DEEP BACK MUSCLES

Deep Back Muscles Epaxial muscles. Epaxial muscles. Hypaxial muscles. Hypaxial muscles. Pharyngeal arch muscles. Pharyngeal arch muscles.

Cutaneous Nerves of the Back Along either side of the midline of the back: Along either side of the midline of the back: Innervated by dorsal (posterior) rami of thoracic spinal nerves. More laterally: More laterally: Innervated by lateral cutaneous branches of the intercostal nerves.

Thoracolumbar Fascia Triangular-shaped sheet of tough connective tissue. Triangular-shaped sheet of tough connective tissue. Partial site of origin of latissimus dorsi and abdominal oblique muscles. Partial site of origin of latissimus dorsi and abdominal oblique muscles.

Thoracolumbar Fascia Laminae Posterior lamina to lumbar spinous processes. Posterior lamina to lumbar spinous processes. Middle lamina to lumbar transverse processes. Middle lamina to lumbar transverse processes. Anterior lamina (deepest) to lumbar transverse processes. Anterior lamina (deepest) to lumbar transverse processes.

Arrangement of Back Muscles Three groups: Three groups:Superficial:Extrinsic.Intermediate:Extrinsic.Deep:Intrinsic.

Superficial Extrinsic Muscles Connect limb to axial skeleton. Connect limb to axial skeleton. Innervated by ventral rami or CN XI. Innervated by ventral rami or CN XI. Include: Include:Trapezius. Latissimus dorsi. Levator scapulae. Rhomboideus major. Rhomboideus minor.

Intermediate Extrinsic Muscles Respiratory muscles. Respiratory muscles. Innervated by ventral (anterior) rami. Innervated by ventral (anterior) rami. Serratus posterior group: Serratus posterior group: Serratus posterior superior. Serratus posterior inferior. Refer to Syllabus: Table II, p. 71. Refer to Syllabus: Table II, p. 71.

INTRINSIC (DEEP) BACK MUSCLES

Intrinsic Back Muscles True intrinsic muscles of the back are innervated by dorsal (posterior) rami. True intrinsic muscles of the back are innervated by dorsal (posterior) rami. Three groups: Three groups:SuperficialIntermediateDeep Refer to Table III, p 73 of Syllabus. Refer to Table III, p 73 of Syllabus.

Spinotransversalis System Consists of the Splenius group: Consists of the Splenius group: Long muscles. Long muscles. Originate from ligamentum nuchae and spinous processes. Originate from ligamentum nuchae and spinous processes.

Spinotransversalis System Run laterally upward to transverse processes and skull. Run laterally upward to transverse processes and skull. Run laterally and upward to insertion. Run laterally and upward to insertion. Two parts: Two parts: Splenius capitis. Splenius cervicis.

Superficial Intrinsic Muscles Splenius capitis: Splenius capitis: O:spinous processes of C7 and T1-4. O:spinous processes of C7 and T1-4. I:superior nuchal line and mastoid. I:superior nuchal line and mastoid. Splenius cervicis: Splenius cervicis: O:spinous processes of T3-6. O:spinous processes of T3-6. I:C1-C4 transverse processes with levator scapulae. I:C1-C4 transverse processes with levator scapulae. Spinotransversalis System Spinotransversalis System

Intermediate Intrinsic Sacrospinalis system: Sacrospinalis system: Erector spinae. Run longitudinally upward: Transverse processes to rib. Rib to rib. Rib to cervical transverse processes. Spinous processes to spinous processes.

Intermediate Layer of Intrinsic Deep Back Muscles Components: Components:Iliocostalis.Longissimus.Spinalis. Refer to Syllabus: Refer to Syllabus: Table III. P 73.

Intermediate Intrinsic Iliocostalis: Iliocostalis: Origin =ilium and sacrum. Insertion =most of the ribs. Lateral part of the erector spinae group. Extends back; keeps erect posture. Components:Lumborum.Thoracis.Cervicis.

Intermediate Intrinsic Longissimus: Longissimus: Origin =transversus processes and sacrum. Insertion = most of ribs. Middle portion of erector spinae group. Components:Thoracis.Cervicis.Capitis.

Intermediate Intrinsic Spinalis: Spinalis: Origin =spinous processes of T11-L2. Insertion =spinous processes of thoracic and lower cervical vertebrae. Components:Thoracis.Cervicis: Usually absent. Capitis: Part of semispinalis capitis.

Deep Intrinsic Muscles Transversospinalis system: Transversospinalis system: From transverse processes to transverse processes. Concealed by erector spinae. Muscles arise laterally and insert medially. Components:Semispinalis.Multifidus.Rotatores.

Semispinalis Traverse a couple of vertebral levels. Traverse a couple of vertebral levels. Components: Components:Thoracis.Cervicis. Origin =T1-4. Insertion =C3-5. Largely covered by semispinalis capitis.

Semispinalis Components: Components:Capitis: Origin =T1-6 and C4-7. Insertion =between superior and inferior nuchal lines.

Multifidus Thick muscle mass. Thick muscle mass. Arises from sacrum and surrounding structures and from transverse processes up to C4. Arises from sacrum and surrounding structures and from transverse processes up to C4. Including mammillary processes of lumbar vertebrae. Traverses 3 segments. Traverses 3 segments. Inserts on spinous processes C2-L5. Inserts on spinous processes C2-L5.

Rotatores Pass from root of transverse process to root of superior spinous process. Pass from root of transverse process to root of superior spinous process. Long: Long: Span two segments. Short: Short: Span one segment.

Intrinsic Segmental Muscles Interspinales. Interspinales. Intertransversarii. Intertransversarii.