Overview
This lecture covers the anatomy and key functions of the human spine, focusing on the structure, curves, vertebrae, spinal segments, and supporting tissues.
Structure of the Spine
- The spine consists of 24 spinal bones called vertebrae, stacked to form the spinal column.
- The spinal column provides the main upright support for the body.
- The spine has three main curves: cervical (neck) curves inward, thoracic (midback) curves outward, and lumbar (low back) curves inward.
- The thoracic outward curve is called kyphosis; the lumbar inward curve is called lordosis.
Lumbar Spine and Sacrum
- The lumbar spine includes five vertebrae, labeled L1 to L5.
- L5 connects to the sacrum, a triangular bone at the base of the spine.
- The sacrum fits between the pelvic bones and links to them via the sacroiliac (SI) joints.
Vertebrae and Spinal Canal
- Each vertebra is made up of a round vertebral body and a bony ring.
- Stacked vertebral rings form the spinal canal, which protects the spinal cord.
Spinal Cord and Nerves
- The spinal cord runs from the brain to the L2 vertebra and then splits into the cauda equina (horse’s tail).
- Nerve roots exit each vertebra, forming nerves that control different body regions: cervical (arms/hands), thoracic (abdomen/chest), lumbar (lower limbs).
Spinal Segments and Joints
- A spinal segment includes two vertebrae, an intervertebral disc, nerve roots, and facet joints.
- The intervertebral disc has a spongy center (nucleus pulposus) for shock absorption, surrounded by the tough annulus fibrosus.
- Facet joints are small synovial joints at the back of the spine, allowing sliding movement and covered by articular cartilage.
Support Structures
- Ligaments connect vertebrae, run in layers, and stabilize the spine.
- Muscles also have layered structure: superficial (covered by fascia), middle (connect ribs, chest, and low back), and deep muscles (stabilize the spine with abdominal muscles).
Key Terms & Definitions
- Vertebra — Individual spinal bone.
- Spinal Canal — Bony tube protecting the spinal cord.
- Kyphosis — Outward curve of the thoracic spine.
- Lordosis — Inward curve of the lumbar spine.
- Sacrum — Triangular bone at the spine’s base connecting to the pelvis.
- Sacroiliac (SI) Joint — Connection between the sacrum and pelvic bones.
- Nucleus Pulposus — Soft, shock-absorbing center of an intervertebral disc.
- Annulus Fibrosus — Tough, ligamentous ring encasing the disc’s center.
- Facet Joint — Synovial joint linking vertebrae at the back.
- Articular Cartilage — Smooth cartilage covering joint surfaces.
- Cauda Equina — Bundle of nerves below the L2 vertebra.
Action Items / Next Steps
- Review spinal anatomy diagrams.
- Study spinal curves and their clinical significance.
- Learn the functions of key supporting ligaments and muscles.