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The human back contains a variety of muscles that support the torso, enable movement, and assist with breathing. These muscles can be divided into three groups: superficial, intermediate, and intrinsic (deep) muscles. The superficial muscles include the latissimus dorsi, trapezius, levator scapulae, and rhomboids. The intermediate muscles include the serratus posterior superior and serratus posterior inferior. The intrinsic muscles include the erector spinae and transversospinalis groups. The erector spinae group can be further divided into three subgroups: the iliocostalis, longissimus, and spinalis. These muscles help extend the neck and vertebral column, as well as move the ribs. The transversospinalis group consists of the semispinalis, rotatores, and multifidus muscles, which help stabilize the spinal segments. This paragraph provides an introduction to the topic of muscles originating at the vertebrae, outlining the different muscle groups and their functions.
| Characteristics | Values |
|---|---|
| Muscle groups | Erector spinae, Transversospinalis, Semispinalis, Rotatores, Multifidus, Iliocostalis, Longissimus, Spinalis, Superficial, Intermediate, Intrinsic |
| Muscle function | Extend and rotate vertebral column, maintain posture, move ribs, elevate and depress rib cage, control breathing, move vertebral column |
| Muscle attachments | Vertebrae, ribs, sacrum, ilium, spine, skull, shoulder blade, clavicle, scapula, humerus, cervical and thoracic vertebrae |
| Muscle shape | Rhomboid, quadrilateral |
| Muscle layers | Superficial (extrinsic), Intermediate, Intrinsic (deep) |
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What You'll Learn
Iliocostalis thoracis
The iliocostalis thoracis is a muscle in the back that is part of the erector spinae group. This group of muscles helps the body maintain good posture. The erector spinae group includes the longissimus, iliocostalis, and spinalis muscles. The iliocostalis thoracis is the most lateral component of the erector spinae group.
The iliocostalis thoracis muscle originates from the superior aspect of the angles of the lower six ribs and ascends to end on the angles of the upper six ribs and the transverse process of the C7 vertebra. This muscle extends and laterally flexes the thoracic spine and is innervated by the lateral branches of the posterior primary divisions (dorsal rami) of the thoracic spinal nerves.
The iliocostalis thoracis muscle is vascularized by the dorsal branches of the posterior intercostal and subcostal arteries. The arterial supply to the iliocostalis muscle has regional systematization, with the iliocostalis thoracis receiving blood from the dorsal branches of the posterior intercostal and subcostal arteries.
The iliocostalis thoracis muscle acts in synergy with the two other erector spinae components, the longissimus and spinalis muscles, to produce movements of the vertebral column. When these muscles contract unilaterally, they produce ipsilateral lateral flexion of the spine, and when acting bilaterally, they extend the spine.
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Multifidus muscles
The multifidus muscle is a series of long, narrow muscles located on either side of the spinal column. It is part of the transversospinal muscle group and is found in the third or deep layer of deep muscles of the back. The multifidus muscle is the thickest muscle in this group. It is located deep relative to the spinal erectors, transverse abdominis, abdominal internal oblique muscle, and abdominal external oblique muscle.
The multifidus muscle runs down both sides of the spine and has several attachment points. It originates on the sacrum and vertebrae and inserts on more superior vertebrae. Each multifidus muscle bridges over three to six vertebral levels, spanning between the transverse and spinous processes of certain cervical, thoracic, and lumbar vertebrae.
The main function of the multifidus muscle is to stabilize the lumbar spine. It helps to extend the lower spine during reaching or stretching. The multifidus muscle works together with the transversus abdominis muscle of the stomach and the pelvic floor muscles of the pelvis to provide stability around the entire torso.
Weak or atrophied multifidus muscles can cause back pain and are associated with lower back pain. They can also lead to other back problems such as herniated discs. Strengthening the core muscles, including the abdominal and oblique muscles, helps to strengthen the multifidus muscle as well.
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Superficial back muscles
The back muscles are divided into three groups: superficial, intermediate, and deep muscles. The superficial back muscles are situated underneath the skin and superficial fascia. They originate from the vertebral column and attach to the bones of the shoulder—the clavicle, scapula, and humerus. All these muscles are associated with movements of the upper limb.
The superficial back muscles include the trapezius, latissimus dorsi, levator scapulae, and rhomboids. The trapezius is a broad, flat, and triangular muscle that forms a trapezoid shape on each side. It originates from the skull, ligamentum nuchae, and the spinous processes of C7-T12, with fibres attaching to the clavicle, acromion, and scapula spine. The upper fibres of the trapezius elevate the scapula and rotate it during arm abduction. The middle fibres retract the scapula, while the lower fibres pull the scapula inferiorly.
The latissimus dorsi originates from the lower back and covers a wide area, arising from the spinous processes of T6-T12, thoracolumbar fascia, iliac crest, and the inferior three ribs. The fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus. The latissimus dorsi extends, adducts, and medially rotates the upper limb, and pulls the pectoral girdle backward when the humerus is fixed against the scapula.
