that may be his large intestine. i just watched a video where a dog explained where does 'it' go inside a bottom, for scientific purposes.
I think it's the "intersection" between the sigmoid colon to rectum. If the peepee's too long, it will reach that place, which means it has to straighten the "intersection" and reach the colon part. I think people call it as second ring. I don't think it's built like a sphincter ani, but going way through it might felt like one. Peepee have to go slowly cuz it's pretty sensitive and hurt when it forcefully enters.
Cmiiw (づ￣ ³￣)づ
Tysm
Um sorry but where exactly did his dick go?! It almost looked like a cervix am I tripping what ws that supposed to be, help