biceps(redirected from biceps brachii)
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biceps (bīˈsĕps), any muscle having two heads, or fixed ends of attachment, notably the biceps brachii at the front of the upper arm and the biceps femoris in the thigh. Originating in the shoulder area, the heads of the biceps merge partway down the arm to form a rounded mass of tissue linked by a tendon to the radius, the smaller of the two forearm bones. When the biceps contracts, the tendon is pulled toward the heads, thus bending the arm at the elbow. For this reason the biceps is called a flexor. It works in coordination with the triceps brachii, an extensor. The biceps also controls rotation of the forearm to a palm-up position, as in turning a doorknob. The size and solidity of the contracted biceps are a traditional measure of physical strength.
a muscle that begins with two heads. The arm biceps in man originates at the shoulder blade and is attached to the tuberosity of the radius; it flexes the arm at the elbow joint and raises it at the shoulder joint. The biceps of the thigh originates at the ischial tuberosity and the thigh bone, and it is attached to the tibia in the region of the head of the fibula; it extends the thigh and flexes the shin.