Overview
This lecture explains the types, structures, and functions of vertebral joints, ligaments, and discs in the spine, including common clinical issues like herniation and nerve compression.
Functions of Vertebral Joints
- Allow flexibility and movement (flexion, extension, rotation) of the spine.
- Maintain spinal stability and proper alignment of vertebrae.
- Protect spinal cord and nerves by stabilizing the vertebral canal.
- Absorb and distribute mechanical forces during daily activities.
- Enable coordinated movements of head and trunk.
Classification & Structure of Vertebral Joints
- Joints classified as fibrous, cartilaginous, synovial, or bony (synostoses).
- Fibrous joints connect bones via dense connective tissue and allow minimal movement.
- Cartilaginous joints connect bones by cartilage and provide more mobility than fibrous joints.
- Synovial joints have fluid-filled cavities allowing extensive movement.
- Bony joints form when separate bones fuse into a single bone over time.
Fibrous Joints & Ligaments
- Fibrous joints in the spine (syndesmoses) are stabilized by ligaments, providing slight movement.
- Long ligaments: anterior longitudinal (prevents hyperextension), posterior longitudinal (limits hyperflexion, supports discs), and superficial posterior sacrococcygeal.
- Short ligaments: ligamenta flava (elastic, assists spine recoil), intertransverse (limit lateral flexion), interspinous (limit flexion), supraspinous (limits flexion, forms nuchal ligament in cervical region).
Cartilaginous Joints & Discs
- All spinal cartilaginous joints are symphyses (permanent, fibrocartilage).
- Intervertebral discs: symphyses between vertebral bodies, act as shock absorbers.
- Lumbosacral and sacrococcygeal symphyses are specialized strength joints.
- Discs consist of tough anulus fibrosus (outer layer) and gelatinous nucleus pulposus (inner core, absorbs shock).
- Disc degeneration or herniation can compress nerve roots, causing pain, numbness, or weakness (e.g., sciatica).
Synovial Joints in the Spine
- Facet (zygapophysial) joints: plane-type synovial joints between articular facets, allow gliding motion.
- Atlanto-axial joint: lateral (plane, gliding) and median (pivot, rotation), stabilize head rotation; median stabilized by transverse ligament.
- Atlanto-occipital joint: between occipital condyles and atlas, allows nodding (flexion/extension); supported by membranes and ligaments.
Bony Joints (Synostoses)
- Complete fusion of bones, no movement.
- Examples: fused sacral and coccygeal vertebrae (sacrum, coccyx).
Key Terms & Definitions
- Fibrous joint — bones joined by dense connective tissue, little movement.
- Cartilaginous joint — bones joined by cartilage; symphyses (permanent, fibrocartilage).
- Synovial joint — movement-permitting joint with synovial fluid and capsule.
- Bony joint (synostosis) — fused bones with no movement.
- Intervertebral disc — fibrocartilage pad between vertebrae, absorbs shock.
- Herniated disc — nucleus pulposus protrudes through anulus fibrosus, compressing nerves.
- Facet (zygapophysial) joint — synovial joint between vertebral articular facets.
Action Items / Next Steps
- Review and memorize the main types and examples of vertebral joints and ligaments.
- Prepare for the next lecture on the bones of the thorax (ribs and sternum).