Anatomy of the Forearm

Human hands close-up

The human body is an extremely complex and intricate machine. The forearm is no exception to this intricacy. The forearm is the lower section of the arm, extending from the elbow to the wrist. Many of the muscles, tendons, and ligaments that control the wrist, hand, and fingers originate in or directly connect to the forearm.

The two largest bones in the forearm are the ulna and the radius. The ulna is the smaller of the two bones, and is located closer to the pinky finger. The radius is the larger bone, and is located closer to the thumb. These bones are fascinating, as the radius actually pivots around the ulna to allow for many movements in the wrist and elbow. These bones both join to the humerus at the elbow joint, and to the carpal bones, which make up the wrist.

Flexor muscles are those that contract and pull another part of the body towards the engaged muscles. The upper arm contains three flexor muscles that allow the forearm to move, the brachialis, the biceps brachii, and the brachioradialis. Extensor muscles allow for another body part to be moved away from the muscle. The extensor muscle that controls the forearm, the triceps brachii, is also located in the upper arm. These upper arm muscles connect to the radius and ulna, allowing for the movement of the forearm. The flexors and extensors controlling the wrist, hands, and fingers are located in the forearm. These muscles connect to the carpals (wrist bones), metacarpals (hand bones), and phalanges (finger bones) via long tendons, which are fibrous connective tissue that joins muscle to bone. Many of these tendons run through a small opening in the middle of the carpal bones, known as the carpal tunnel. A major nerve, the median nerve, also runs through this tunnel. Irritation and inflammation within the carpal tunnel is the cause of carpal tunnel syndrome, one of the most commonly known afflictions of the forearm, wrist, and hand.

The anatomy of the arm is so complex that there are entire units in college level anatomy classes dedicated to the subject. Please visit any of the references cited below if you are interested in learning more in-depth information about the names and purposes of individual components of the forearm.


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