Spine Anatomy and Function

Overview

• The spine, also known as the backbone or vertebral column, is comprised of 33 bones called vertebrae.
• Functions of the vertebrae:
  • Provide body support.
  • Protect the spinal cord from injury.

Division of Vertebrae

1. Cervical Vertebrae

   • Located in the neck region.
   • Consists of 7 vertebrae: C1 to C7.
   • Supports the head (weighing 10-13 pounds).
   • C1 (Atlas) and C2 (Axis) allow for significant head motion:
     • C1 is ring-shaped and attaches to the skull, allowing head nodding (yes motion).
     • C2 serves as a pivot for C1, allowing head shaking (no motion).
     • Features an odontoid process known as the dens for pivoting.

2. Thoracic Vertebrae

   • Located in the mid-upper back.
   • Consists of 12 vertebrae: T1 to T12.
   • Support the ribcage and protect the heart and lungs.
   • Limited range of motion.

3. Lumbar Vertebrae

   • Located in the lower back.
   • Consists of 5 vertebrae: L1 to L5.
   • Bear the weight of the upper body; larger to support stress.

4. Sacral Vertebrae

   • Consists of 5 fused vertebrae: S1 to S5.
   • Connect spine to hip bones, forming the pelvic girdle with hip bones.

5. Coccyx (Tailbone)

   • Composed of 4 fused bones.
   • Provides attachment for ligaments and muscles of the pelvic floor.

Structure of a Vertebra

• Components of a Vertebra:

  • Body: Weight-bearing part.
  • Vertebral Arch: Protects the spinal cord.
  • Processes: Facilitate muscle attachment.

• Vertebral Arch

  • Made of two pedicles and laminae.
  • Encases the spinal cord in the vertebral foramen.

• Processes

  • Bony structures arising from the vertebral arch.
  • Form facet joints:
    • Allow back motion.
    • Each vertebra has two pairs of facet joints.
    • Facet joints connect above and below vertebrae.
  • Includes transverse and spinous processes.

Intervertebral Discs

• Located between vertebrae except between C1 and C2.

• Act as cushions to prevent bones from rubbing.

• Composition:

  • Annulus: Several fibrocartilage layers.
  • Nucleus: Gel-filled center, distributes pressure evenly.

• Nucleus Characteristics

  • Contains proteoglycans, which are hydrophilic.
  • Absorbs fluid at night; fluid is expelled during the day due to upright pressure.

• Aging Effects

  • Discs lose ability to absorb fluid, flatten, and become brittle, contributing to height loss.

Conclusion

• Importance of support and protection provided by the spine.
• Request for support and suggestions for future content.