called Splenius Muscles, which are divided  
into two set of muscle fibers.
There’s the Splenius Capitis,  
which originate at the spinous process of 
C3-T3 and insert at the mastoid process. 
Then there’s the Splenius Cervicis, which 
originate at the spinous process of T3 to T6  
and insert at the Transverse process 
of C1-C2. So that’s these ones. 
The last one is the Iliocostal muscle, as 
you see here. And there are three parts  
to this muscle based on the location as 
well. There’s the Iliocostalis Lumborum,  
which originate at the thoracolumbar fascia, 
the Iliac crest and the Dorsal Sacrum. And  
then it inserts at the 6 lower ribs.
Then there’s the Iliocostalis Thoracis,  
which originate at the 6 lower ribs 
and insert at the 6 upper ribs. 
Then there’s the Iliocostalis 
Cervicis, which originate the 6  
upper ribs, and insert at the 
Transverse Process of C4 to C6. 
Awesome. So that was all the 
deep muscles of the back. 
We’ve covered the Spinospinal system and the 
Spinotransverse system, which are considered a  
part of the 1st layer, the most superficial one. 
We’ve gone through the Transversospinal system,  
which are considered a part of the 2nd 
layer, except the short muscle fibers of  
rotatores muscles, they’re considered a part 
of the 3rd layer. And we’ve gone through the  
suboccipital muscles and the system of short 
muscles, which are considered the 3rd and the  
deepest muscles we have in the back. And that 
my friends are the deep muscles of the back.