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Other Terms: Skeleton axiale, Squelette axial
It consists of the skull, vertebral column, ribs, and sternum. This is the most primitive part of the vertebrate skeletal system. The majority of its bony elements, from the basicranium to the end of the vertebral column, form as serial homologues derived from the segmental embryonic somites. The vertebrae form a strong, flexible rod that serves as the main axial support of the body while still allowing for undulatory movements. It, along with the cranium, protects the delicate central nervous system. The cranium also fixes in space important nervous structures, such as the internal ear, that would not be able to function properly in an unstable environment. Additionally, the skull plays an important role in the acquisition and processing of food, respiratory gases, and sensory input such as sound.
Axial is the adjectival form of the Latin word axis that comes from the Greek word axon or axel. The Greek axon derives from the Sanskrit word aksha meaning wheel. Axis originally meant that which something turns around. It now designates the central line of something. The word skeleton comes from the Greek term skello meaning to make dry. Early anatomists used the word to describe a dried body or mummy. Later, anatomists applied it to the dried bones of an animal in their natural position. In modern parlance it applies to any supporting or protecting framework.
The axial skeleton is the most highly jointed region of the skeletal system. The joints include each of the three joint categories. With the exception of the synovial temporomandibular joint, the joints show limited ranges of motion.
Ossification of the axial skeleton involves both endochondral and intramembranous bone formation. The vertebral column, ribs, sternum, and basicranial bones form endochondrally. The rest of the skull bones form intramembranously.