Is the skin naturally darker, or does the shit stain it after a while?
Guy on IRC found this Reddit comment:
The anal sphincter is not just skin, it also contains a muscle used to either open or close; in this regard it serves a very similar function to the lips on your face (although the lips are more versatile and also play a role in speaking) and you will note that lips also have a deeper color than the rest of the skin on your face (although the actual color of lips is often concealed by lipstick which is used to exaggerate the natural color). The muscle has a richer blood supply than the skin, which affects the color.
I researched it and it seems plausible. From Wikipedia:
The anal canal above the pectinate line is supplied by the terminal branches of the superior rectal (hemorrhoidal) artery, which is the terminal branch of the inferior mesenteric artery ... The external anal sphincter (or sphincter ani externus ) is a flat plane of muscular fibers, elliptical in shape and intimately adherent to the skin surrounding the margin of the anus.
So maybe it has more to do with the muscles underneath the skin rather than the actual butthole. Now that I think about it, only a certain part of the butthole is darker, not the entire thing.
Guy on IRC found this Reddit comment:
>The anal sphincter is not just skin, it also contains a muscle used to either open or close; in this regard it serves a very similar function to the lips on your face (although the lips are more versatile and also play a role in speaking) and you will note that lips also have a deeper color than the rest of the skin on your face (although the actual color of lips is often concealed by lipstick which is used to exaggerate the natural color). The muscle has a richer blood supply than the skin, which affects the color.
I researched it and it seems plausible. From Wikipedia:
>The anal canal above the pectinate line is supplied by the terminal branches of the superior rectal (hemorrhoidal) artery, which is the terminal branch of the inferior mesenteric artery ... The external anal sphincter (or sphincter ani externus ) is a flat plane of muscular fibers, elliptical in shape and intimately adherent to the skin surrounding the margin of the anus.
So maybe it has more to do with the muscles underneath the skin rather than the actual butthole. Now that I think about it, only a certain part of the butthole is darker, not the entire thing.
I assume its stained. Isn't that why some people bleach it?