There is an entire culture within our culture.  "Knotting" is a physical union between a woman & a canine partner.  The experience a woman feels is beyond description.  If her partner penetrates her vagina deeply enough, the canine's glands will swell to the point where they both are "stuck" together until the swelling subsides. This can last anywhere from 10 to 30 minutes. During this union, her partner is continuously ejaculating inside her.  The swollen glands are pressing against her most sensitive pleasure receptors.  The typical human penis only provides 3ml in volume of ejaculate, the canine can reach 20ml or more in volume.  The shape & size of the canine penis is generally larger & straighter than his human counterpart when erect, allowing him to touch or enter her cervix.  There have been numerous studies of this genre of sexuality, These relationships are far more prevalent than one would believe, going back centuries.  Watching such videos is almost a cause of jealousy in human male viewers, these women can be seen genuinely emotionally attached to their canine partner in a very loving way.