The adult spine is a column of 33 bones that
protects the spinal cord and enables us to stand upright. Each
bony segment of the spine is referred to as a vertebra (two
or more are called vertebrae).
spine has five regions containing groups of similar bones, listed
from top to bottom: 7 cervical vertebrae in the neck, 12 thoracic
vertebrae in the mid-back (each attached to a rib), 5 lumbar
vertebrae in the lower back, 5 sacral vertebrae fused together
to form one bone in the hip region, and 4 coccygeal bones fused
together that form our tailbone.
the front of each vertebra is a block of bone called the vertebral
body. The vertebral body consists of an inner core of soft cancellous
bone, surrounded by a thin outer layer of hard cortical
bone. Vertebrae are stacked on top of each other and enable us
to sit/stand upright.
in the the cervical, thoracic and lumbar regions are separated
from each other and cushioned by a rubbery soft tissue called
the intervertebral disc. Segments of bone that extend
outward at the back of each cervical, thoracic and lumbar vertebral
body surround and protect the spinal cord and its nerve roots.
You can feel these bones, known as the posterior spinous
processes, when you run your hand along the middle of your
vertebral bodies in the thoracic and lumbar regions have
the greatest risk for fracture due to osteoporosis. Cancer
and benign tumors can lead to fracture of the cervical, thoracic
and lumbar vertebrae.