The Spine

1. Overall Structure of the Spine
2. Structure of the Vertebrae
3. Ligaments of the Vertebral Column
4. Joints of the Vertebral Column
5. Cervical Spine
   
   • Characteristic Features
   • Atlas (C1)
   • Axis (C2)
6. Thoracic Spine
   
   • Characteristic Features
7. Lumbar Spine
   
   • Characteristic Features
8. Sacrum and Coccyx
9. Quiz

The vertebral column is composed of 33 vertebrae; 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4 coccygeal.

Its functions include:

• Protection of the spinal cord and cauda equina
• Flexible movement
• Provide support for the body to maintain an upright position
• Haematopoiesis (via red bone marrow within vertebral bodies)
  

Diagram - Regions of the vertebral column

Creative commons source by Laboratoires Servier [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

Structure of Vertebrae

The anterior part of the vertebrae is the vertebral body. Vertebral bodies increase in size as they lie more inferiorly in the spine, as the lower vertebrae support more weight. The vertebrae are separated by intervertebral discs.

The posterior part of a vertebra is formed by the vertebral arch. This arch forms the rear of the vertebral foramen. The foramina line up to form the vertebral canal which contains the spinal cord and cauda equina. There are also several bony landmarks to allow for attachment of ligaments and muscles.

Diagram - Labelled structure of lumbar vertebrae 

Public Domain Source Anatomy of the Human Body, by Henry Gray, edited by Dr. Emily Smith [Public domain]

Ligaments of the Vertebral Column

Ligaments around the vertebral body:

• The anterior longitudinal ligament runs along the anterior aspect of the vertebral bodies and prevents hyperextension of the vertebral columns.
• The posterior longitudinal ligament runs along the posterior aspect of vertebral bodies and prevents hyperflexion of the vertebral column.

Ligaments around the vertebral arch:

• Ligamentum flavum is located between the laminae of vertebrae.
• Interspinous ligaments are located between spinous processes.
• Supraspinous ligament runs along the tips of the spinous processes.
• Intertransverse ligaments are located between transverse processes.

Diagram - The ligaments of the vertebral column

Public Domain Source Anatomy of the Human Body, by Henry Gray, edited by Dr. Emily Smith [Public domain]

Joints of the Vertebral Column

The joints between vertebral bodies are cartilaginous joints; they articulate with each other indirectly via intervertebral discs. These joints allow the weight bearing property of the vertebral column.

The intervertebral discs have two distinct regions:

• Annulus fibrosus is the outer region which is very strong and is a major shock absorber.
• Nucleus pulposus is the inner softer region.

Articular facets are joints between the vertebrae which allow movement. There is one on either side of the vertebrae.

Diagram - The structure of intervertebral discs

Creative commons source by OpenStax College [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]