The vertebral column is an essential part of the human skeletal system, comprising 24 vertebrae, along with the sacrum and coccyx, which provide structural support and protection for the spinal cord. The vertebrae are categorized into three primary regions: the cervical spine, consisting of seven vertebrae (C1–C7); the thoracic spine, consisting of 12 vertebrae (T1–T12); and the lumbar spine, with five vertebrae (L1–L5).
The coccyx, commonly referred to as the tailbone, is situated at the inferior end of the vertebral column and is formed from the fusion of typically four coccygeal vertebrae. However, the number of coccygeal bones may vary, with some individuals having three to five. In most cases, the coccyx is a single bone, but occasionally, the first coccygeal vertebra can be separate from the others. It connects with the fifth sacral segment, and unlike other vertebrae, coccygeal vertebrae lack pedicles, laminae, and spines.
Functionally, the coccyx is not a weight-bearing structure in a standing position, but it may support some body weight while a person is seated. The first cervical vertebra is unique as it supports the skull. Intervertebral disks found between each vertebra act as shock absorbers, contributing to the column’s flexibility and resilience.
The thoracic cage, which protects the vital organs of the chest, comprises 12 pairs of ribs and the sternum. The appendicular skeleton includes all of the bones of the upper and lower limbs, plus those that anchor the limbs to the axial skeleton, totaling 126 bones in adults.
During embryonic development, vertebrae form in mesenchyme and cartilage and typically begin to ossify in fetal life. The coccyx resembles a miniature sacrum in shape and is variably fused in the adult.
For further reading and visual understanding, refer to detailed anatomical illustrations and discussions available at these sources:
Anatomy and Physiology,
Bones of the Pelvis and Perineum,
Divisions of the Skeletal System,
Bones of the Lower Limb,
Orthopedic Medical Devices: Vertebral Column,
URMC: Spinal Column,
Bones of the Back,
Human Anatomy, and
Duke Anatomy.
