| Spine Anatomy
Besides this outline, here are some other sites to learn more about the spine:
General Spinal Anatomy
North American Spine Society
National Institutes of Health
Discovery Health
Spine Universe
Function of the Spine
1. Maintains structure of trunk.
2. Protects nervous system.
3. Curves of the spine absorb and distribute forces.
Twenty-four moving vertebrae
7 cervical vertebrae
- smaller
- much rotational movement
- secondary curve–lordotic
12 thoracic vertebrae
- primary curve–kyphotic
- ribs are attached–movement more limited
5 lumbar vertebrae
- most problems occur here L4/L5/S1
- much more weight bearing
- all motion in the low back occurs here
- lordotic curve–allows human gait
Sacrum–5 fused bones
- triangular shape
- forms part of pelvis
Coccyx–tailbone
Pelvis
1. Formed by hip bones and sacrum therefore attaches directly to spine.
2. Functions as a solid moving part.
3. Many muscles attached here, so its movement affects lumbar movements and positioning.
Discs
Two main parts
- Annulus: Outer concentric rings of cartilage, like a radial tire.
- Nucleus: Jell-like pulp inside annulus which dries as we get older, 88% water when born.
1. Link two adjacent vertebrae to which they are firmly attached.
2. Function to distribute force and shock throughout the spine.
3. Bigger and thicker in lumbar area.
4. Movement affects position of nucleus
- Flexion (forward bending) exerts pressure on front of disc and pushes nucleus backwards.
- Extension (bending backwards) exerts pressure on back of disc and pushes nucleus forward.
These forces and pressures can cause the outer cartilaginous rings to tear and eventually the nucleus may bulge out. This is what we call a disc bulge or herniation.
Joints/Facets
1. These allow the body to move. Important to use big joints such as the hip joint where the legs attach to the pelvis for movement vs. continual forward and backward bending of the spine.
2. Your facet joints are on the back of the spine on each side, where one vertebrae slightly overlaps the adjacent vertebra. Their purpose is to guide and restrict movement of the spine. Leaning or arching backward while lifting heavy objects can irritate the facet joints.
Foramen/Nerve Roots
1. Foramen are canals between adjacent vertebra that are formed by the overlapping of the facet joints. Nerve roots exit from the spinal cord through these canals.
2. Nerves for the neck, shoulder, arms, and hands exit through cervical foramen. Nerves for the buttock, hips, legs, and feet exit through lumbar foramen. These lumbar nerve roots combine to form the sciatic nerve.
3. Spinal movements affect the size of the foramen. Bending forward increases space for the nerve. Bending backward and/or twisting decreases the foraminal space.
4. A narrowing of this foramen is called stenosis. If there is not enough space for the nerve root to move through the canal, normal movement can irritate. Stenosis can be congenital, can occur with age, or can be caused by a herniated disc pushing into the canal space.
Ligaments
1. Long bands of ligaments run length of spine both in front and back.
2. small ligaments attach individual vertebrae to one another.
3. Restrict movement in the end range, therefore important not to stretch out ligaments.
Muscles
1. Most important in movement of structure.
2. Muscle groups are very complex. Imbalance in one muscle affects the complete system, so flexibility and strength are important components in using muscles correctly.
Important Muscle Groups for Back Patients
1. Abdominal
- Control center for trunk strength several layers which wrap all the way around to the back, also attached to bottom of rib cage and top of hip bones.
2. Back Extensors
- Help in building abdominal brace.
- Postural muscles to hold us upright.
- Not meant to lift heavy objects.
3. Legs-Hamstrings/Quadriceps/Calves
- Biggest, most powerful muscles in the body.
- The legs can be strengthened for very heavy work.
- Attach to pelvis therefore hip joint tightness and muscular inflexibility, especially hamstring tightness, will pull on pelvis and change position of the low back.
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