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The iliocostalis muscle is a deep back muscle that is part of the erector spinae (sacrospinalis) muscle group. It originates from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5. The iliocostalis muscle is responsible for laterally flexing and extending the spine, as well as aiding in rotation of the spinal column. It lies over the posterior surface of the thoracic cage and is covered by the serratus dorsalis muscle. The iliocostalis muscle is divided into three regional parts: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum.
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What You'll Learn
Iliocostalis is a deep back muscle
The iliocostalis muscle is located over the most lateral part of the ribs and is covered by the serratus dorsalis muscle. It originates from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5. The muscle is supplied by the dorsal rami of spinal nerves.
The iliocostalis can be further divided into three regional parts according to their origin: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. The iliocostalis cervicis arises from the superior aspect of the third to sixth ribs and attaches to the posterior tubercles of the transverse processes of the fourth to sixth cervical vertebrae. It functions to laterally flex and extend the lower cervical region. The iliocostalis thoracis arises from the upper borders of the lower six ribs and inserts into the upper borders of the angles of the upper ribs. The iliocostalis lumborum is divided into lumbar and thoracic parts, with the lumbar part originating from the lateral crest of the sacrum, medial end of the iliac crest, and thoracolumbar fascia, and the thoracic part originating from the same site as the lumbar part.
The iliocostalis muscle is a powerful extensor of the back, contributing to the control and support of the orientation of the lumbar spine. It also assists as an accessory muscle of expiration due to its insertion on the ribs.
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It is part of the erector spinae muscle group
The iliocostalis muscle is indeed a deep muscle of the back. It is part of the erector spinae muscle group, which also includes the longissimus and spinalis muscles. These three muscles work together to facilitate several important functions in the human body.
The erector spinae muscles are responsible for aiding in extension, lateral flexion, and rotation of the spinal column. They are arranged into longitudinal cords, with the iliocostalis muscle being the most lateral and composing the lateral cord. The longissimus muscle lies medial to the iliocostalis and forms the intermediate cord, while the spinalis muscle, the most medial of the three, makes up the medial cord.
The iliocostalis muscle has a unique structure and origin. It originates from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5. The muscle is horizontally divided into three regional parts: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. Each of these parts has distinct attachments and functions.
The iliocostalis cervicis arises from the angles of the third to sixth ribs and attaches to the transverse processes of the fourth to sixth cervical vertebrae. It plays a role in flexing and extending the lower cervical region. The iliocostalis thoracis, on the other hand, arises from the upper borders of the angles of the lower six ribs and inserts into the upper borders of the ribs.
The iliocostalis lumborum, the third part, is further divided into lumbar and thoracic parts. The lumbar part originates from the lateral crest of the sacrum, the medial end of the iliac crest, and the thoracolumbar fascia. It inserts into the transverse processes of vertebrae L1 to L4. The thoracic part of the iliocostalis lumborum shares the same origin as the lumbar part and inserts into the angles of ribs 5 to 12.
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It aids in extension, lateral flexion, and rotation of the spine
The iliocostalis muscle is a deep back muscle that is part of the erector spinae (sacrospinalis) muscle group. It aids in extension, lateral flexion, and rotation of the spine.
The iliocostalis muscle is located over the most lateral part of the ribs and is covered by the serratus dorsalis muscle. It lies very deep to the fleshy portion of the serratus posterior muscle. The dorsal surface of its cervical part is covered by the splenius capitis and rhomboid muscles, while the thoracic and lumbar segments lie beneath the thoracolumbar fascia. The superior and inferior portions of the thoracic part lie deep to the serratus posterior superior and inferior muscles, respectively.
