Dominic Stone
The iliocostalis muscle is a deep muscle in the back that is part of the erector spinae (sacrospinalis) muscle group. It aids in extension, lateral flexion, and rotation of the spinal column. The iliocostalis muscle has several parts, including the iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum, which have different origins and insertions. The cervicis segment extends from the cervical vertebrae to the fourth cervical vertebra, providing weak support for lateral flexion and extension at the base of the neck during unilateral and bilateral contractions, respectively. The thoracis arises from the upper borders of the angles of the lower six ribs and inserts into the upper borders of the angles of the upper ribs. The lumborum originates at the medial end of the dorsal segment of the iliac crest and the lateral crest of the sacrum.
| Characteristics | Values |
|---|---|
| Location | Deep muscles of the back |
| Function | Aids in extension (bending backward), lateral flexion (bending to the side), and rotation of the spinal column |
| Components | Iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum |
| Innervation | Dorsal rami of upper thoracic and lower cervical spinal nerves |
| Origin | Iliac crest, sacrum, thoracolumbar fascia, and spinous processes of the vertebrae from T11 to L5 |
| Insertion | Inferior borders of the angles of the lower six to nine ribs |
| Contraction | Unilateral or bilateral |
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What You'll Learn
- The iliocostalis is part of the erector spinae muscle group
- It originates from the iliac crest, sacrum, and vertebrae
- It has three segments: cervicis, thoracis, and lumborum
- The cervicis section offers weak support for lateral flexion at the neck's base
- The thoracis section starts from the angles of the lower six ribs
The iliocostalis is part of the erector spinae muscle group
The iliocostalis muscle is a deep back muscle that is part of the erector spinae muscle group. The erector spinae muscles are the intermediate layer of the deep, intrinsic muscles of the back. They extend on either side of the vertebral column, from the base of the cranium to the pelvis. The erector spinae group includes three muscles: the iliocostalis, longissimus, and spinalis. These muscles work together to produce movements of the vertebral column.
The iliocostalis is the most lateral of the erector spinae muscles. It is divided into three regional parts: the iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. The iliocostalis cervicis arises from the third to sixth ribs and attaches to the transverse processes of the fourth to sixth cervical vertebrae. The iliocostalis thoracis arises from the angles of the seventh to twelfth ribs and attaches to the angles of the first to sixth ribs and the transverse process of the seventh cervical vertebra. The iliocostalis lumborum originates from three points: the lateral crest of the sacrum, the medial end of the iliac crest, and the thoracolumbar fascia. It attaches to the angle of the fifth to twelfth ribs, the transverse processes of the first to fourth lumbar vertebrae, and the adjacent thoracolumbar fascia.
The function of the iliocostalis muscle is to extend and laterally flex the spine. When these muscles contract unilaterally, they produce ipsilateral lateral flexion of the spine, and when they act bilaterally, they extend the spine. The iliocostalis muscle is innervated by the lateral branches of the posterior rami of the cervical, thoracic, and lumbar spinal nerves. It receives arterial supply from the occipital, deep cervical, vertebral, posterior intercostal, subcostal, lumbar, and lateral sacral arteries.
The erector spinae muscles help to maintain posture by steadying the spine on the pelvis during walking. They also work to smoothen the bending of the vertebral column during forward flexion of the spine. The iliocostalis muscle is an important part of the erector spinae group, helping to produce movements and maintain posture in the vertebral column.
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It originates from the iliac crest, sacrum, and vertebrae
The iliocostalis muscle has a common origin from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5. The iliocostalis muscle is the muscle immediately lateral to the longissimus, and it lies deep to the fleshy portion of the serratus posterior muscle.
The iliocostalis muscle has three parts: the iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. Each part originates from different parts of the body and serves different functions.
The iliocostalis cervicis arises from the angles of the third, fourth, fifth, and sixth ribs. It is inserted into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae.
The iliocostalis thoracis arises from the upper borders of the angles of the lower six ribs. It becomes muscular and is inserted into the upper borders of the angles of the upper six ribs and into the transverse process of the seventh cervical vertebra.
The iliocostalis lumborum is inserted by flattened tendons into the inferior borders of the angles of the lower six to nine ribs.
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It has three segments: cervicis, thoracis, and lumborum
The iliocostalis muscle is a deep back muscle that is part of the erector spinae muscle group. It is horizontally divided into three regional parts according to their origin: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum.
