Answer :
Facial expressions are variable because the muscles of facial expression insert into the skin, allowing for intricate movements that convey emotions hence option 2) is the correct answer.
Facial expressions are highly variable due to the unique structure of facial muscles, which are known to insert into the skin instead of onto bones as seen in most other muscles of the body. These muscles provide the ability for a wide range of expressions by moving the skin around our eyelids, nose, and mouth.
When considering muscles of facial expression and their points of insertion, it is noteworthy that these muscles do not insert on the mandible, which is the lower jaw bone, nor directly onto the facial bones. These bones serve as attachment points for other muscles which control chewing and other functions. Rather, the muscles of facial expression insert onto the skin, which allows for the intricate movements necessary to convey emotions hence option 2) is the correct answer.