The iliocostalis muscle is horizontally divided into three regional parts according to their origin: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. The lumbar part of iliocostalis lumborum originates from the lateral crest of the sacrum, the medial end of the iliac crest, and the thoracolumbar fascia. It inserts into the transverse processes of vertebrae L1-L4 and the adjacent part of the middle layer of the thoracolumbar fascia. The muscle fibres are arranged 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 of iliocostalis lumborum originates from the same site as the lumbar part, with fibres that course superiorly over the back and insert into the angle of ribs 5-12, lateral to iliocostalis thoracis. The muscle fibres of the thoracic part are serially aligned, with those attaching to the fifth rib being the most medial and inferior, and those inserting to the twelfth rib being the most lateral and superior.
The function of the iliocostalis muscle is to aid in extension, lateral flexion, and rotation of the spine. It extends the spine when contracting bilaterally and laterally flexes the spine when contracting unilaterally. The muscle is supplied by the dorsal rami of spinal nerves.
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It originates from the iliac crest, the sacrum, and the thoracolumbar fascia
The iliocostalis muscle is a deep back muscle that is part of the erector spinae muscle group. It 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 regional parts according to their origin: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum.
The lumbar part of the iliocostalis lumborum originates from the iliac crest, the sacrum, and the thoracolumbar fascia. Specifically, it originates from the lateral crest of the sacrum, the medial end of the iliac crest, and the thoracolumbar fascia. It then courses superiorly and inserts into the transverse processes of vertebrae L1-L4 and the adjacent part of the middle layer of the thoracolumbar fascia. The muscle fibres attaching to L1 are the most superficial and medial, while those inserting to L4 are the deepest and most lateral.
The thoracic part of the iliocostalis lumborum originates from the same site as the lumbar part, in the form of an aponeurotic sheath covering the lumbar part. Fibres course superiorly over the back and insert into the angle of ribs 5-12, laterally to the iliocostalis thoracis. The muscle fibres of the thoracic part are serially aligned, with those attaching to the fifth rib being the most medial and inferior, and those inserting to the twelfth rib being the most lateral and superior.
The iliocostalis cervicis arises from the angles of the third, fourth, fifth, and sixth ribs, and is inserted into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae. 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 tendons become muscular and are inserted into the upper borders of the angles of the upper six ribs and the back of the transverse process of the seventh cervical vertebra.
The function of the iliocostalis muscle is to extend the spine when contracting bilaterally and to laterally flex the spine when contracting unilaterally. It assists as an accessory muscle of expiration due to its insertion on the ribs.
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It is divided into three regional parts: cervicis, thoracis, and lumborum
The iliocostalis muscle is divided into three parts: cervicis, thoracis, and lumborum. These three regional parts are components of the erector spinae muscle group.
Iliocostalis cervicis, or cervicalis ascendens, arises from the angles of the third to sixth ribs. It is inserted into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae. This muscle laterally flexes and extends the lower cervical region, helping to maintain an erect posture and stabilize the vertebral column during flexion in the upper torso.
Iliocostalis thoracis, or musculus accessorius, arises from the upper borders of the angles of the lower six ribs, medial to the tendons of insertion of the iliocostalis lumborum. These tendons become muscular and are inserted into the upper borders of the angles of the upper ribs. When acting unilaterally, it is a lateral flexor of the thoracic spine.
Iliocostalis lumborum is the lower (lumbar) portion of the iliocostalis muscle. It is inserted by flattened tendons into the inferior borders of the angles of the lower six to nine ribs. This muscle is vital for allowing free movement of the spine, as it helps to support and control the orientation of the lumbar spine. Injury to the iliocostalis lumborum may result in pain in the lower back or buttocks, often caused by common daily activities such as lifting heavy objects, rotating while lifting, or sitting for extended periods.
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Frequently asked questions
Yes, the iliocostalis is a deep back muscle.
The iliocostalis muscle is one of the three erector spinae muscles that aid in extension (bending backward), lateral flexion (bending to the side), and rotation of the spinal column.
The iliocostalis muscle originates from the iliac crest, the sacrum, the thoracolumbar fascia, and the spinous processes of the vertebrae from T11 to L5.
The iliocostalis muscle inserts into the ribs and the transverse processes of the vertebrae.
