Intertransversarii muscle group

The intertransversarii muscles are small and short muscles found in the deepest layer of the intrinsic back muscles that stretch between the transverse processes of the adjacent vertebrae. Most intertransversarii pairs are located within the cervical and lumbar regions of the spine with some small muscular slips present in the lower thoracic region.

Cervical intertransversarii

The cervical intertransversarii are comprised of seven pairs of anterior and posterior muscles that extend along the sides of the cervical spine. These muscles are better developed than the lumbar intertransversarii muscles.

Summary

• origin:

  • anterior cervical intertransversarii -: anterior tubercles of transverse processes of cervical vertebrae

  • posterior cervical intertransversarii -: superior borders of transverse processes of cervical vertebrae

• insertion:

  • anterior cervical intertransversarii -: anterior tubercles of transverse processes of adjacent cervical vertebrae

  • posterior cervical intertransversarii -: inferior borders of transverse processes of adjacent cervical vertebrae above

• blood supply: vertebral, deep cervical and occipital arteries

• innervation:

  • anterior cervical intertransversarii -: ventral rami of cervical spinal nerves

  • posterior cervical intertransversarii -: ventral and dorsal rami of cervical spinal nerves

• action: lateral flexion of cervical spine, stabilisation of cervical spine

Gross anatomy

Origin

Each anterior cervical intertransversarii muscle originates from the anterior tubercle of the transverse process of the cervical vertebra. Each posterior cervical intertransversarii muscle originates from the superior border of the transverse process of the cervical vertebra.

Insertion

Each anterior cervical intertransversarii muscle inserts on the anterior tubercle of the adjacent cervical vertebra, while each posterior cervical intertransversarii muscle inserts on the inferior border of the transverse process of the adjacent cervical vertebra above.

Arterial supply

The anterior cervical intertransversarii muscles receive arterial blood supply from the occipital, deep cervical and vertebral arteries. The occipital artery arises from the external carotid artery, the deep cervical artery originates from the costocervical trunk, while the vertebral artery is a branch of the subclavian artery. The posterior cervical intertransversarii muscles are supplied by the ascending cervical artery of the thyrocervical trunk.

Innervation

The anterior cervical intertransversarii muscles are innervated by the ventral rami of the cervical spinal nerves, while the posterior cervical intertransversarii are supplied by the ventral and dorsal rami of the cervical spinal nerves.

Action

The anterior and posterior cervical intertransversarii muscles aid in lateral flexion of the cervical spine in addition to stabilising the cervical spine.

Lumbar intertransversarii

The lumbar intertransversarii are composed of four pairs of muscles located on either side of the lumbar spine extending between the transverse processes of two adjacent lumbar vertebrae. Each pair consists of a medial and lateral component, namely, the medial and lateral lumbar intertransversarii muscles.

Summary

• origin:

  • medial lumbar intertransversarii -: accessory processes of L1 - L4 vertebrae

  • lateral lumbar intertransversarii -: transverse and accessory processes of L1 - L4 vertebrae

• insertion:

  • medial lumbar intertransversarii -: mammillary processes of adjacent lumbar vertebrae

  • lateral lumbar intertransversarii -: transverse processes of adjacent lumbar vertebrae

• blood supply: branches of lumbar arteries

• innervation: ventral rami of lumbar spinal nerves

• action: lateral flexion of lumbar spine, stabilisation of lumbar spine

Gross anatomy

Origin

The lateral lumbar intertransversarii muscles originate from the transverse and accessory processes of the 1^st to 4^th lumbar vertebrae (L1 - L4). The medial lumbar intertransversarii muscles arise from the accessory processes of the first four lumbar vertebrae (L1 - L4).

Insertion

The muscle fibres of the lateral lumbar intertransversarii insert on the transverse processes of the adjacent lumbar vertebrae. The medial lumbar intertransversarii muscles insert on the mammillary processes of the adjacent lumbar vertebrae.

Arterial supply

The lumbar intertransversarii muscles receive arterial blood supply from the dorsal branches of the lumbar arteries that arise from the abdominal aorta. 

Innervation

The lumbar intertransversarii muscles are innervated by the ventral rami of the lumbar spinal nerves.

Action

The lumbar intertransversarii muscles aid in lateral flexion and stabilisation of the lumbar spine.