Sesamoid bone

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Sesamoid bone
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Sagittal section of right knee-joint.
Sesamoidbone.png
Sesamoid bones at the distal end of the first metatarsal bone of the foot.
Details
Latin ossa sesamoidea
Identifiers
TA A02.0.00.016
FMA FMA:32672
Anatomical terms of bone

In anatomy, a sesamoid bone (/ˈsɛsəmɔɪd/[1][2]) is a bone embedded within a tendon.

Structure[edit]

Sesamoid bones can be found on joints throughout the body, including:

Sesamoid bones over the metatarsophalangeal joint of the great toe of the left foot of an adult woman
  • In the neck - The hyoid bone, found in the anterior neck which is responsible for muscle attachment, stability of the mandible, tongue and has uses is voice and sound production. Unlike other sesamoids, this bone is not found within the tendons of a muscle, but held between muscles (mainly the suprahyoids and infrahyoids).

Clinical significance[edit]

  • A common foot ailment in dancers is sesamoiditis.
  • A bi-partite sesamoid bone is when the sesamoids are in 2 separate entities — usually congenital, but may be related to a history of trauma.
  • Sesamoid bones have a very limited blood supply. They are very difficult to heal when not treated early and often lead to Avascular Necrosis which is bone death caused by lack of blood supply.[5]

Other animals[edit]

In equine anatomy, the term sesamoid bone usually refers to the two sesamoid bones found at the back of the fetlock or metacarpophalangeal/metatarsophalangeal joints in both hindlimbs and forelimbs. Strictly these should be termed the proximal sesamoid bones whereas the navicular bone should be referred to as the distal sesamoid bone. The patella is also a form of sesamoid bone in the horse.

In both the giant panda[6] and the red panda,[7] the radial sesamoid is larger than the same bone in counterparts such as bears. It is primarily a bony support for the pad above it, allowing the panda's other digits to grasp bamboo while eating it. The panda's thumb is often cited as a classical example of exaptation, where a trait evolved for one purpose is commandeered for another.[8]

See also[edit]

Footnotes[edit]

  1. ^ OED 2nd edition, 1989 as /sεsəmɔɪd/.
  2. ^ Entry "sesamoid" in Merriam-Webster Online Dictionary.
  3. ^ Tim D. White, Human Osteology, 2nd edition (San Diego: Academic Press, 2000), 199, 205.
  4. ^ White, Human Osteology, 2nd edition, 257-261.
  5. ^ http://www.footankleinstitute.com/sesamoid-fracture/
  6. ^ Arthro.com: The Panda's Thumb
  7. ^ Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas PNAS December 30, 2005
  8. ^ The Panda's Peculiar Thumb, Nature Magazine Vol. LXXXVII No. 9, Nov. 1978, by Stephen J. Gould

References[edit]