206 bones in an adult, but well over 270 in a newborn
The difference is fusion, chiefly in the skull, sacrum and coccyx
Science · Medicine & the body
The human skeleton
Vesalius, 1543
Medicine — osteology and the skeletal system
The internal framework of bone and cartilage that supports the body, protects the organs, anchors the muscles, stores calcium and houses the marrow in which blood cells are made. An adult has 206 named bones, a newborn well over 270, because several — notably the sacrum, the coccyx and the plates of the skull — fuse during growth. It is conventionally split into the axial portion of 80 bones running up the midline and the appendicular portion of 126 in the limbs and their girdles.
How to spot them
- ▸206 bones in an adult, more than 270 at birth
- ▸Axial 80 (skull, hyoid, ossicles, vertebral column, sternum, ribs) and appendicular 126 (limbs and girdles)
- ▸Femur longest, stapes smallest, hyoid the only bone articulating with no other
- ▸Osteoblasts build, osteoclasts resorb, osteocytes maintain
- ▸Vesalius's 1543 'De Humani Corporis Fabrica' is the founding text
Key facts
An axial portion of 80 bones and an appendicular portion of 126
The standard division: midline versus limbs and girdles
Its longest and strongest element is the femur; its smallest is the stapes
The extremes of the 206
The hyoid is the only one of its bones that articulates with no other
It is slung in the neck by muscles and ligaments alone
7 cervical, 12 thoracic and 5 lumbar, then the sacrum and the coccyx
The 26 bones of the adult vertebral column
Scaphoid, lunate, triquetrum and pisiform; trapezium, trapezoid, capitate and hamate
The eight carpal bones of the wrist
Osteoblasts build it, osteoclasts resorb it, osteocytes maintain it
It is continuously remodelled throughout life
Vesalius's 'De Humani Corporis Fabrica' of 1543, with its woodcut plates (1543)
Andreas Vesalius's book, which corrected Galen from dissection
Key ideas
- It is a living organ, not scaffolding: about 10 per cent is replaced each year, and it holds roughly 99 per cent of the body's calcium as a reservoir.
- Bone gets its stiffness from the mineral hydroxyapatite and its toughness from collagen fibres; remove one and it crumbles, remove the other and it bends.
Quick-fire facts
- •206 bones in a typical adult; a newborn has around 270–300, many of which fuse
- •Axial: 22 skull bones, 1 hyoid, 6 auditory ossicles, 26 vertebrae, the sternum and 24 ribs — 80 in all
- •The appendicular portion has 126 bones, including 27 in each hand and 26 in each foot
- •The femur is the longest and strongest bone; the stapes in the middle ear is the smallest
- •The hyoid is the only bone that articulates with no other bone
- •The patella is the largest sesamoid bone; the clavicle is the first to begin ossifying and the most commonly fractured
- •There are 12 pairs of ribs: seven true, three false and two floating
- •The mandible is the only freely movable bone of the skull
- •Bone tissue comes as dense cortical (compact) bone and lattice-like cancellous (spongy) bone; compact bone is organised into osteons or Haversian systems
- •Red marrow produces red cells, white cells and platelets; in adults it is largely confined to flat bones such as the pelvis, sternum and vertebrae
- •Synovial joints include ball-and-socket (hip, shoulder), hinge (elbow, knee), pivot (atlas and axis), saddle (thumb), condyloid and plane types
- •Andreas Vesalius published 'De Humani Corporis Fabrica' in 1543, founding modern anatomy
- •Osteoporosis is loss of bone density; rickets in children and osteomalacia in adults follow vitamin D deficiency
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Sources
- OpenStax, Rice University — Anatomy and Physiology 2e — Divisions of the Skeletal System
- Henry Gray (Susan Standring, ed.) — Gray's Anatomy