Back muscles

The back comprises the dorsal part of the neck and the torso (dorsal body cavity) from the occipital bone to the top of the tailbone. The muscles of the back can be divided in three main groups according to their anatomical position and function. The superficial muscles participate in the movements of the upper limb, the intermediate muscles support the respiratory function, and the deep muscles are involved in the posture and rotation of the vertebral column. The first two groups include the extrinsic muscles, which are innervated by the anterior branches of the spinal nerves, while intrinsic muscles of the latter group are innervated by the posterior branches. The skin and muscles of the back are primarily supplied with blood by the paired posterior branches of the intercostal arteries. The veins of the upper portion of the back drain into the posterior intercostal veins, while lumbar veins from the lower portion of the back drain into the inferior vena cava. Similarly, the intercostal lymph nodes receive drainage from the thoracic portion of the back, while the inguinal lymph nodes drain from the lumbar back.

The organs, blood vessels, lymphatic vessels, and nerve pathways of the neck (see “Overview of head and neck region”), the spinal cord, and the vertebral column (the spine) are covered in their own articles.

• Consist of:
  • Rectus capitis posterior minor
  • Obliquus capitis superior
  • Rectus capitis posterior major
  • Obliquus capitis inferior
• See “Suboccipital muscles” in “Overview of the head and neck region” for more details.

The extrinsic suboccipital muscles include rectus capitis lateralis and rectus capitis anterior muscles, which are prevertebral muscles of the neck. See prevertebral muscles in the article “Overview of the head and neck region” for more details.

Superficial back muscles are the first layer of muscles below the skin and superficial fascia. These muscles connect the clavicula, scapula, and humerus to the axial skeleton, and the main function is related to the movement of the upper limb. They are also covered in relation to the shoulder and shoulder girdle in the article “Shoulder, axilla, and brachial plexus.” The latissimus dorsi is covered in the article on the “Chest wall” as well.

Two muscles (the serratus posterior superior and inferior) belong to the intermediate group of back muscles. They are immediately deep to the muscles in the superficial group and pass obliquely outward from the vertebral column to attach to the ribs. These muscles support the respiratory function and are also covered under chest wall muscles in the “Chest wall” article.

The intrinsic back muscles are divided based on their function in four groups.

• Spinotransverse system: the extensors and rotators of the head and neck
  • Splenius capitis
  • Splenius cervicis
• Sacrospinal system (erector spinae): the extensors and rotators of the vertebral column
  • Iliocostalis
  • Longissimus
  • Spinalis
• Transversospinal system
  • Short rotatores
  • Long rotatores
  • Multifidus
  • Semispinalis
• Segmental muscles
  • Levatores costarum
  • True segmental muscles
    • Interspinales
    • Intertransversarii

Spinotransverse system

Erector spinae (sacrospinal system)

Transversospinal system

Segmental muscles

The interspinales muscles skip one vertebral segment, the spinalis muscles skip multiple segments.

Vascular supply

Neck

• See “Arteries and veins” in “Overview of the head and neck region” for more details.

Back

Vertebral body

• See the “Vasculature and lymphatics” in “Vertebral column.”

Lymphatics