The Skeleton and Joints: Vertebral Column and Vertebrae Structure

The Skeleton and Joints

Overview

The human skeleton provides the structural framework for the body and is essential for movement, protection, and support. This section focuses on the vertebral column and the structure of vertebrae, which are central to the axial skeleton.

The Vertebral Column

Characteristics and Functions

• Vertebral column (spine or spinal column): Extends from the skull to the pelvis and forms the body's central support structure.

• Functions:

  • Transmits the weight of the trunk to the lower limbs.

  • Surrounds and protects the spinal cord.

  • Provides attachment points for ribs and muscles.

• Structure: Composed of 26 irregular bones (vertebrae) arranged in five major regions.

Regions of the Vertebral Column

• Cervical (neck): 7 vertebrae (C1–C7)

• Thoracic (upper back): 12 vertebrae (T1–T12)

• Lumbar (lower back): 5 vertebrae (L1–L5)

• Sacrum: 1 bone formed from the fusion of 5 sacral vertebrae; articulates with the hip bones.

• Coccyx: 1 bone formed from the fusion of 4 small vertebrae; forms the terminus of the column.

Mnemonic for remembering vertebral counts: 7 am (cervical), 12 noon (thoracic), 5 pm (lumbar).

General Structure of the Vertebrae

Common Features

Despite regional differences, all vertebrae share a common structural pattern:

• Body (centrum): The anterior, weight-bearing region of the vertebra.

• Vertebral arch: Composed of two pedicles and two laminae, forming the posterior part of the vertebra.

• Vertebral foramen: The opening enclosed by the body and vertebral arch; forms the vertebral canal for the spinal cord.

• Intervertebral foramina: Lateral openings between adjacent vertebrae for the passage of spinal nerves.

Processes of the Vertebrae

• Spinous process: Projects posteriorly from the vertebral arch; serves as a site for muscle and ligament attachment.

• Transverse processes (2): Project laterally from each side of the vertebral arch; also serve as attachment sites.

• Superior and inferior articular processes: Protrude from the vertebral arch and form joints with adjacent vertebrae.

Ligaments of the Vertebral Column

Major Ligaments and Their Functions

• Anterior longitudinal ligament: Runs along the anterior surface of the vertebral bodies; prevents hyperextension of the spine.

• Posterior longitudinal ligament: Runs along the posterior surface of the vertebral bodies inside the vertebral canal; prevents hyperflexion.

• Ligamentum flavum: Connects adjacent vertebrae; contains elastic fibers to allow for flexibility and recoil.

• Supraspinous ligament: Connects the tips of the spinous processes from the neck to the sacrum.

• Interspinous ligament: Connects the spinous processes of adjacent vertebrae.

Table: Regions of the Vertebral Column

Region	Number of Vertebrae	Main Features
Cervical	7	Smallest, lightest; support the head; allow for a wide range of motion
Thoracic	12	Articulate with ribs; have long spinous processes
Lumbar	5	Largest vertebrae; support most of the body weight
Sacrum	5 (fused)	Forms posterior wall of pelvis; articulates with hip bones
Coccyx	4 (fused)	Small, triangular; forms the terminus of the column

Key Terms and Definitions

• Vertebral foramen: The canal through which the spinal cord passes.

• Pedicle: Short, thick process that projects posteriorly from the vertebral body, forming the sides of the vertebral arch.

• Lamina: Flattened or arched part of the vertebral arch, forming the roof of the vertebral foramen.

• Spinous process: Bony projection off the posterior (back) of each vertebra.

• Transverse process: Lateral projections on both sides of the vertebra.

Example: Clinical Relevance

• Herniated disc: Occurs when the nucleus pulposus (inner core of the intervertebral disc) protrudes through the annulus fibrosus (outer ring), potentially compressing spinal nerves and causing pain or neurological symptoms.

Additional info: The vertebral column's curvatures (cervical, thoracic, lumbar, sacral) help absorb shock and maintain balance during movement.