What is the name of the extensor muscle that straightens the elbow?

The extensor muscle responsible for straightening the elbow is the triceps. This muscle is located at the back of the upper arm and is primarily involved in extending the forearm at the elbow joint. When the triceps contracts, it pulls on the elbow joint, allowing the arm to straighten out from a bent position.

The deltoid muscle, located on the shoulder, is mainly involved in shoulder abduction and does not play a role in elbow extension. The biceps muscle, located on the front of the upper arm, functions primarily to flex the elbow and supinate the forearm, rather than extend it. Femoris, often referring to a group of muscles located in the thigh, is unrelated to elbow movement since it is not involved in the actions of the arm. Thus, the triceps is uniquely positioned and is the correct muscle for straightening the elbow.