You use your hands so often you probably don’t give much thought to, or even realize, how complicated they are: our hands are made up of an intricate network of bones, muscle, cartilage, tendon, and other tissue, allowing us to perform a variety of different functions.
There are 27 bones in each hand, which allows for both gross and fine motor movements. Gross motor movements include picking up and moving large objects, doing heavy labor, and other large, sweeping motions, while fine motor movements are more subtle: holding something tiny, manipulating chopsticks, or drawing an intricate design.
In the palm (the widest, flattest part of the hand) are five long bones that connect the wrist to the fingers; these are the metacarpals. Minute muscles control their movement, allowing the palm to spread or contract; the end of the bone that connects in a joint to the fingers is rounded, which allows the fingers to rotate 360 degrees.
The fingers are made of phalanges, thin bones that connect in hinge joints to each other – the fingers have three phalanges while the shorter thumbs have only two. The mechanism that controls the movement of the fingers – causing them to flex, rotate, stretch – is a group of muscles that pull on tendons in a system that extends through the length of the forearm. The opposable thumb, in which our thumb can reach across the hand to touch the last two fingers, is unique to humans.
There are three nerves that run through the hand: the radial, median, and ulnar nerves. Aside from their sensory properties, which allow us to feel sensations like pain and tickling, they also contribute to the pinching, grasping, and extending motions of the hand.
The hand also has a system of veins, some of which you can see by looking at the back of your hand. These veins are connected to arteries in the forearm, wrist, and palm, and they supply blood to the muscles, skin, and other tissue throughout the hand.
At the tip of each finger is a fingernail. These are specialized parts of the skin made up of keratin, a strong protein that also makes up our hair, as well as claws, scales, and beaks on other animals.