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metacarpal bones in the hand and digits in the fingers. The
muscle that extends, or straightens, the arm is the triceps,
which arises on the humerus and attaches to the ulna at the
elbow; the brachialis and biceps muscles act to bend the arm at
the elbow. A number of smaller muscles cover the radius and ulna
and act to move the hand and fingers in various ways. The
pectoralis muscle,... What made you want to look up "brachialis
muscle"? Please share what surprised you most...