Spinalis

An article about the spinalis muscle, part of the erector spinae group

Diagram of the spinalis muscle

The spinalis is a muscle located in the back, part of the erector spinae muscle group. It is the most medial of the three muscles that comprise the erector spinae, the others being the longissimus and the iliocostalis. The spinalis muscle is responsible for extending and laterally flexing the vertebral column.

Anatomy

The spinalis muscle is divided into three parts:

• Spinalis thoracis: This is the largest and most prominent part of the spinalis muscle. It originates from the spinous processes of the lower thoracic and upper lumbar vertebrae and inserts into the spinous processes of the upper thoracic vertebrae.

• Spinalis cervicis: This part is often poorly developed or absent. When present, it originates from the spinous processes of the lower cervical and upper thoracic vertebrae and inserts into the spinous processes of the cervical vertebrae.

• Spinalis capitis: This part is usually indistinguishable from the semispinalis capitis muscle. It originates from the spinous processes of the upper thoracic and lower cervical vertebrae and inserts into the occipital bone of the skull.

Function

The primary function of the spinalis muscle is to extend the vertebral column. It also plays a role in lateral flexion of the spine. The spinalis, along with the other muscles of the erector spinae group, helps maintain posture and stabilize the spine during movement.

Innervation

The spinalis muscle is innervated by the posterior rami of the spinal nerves. These nerves provide the necessary motor signals for muscle contraction and sensory feedback from the muscle.

Blood Supply

The blood supply to the spinalis muscle is provided by the dorsal branches of the posterior intercostal arteries and the lumbar arteries. These vessels ensure that the muscle receives adequate oxygen and nutrients to function effectively.

Clinical Significance

Injuries or conditions affecting the spinalis muscle can lead to back pain and impaired movement. Conditions such as muscle strain, spinal stenosis, and herniated discs can impact the function of the spinalis and other muscles in the erector spinae group.

Related pages

• Erector spinae
• Longissimus
• Iliocostalis
• Vertebral column
• Back pain