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24

The uniqueness of irises and fingerprints are, as you said, limited to the number of possible permutations of irises and fingerprints. A similar problem exists in computer science, and is known as a hash collision. Given sufficient samples, there will always be a collision for a hash of finite size. However, the sample space is sufficiently large for iris ...


13

Developmentally, the urinary and genital systems (typically you will hear them referred to as "urogenital system") are derived from the same embryonic tissue, the intermediate mesoderm. The embryonic kidneys are drained by the mesonephric duct in both females and males. This embryonic tissue also gives rise to the ovaries and testes. The mesonephric duct ...


11

Short answer The relative large surface area of the white sclera in humans has been linked to an enhanced ability to detect eye gaze. Background The white of the eye is caused by the sclera. Human eyes indeed have the highest relative amount of visibly exposed white sclera. The amount of visible sclera provides information about the orientation of the ...


7

It is logically clear that the ankle could only partly be analyzed in the group of joints that are below its height. There is no direct way to measure the pressure on ankle joint (on talus bone), but from the logic it is clear that it should be the point of highest pressure in the group of points lister in the question, however the pressure is distributed ...


7

Short answer Oxytocin release has been associated with the cutaneous low-threshold (CT) afferent fibers in hairy skin. Background Oxytocin is released from the paraventricular nucleus in the brain in response to low intensity stimulation of the skin, such as touch, stroking and warm temperatures. In a recent review Uvnäs-Moberg et al. (2015) report that ...


6

@March Ho's answer is an excellent answer based on the assumption that all of the observed phenotypic variance is due to genetic variance. Environmental variance The genetic variance is not the only underlying variance that can explain variance in phenotypic traits. There is probably quite a lot of phenotypic variance that is caused by the underlying ...


6

In short, without direct physical evidence (forensic or medical examination), testimony, or documentation to act as proof, you are left up to the discretion of the court to determine whether evidence is admissible and up to a jury to decide if it is reasonable to presume that a person depicted is of a certain age if no other evidence to the contrary is ...


5

Yes, such a conditions exists. It is called "situs inversus" (literally "inverted sites"). All major organs are placed on the opposite site, the condition is relatively rare with an incidence rate of 1:10.000. There are some even rarer forms occuring, when the organs are flipped, but the heart is still on the left side (levocardia) as opposed to the case ...


5

Short answer Sciatic nerve pain cannot be caused by a full colon. background The sciatic nerve runs at the back of the pelvis down the the leg. The sciatic nerve exits the spine from the lumbar spine to S3 in the sacrum (Fig. 1). Fig.1. Left: sciatic nerve overview. Right: Sacral plexus. Source: Manchester Bedford Clinic Hence the sciatic nerve does ...


5

"Position of the pelvis" is pretty vague, but there are very clear differences in pelvic morphology between females and males. This sexual dimorphism looks like: Female pelves are wider and flatter, which I think you could tell from surface anatomy. Of course if you could palpate, then you could tell for sure.


5

There is quite a lot of misunderstanding about alcohol (and caffeine) as a diuretic. It's not nearly as cut and dry as you're presenting. There is no answer to your question. Sodium and water are very tightly regulated, and a lot has to go wrong before they fail. If alcohol could easily derail water regulation, there would be far, far fewer alcoholics in ...


4

The place where the cord was cut do not stay with us - it falls in a week +- after the birth, while the umbilicus is the only visible natural scar formed by natural processes, not by gynecologists: Multiple sources say the umbilicus has a scar tissue in it. After birth the umbilicus is the only naturally formed visible scar on the body. Br J Plast ...


4

First off, I would be careful generalizing people's experiences with this exercise (..."Try it...You'll have trouble long before you reach 90 degrees"...): Source: Yoga Tune Up The muscles you are feeling at 90o, and the lady pictured above perhaps not even at 180o are the hamstrings. They run along the back of your thigh, attaching at both the hip and ...


4

I have some insight into this from an engineering perspective. Years ago, I worked on some computational and search algorithms which used a growth factor to determine how far to widen a search space, or how much more memory to allocate. For some of these algorithms, I ran a series of random trials to search for an optimal growth factor and found that for ...


