True or false: the thoracic limb has a reciprocal apparatus?

True or false: the thoracic limb has a reciprocal apparatus?

• A. True
• B. False
• C. Not specified
• D. Both

Answer: (B)

A reciprocal apparatus is a linked mechanism in which movement of one joint causes movement of another, keeping two joints in sync during a stride. In many quadrupeds, this linkage is found in the hind limb, where the stifle (knee) and the hock (tock) are functionally connected so that extending or flexing one joint tends to move the other in tandem. The forelimb, or thoracic limb, does not have this same true reciprocal mechanism; the elbow and carpus are not mechanically coupled in the same coordinated way, so they can move with more independent control. Therefore the statement is false: the thoracic limb does not possess a reciprocal apparatus.

A reciprocal apparatus is a linked mechanism in which movement of one joint causes movement of another, keeping two joints in sync during a stride. In many quadrupeds, this linkage is found in the hind limb, where the stifle (knee) and the hock (tock) are functionally connected so that extending or flexing one joint tends to move the other in tandem. The forelimb, or thoracic limb, does not have this same true reciprocal mechanism; the elbow and carpus are not mechanically coupled in the same coordinated way, so they can move with more independent control. Therefore the statement is false: the thoracic limb does not possess a reciprocal apparatus.