List of bones of the human skeleton

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The skeleton of an adult human consists of 206 bones. It is composed of 270 bones at birth, which decreases to 206 bones by adulthood after some bones have fused together.[1] It consists of 80 bones in the axial skeleton (28 in the skull and 52 in the torso) and 126 bones in the appendicular skeleton (32 × 2 in the upper extremities including both arms and 31 × 2 in the lower extremities including both legs). Many small and often variable bones, such as some sesamoid bones, are not included in this count.

Introduction[edit]

The number of bones in the skeleton changes with age, as multiple bones fuse, a process which typically reaches completion in the third decade of life. 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 this 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.

Bones[edit]

Spine (vertebral column)[edit]

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

  • The cervical vertebrae (7)
  • The thoracic vertebrae (12)
  • The lumbar vertebrae (5)
    • Additional lumbar vertebrae
  • The sacral vertebrae (5 at birth, later fused into one)
  • The coccygeal vertebrae (5 at birth, some or all of the bones 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)[edit]

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

  • The sternum (1)
  • The ribs (24, in 12 pairs)
    • It is important to note that three pairs (the 8th, 9th and 10th), also known as false ribs, are attached to each other. They are also attached to the 7th rib by cartilage and synovial joints. Also two pairs of floating ribs (the 11th and 12th), have no anterior attachment.
    • Cervical ribs are extra ribs that occur in some humans.

Skull (cranium)[edit]

There are 22 bones in the skull. Including the hyoid and the bones of the middle ear, the head contains 29 bones.

Arm[edit]

There are a total of 64 bones in the arm.

Pelvis (pelvic girdle)[edit]

The coxal bone, or hip bones, has three regions: ilium, ischium, and pubis (2)

  • The sacrum and the coccyx attach to the two hip bones to form the pelvis, but are more important to the spinal column. For this reason it is omitted from the pelvic girdle.

Leg[edit]

Sesamoid bones[edit]

See also[edit]

References[edit]

  1. ^ Mammal Anatomy: An Illustrated Guide. 9780761478829: Marshall Cavendish. 2010. p. 129.