Extensor muscle and Skeletal muscle

Extensor muscle noun - A skeletal muscle whose contraction extends or stretches a body part.

Skeletal muscle and extensor muscle are semantically related. In some cases you can use "Skeletal muscle" instead a noun phrase "Extensor muscle".

Skeletal muscle noun - A muscle that is connected at either or both ends to a bone and so move parts of the skeleton; a muscle that is characterized by transverse stripes.

Extensor muscle and skeletal muscle are semantically related. Sometimes you can replace phrase "Extensor muscle" with "Skeletal muscle", this phrases are similar.