The elbow is a hinge joint. It connects the further end of the humerus and the nearest ends of two lower-arm bones: the ulna and radius. The elbow flexes and extends the forearm, and rotates the ...

Included in the package are six well-preserved arm and leg bones, each of which is labeled. There is one radius (R1) and one ulna (U1); these are the two bones that connect the wrist and elbow.

Skeletal muscle is joined to bones. Its cells contract ... which is just a fancy way of saying two muscles that pull in opposite directions. For example, in your arm, your biceps and triceps ...

And yet, its humerus (an arm bone) is quite human-like. Characteristics of its tibia (a lower leg bone) indicate that A. anamensis walked on two feet. This species includes "Lucy," the 3.2 million ...