Sesamoid bone

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In anatomy, a sesamoid bone is a bone embedded within a tendon.

Sesamoid bones are typically found in locations where a tendon passes over a joint. Functionally, they act to protect the tendon and to increase its mechanical effect. The presence of the sesamoid bone holds the tendon slightly further away from the center of the joint and thus increases its moment arm. The sesamoid prevents the tendon from flattening into the joint as the tendon tension increases, and therefore also maintains a more consistent moment arm through a variety of possible tendon loads.

Human anatomy

Examples in human anatomy include:

• The patella, a bone at the front of the knee.
• The sesamoid bones of the first metatarsal of the foot. This area is beneath the pad on the foot just proximal to the big toe. These two bones serve to protect the tendon that flexes the toe, by protecting it from the body's weight.
• The pisiform, a carpal bone of the hand.

Horse anatomy

In the horse, 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.

Panda anatomy

In the giant panda, the radial sesamoid has evolved to be larger than the same bone in counterparts such as bears. It is primarily a bony support for the pad above it, a support so the panda's other digits can grasp bamboo while eating it. [1] Some creationism and intelligent design proponents claim that this "thumb" is evidence of a gap in Charles Darwin's theory. A school textbook created by intelligent design proponents was titled Of Pandas and People as a reference to this controversy. Zoologists and other scientists have pointed out that this is not a true opposable thumb, and that the panda is a good argument in favor of evolutionary theory. [2]de:Sesambein eo:Sezamoido is:Sesambein pt:Osso sesamóide