Human Gross Anatomy - Back Muscles O,I,N,As

OINAs of Back Muscles

Iliocostalis (Lumborum)

Origin: Sacrum, iliac crest, and lumbar vertebrae; Insertion: Angles of ribs 6-12; Innervation: Posterior rami of thoracic and lumbar spinal nerves; Actions: Extends and laterally flexes the vertebral column.

Iliocostalis (Thoracis)

Origin: Angles of ribs 7-12; Insertion: Angles of ribs 1-6 and transverse processes of C7; Innervation: Posterior rami of thoracic spinal nerves; Actions: Extends and laterally flexes the vertebral column.

Iliocostalis (Cervicis)

Origin: Angles of ribs 3-6; Insertion: Transverse processes of C4-C6; Innervation: Posterior rami of cervical spinal nerves; Actions: Extends and laterally flexes the vertebral column.

Longissimus (Thoracis)

Origin: Transverse processes of lumbar vertebrae; Insertion: Transverse processes of T1-T12 and ribs 9-10; Innervation: Posterior rami of thoracic spinal nerves; Actions: Extends and laterally flexes the vertebral column.

Longissimus (Cervicis)

Origin: Transverse processes of T1-T5; Insertion: Transverse processes of C2-C6; Innervation: Posterior rami of cervical spinal nerves; Actions: Extends and laterally flexes the vertebral column.

Longissimus (Capitis)

Origin: Transverse processes of T1-T5 and articular processes of C4-C7; Insertion: Mastoid process of temporal bone; Innervation: Posterior rami of cervical spinal nerves; Actions: Extends and rotates the head.

Spinalis (Thoracis)

Origin: Spinous processes of T11-L2; Insertion: Spinous processes of T1-T8; Innervation: Posterior rami of thoracic spinal nerves; Actions: Extends the vertebral column.

Spinalis (Cervicis)

Origin: Ligamentum nuchae and spinous process of C7; Insertion: Spinous processes of C2; Innervation: Posterior rami of cervical spinal nerves; Actions: Extends the vertebral column.

Spinalis (Capitis)

Origin: Blends with semispinalis capitis; Insertion: Occipital bone; Innervation: Posterior rami of cervical spinal nerves; Actions: Extends the head.

Rotatores (Brevis)

Origin: Transverse processes of thoracic vertebrae; Insertion: Spinous processes of the vertebra directly above (1 segment above); Innervation: Posterior rami of spinal nerves; Actions: Provides fine segmental movement and stability of the spine.

Rotatores (Longus)

Origin: Transverse processes of thoracic vertebrae; Insertion: Spinous processes of the vertebra two segments above; Innervation: Posterior rami of spinal nerves; Actions: Provides fine segmental movement and stability of the spine.

Semispinalis (Thoracis)

Origin: Transverse processes of T6-T10; Insertion: Spinous processes of T4-T6 and C5-C7; Innervation: Posterior rami of thoracic spinal nerves; Actions: Extends and rotates the thoracic spine.

Semispinalis (Cervicis)

Origin: Transverse processes of T1-T6; Insertion: Spinous processes of C2-C5; Innervation: Posterior rami of cervical spinal nerves; Actions: Extends and rotates the cervical spine.

Semispinalis (Capitis)

Origin: Transverse processes of C4-T5 and articular processes of C5-C7; Insertion: Occipital bone between the superior and inferior nuchal lines; Innervation: Posterior rami of cervical spinal nerves; Actions: Extends and rotates the head.

Trapezius

Origin: External occipital protuberance, nuchal ligament, and spinous processes of vertebrae C7-T12; Insertion: Lateral third of clavicle, acromion, and spine of scapula; Innervation: Spinal accessory nerve (CN XI) and anterior rami of C3-C4; Actions: Elevates, retracts, and rotates the scapula.

Latissimus Dorsi

Origin: Spinous processes of T7-L5, iliac crest, and lower three ribs; Insertion: Intertubercular groove of the humerus; Innervation: Thoracodorsal nerve; Actions: Extends, adducts, and medially rotates the arm.

Rhomboid Major

Origin: Spinous processes of T2-T5; Insertion: Medial border of scapula; Innervation: Dorsal scapular nerve; Actions: Retracts and elevates the scapula.