4

It is something of a misnomer to speak of CSF “circulation,” particularly in the spinal canal, as there is no continuous loop circulation of CSF as there is in the cardiovascular system. For quite some time, it has been known that CSF movement results from the formation of new CSF and motion of cilia on the surface of the choroid plexus and ependyma ...


4

Short answer There are no functional nociceptors present in the umbilical cord. Background Having had the opportunity to cut the umbilical cord of one of my kids, I can anecdotally confirm neither newborn nor mother gave any sign of pain during the procedure. That is, when cutting the umbilical after the birth of a full-term baby. The only person clenching ...


4

The female mammary gland tissue contains androgen receptors (testosterone is an androgen). So this tissue is sensitive to androgens, and they inhibit the estrogen-induced proliferation. The inactivation of the androgen receptor on the other hand leads to an accelerated growth of the pubertal mammary gland and to the upregulation of estrogen receptor α ...


4

There's really two answers to the question. The first is overall symmetry: mammals, like all tetrapods, are bilaterally symmetric. This comes from a distant common origin with other bilaterally symmetric organisms. Organisms which evolved from this common ancestor often have organs in pairs, probably evolving as a re-use of regulatory genes. The other ...


4

Based on the location of that cross section in the upper arm the vein in question appears to be the basilic vein. The basilic and cephalic veins are the largest veins (most of the time) in the upper arm. Here is a nice diagram from wikipedia that shows both. The cephalic vein is much more superficial than the basilic vein, as you can somewhat appreciate in ...


4

According to this article appearing on the website of the American Association of Neurological Surgeons, gunshot injuries to the head are fatal in 90 per cent of cases. Many victims die before reaching the ER, and the 50 per cent who survive the initial trauma die in the ER.


4

In the vertical plane, bending of the fingers is indeed referred to as flexion, while straightening is called extension. In the horizontal plane, spreading the fingers is called abduction, and approximation is called adduction (Fig. 1). Fig. 1. Finger movements and terminology. source: US Dept. of Veteran Affairs


3

There is a model of an adult, male, real human brain here: http://brainder.org/download/brain-for-blender/ It can be imported into Blender or any other 3D application that can read Wavefront OBJ or Stanford PLY formats.


3

I would strongly question whether the underlying claim that testicular asymmetry is generally true. While there is no known clinical significance of testicular asymmetry, most men probably have no noticable difference in testicular size. There have been a number of studies over several decades, and findings have been inconsistent. Braus (1956) stated that ...


3

This appears to be the sternalis muscle. The reason it is not mentioned may because it is not present in all individuals, and is therefore relatively poorly characterised. The image is from An Atlas of anatomy by regions by John Charles Boileau Grant. Another image of the muscle can be found in Pocket Atlas of Human Anatomy by Thieme:


3

The vertebral column is a bony, segmented structure that supports the torso/head and thorax. The spinal cord is a bundle of nerves that runs inside the structure of the vertebral column. So - they run together, but are completely separate.


3

The vertebral foramen What is it, and what passes through it? A number of structures pass through the foramen. These are the root of each spinal nerve, dorsal root ganglion, the spinal artery of the segmental artery, communicating veins between the internal and external plexuses, recurrent meningeal (sinu-vertebral) nerves, and transforaminal ligaments. ...


3

According to this article female ejaculate is produced by the Skene glands.


2

CSF is actively pumped in an ebb and flow manner by the pressure with our respiratory mechanism transmitted through the pelvic diaphram onto the sacral bone that pulls on the spinal dural membranes attached at S2. Think about it: the pelvic and thoracic diaphragm are linked in a respiratory phasic contraction (confirmed with MRI). The pulling on the sacral ...


2

kmm gives what is likely the best possible answer, as it is argued from causality rather than teleology. As my ninth grade biology teacher used to say, "there is no 'why' in biology, only 'how'". On the other hand, it is fun to speculate! Here's my two cents in the form of a Bad ad hoc Hypothesis: Holes going into the body are an expensive and risky ...


2

I would just modify the excellent previous by pointing out that the embryology describes a local maxima of fitness whose barrier to change is higher than any selective pressure. The re-use of the "logic" of the intermediate mesoderm was either initially a bifurcation from one or the other, or, was of enough selective advantage to have the two developmental ...



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