They are all under your skin.
flipcerucia
Muscles, nerves, bone, and guts.
Into the skin, in this case directly under the top layer of skin.
Both the origin and insertion points attach muscles to bone. The muscles are moving the bones so they must be attached directly to bone.
The skin is superficial to the muscles. The muscles are deep to the skin.
The fluttering movement under a persons skin is muscles trying to relax, but the nerve endings is basically what a person feels. The nerve endings a part of the muscles and the last thing to relax in a body.
Leg muscles are deep to the skin of your leg. The skin is superficial to the muscles.
Connective tissue is in the Dermis which is the secons layer of skin.
In the way you are using "superficial" it will mean " being on or near the surface".Thus the answer is "YES" the skin is a superficial organ - BUT -"NO" the skin is not "superficial" specifically to muscles - it does not surround muscles, it surrounds the whole body and the muscles are beneath (and some in - the ones that raise the hairs) the skin.
Yes, all muscles are deep to skin
No. The skin is superficial to the skeletal muscles.