extensor vs skeletal muscle

extensor and skeletal muscle both are nouns.

Word	Noun	Adjective	Verb	Adverb
extensor	Yes	No	No	No
skeletal muscle	Yes	No	No	No

As nouns, skeletal muscle is a hypernym of extensor; that is, skeletal muscle is a word with a broader meaning than extensor:

extensor: a skeletal muscle whose contraction extends or stretches a body part
skeletal muscle: 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

Other hypernyms of extensor include striated muscle.

extensor (noun)	skeletal muscle (noun)
a skeletal muscle whose contraction extends or stretches a body part	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