In Depth: Hand
Hands are capable of a wide variety of functions, including gross and fine motor movements. Gross motor movements allow us to pick up large objects or perform heavy labor. Fine motor movements enable us to perform delicate tasks, such as holding small objects or performing detailed work.
The complex abilities of the hand are part of what make humans unique. Only humans have the ability to bring our thumbs across the hand to connect with our ring and pinkie fingers. This ability provides us with the dexterity to use tools. It also gives us a forceful grip.
The hand can be considered in four segments:
- Fingers: Digits that extend from the palm of the hand, the fingers make it possible for humans to grip the smallest of objects.
- Palm: This is the bottom of the body of the hand.
- Back (opisthenar): The back of the hand shows the dorsal venous network, a web of veins.
- Wrist: The connection point between the arm and the hand, the wrist enables hand movements.
Each hand consists of 19 bones. The palm includes five metacarpals, and each finger except the thumb contains one proximal phalanx, one middle phalanx, and one distal phalanx. The thumb doesn’t have a middle phalanx. Each bone is connected by a series of ligaments.
Each fingertip—distal phalanx and accompanying tissue—contains a fingernail. These structures are made of keratin, a tough protein. Similar types of keratin also make up human hair, the scales and claws of reptiles, and the feathers, claws, and beaks of birds.
The palm of the hand doesn’t contain melanin (skin pigment) or hair follicles. The only other place on the body that lacks both of these is the sole of the foot. These two surfaces also have thicker skin than other places of the body.
Although fully functional hands can accomplish great things, they are susceptible to a number of ailments, including:
- Nerve disorders
- Finger clubbing
- Carpal tunnel syndrome
- Fractured bones
- Sprains, strains, cuts, and bruises