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First, I think it worthwhile considering 'Why would internal symmetry be beneficial?' Developmental simplicity jumps to mind immediately. You can also consider relationship to external organs; the stomach and esophagus are lined up with the mouth which is symmetrical about the sagittal plane. Or maybe even balance; the lungs are large organs and if put to ...

Smith et al. (2009) provide a survey of the morphology of the cecal appendix. One current hypothesis is that the appendix provides "safe harbor" for symbiotic gut bacteria. Among mammals, there is a vast array of cecal appendices: In summary: A comparative anatomical approach reveals three apparent morphotypes of the cecal appendix, as well as ...

Aside from humans, it is largely rodents and most notably rabbits that have an appendix. Therefore, using rabbits as my example: In rabbits, the appendix is thought to have a key role in the development of the immune system. Specifically it has been shown experimentally that when neonatal rabbits are given an appendectomy levels of Immunoglobulin A and G ...

The problem is that real organs are just damn complex - yes the kidney's prime role is just to be a filter, but in order to do so it must be plugged in to a dozen regulation mechanisms - osmotic balance, ion management, protein management and a plethora of more subtle ones. Moreover it is a part of body, so it must also follow all the standard protocols to ...

I was told in my undergraduate degree that males produce sperm all the time, and that under conditions of no sexual stimulation, that sperm is excreted involuntarily every 15-16 days, at night, while dreaming. I was also told that the renewal rate of sperm is higher under regular sexual stimulation, which increases the fertility of the sperm that is ...

The appendix was thought to be vestigial in humans until recently. Now it appears that, like rabbits, it is a safe harbour for symbiotic bacteria in the intestines. Source: Bollinger, Barbas, Bush, et al. J Theor Biol. 2007 Dec 21;249(4):826-31. Epub 2007 Sep 7.

Building on the answer given by Sean Connolly above, it would be very easy to imagine evolutionary scenarios where organs are more likely to develop asymmetrically than symmetrically. For instance, imagine an organism that has a simple digestive system that consists only of a single undifferentiated intestine that runs directly from mouth to anus in a ...

It's old and I can't get access to this issue of the Annals of the New York Academy of Science, but it looks like it has some relevant information. Sifting through the abstracts it seems the vasculature of the fetal liver is completed at around 8 weeks although is still different to the adult vasculature because of the umbilical vein. The growth of the organ ...

Not entirely on your question but I think sufficiently relevant: This paper (freely available) identified a non-causal link between ejaculatory frequency and incidence of prostate cancer. Men were asked their age at first ejaculation, the maximum number of ejaculations ever experienced in 24 h, and to estimate the average number of times that they had ...

I found that a search through Google Books was helpful... While without the excretion of feces, it might seem as if the liver would not be active, but the liver tissue is not only active in development and tissue generation but serves direct physiological function as well. After initial phases of development, the liver produces fetal red blood cells which ...

Since cells are the origin of every life, any tissue must at least be based on cells. Some tissue matter is outside the cells (plant cell walls), some apparently non-cellular tissue is really a bloated organelle. Both happens. As to your theses, yes, an example are oil reservoirs in plants no, these are just big cells. A striking example is spinal cord ...

On the question "would this possible?", my answer is yes. It is not unimaginable that organs could be grown without MHC proteins, although, as you mentioned, there's no guarantee that essential functions of the organ wouldn't be affected as well. This is not science-fiction at all. The question deserves a good answer by someone who works in the field!