Axial Skeleton
Definition
The 80-bone central structural column of the human skeleton: the skull (29 bones), the vertebral column (26 bones including sacrum and coccyx), and the thoracic cage (25 bones comprising the sternum and 12 pairs of ribs).
- Total bones
- 80
- Skull
- 29 bones
- Vertebral column
- 26 bones, sacrum and coccyx fused
- Thoracic cage
- 25 bones, sternum plus 12 rib pairs
Common questions
What does the appendicular skeleton include by contrast?+
The appendicular skeleton covers the limb bones and the shoulder and pelvic girdles, essentially everything in the body outside the central 80-bone axial column.
Why is the vertebral column often counted as 26 bones rather than 33?+
The adult sacrum is a single fused bone formed from five vertebrae, and the coccyx is a single fused bone formed from several more, so counting each as one bone rather than separate segments gives 26.
Related terms
- Appendicular Skeleton
- The 126-bone system of the human limbs and their girdles: the pectoral girdle (4), upper limbs (60), pelvic girdle (2 os coxae),...
- Endochondral Ossification
- The process by which bone replaces a cartilage precursor. All long bones, the vertebrae, the ribs, and the cranial base form by...
- Epiphyseal Fusion
- The obliteration of the cartilaginous growth plate and bony union of the epiphysis with the diaphysis. Fusion sequence and timing form the...
- Intramembranous Ossification
- The process by which bone forms directly from a mesenchymal membrane without a cartilage intermediate. Produces the flat bones of the skull...
- Medial Clavicle Epiphysis
- The last secondary ossification centre to fuse in the human skeleton, completing at 21 to 30 years depending on sex and population....
- Mukherjee 1955 Dataset
- Sub-adult skeletal age reference data published by P. K. Mukherjee and colleagues from AIIMS New Delhi, demonstrating that several epiphyses fuse 1...
- Primary Ossification Centre
- The initial site of bone tissue formation in a developing skeletal element. In long bones, the primary centre forms the diaphysis (shaft)...
- Scheuer-Black Framework
- The reference system for developmental skeletal age estimation published by Louise Scheuer and Sue Black in 'Developmental Juvenile Osteology' (Academic Press, 2000)....
- Secondary Ossification Centre
- An epiphysis: a discrete bony island that forms postnatally at the articular end of a long bone, separated from the diaphysis by...