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Occurrence and Ease of Articulation of Sign Language Handshapes: The Taiwanese
Chapter Two: The Anatomy and Physiology of the Human Hand
First developing an understanding of the anatomy and physiology of the human hand and the relevance of each to handshapes will enable the reader to follow the theory I propose with respect to ease of articulation for handshapes. Although I adhere to the standard distinction between anatomy (i.e., the description of parts of the body and their potential for movement) and physiology (the study of how the parts move and interact) (Galley and Forster 1987), my discussion of the two areas will be intertwined.
The anatomy and physiology of the human hand are tremendously complicated; therefore, making hard and fast conclusions about all aspects of physiology is unwise (and maybe even impossible). Enormous fields of study such as anatomy, physiology, and biomechanics are engaged in the task of understanding how the human body works (Wells 1966). Discoveries made in these areas alter previous paradigms, and consequently, aspects of both anatomy and physiology are still not well understood. For example, variation exists across humans with respect to the number and arrangement of extensor tendons (Schenck 1964).
Beyond anatomy, the precise functions of anatomical structures are not necessarily clear. For example, questions still arise as to which smaller movements combine to form a larger movement and which muscles participate (and how much) in executing particular movements (Wells 1966)—questions that are particularly important here. Different muscle groups might work together to achieve a given movement, though one muscle might be primarily responsible. But in another movement, the same muscles might participate in different ways. So, a given muscle might act as a prime mover (i.e., actually doing some action) in one movement, as an antagonist (i.e., permitting the action by relaxing) in another, and as a synergist (i.e., helping the prime mover to complete the action) in a third. To complicate matters, in accomplishing an action, a prime mover or a synergist may participate minimally (say, only 10–20 percent) or maximally (say, 80–100 percent). Clearly then, it is impossible to say that a given muscle is a prime mover, an antagonist, or a synergist because it may function as a prime mover for one movement, as an antagonist for another, and as a synergist for a third.
13. Because, anatomically and physiologically, the thumb both resembles and differs from the other four fingers, the need sometimes arises to distinguish the thumb from the rest of the fingers. Throughout the chapter, my use of the phrase the five digits should be interpreted as including the thumb and four fingers. The phrase the fingers should be interpreted as excluding the thumb.