Essay on Important groups in which the Vertebral Column is Grouped!
It is a string like vertebrae which lies in the mid dorsal line of the neck and trunk. It is made up of 33 vertebrae in which 26 bones are visible because five sacral vertebrae are fused to form one sacrum and four coccygeal vertebrae are fused to form one coccyx. It displays four curves to enhance balancing power and firmness for upright posture of body.
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The curvatures are cervical, thoracic, lumbar, pelvic (= sacral). Each vertebra has centrum and neural arch in which the latter encloses a neural canal for spinal cord. Between the centra of adjacent vertebrae there are elastic pads of fibro cartilage, the intervertebral discs which provide mobility to the vertebrae, check undue friction and take up shocks.
Displacement of the vertebrae from its normal position due to displacement or degeneration of a part of intervertebral disc is called slip disc.
I. Cervical Vertebrae:
Possess reduced heads of cervical ribs. All cervical vertebrae except 7th possess vertebrarterial canals for the passage of cervical blood vessels and nerves. 1st cervical vertebrae are ATLAS without having centrum. It is articulated to skull through occipital condyles for nodding movements. Zygopophyses are absent.
IInd cervical vertebra is AXIS. It contains odontoid process that fits into the odontoid canal of atlas to provide head with sideways rotation.
II. Thoracic Vertebrae:
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Ribs of 1st nine thoracic vertebrae are long and ventrally articulated with breast bone and remaining vertebrae has floating ribs. This shows that these vertebrae have the regions for attachment of ribs.
III. Lumbar Vertebrae:
These vertebrae are largest, heaviest and strongest as they bear weight of the abdominal viscera. Anterior lumber (first two) bears a median ventral process of centrum called hypopophysis. These vertebrae possess additional processes like metapophysis and anapophysis.
IV. Sacral Vertebrae:
First five sacral vertebras fused to form sacrum. It is a strong and short supporting pelvic girdle as it (sacrum) articulates with the ilium of pelvic girdle.
V. Caudal Vertebrae:
Mainly 3 to 4 caudal vertebrae fused to form small triangular bone called coccyx. It is a vestigial tail.