Your spine is also called your backbone or vertebral column is composed of 33 bones called vertebrae. Which provides your body with support and protects your spinal cord from injury.
The vertebrae can be divided into five group’s cervical, thoracic, lumbar, sacral, coccyx. Each of which has unique features suited to its functions there are
- 7 Cervical vertebrae numbered C1 to C7.
- 12 Thoracic vertebrae numbered T1to T12.
- 5 Lumbar vertebrae numbered L1 to L5.
- 5 Sacral vertebrae numbered S1 to S5.
- Coccyx
The upper 24 vertebrae are articulating separated by intervertebral discs the sacral vertebra and the bones of the coccyx are fused.
The cervical vertebrae (neck) which are the vertebrae of your neck support your head. Which weighs around 10 to 13 pounds.
C1 and C2 are specialized Vertebrae,
- Allow for the greatest range of motion of all the vertebrae
- C1 is called “ATLAS”. Ring Shaped and attaches directly to your skull
- C1 allows you to nod your head
- C2 is called “AXIS”. Serves as an axis around which C1 pivots
- C1 is able to pivot on C2 thanks to a specialized process called DENS, or ODONTOID process
The Thoracic vertebrae are the vertebrae of your mid and upper back. Hold the ribcage and protect your heart and lungs. They have a limited range of motion.
The Lumbar vertebrae are the vertebra of the lower back. Bear the weight of your upper body and are larger in order to support the stress. Especially when you lift something heavy.
The Sacral vertebrae connect your spine to your hip bones these vertebrae are fused together with your hip bones, they form the pelvic girdle.
The coccyx or tailbone is made up of four fused which provide an attachment point for ligaments and muscles of the pelvic floor.
Parts of a Vertebra:
A vertebra has three parts
- Body
- Vertebral arch
- Processes
The body bears weight, the vertebral arch houses, and the spinal cord and the processes allow for muscle attachment. The vertebral arch is made up of two supporting pedicles and two laminae.
Space inside which houses the spinal cord is called the vertebral foramen. Under each pedicle spinal nerves exit and pass through the intervertebral foramina.
Seven bony processors arise from each vertebral arch to form facet joints and processes for muscle attachment.
Facet joints allow for back motion each vertebra has two pairs of facet joints one pair connects to the vertebra above and one pair that connects to the vertebra below.
There is also a pair of transverse processes and a spinous process.
Between the vertebras are the intervertebral discs, which provide cushioning and prevent the bones from rubbing together.
Discs are composed of an annulus. Which is made up of several layers or lamina of fibrocartilage.
Criss-crossing fibrous bands attach between the bodies of the vertebrae above & below and a gel-filled center called the nucleus.
The nucleus distributes the pressure evenly within each disc during compression.
The nucleus is full of proteoglycans large molecules with sugar subunits that are very hydrophilic. This structure swells with water unless it experiences constraints from the surrounding tissues.
Hence, the nucleus absorbs fluid at night or when you are lying down and then this fluid is pushed out during the days. When you are upright and pressure is applied to the intervertebral discs. We shorten as we age because the discs lose the ability to reabsorb fluid during rest and they flatten and become more brittle.
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