Final answer:
The major brevis muscle would be large but short, as brevis means 'short' in Latin. The triceps brachii is the muscle that extends the forearm, not muscles with names indicative of size, shape, or location such as deltoids or rectus abdominis.
Step-by-step explanation:
The major brevis muscle refers to muscles that are large but short. The term brevis is Latin for 'short', which indicates the length of the muscle. In anatomical nomenclature, muscle names often reflect their size, shape, location, or function. For instance, the gluteus maximus is the largest muscle in the group of gluteal muscles, the rectus abdominis is a straight muscle in the anterior wall of the abdomen, and the biceps brachii has two heads and helps with the flexion of the elbow. When extending the forearm, the muscle responsible is the triceps brachii. The triceps brachii is the larger muscle on the back of the upper limb, which specifically extends the forearm at the elbow. Conversely, muscles like the deltoid, named for its triangular shape resembling the Greek letter delta, cover the shoulder and are involved in various arm movements. Muscles with distinctive shapes often have names that reflect those shapes, such as orbicularis muscles, which are circular.