Erector spinae muscles
The erector spinae muscles comprise the intermediate layer of the deep (intrinsic) muscles of the back. They extend on either side of the vertebral column, between the base of the cranium superiorly and pelvis inferiorly. The erector spinae are divided into three groups, from medial to lateral:
- Spinalis muscles
- Longissimus muscles
- Iliocostalis muscles
The function of the spinal erectors is to move the vertebral column. Bilateral contraction of these muscles extends the spine, while unilateral contraction causes lateral flexion (ipsilateral). They also help to maintain posture by steadying the spine on the pelvis during walking.
|Definition||Three groups of deep muscles located on either side of the vertebral column|
Bilateral contraction - extension of spine
Unilateral contraction - lateral flexion of spine (ipsilateral)
|Mnemonic||I Like Standing (stands for Iliocostalis, Longissimus & Spinalis)|
This article will discuss the anatomy and functions of the erector spinae group of muscles.
The spinalis muscles are the most medial erector spinae muscles. They are divided into three regional groups, from superior to inferior:
- Spinalis capitis muscle originates from the spinous processes of C7-T1 vertebrae and inserts into the midline of the occipital bone.
- Spinalis colli muscle originates from the same points as spinalis capitis, but also from the nuchal ligament. It inserts to the spinous processes of C2-C4 vertebrae.
- Spinalis thoracis muscle extends from the spinous process of T11-L2 vertebrae until the spinous process of T2-T8 vertebrae.
The spinalis muscles are innervated by the lateral branches of the posterior rami of the cervical, thoracic and lumbar spinal nerves. The blood supply to the spinalis muscles comes from the vertebral, deep cervical, occipital, intercostal and lumbar arteries. The function of the spinalis muscles is to extend and laterally flex the cervical and thoracic regions of the spine.
Learn more about these erector spinae group by reading the following article:
The longissimus muscles are the central erector spinae muscles. They are also the thickest and the longest. The longissimus muscles are divided into three regional groups, similar to the spinalis muscles. These include, from superior to inferior:
- Longissimus capitis muscle originates from the transverse processes of vertebrae C4-T5 and inserts into the mastoid process of temporal bone.
- Longissimus colli muscle extends between the transverse processes of vertebrae T1-T5 and transverse processes of vertebrae C2-C6.
- Longissimus thoracis muscle consists of thoracic and lumbar parts. The thoracic part travels from the L1-L5 vertebrae, sacrum and posterior iliac crest until the thoracic vertebrae and inferior six ribs. The lumbar part extends between the region surrounding the anteromedial aspect of ilium and L1-L5 vertebrae.
The longissimus muscles have an identical innervation to the spinalis muscles; from the lateral branches of the posterior rami of the adjacent spinal nerves. They receive arterial blood from branches of the vertebral, deep cervical, occipital, transverse cervical, intercostal and sacral arteries. The function of the longissimus muscles is to extend and laterally flex (ipsilateral) the spine. Longissimus capitis also helps to rotate the head ipsilaterally.
Learn all the details about the longissimus muscles by taking a look at the article provided below:
The iliocostalis muscles are the most lateral erector spinae muscles. According to their attachments and location, they are regionally divided into three groups, from superior to inferior:
- Iliocostalis colli muscle originates from the angle of ribs 3 to 6 and inserts into the transverse processes of vertebrae C4-C6.
- Iliocostalis thoracis muscle arises from the angles of ribs 7-12 and attaches to the angles of ribs 1-6 and transverse process of vertebra C7.
- Iliocostalis lumborum muscle originates from three points; lateral crest of sacrum, medial end of iliac crest and thoracolumbar fascia. It attaches to the angle of ribs 5-12, transverse processes of vertebrae L1-L4 and adjacent thoracolumbar fascia.
The erector spinae comprise of many muscles and a lot of attachments. Simplify your learning by focusing on the key facts using Kenhub’s muscle anatomy and reference charts!
Similar to the other erector spinae groups, iliocostalis muscles are innervated by the lateral branches of the posterior rami of the cervical, thoracic and lumbar spinal nerves. Arterial supply is via branches of the occipital, deep cervical, vertebral, posterior intercostal, subcostal, lumbar and lateral sacral arteries. The function of the iliocostalis muscle is to extend and laterally flex (ipsilateral) the spine.
For more anatomical details about the iliocostalis muscles, read the following article:
Sometimes you might draw a blank and forget what the muscles constitute the erector spinae. Well, worry not! This simple mnemonic will always help you out. Just remember 'I Like Standing', which stands for (lateral to medial):
And you're all set!
Before you finish up, why not test your new knowledge with a quiz made specifically for this topic!
Back pain is an extremely common issue. It is one of the leading reasons why people visit their doctors and the second most common cause of people missing work, only after headaches. Localized lower back pain is usually muscular, related to spasming of the muscle as a result of guarding, or contraction of the muscles in anticipation of pain. Common causes of back pain are sprains and strains.
Strains consist of a degree of tearing or stretching of the muscle fibers. Erector spinae muscles are most commonly affected by back strains. Back strains are usually the result of incorrect balancing of a load on the vertebral column, placing strain on the muscles. Using the back as a lever when lifting objects places immense strain on the back muscle, which is why lifting should usually be focused at the knees. The muscles spasm as a protective mechanism after injury.
Spasms are involuntary contractions of muscles which present as cramps, pain, and decreased function. Adequate warm up and stretching, as well as exercises to increase the muscle tone of the back muscles, such as erector spinae, are the main mechanisms for preventing back strains and back pain by stabilizing the vertebral column.
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