One of the most weird and wonderful products of evolution is the penis bone, or baculum. The baculum is an extra-skeletal bone, which means it is not attached to the rest of the skeleton but instead floats daintily at the end of the penis. Depending on the animal, bacula range in size from under a millimetre to nearly a metre long, and in shape, varying from needle-like spines to fork like prongs.
All rights reserved. Bigger is better—at least when it comes to a woman's penis preferences, a new study says. The findings suggest that female choice may have driven the evolution of larger penises in humans.
Reproduction is the process by which organisms make more organisms like themselves. But even though the reproductive system is essential to keeping a species alive, unlike other body systems, it's not essential to keeping an individual alive. In the human reproductive process, two kinds of sex cells, or gametes pronounced: GAH-meetzare involved.
The human penis is a main portal of entry for numerous pathogens, and vaccines able to control resulting infections locally are highly desirable. However, in contrast to the gastrointestinal or vaginal mucosa, the penile immune system and mechanisms inducing a penile immune response remain elusive. In this descriptive study, using multiparametric flow cytometry and immunohistochemistry, we characterized mucosal immune cells such as B, T, and natural killer NK cells from the urethra, fossa, and glans of human adult penile tissues. All penile regions contain CD56 dim NK cells surface expressing the natural cytotoxicity receptor NKp44 and the antibody-dependent cell cytotoxicity receptor CD
Adrenaline, noradrenaline and phenylephrine caused contraction of the corpus cavernosum muscle of the human penis. These sympathomimetic amines did not product inhibitory effects even in the presence of the alpha-adrenoreceptor blocker, phentolamine. The effect of dopamine was similar to that produced by these three sympathomimetic amines.
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Republish our articles for free, online or in print, under Creative Commons licence. Humans have a much longer and wider penis than the other great apes. Even the largest of gorillas, more than twice as heavy as a human, will have a penis just two and half inches long when erect.
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All rights reserved. You may be surprised to discover just how highly specialized a tool it is. For the evolutionary psychologist, the pressing questions are, essentially, Why is it like that? But in the case of the human penis, all signs point to a genuine adaptive reason that it has come to look the way it does.