List of bones of the human skeleton

The human skeleton of an adult consists of around 206 to 213 bones, depending on the counting of sternum (which may alternatively be included as the manubrium, body of sternum, and the xiphoid process).[1] It is composed of 270 bones at the time of birth,[2] but later decreases to 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. Many small accessory bones, such as sesamoid bones, are not included in this count. There are 20 major bones.

Introduction

As a person ages, some bones fuse, a process which typically lasts until sometime within the third decade of life. Therefore, the number of bones in an individual may be evaluated differently throughout a lifetime. In addition, the bones of the skull and face are counted as separate bones, despite being fused naturally. Some reliable sesamoid bones such as the pisiform are counted, while others, such as the hallux sesamoids, are not.

Individuals may have more or fewer bones than the average (even accounting for developmental stage) owing to anatomical variations. The most common variations include sutural (wormian) bones, which are located along the sutural lines on the back of the skull, and sesamoid bones which develop within some tendons, mainly in the hands and feet. Some individuals may also have additional (i.e., supernumerary) cervical ribs or lumbar vertebrae. Amputations or other injuries may result in the loss of bones. Complete bone fractures may split one bone into multiple pieces. Other genetic conditions may result in abnormally higher (e.g. polydactyly or conjoined twins) or lower (e.g. oligodactyly) counts of bones.

Bones

The axial skeleton, comprising the spine, chest and head, contains 80 bones. The appendicular skeleton, comprising the arms and legs, including the shoulder and pelvic girdles, contains 126 bones, bringing the total for the entire skeleton to 206 bones.

Spine (vertebral column)

A fully grown adult features 26 bones in the spine, whereas a child can have 34.

  • Cervical vertebrae (7 bones)
  • Thoracic vertebrae (12 bones)
  • Lumbar vertebrae (5 bones)
  • Sacrum (5 bones at birth, fused into one after adolescence)
  • Coccygeal vertebrae/Cordal (set of 4 bones at birth; some or all fuse together, but there seems to be a disagreement between researchers as to what the most common number should be. Some say the most common is 1, others say 2 or 3, with 4 being the least likely. It is counted as 1 in this article.)

Chest (thorax)

Various bones of the human skeletal system.

There are usually 25 bones in the chest but sometimes there can be additional cervical ribs in men. Cervical ribs occur naturally in other animals such as reptiles.

Skull

There are 23 bones in the skull. Including the bones of the middle ear and the hyoid bone, the head contains 29 bones.

Arm

There are a total of 64 bones in the arms, 32 in each arm

Pelvis (pelvic girdle)

The pelvis (or hip bone) is made up of three regions that have fused to form 2 coxal bones. They are: ilium, ischium, and pubis

  • The sacrum and the coccyx attach to the two hip bones to form the pelvis, but are more important to the spinal column, where they are counted.

Leg

There are a total of 60 bones in the legs.

See also

References

  1. ↑ Human Body (206). Rensselaer Polytechnic Institute
  2. ↑ Mammal anatomy : an illustrated guide. New York: Marshall Cavendish. 2010. p. 129. ISBN 9780761478829.
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