Bones of the Back
By Cameron Delicato, PTA
Bones of the Back Overview
The spine is made up of 33 bones called vertebrae. The vertebral column is split up into 5 different sections: cervical, thoracic, lumbar, sacrum, and the coccyx. The column itself provides four key functions for the body:
- Protection: Surrounds and protects the spinal cord within the spinal canal.
- Support: Carries the weight of the body.
- Axis: Forms the central axis of the body
- Movement: Roles in both posture and movement.
This is the uppermost section of the bones of the back (spine). The cervical spine is made up of 7 individual vertebrae. There are 3 distinguishable characteristics in cervical vertebrae:
- Bifid Spinous Process: The spinous process bifurcates (branches into two ends) at the bottom. However, the exceptions are the C1 (no spinous process) and C7 (spinous process is longer than other cervical vertebrae).
- Transverse Foramina: Opening in each transverse process, through which the vertebral arteries travel to the brain).
- Triangular vertebral Foramen.
Cervical vertebrae levels C1 (called atlas) and C2 (axis) are unique in their characteristics to specialize in allowing for movement of the head.
There are 12 thoracic vertebrae, which are larger than cervical spine and gradually increase in size as levels go lower down to lumbar spine. The main distinguishable function of the thoracic spine vertebrae is the articulate with the ribs. Each thoracic vertebra has 2 “demi facets” which are there to articulate with the heads of 2 different ribs.
There are 5 vertebrae in the lumbar spine, which make up the largest section in the vertebral column. They are structurally made up to support the weight of the torso (upper body). Lumbar vertebrae have very large bodies, which are kidney-shaped, and they lack characteristics like thoracic and cervical sections such as having no transverse foramina, costal facets, or bifid spinous processes.
However, the size and orientation allows for clinical access to the spinal cord between the vertebrae (which is not possible in thoracic section), allowing for procedures such as: epidural anesthesia administration and lumbar puncture.
Bones of the Back: Sacrum
This is a collection of 5 fused vertebrae. It is described as an inverted triangle, with the lateral walls of the sacrum including facets for articulation with the pelvis at the sacro-iliac joints (SI-joint). That connection creates a support at the base of your spine, helping to support the weight of the upper body.
This is a small bone which articulates with the bottom of the sacrum. It functions as an attachment point for some muscles of the pelvic floor, while also functioning as support and stabilization when a person is in a sitting position.