Supernumerary body part considered to have lost much or all of their original function through evolution. These body parts can be classed as additional to the required functioning of the body. In human anatomy the vermiform appendix is sometimes classed as a vestigial remnant. Prosthesis is an artificial extension that replaces a body part, and cybernetics is the study of computer technology in relation to organisms which can include replacement or additional body parts. Body integrity identity disorder (BIID) is a psychiatric disorder in which a person thinks that they have one or more additional limbs than they should, despite having two arms
Limbs of the horse consists of the suspensory ligament, the check ligament, the deep digital flexor tendon, the superficial flexor tendon, the common digital extensor tendon and the sesamoid bones. Horses use a group of ligaments, tendons and muscles known as the stay apparatus to "lock" major joints in the limbs, allowing them to remain standing while relaxed or asleep. The lower part of the stay apparatus consists of the suspensory apparatus, which is the same in both sets of limbs, while the upper portion differs between the fore and hind limbs. The upper portion of the stay apparatus in the forelimbs includes the