Urogenital opening explained

The urogenital opening is where bodily waste and reproductive fluids are expelled to the environment outside of the body cavity. In some organisms, including monotremes,^[1] birds and many fish, discharge from the urological, digestive, and reproductive systems empty into a common sac called the cloaca.

In placental mammals, these three systems are more separated. In females, separate orifices have evolved for all three, while in males, a common urinary meatus discharges both urine and semen from the urethra.^[2] In marsupials,^{[3] [4]} rabbits^{[5] [6]} and pigs, the female urethra and vagina open into a urogenital sinus with a common urogenital opening.^[7]

Notes and References

1. Book: Withers, Philip C. . Ecological and Environmental Physiology of Mammals . Cooper . Christine E. . Maloney . Shane K. . Bozinovic . Francisco . Neto . Ariovaldo P. Cruz . 2016-10-27 . Oxford University Press . 978-0-19-109267-1 . en.
2. Book: Libbie Henrietta Hyman. Hyman's Comparative Vertebrate Anatomy. 15 September 1992. University of Chicago Press. 978-0-226-87013-7. 583–.
3. Book: Nowak, Ronald M. . Walker's Marsupials of the World . 2005-09-12 . JHU Press . 978-0-8018-8211-1 . en.
4. Book: Withers . Philip C. . Ecological and Environmental Physiology of Mammals . Cooper . Christine E. . Maloney . Shane K. . Bozinovic . Francisco . Neto . Ariovaldo P. Cruz . 2016-10-27 . Oxford University Press . 978-0-19-109267-1 . en.
5. Book: Smith . David G. . A Dissection Guide & Atlas to the Rabbit . Schenk . Michael P. . 2019-02-01 . Morton Publishing Company . 978-1-61731-938-9 . en.
6. Book: Lukefahr . Steven D. . Rabbit Production, 10th Edition . McNitt . James I. . Cheeke . Peter R. . Patton . Nephi M. . 2022-04-29 . CABI . 978-1-78924-978-1 . en.
7. Book: Smith . David G. . Exploring Zoology: A Laboratory Guide . Schenk . Michael P. . 2014-01-01 . Morton Publishing Company . 978-1-61731-157-4 . en.