Rhomboid Minor

Origin: Spinous processes of C7-T1; Insertion: Medial border of scapula; Innervation: Dorsal scapular nerve; Actions: Retracts and elevates the scapula.

Levator Scapulae

Origin: Transverse processes of C1-C4; Insertion: Medial border of scapula; Innervation: Dorsal scapular nerve and cervical nerves C3-C4; Actions: Elevates the scapula and tilts glenoid cavity inferiorly.

Serratus Posterior Superior

Origin: Nuchal ligament and spinous processes of C7-T3; Insertion: Superior borders of ribs 2-4; Innervation: Intercostal nerves; Actions: Elevates the ribs during respiration.

Serratus Posterior Inferior

Origin: Spinous processes of T11-L2; Insertion: Inferior borders of ribs 8-12; Innervation: Anterior rami of T9-T12 spinal nerves; Actions: Depresses the ribs during respiration.

Splenius Capitis

Origin: Spinous processes of C7-T3 and nuchal ligament; Insertion: Mastoid process and lateral third of superior nuchal line; Innervation: Posterior rami of middle cervical nerves; Actions: Extends, rotates, and laterally flexes the head.

Splenius Cervicis

Origin: Spinous processes of T3-T6; Insertion: Transverse processes of C1-C3; Innervation: Posterior rami of lower cervical nerves; Actions: Extends, rotates, and laterally flexes the neck.

Multifidus

Origin: Sacrum, ilium, transverse processes of lumbar, thoracic, and cervical vertebrae; Insertion: Spinous processes of vertebrae 2-4 segments above origin; Innervation: Posterior rami of cervical, thoracic, and lumbar spinal nerves; Actions: Stabilizes the vertebral column during movement.

Interspinales

Origin: Spinous processes of vertebrae; Insertion: Spinous processes of adjacent vertebrae; Innervation: Posterior rami of spinal nerves; Actions: Aids in extension and stabilization of the vertebral column.

Intertransversarii

Origin: Transverse processes of vertebrae; Insertion: Transverse processes of adjacent vertebrae; Innervation: Posterior and anterior rami of spinal nerves; Actions: Aids in lateral flexion and stabilization of the vertebral column.

Quadratus Lumborum

Origin: Iliac crest and iliolumbar ligament; Insertion: Transverse processes of L1-L4 and inferior borders of ribs 11-12; Innervation: Anterior rami of T12 and L1-L4; Actions: Laterally flexes the vertebral column and extends the lumbar spine.

Extrinsic Superficial Layer

Includes Trapezius, Latissimus Dorsi, Levator Scapulae, Rhomboid Major and Minor Muscles

Extrinsic Intermediate Layer

Includes Serratus Posterior Superior and Inferior Muscles

Intrinsic Superficial Layer

Includes Splenius Capitis and Splenius Cervicis Muscles

Intrinsic Intermediate Layer

Includes Erector Spinae Muscles such as Iliocostalis, Longissimus, and Spinalis.

Intrinsic Major Deep Muscles

Includes Transversospinalis Muscles such as Semispinalis, Multifidus, and Rotatores (Brevis and Longus)

Intrinsic Minor Deep Muscles

Includes Intertransversarii and Interspinalis

Rectus Capitis Posterior Major

Origin: Spinous process of the axis (C2); Insertion: Lateral aspect of the inferior nuchal line of the occipital bone; Innervation: Suboccipital nerve; Actions: Extends and rotates the head.

Rectus Capitis Posterior Minor

Origin: Posterior tubercle of the atlas (C1); Insertion: Medial aspect of the inferior nuchal line of the occipital bone; Innervation: Suboccipital nerve; Actions: Extends the head.

Obliquus Capitis Superior

Origin: Transverse process of the atlas (C1); Insertion: Between the superior and inferior nuchal lines of the occipital bone; Innervation: Suboccipital nerve; Actions: Extends and laterally bends the head.

Obliquus Capitis Inferior

Origin: Spinous process of the axis (C2); Insertion: Transverse process of the atlas (C1); Innervation: Suboccipital nerve; Actions: Rotates the atlas and therefore the head to the same side.