1. “The initial, emission, stage in the ejaculation process is produced by contractions of the smooth muscle in the capsules of the testes, seminal vesicles, and prostate and the smooth muscle of the ducts of the epididymis and vas deferens.” [2] In women the testes develop into the ovaries, but the seminal vesicles, epididymis, and vas deferens appear to become vestigial, based on current medical knowledge, which means they do not developed into functional structures.
2. While the insertion of the penis into the vagina during sexual intercourse significantly increases the likelihood of conception, the external prominence of the human penis is not required for reproduction to occur. In theory and practice a man and woman who possess a clitoris or micropenis could reproduce if they engaged in what we commonly call outercourse, if they had the internal reproductive organs we commonly associate with their respective genders.
3. Ejaculating on the vulva can and does result in conception, as demonstrated by the occurrence of virginal couples conceiving a babybaby [Case 1]. The practice of subincision would also provide evidence to support the theory that ejaculating on the vulva is sufficient to maintain a society, and given the challenges presented by the nomadic lifestyle of societies that engage/ed in this practice, this would possibly act as a natural means of reducing the birthrate, avoiding the strain that overpopulation would place on their community and environment. This means men with hypospadias or a micropenis would most likely be able to reproduce without the need for “surgical correction.”
4. Given that eighty-six percent of women said in a survey on this website that they produce sufficient vaginal lubrication for it to lubricate their vulva, sperm could potentially swim their way from the moist vulva into a woman's vagina and find their way to her egg cell, ovum. In addition to providing a liquid environment for sperm to utilize, vaginal lubrication reduces the normally acidic level of the vagina and vulva, making them more hospitable to sperm.
5. "The close physical proximity of the urethra and the clitoris to the anterior vaginal wall suggests an association between these anatomical structures and sexual function. In fact, the anterior vaginal wall is an active organ, transmitting during intercourse, the effect of penile thrusting in the vagina to the clitoris, by stretching the two ligaments that insert around its base." Source
6. "The distal vagina is a structure that is so interrelated with the clitoris that it is a matter of some debate whether the two are are truly separate structures. The same relationship applies to the female urethra. Though in anatomical terms it is possible to dissect one structure fully from the other, the three structures (distal vagina, clitoris, and urethra) share blood supply and innervation." Source

1. How Big is Big? by Dr. Zev Wanderer & Dr. David Radell 1982 [Book]
2. The Science of Orgasm by Barry R. Komisaruk, Carlos Beyer-Flores, & Beverly Whipple [Book]
3. The Female Prostate: history, functional morphology, and sexology implications by Dr. Milan Zaviacic 2001 (PDF File)
4. Urological Survey: Neuroanatomy of the human female lower urogenital tract. By Yucel S, De Souza A Jr, Baskin LS. J Urol. 2004; 172: 191-5 (PDF File)

Non-Cited References:

1. Quantification of Intramuscular Nerves Within the Female Striated Urogenital Sphincter Muscle By Meghana A Pandit, MBBS, MRCOG, John O. L. Delancey, MD, James A. Ashton-Miller, PhD, Jyothsna Iyengar, Mila Blaivas, MD, PhD, and Daniele Perucchini, MD (Article and PDF File)
2. Female Pelvic Floor Anatomy: The Pelvic Floor, Supporting Structures, and Pelvic Organs. Sender Herschorn, MD, FRCSC (Article and PDF File)
3. The Functional Anatomy of the Female Pelvic Floor and Stress Continence Control System. By James A. Ashton-Miller, Denise Howard, and John O. L. DeLancey (Article and PDF File)
4. Urinary Incontinence: Anatomy and physiology of the pelvic floor by W.A Silva, M.M. Karram (PDF File)
5. Pharmacology of the Lower Urinary Tract: Basis for Current and Future Treatments of Urinary Incontinence by Karl-Erik Andersson and Alan J. Wein (Article and PDF File)