This text is an anatomical description of the muscles of the forearm focusing on their attachment and function. It explains how muscles such as the supinator and extensors interact with bones like the radius and humerus to facilitate hand movement. The composition and position of muscles influencing thumb and finger movements are also discussed.
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The upper side: the part that is towards the little finger is called the inner side, and the one towards the thumb, the outer side. Hence, the forearm is composed of two masses, which are separated above the arm by the muscle with two heads that inserts into the radius, and below, these masses are separated by the elbow.
The mass on the outer side or thumb side contains the long supinator of the radius, which is to say, the one that helps to elevate it. It originates at the humerus bone, beside the muscle with two heads, and inserts into the radius, fairly close to the knot, where the joint of the arm and hand is formed. Beside this, you can see the superior extensor of the carpus, which helps to expand this part of the hand: it originates from the humerus and inserts into the hand. Next to the long supinator, near the knot, there appears a muscle that originates from the radius, and passing obliquely over the supinator, inserts into the thumb; it is also called the extensor of the thumb. Alongside these muscles, turning towards the underside of the arm, there are two muscles one after the other, one of which is called the extensor of the fingers, and the other the extensor of the little finger. Finally, near the elbow, there is another muscle called the inferior extensor of the carpus. Thus, this mass is composed of all the extensors.
The mass on the inner side, on the other side of the muscle with two heads, contains the round pronator of the radius: it is a rather short muscle that also originates from the humerus, and inserts obliquely into the radius that it lowers, just as the long supinator raises the other mass. The following muscle is called the superior flexor of the carpus; it provides movement to the part of the hand that is attached to the knot. Next to this is the flexor of the fingers and the palm of the hand, which gives
Translation Notes
Supinator: A muscle that rotates the forearm to turn the palm up or forwards.
Extensor: A muscle whose contraction extends or straightens a limb or other part of the body.
Carpus: The cluster of bones in the wrist between the radius and ulna and metacarpus.
Humerus: The bone of the upper arm or forelimb, forming joints at the shoulder and the elbow.
Radius: One of the two large bones of the forearm, located on the thumb side.