The levator scapulae is a small strap-like muscle that begins in the neck and descends to attach to the scapula. It originates from the transverse processes of the C1-C4 vertebrae and attaches to the medial border of the scapula.
The rhomboid muscles are two small quadrangular muscles located between the medial margins of the scapulae. The rhomboid major muscle originates from the spinous processes of the vertebrae T2-T5 and inserts into the medial border of the scapula, while the rhomboid minor muscle originates from the nuchal ligament and spinous processes of vertebrae C7 and T1.
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Intermediate back muscles
Back muscles can be divided into three groups: superficial (extrinsic) back muscles, intermediate back muscles, and intrinsic (deep) back muscles. The intermediate back muscles are located just above and below the rib cage and help move the ribs, including during breathing. There are two major muscles within this category: the serratus posterior superior and the serratus posterior inferior.
The serratus posterior superior is a thin, quadrilateral-shaped muscle located at the upper and back part of the thoracic spine. It lies deep to the rhomboids and aids inspiration by elevating ribs 2 to 5, where it attaches. The serratus posterior inferior is located at the junction of the thoracic and lumbar regions. It originates from vertebrae T12 down to L3 and inserts into the 9th to 12th ribs. It acts to draw the lower ribs backward and downward and assists in trunk rotation and extension, as well as forced expiration.
The intermediate back muscles also include the erector spinae, which are a group of muscles that work together to extend the vertebral column and maintain good posture. The erector spinae include the longissimus, iliocostalis, and spinalis muscles. These muscles have a common tendinous origin and play a role in the movement of the thoracic cage and flexion of the upper vertebral column and head.
The iliocostalis muscles, such as the iliocostalis thoracis, originate on the ilium of the pelvic girdle and insert on the ribs or the costal bones. They help to extend the neck and the vertebral column and can move the ribs due to their attachments. The longissimus muscle is the largest of the three columns and is situated between the iliocostalis and spinalis. It can be divided into three parts: thoracic, cervicis, and capitis. The spinalis muscle is located medially within the erector spinae and is the smallest of the three muscle columns. It can also be divided into three parts: thoracic, cervicis, and capitis.
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Intrinsic back muscles
The muscles of the back can be divided into three groups: superficial, intermediate, and intrinsic. The intrinsic back muscles, also known as the deep muscles, are those that fuse with the vertebral column. They extend from the skull base to the sacrum and are associated with the movements of the vertebral column and the control of posture. These muscles are well-developed and covered by deep fascia, which plays a key role in their organisation.
The intrinsic back muscles consist of four layers: superficial, intermediate, deep, and deepest. They lie on each side of the vertebral column and act together to support and maintain the body's posture, as well as produce movements of the head, neck, and trunk. The main functions of these muscles are flexion, extension, lateral flexion, and axial rotation of the vertebral column.
The superficial layer of the intrinsic back muscles is composed of the splenius muscles, which include the splenius capitis and splenius cervicis. These flat muscles are located on the posterolateral aspect of the neck and the posterior upper thorax, overlying the deep muscles of the neck. The splenius capitis arises from the spinous processes of vertebrae C7-T3 and the lower half of the nuchal ligament, while the splenius cervicis arises from the spinous processes of vertebrae T3-T6 and inserts onto the transverse processes of vertebrae C1-C3 or C4.
The intermediate layer contains the erector spinae muscles, which include the iliocostalis, longissimus, and spinalis muscles. These muscles form a column known as the erector spinae and play a role in the movement of the thoracic cage and flexion of the upper vertebral column and head. The iliocostalis muscles originate on the ilium of the pelvic girdle and insert on the ribs or costal bones, helping to extend the neck and vertebral column, as well as move the ribs. The spinalis muscle is located medially within the erector spinae and is the smallest of the three muscle columns. It can be divided into the thoracic, cervicis, and capitis, although the cervicis part is absent in some individuals.
The deep intrinsic muscles, also known as the transversospinales, are located underneath the erector spinae. They are a group of short muscles associated with the transverse and spinous processes of the vertebral column. There are three major muscles in this group: the semispinalis, multifidus, and rotatores. The semispinalis is the most superficial of the deep intrinsic muscles and can be divided by its superior attachments into thoracic, cervicis, and capitis. It originates from the transverse processes of C4-T10 and attaches to the spinous processes of C2-T4 and the occipital bone of the skull. The multifidus muscle originates on the sacrum and vertebrae and inserts on more superior vertebrae, helping to extend and rotate the vertebral column.
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Frequently asked questions
Some muscles that originate at the vertebrae include the multifidus, levator scapulae, rhomboids, serratus posterior superior, serratus posterior inferior, and the erector spinae.
The erector spinae muscles are responsible for extending the vertebral column and maintaining good posture.
The three groups of back muscles are the superficial, intermediate, and intrinsic (deep) muscles.
The multifidus muscles extend and rotate the vertebral column. They also serve to stabilise movements and take weight off the vertebral discs.
