The elbow is bent so that the upper arm is at a right angle to the lower arm. It can be said that the upper arm is ________ to the lower arm.

A right angle measures 90 degrees. When two body parts meet at a right angle, they are perpendicular, so the upper arm is perpendicular to the lower arm. Parallel means side by side without meeting, while ventral and dorsal describe directions on the body.

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