Why are human bodies asymmetrical? - Leo Q. Wan
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You have probably seen this in movies and TV series before. Someone was shot/stabbed on the left of the chest, but he/she survived, because the heart was luckily on the right side of the body. In popular culture, the reverse of visceral organ positioning can often add a twist to a story. Add your favorite story to this list of fictional characters with situs inversus on Wikipedia. Did you think of any examples that you could add to the list?
Internal organ positioning and gut looping
In the animation, we have shown the asymmetric development of embryonic heart. The asymmetric positioning of most other visceral organs is related to the asymmetric gut looping, starting at week 4 of embryonic development. The vertebrate gastrointestinal tract and its accessory organs (ie, thyroid, lungs, liver, and pancreas) develop from a midline epithelium tube through a series of direction rotations. This video has much more for you to learn, if interested!
Cell chirality on a Petri dish
The cell is probably chiral. Chirality of individual cells can be seen in the migration of neutrophils, which have a tendency to move toward the left side. When dozens of cells are cultured onto a ring-shaped geometry using the micropatterning technique, these cells form a confluent layer with the cells chirally aligned. More interestingly, the cells on the inner and outer rings migrate in opposite directions. The migration direction on both boundaries can be reversed if the cells are exposed to drugs that interfere with actin, a major element in cytoskeleton. For more detail, this review article on cell chirality observed on a Petri dish might just have what you are interested in!
A gene in snails that determines whether their shells twist clockwise or anti-clockwise has been discovered by a team of international researchers. It could offer clues to how the same gene affects body asymmetry in other animals including humans, they report.
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