Written by Michele Wheat
It isn't often that people give much thought to their hands and how they work or to the amazing range of movement that makes it possible to accomplish even the most simple daily tasks. Human hands have the ability to move and function in a way that sets them apart from most other animals with the exception of primates. Equipped with four fingers and a thumb, a person's hands have the ability to create the most intricate of designs and handle the most fragile of items. Without the function and movement of the wrists, fingers, and thumb, one could not drive a car, cook a meal, sign their name, or perform other basic tasks without a prosthetic or some other form of assistance. This natural and unassisted ability is possible courtesy of bones, muscles, connective tissue, and nerves of the hands, fingers, and wrists.
When examining the human hand, its many parts, and how it functions, one can start by first understanding how the wrist is made and how it works. The wrist is a joint that attaches a person's hand to their arm or, more specifically, their forearm. It allows the hands to accomplish a range of movement from side to side as well as forward and back. It can even be rotated in a circular fashion. Each wrist is made up of eight fairly small bones that are known as the carpal bones. There are two rows of these bones, all of which are connected by ligaments that allow for both mobility and stability. The first row of carpal bones, which is closest to the fingers, includes the trapezium, trapezoid, capitate, and hamate. The second row of carpal bones is located where the wrist bends. These carpal bones are the scaphoid, lunate, triquetrum, and pisiform.
The bones at the middle of each hand, between the wrist and the fingers, are called the metacarpals. There are five metacarpals that are articulated by the carpometacarpal joints. The carpometacarpal joints also articulate the distal row of the carpal bones, which are located closest to the middle of the hand or the metacarpals. Each hand also has five digits: four fingers and a thumb. There are two joints and three bones, or phalanges, per finger, called the distal, middle (or intermediate), and proximal phalanges. The smallest of these bones are the distal phalanges, which are the fingertips. Following the middle bones, called middle phalanges, are the proximal phalanges, which are located closest to the metacarpals. A person's thumbs consist of one joint and two phalanges, the distal and the proximal. On each hand, there are a total of 14 phalanges.
The hands also include ligaments and tendons, both of which are types of connective tissue. Ligaments are tissue that attaches bones to other bones while providing them with support and protection. The tendons in one's hand are connective tissue that attaches muscle to bone. Tendons include flexors and extensors. Additionally, the hand also includes three nerves called the ulnar, median, and radial nerves. The median nerve, which is responsible for pinching, has two branches that innervate the muscles in the hand. The muscles that are associated with one's thumbs and their movement are innervated by the recurrent branch of the median nerve. These muscles are called the thenar muscles. There are two lateral lumbricals, which are muscles that control flexion of the index and middle fingers. These muscles are innervated by the palmar digital branch of the median nerve. The ulnar nerve, which travels from the wrist to the shoulder, is responsible for grasping. It innervates many of the muscles in the hand, which include the medial two lumbricals, the hypothenar muscles, the interossei of the hand, and the adductor pollicis. The deep branch of the ulnar nerve innervates many of the intrinsic hand muscles. From the anterior compartment of the forearm, it supplies the muscles that flex the fingers and also the muscles that flex and adduct the hand where it meets the wrist. The third nerve found in the hand, which is the radial nerve, allows for the extension of the fingers and wrists and hand position. It also helps provide sensation to the hand and the wrist.
The muscles and tendons in the hands are what enables movement. Two important sets of muscles are the extensors and the flexors. The extensors are the muscles that allow for straightening of the hand, thumb, and fingers, while the flexors allow for bending. There are also the short hand muscles that make abduction and adduction of the fingers possible. In all, there are more than 30 muscles in the hand and forearm that allow for movement such as the grasping and moving of objects.
Sign up to receive great offers in your inbox. We won’t sell your info or sign you up for cat facts.