eighty
Anus. The muscles of the anus are called sphincters, or in doctor terminology, sphincter complexes.
sphincter muscles
Because the muscles in your anus squeeze them.
Oxygen when water is pumped through their anus using the muscles of their cloaca.
Muscles expand then contract to induce movement.
yes, when the anus scrunched when you push the poop out you use the muscles on the anus. :^)
aside from the pelvis which is the bone supporting your genital region and connecting your legs to your torso then no. The anus is a collection of nerves and muscles.
the two anal sphincter muscles
The anus is the external opening of the rectum. Closure is controlled by sphincter muscles. Feces are expelled from the body through the anus during the act of defecation, which is the primary function of the anus. The rectum shortens, as material is forced into the anal canal.
smooth
First of all, your anus is a sphincter, it cannot get hard unless the muscles surrounding the sphincter contract. If you are having pain, then you should be concerned if you have any rectal bleeding as you may have torn the inside of your anus from anal sex, or 'up and down to anus.' Otherwise, you may have just caused some stress to the muscles and nerves within the anus.
Amyl nitrate is a chemical that is most commonly used to relax the muscles in the anus.