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8

The concept of transgenders has nothing to do with sexual organs at birth. Transgenders is a concept that has to do with sociology, not biology. See the wiki link. Hermaphroditism (sometimes called intersex) has to do with biology. The wiki link makes a great job at defining intersex. In short: A transgender person is born anatomically either male or ...


7

Individuals have not only hand dominance but also a dominant foot, eye and ear. There has also been a belief that this sidedness applies to chewing as well. However, the short answer is that no one is sure, but that it may be related to handedness. I only looked at studies done after 2000. One large study[1] found a questionable to weak correlation, not ...


6

Questions of the type, "why does organism X have feature A?" invite teleological (just so) explanations which are difficult to substantiate. For example, the number of teats on a cow are difficult to explain in terms of providing milk to humans! We should look to evolutionary history to explain human traits, not "just so" stories. The simple answer is that ...


5

As part of your question, you ask if other animals can create sound without continuous airflow. Many insects (e.g. cicadas and moths) do exactly this by using tymbals. A tymbal/timbal is an external membrane organ that is controlled by muscles or wing movements, that cause the membrane to flip back and forth, creating clicks or other sounds. So in many ways ...


4

Here is a list of woodwind instruments. Do you know of any (non-open) reed instrument that produces a note without anyone blowing air through them? Imagine a clarinet being played on someone's lap pouring out a melody. That would be very, very remarkable indeed. Our ability to produce sound from our throats is in theory like a reed instrument in music. ...


4

Here is my overly succinct answer. I doubt we will ever know this for sure. But, it basically comes down to ancestral bilateral symmetry in development; this defaults to two organs and is broadly symmetrical except where the organs are central. Further exceptions to symmetry occur where evolution pressured the body into not bothering to grow the second of ...


4

Via deep scientific analysis (i.e. trying it myself 5 seconds ago), I have determined that you can in fact speak while breathing in, it just sounds funny. Think of the vocal chords as being like the body of a flute. As air passes by them, they vibrate and make sounds. Through careful modulation of their shape, specific sounds can be reproducibly made (this ...


4

Limb lengthening surgery is usually used to treat sequelae caused by bone disease, trauma, pygmyism or inflammation. I personally do not recommend to use surgical methods to increase height. Typically Limb Lengthening requires Achilles pre-lengthening surgery and a lot of postoperative rehabilitation. Moreover, Limb lengthening surgery may cause pain, ...


3

In doing search into muscle stem cells, I found some articles which discuss roles of satellite stem cells and non satellite cells involved in muscle regeneration: (Yin, Price and Rudnicki, 2013,Seale and Rudnicki, 2000, and Mitchell et al, 2010). Other articles, that I found discussed the splicing of insulin-like growth factors (IGF-1) into the satellite ...


2

You are looking for the Trigeminal nerve, the largest nerve in the face. Here it is with its branches. It is both afferent and efferent. Afferent and efferent components of the facial nerve in the bullfrog (Rana catesbeiana) Cranial Nerves Illustrated: Figure V-4 General sensory component of the trigeminal nerve, ophthalmic (V1) division. General ...


2

Reverse signals (dendrite -> axon) do occur in neurons, and are called back propagating action potentials (bAPs). However, whatever role bAPs play in the nervous system at large is subtle/small enough that we don't really understand them at all. In any case, as @luigi points out, pinched nerves don't have anything to do with bAPs. The reason why a pinch in ...


2

It seems that just a Russian researcher named Dr Alexander Teplyashin has made any progress into using stem cells for LL (Limb lengthening). Conventional way to go about it would always be surgeries which are detailed in Wikipedia (reference). This is a relatively new development, so I could not find any relative publications to support the claim of this ...


1

Your pet dog needs more than two nipples because she can have up to 11 or more puppies. If she had two nipples, most of them sound starve. Twins are rare enough in humans. Two nipples are fine, and fit with bilateral symmetry. All primates have two nipples. So do many animals with one, two, and rarely three offspring at a time. Elephants: 2 teats, 1 calf ...


1

That conversation is strange. While different tables exist, the very first elements seem messed up. If the body is 60 (some sources say 70)% water, then oxygen has to be the most abundant element by weight (water - H2O - has a molecular weight of ~18 g/mol, with hydrogen contributing only 2g/mol of that weight). The usual figures are roughly Oxygen (65%), ...



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