The arms and central disc of Asteroidea differ from those of Ophiuroidea discussed earlier as the central disc & arms are smaller than brittle stars.
The arm can be divided into the upper arm, which extends from the shoulder to the elbow, the forearm, which extends from the elbow to the hand, and the hand. Anatomically, the shoulder girdle, with its bones and corresponding muscles, is by definition part of the arm.
The upper limb or arm is the functional unit of the upper body. It consists of 3 parts: upper arm, forearm and hand. It extends from the shoulder joint to the fingers and contains 30 bones. It also consists of many nerves, blood vessels (arteries and veins), and muscles.
Learn more about arms here:https://brainly.com/question/357325
#SPJ4
