The Spine: Support System for Body
Parts of the Spine
The spine is composed of many parts that function together to allow you to move...and a whole lot of other things! Let’s focus on movement for now.
Vertebrae - The Bones of the Spine
The vertebrae are the bony segments of your spine. They are joined to each other throughout the spine by "articulations" that allow smooth movement between the bones. The round part of the vertebra is called the "body" and the pointy part to the back is the "spinous process."
Within each section, there are a number of bones named for their number in the segment: 7 cervical vertebrae (C1-C7), 12 thoracic vertebrae (T1-T12), 5 lumbar vertebrae (L1-L5), 1 sacrum made of 5 fused vertebrae, 1 coccyx made of 4 fused coccygeal vertebrae. The coccyx is the lowest point of the spine that bends when you sit down and acts like a shock absorber while you sit. It's also known more commonly as the tailbone.
Facet joints connect the vertebrae of the spine and allow movement. One faces up and one faces down to connect with the adjacent vertebrae.
The intervertebral disc (or disc for short) acts like the shock absorber of the spine. It holds the bony vertebrae apart and gives space in the spinal canal for the spinal cord and its nerves to pass through on their way to the extremities of the body. Its center is the “nucleus pulposus” which is normally 80% water-filled. The outer part is the “annulus fibrosus” which is made of rubberband-like rings (annular fibers) which hold the nucleus in place.
The spinal column has 4 curves - cervical, thoracic, lumbar and sacral - and 5 sections - cervical (C1-C7), thoracic (T1-T12), lumbar (L1-L5), sacral (S1-S5), and coccygeal.
- Two curves are concave posteriorly (cervical and lumbar).
- Two are concave anteriorly (thoracic and sacral).
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