The cervicis section is in the middle of the three segments. It arises from the superior aspect of the angle of the third through sixth ribs and attaches superiorly onto the posterior tubercles of the transverse processes of the C4 to C6 vertebrae. It laterally flexes and extends the lower cervical region and is innervated by the dorsal rami of the upper thoracic and lower cervical spinal nerves.
The iliocostalis thoracis arises by flattened tendons from the upper borders of the angles of the lower six ribs, medial to the tendons of insertion of the iliocostalis lumborum. These become muscular and are inserted into the upper borders of the angles of the upper six ribs and the transverse process of vertebra C7. 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 lumborum is the most inferior (lowest) of the three segments. It is divided into lumbar and thoracic parts. The lumbar part originates from the lateral crest of the sacrum, medial end of the iliac crest, and thoracolumbar fascia. It courses superiorly and inserts into the transverse processes of vertebrae L1-L4 and the adjacent part of the middle layer of thoracolumbar fascia. The muscle fibres are laminated so that those attaching to L1 are the most superficial and medial, while those inserting to L4 are the deepest and most lateral. The thoracic part originates from the same site as the lumbar part, in the form of an aponeurotic sheath covering the lumbar part.
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The cervicis section offers weak support for lateral flexion at the neck's base
The iliocostalis muscle is a deep muscle in the back and is one of three muscles that make up the erector spinae group, the others being the spinalis and longissimus. The erector spinae muscles work together to produce movements of the vertebral column. The iliocostalis is the most lateral of the three muscles.
The iliocostalis is divided into three distinct regions based on their point of origin: the iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. The cervicis section is in the middle, the lumborum is the lowest, and the capitis is the highest.
The cervicis section of the iliocostalis muscle originates at the angles of the third to sixth ribs and attaches to the posterior tubercles of the transverse processes of the fourth to sixth cervical vertebrae. It is involved in neck extension and lateral flexion at the base of the neck. During unilateral contractions, the cervicis section provides weak support for lateral flexion at the base of the neck. This is because it is not a strong lateral flexor of the neck, so it provides weak assistance to other muscles during this movement.
During bilateral contractions, the cervicis section contributes to neck extension, which involves bending the neck backward. Similar to lateral flexion, the cervicis section offers weak assistance during neck extension because it is not a strong extender of the neck.
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The thoracis section starts from the angles of the lower six ribs
The iliocostalis muscle is one of the deep muscles of the back. It is part of the erector spinae group, which includes the iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. These muscles work together to produce movements of the vertebral column, such as extension (bending backward), lateral flexion (bending to the side), and rotation.
The iliocostalis thoracis muscle specifically starts from the superior aspect of the angles of the lower six ribs. This is known as its origin. From there, it ascends to end on the angles of the upper six ribs and the transverse process of the C7 vertebra. This muscle is responsible for extending and laterally flexing the thoracic spine.
The iliocostalis thoracis is the most lateral component of the erector spinae group. It lies deep to the fleshy portion of the serratus posterior muscle. The muscle is supplied by the dorsal rami of the thoracic spinal nerves, which provide innervation.
The thoracis section of the iliocostalis muscle is important for various day-to-day activities. It helps to stabilize the spine and maintain proper posture. This is especially noticeable during activities such as lifting objects, sitting upright, and standing upright. In swimming, the thoracis section also helps to maintain the proper body position, particularly during freestyle and backstroke strokes.
The iliocostalis thoracis muscle works in synergy with the other erector spinae components, the longissimus and spinalis muscles. When the thoracis section contracts on one side, it results in lateral flexion of the trunk and vertebral column. When both sides contract together, it causes an extension of the trunk and vertebral column.
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Frequently asked questions
The iliocostalis muscle is a deep muscle in the back that is part of the erector spinae muscle group.
The iliocostalis muscle is located in the back, immediately lateral to the longissimus muscle.
The iliocostalis muscle aids in extension (bending backward), lateral flexion (bending to the side), and rotation of the spinal column. It helps to stabilize the spine and maintain proper posture.
The iliocostalis muscle is divided into three parts: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum.
The iliocostalis cervicis originates from the angles of the third to sixth ribs and inserts into the posterior tubercles of the transverse processes of the fourth to sixth cervical vertebrae.
