Human Hand Models
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Anatomical models of the hand – for teaching, training, demonstration and understanding of the unique intricacies of the complex human hand for use in medical, healthcare, and educational settings
The human hand is one of the most complex and highly functional musculoskeletal components of the human body. Its unique design involving 27 bones, 27 joints (10 ginglymus joints, 4 condyloidal joints, 13 arthrodial joints - intercarpal, intermetacarpal, and carpometacarpal), over 100 ligaments, and multiple intrinsic and extrinsic muscles acting on the joints of the hand, enable the human hand to perform myriad movements allowing us to grip and use multiple tools and perform multiple functions.
Unique characteristics that enable and enhance our ability to grip, hold, and use tools include:
- A medial and lateral arch that run the length of the hand and place our hand in cupping shape, which positions our hands to wrap our fingers around an object. A transverse arch runs perpendicular to the metatarsals and because the metacarpophylangeal (MCP) joints of the little and ring fingers are more mobile, it enables them to more fully wrap around an object. The greater stability of the MCP joints of the middle and index fingers, allows for a firmer grip. This dual capability of mobility and stability among the four different fingers, maximizes the gripping and holding potential of the hand.
- An opposable elongated thumb enables the hand to provide a force-counter force to the fingers for more effective grip. The carpometacarpal (CMC) joint of the thumb is a joint that can move in all three planes of motion. This combined with the human’s elongated thumb, allows for complete opposition to the other four fingers. A total of five uniquely positioned muscles are involved in applying the force and movement to position and flex the thumb for opposition to flexion of the fingers.
- The flexor digitorum profundus and flexor digitorum superficialis muscles that originate in the forearm and insert on the middle and distal phalanges of all four fingers. A unique “pulley” feature occurs when the deeper flexor digitorum profundus muscle tendons emerge and pass through the split tendons of the more superficial flexor digitorum superficialis muscle. The location where the deeper tendons emerge through the split tendons of the more superficial muscle creates a pulley system that increases the mechanical advantage and the resultant force it can produce in flexing the four fingers for gripping and holding objects.
- Unlike the skin on the back of the hand, the skin on the palm is anchored, via tiny ligaments, to the underlying palmar aponeurosis, a tough connective tissue covering most of the palm. Consequently, when holding something heavy the skin on the palm stays put, in place and does not slide downward under the weight of the object being held. If the human grip was backward, the skin on the back of the hand, which is not anchored down, would move about and hinder grip. However, because we don’t grip with the back of our hand, but rather flex our fingers through a good range of motion, we need movement on the back of the hand, and stationary skin.
ProHealthcareProducts.com offers skeletal hand models with ligaments only, or with removable ligaments and muscles.