Human spine or vertebral column is a structure made of multiple small units called vertebra and extends from just below the base of skull to a point jut below the beginning of gluteal cleft. You can palpate the lower part by following the spine till its lower end.
A vertebra is smallest unit of vertebral column. Plural term is vertebrae. Vertebrae have been modified according to the function they are expected to serve in different parts of spine.
To a naked and unaccustomed eye, the spine appears as a straight column. But that is not the case. It appears straight in antero-posterior view (That means looking from front or back) but in lateral view or looking from a side, we can see multiple curves in different regions.
These curves are called kyphotic if they are concave in anterior(front) and convex on posterior (back) and lordotic if they are convex in anterior and concave on posterior.
Regions of Spine
It is divided into five regions
Cervical : This part is present in the neck and consists of first seven vertebrae. Each vertebra is known by C followed by number of the vertebra. Thus first vertebra is called C1 and last vertebra is called C7. It has a normal lordotic curve.
Thoracic : This is also called Dorsal spine. It is below cervical and spans upper trunk or thorax or area corresponding to chest. It contains total of 12 vertebrae and are designated as T1 to T12 in a fashion similar to we discussed for cervical vertebrae. It has a normal kyphotic curve.
Lumbar : It follows Thoracic and consists of 5 vertebrae, L1 to L5. Some of people might have anatomical variations in which 4 or 6 vertebrae might be present in Lumbar spine. In both cases, extra vertebra is added to or taken from Sacral spine. Accordingly,if there are 4 lumbar vertebrae, it is called sacralization of lumbar vertebra and if there are 6 lumbar vertebrae, it is called lumbarization of sacral vertebra.
Sacral : Itis composed of five sacral vertebrae S1 to S5. in contrast to other parts we just discussed, vertebrae in sacral spine are fused to each other. This part of spine follows lumbar spine and is present in pelvic area.
Coccyx or Coccygeal : This is also known as tail bone. It is the final segment of the human vertebral column, of four fused vertebrae (the coccygeal vertebrae) below the sacrum.
Function of spine is to support and transmit weight of trunk to lower limbs, to aid in motion of the trunk and to support and protect spinal cord & other vital organs. Spinal Cord is the structure that transmits neural fibers. These fibers further supply the organs in form of nerves.
Vertebrae are the structural units of spine. They are stacked together to form entire vertebral column.Between each vertebra are cushion like structures called intervertebral discs which act as shock absorbers and also permit some movement between the vertebral bodies. Various ligaments stabilize the spine and also allow movements.
Movements of spine occur at special joints called facet joints that are formed between two adjacent vertebrae. Various muscles carry out the movements of spine. These muscles are important for maintaining posture and transmission of loads created during normal activities, work, and play. Strength of these muscles is important and lack of strength would lead to various backache problems.
Vertebrae are shaped in such a way that the spinal cord is protected from damage by the bones of the entire spinal column.
The vertebrae are responsible for transmission of of the weight. Each vertebra consist of an anterior body which is attached to a posterior ring called posterior neural arch. Two struts of bones called pedicles arise from body and join two converging struts called laminae. Pedicles, laminae and posterior surface of body forms boundaries of spinal canal. This spinal canal is the space where spinal cord passes. There is a transverse process on either side of the arch which serves as attachment to varoius muscles and ligaments. Dead posteriorly is the posterior spinous process that can be felt on our back as bumps. Posterior spinous processes also serve as attachment to ligaments and muscles of spine.
Adjacent to base of transverse processes are bony projections that go superior and inferior. These are called superior and inferior articular facets and take part in formation of facet joints. There are two facet joints between each between each pair of vertebrae one on each side.They are primarily designed to allow the vertebral bodies to rotate with respect to each other.
The discs are designed to absorb the stresses carried by the vertebral column while allowing the vertebral bodies to move with respect to each other. They made up of a strong outer ring of fibers called the annulus fibrosus that contains nucleus pulposus.
The neural foramen is the opening where the nerve roots exit the spine and travel to the rest of the body. There are two neural foramen located between each pair of vertebrae, one on each side.
Muscles and Ligaments
Various muscles and ligments attach to spine. They help the spine to stabilize and allow it to carry various movements.
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