Vertebrae Column

Vertebral Column - Overview

  • Also known as the spinal column or spine.

  • Composed of vertebrae (singular: vertebra), separated and united by intervertebral discs.

  • Acts as a flexible column that supports head, neck, and body, enabling movement and protecting the spinal cord.

Structure of the Vertebral Column

  • Consists of:

    • 24 vertebrae in adults, plus sacrum and coccyx.

    • Divided into three regions:

    • Cervical (C1–C7)

    • Thoracic (T1–T12)

    • Lumbar (L1–L5)

  • Total of five regions, with vertebrae in each region named and numbered in descending order.

  • Curvature includes:

    • Primary:

    • Thoracic curvature

    • Sacrococcygeal curvature

    • Secondary:

    • Cervical curvature

    • Lumbar curvature

Development and Modifications

  • Originally 33 vertebrae develop, reduced to 24.

  • Sacrum forms by fusion of five sacral vertebrae; coccyx formed by fusion of four coccygeal vertebrae.

  • All mammal species have seven cervical vertebrae despite size variation (e.g., giraffes have cervical vertebrae of up to 11 inches tall).

Curvatures of the Vertebral Column

  • Adult vertebral column has four curvatures for strength, flexibility, and shock absorption:

    • Primary Curvatures:

    • Thoracic

    • Sacrococcygeal (retained from fetal position, concave anteriorly)

    • Secondary Curvatures:

    • Cervical (develops as the infant holds head up)

    • Lumbar (develops as the child begins to walk)

  • Secondary curves are concave posteriorly and develop gradually after birth.

Disorders of the Vertebral Column

  • Developmental anomalies, obesity, or pathological changes can enhance normal curvature, resulting in abnormalities:

    • Kyphosis: Excessive posterior curvature in thoracic region.

    • Can be caused by osteoporosis weakening anterior portions leading to vertebral collapse.

    • Lordosis: Excessive anterior curvature in lumbar region, often linked to obesity or pregnancy.

    • Leads to anterior shift in the line of gravity resulting in pelvic tilt and enhanced lumbar curve.

    • Scoliosis: Lateral bending and twisting of the vertebral column.

    • Common among girls, often unknown causes; may involve muscular weakness or differential growth rates.

    • Identified when the individual stands in anatomical position or bends forward.

General Structure of a Vertebra

  • Typical vertebra consists of:

    • Body (front, weight-bearing)

    • Vertebral arch (posterior area) comprising:

    • Paired pedicles

    • Paired laminae

    • Processes: transverse, spinous, superior articular, inferior articular.

    • Vertebral foramen for spinal cord passage.

  • Adjacent vertebrae separated and united by intervertebral discs.

  • Vertebral canal formed by alignment of vertebral foramina, protecting the spinal cord.

Regional Characteristics of Vertebrae

Cervical Vertebrae

  • Characterized by:

    • Small bodies (least weight supported).

    • Bifid spinous processes (Y-shaped).

    • Short transverse processes with transverse foramen for spinal nerve passage.

    • C1 (Atlas): ring-shaped, no body or spinous process, supports skull.

    • C2 (Axis): features the dens, allowing head rotation.

Thoracic Vertebrae

  • Larger bodies than cervical vertebrae.

  • Long spinous processes that overlap the next inferior vertebra.

  • Articulation sites (facets) for rib attachment (costal facets).

Lumbar Vertebrae

  • Characterized by:

    • Large, thick bodies (greatest weight bearing).

    • Short, blunt spinous processes projecting posteriorly.

    • Large articular processes oriented for stability.

Sacrum and Coccyx

  • Sacrum:

    • Triangular, formed by the fusion of five sacral vertebrae (fuses after 20 years).

    • Forms part of the pelvis, articulates with ilium.

    • Contains sacral canal for spinal nerve passage.

  • Coccyx:

    • Formed by fusion of four coccygeal vertebrae, articulates with sacrum.

Intervertebral Discs and Ligaments

Intervertebral Discs

  • Fibrocartilaginous pads filling gaps between adjacent vertebrae.

  • Composed of two parts:

    • Anulus Fibrosus: Tough fibrous outer layer.

    • Nucleus Pulposus: Gel-like center, high water content, aids in weight bearing.

  • Discs account for ~25% of height, thin in cervical, thick in lumbar regions.

  • Herniation risk increases with age; can lead to disc protrusion and nerve compression (most common at L4/L5, L5/S1, C5/C6, C6/C7).

Ligaments of the Vertebral Column

  • Provide overall support and stability:

    • Anterior Longitudinal Ligament: Runs along the front; resists backward bending.

    • Supraspinous Ligament: Connects spinous processes; effective during forward bending.

    • Nuchal Ligament: Expanded supraspinous in the cervical region, supports skull.

    • Posterior Longitudinal Ligament: Located anterior to spinal cord, supports spinal stability.

    • Ligamentum Flavum: Paired ligaments connecting laminae, elastic properties aid in bending.

  • Whiplash injuries resulted mainly from lack of headrests in cars, leading to overstretching of ligaments.