Long, short, flat and irregular
Anatomists sort bones by their shape. A long bone such as the femur is a shaft with a wider end at each side. The limbs are built of long bones, down to the small bones of the fingers and toes. Short bones such as the carpals of the wrist are about as wide as they are long.
Bones sorted by shape: flat, sutural, short, irregular, long and sesamoidWikimedia Commons, BruceBlaus (Blausen Medical), CC BY 3.0 (Blausen 0229 ClassificationofBones.png)
Flat bones are thin curved plates, such as the parietal bones of the skull roof, the sternum, the ribs and the shoulder blades. They shield organs and give muscles broad surfaces. Irregular bones fit neither group: a vertebra is one.
Sesamoid bones grow inside a tendon where it runs over a joint. The patella, the kneecap, is the largest of them.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapter on bone and cartilage.
- J. Gordon Betts and others, Anatomy and Physiology (Houston: OpenStax, 2013), section 6.2, Bone classification.
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