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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 ...


10

Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking only of bipedal humans. In anatomy, the dorsum is the upper side of animals that typically run fly, swim or crawl in a horizontal position. In vertebrates 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 ...


6

Artificial amniotic fluid has been used on goats, and for premature human babies. In the 1996 experiment, Thomas Shaffer, a scientist at Temple University, used an oxygenated liquid in a clinical trial with thirteen infants born at twenty-three to twenty-four weeks who were not expected to survive, and seven babies were discharged healthy. Jonathan Knight, ...


6

It is impossible at present to reproduce all the conditions of a womb. A womb is more than a warm fluid-filled home for nine months. A few days after fertilization, the trophoblast portion of the conceptus attaches itself to the uterine wall where it develops into a placenta and umbilical cord while the rest (the epiblast) becomes the baby. Throughout the ...


6

Arterial Baroreceptors felling the pressure. Arterial blood pressure is normally regulated within a narrow range, with a mean arterial pressure typically ranging from 85 to 100 mmHg in adults. It is important to tightly control this pressure to ensure adequate blood flow to organs throughout the body. This is accomplished by negative feedback systems ...


6

Citing your source would help to answer. In order to test an elastic modulus, you need to apply some non-zero strain. If the strain is infinitesimal, then compression and stretch modulus will be equal. But if it is finite, then there can be a difference due to the structure of the material. In bone, I believe porosity will provide most of the dissymetry ...


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

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

Anatomically speaking, the palate is the roof of the mouth, separating the oral cavity (mouth) from the nasal cavity (inner nose). While the palate may be sensitive to heat and spiciness (via the capsaicin receptor, for example), it does not contain any taste buds, which are located on the tongue, and are part of the taste-sensing system. The other part of ...


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

This doesn't really answer the question and I only post it at the asker's request. NASA has measured the dimensions of the back in 40 year old American males and 40 year old Japanese females in the year 2000 at 1G. Of course gravity matters to NASA… From figure 3.3.1.3-1 (American male). All data in centimetres: 921 Waist back 5th percentile: 43.7 ...


5

Sounds such as certain phonemes are made merely with the use of air flow and movement of the lips or tongue, without the need for action of the vocal chords. Think of 'f', 's', 't', k in the English language. These are called unvoiced phonemes in phoniatrics (see the phonemic chart). Also, clicking sounds and whistling can be made without use of the vocal ...


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

Dors/dorsum in Latin simply means "back", and it is rather normal and reasonable to use the equivalent term in English with regard to the extremities (hands and feet), see "back of my hand". It is medical convention to refer to the non-gripping surfaces of the feet and hands, as well as the upper (towards the brain) surface of the tongue as "dorsal". My ...


4

Short answer(s) Someone with a damaged larynx may still speak with the use of a speech aid (electronic larynx). The ability to understand speech does not necessarily mean one can speak normally. There are neurological disorders where folks can understand speech, but have difficulty producing it. Background A full removal of the larynx (laryngectomy) ...


4

You can whisper without a larynx. "Patients who have undergone partial or full laryngectomy are typically unable to speak anything more than hoarse whispers, without the aid of prostheses or specialized speaking techniques." (source) So the remainder of the vocal tract is capable of enough modulation to present typical human speech in many languages. I ...


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

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 ...


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

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

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 ...


3

Short answer Given your comments you are referring to the cause of fainting after being triggered by certain stressors. The reason is a sudden drop in blood pressure due to parasympathetic nervous system activation (vagus nerve activity). This leads to reduced blood flow to your brain, which results in a brief loss of consciousness (Mayo Clinic). Background ...



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