Deep Back Muscles Anatomy Quiz

Deep Back Muscles

• Deep back muscles are also known as intrinsic back muscles, paraspinals, or epaxial muscles.
• Superficial Back Muscles: derived from the hypaxial portion of the myotome and support the upper limb.
• Deep Back Muscles: derived from the epimere portion of the myotome and support and move the vertebral column.
• Superficial Back Muscles are innervated by the ventral rami.
• Deep Back Muscles are innervated by the dorsal rami.

Splenius Muscles

• Splenius Capitis: originates from the spinous processes of the lower cervical and upper thoracic vertebrae and inserts on the mastoid process of the temporal bone and the occipital bone.
• Splenius Cervicis: originates from the spinous processes of the upper thoracic vertebrae and inserts on the transverse processes of the upper cervical vertebrae.
• Bilateral Contraction (Both Sides): head and neck extension.
• Unilateral Contraction (One Side): rotation of the head to the same side as the contracting muscle, synergistic with the Sternocleidomastoid (SCM) muscle.

Erector Spinae Muscles

• Iliocostalis: originates from the iliac crest and sacrum, and inserts segmentally along the ribs.
• Longissimus: originates from the lumbar vertebrae, ribs, and ends at the mastoid process of the temporal bone.
• Spinalis: originates along the spinous processes of the back.
• Bilateral Contraction: posture and vertebral extension.
• Unilateral Contraction: lateral vertebral flexion.

Transversalis Spinalis Muscles

• Semispinalis: arises from the transverse processes and spans 4-6 vertebrae to attach to a superior adjacent spinous process; upper fibers extend to the occipital bone.
• Rotatores: arises from the transverse processes and spans 1-2 vertebrae to attach to a superjacent spinous process, primarily in the thoracic region.
• Multifidus: arises from the sacrum and transverse processes, courses 2-4 vertebral lengths to a superjacent spinous process, primarily in the lower back.
• Actions of Transversalis Spinalis Muscles: primarily focus on maintaining posture alongside the erector spinae, and also contribute to proprioception (body awareness).

Suboccipital Muscles

• Rectus Capitis Posterior Minor:
• Rectus Capitis Posterior Major:
• Obliquus Capitis Inferior:
• Obliquus Capitis Superior:
• Suboccipital Triangle: formed by the suboccipital muscles, containing the vertebral artery which travels up the transverse foramina of the cervical vertebrae, through the C1 foramina, and then into the skull via the foramen magnum.

Innervation of Deep Back Muscles

• All deep back muscles are segmentally innervated by branches of the dorsal rami at every neurological level from the cervical to the sacral levels.