This tag is for questions about the general biological features of human beings (as opposed to the biology of non-humans).

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3answers
99 views

Are missing limbs hereditary?

So with my basic understanding of biology, DNA can change over time. Does this mean that if one (or both) parents have something major missing (like a limb), the kid will come out without a limb? ...
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0answers
109 views

Why did humans evolve the ability to feel such a high level of heat pain? [closed]

It's probably because our ancestors were frequently around 300°C metal which badly damages flesh in a fraction of a second because they made fires to cook. I don't see why that would cause natural ...
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1answer
211 views

What is the normal blood water content

What is the normal water volume per 1 L of blood, and how much deviation from that norm causes dehydration or hyponatremia?
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1answer
116 views

Why would glucocorticoids promote glycogenesis and not glycogenolysis?

I read in a textbook that glucocorticoids can stimulate the synthesis of glycogen. I do not understand this at all—shouldn’t glucocorticoids try to increase the blood level of glucose? Why would they ...
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0answers
41 views

Why do workouts cause your muscles to feel heavy?

I know that muscle activity causes your muscles to build up lactic acid. Is this the specific reason that your muscles begin to feel heavy? How does this relate to the healing or inflammation process ...
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0answers
27 views

Is there any evidence to suggest that exercise reduces the side effects of caffeine?

I heard a friend say: I'm not drinking coffee this week. My body can only process the caffeine if I run at least 15km a week. I found this claim fascinating - that exercise temporarily ...
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1answer
167 views

Are human teeth only diphyodont or both diphyodont and monodont?

Many books say human teeth are only diphyodont .But premolars appear only once and one molar appears later which should be considered monophyodont. Dental Formulae : CHILD - 1. Incissor -2/2 2. ...
5
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2answers
224 views

Does soap kill human cells?

I see many products, particularly hand soap and cleaning products, that claim to kill 99.9% or more of bacteria. This makes me wonder, if the chemicals are potent enough to break down bacterial cell ...
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1answer
71 views

When you blow through your nose while holding it closed to “depop” you ears, why do you sometimes feel it in your eyes?

After your ears have "popped", for example on a flight, I heard you are supposed to hold your nostrils closed and blow through your nose to readjust the pressure to the normal level. Why do you ...
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1answer
119 views

If all bacteria in human gut are dead, can they be there again?

If someone likes to eat chocolate, she may have gut bacteria which like chocolate according to some articles that I have read. ...
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1answer
58 views

Movement of sperm to the egg

Sperm swims through semen and reaches the haploid egg in the oviduct during fertilisation. Once the sperm reaches the cervix, through what does the sperm swim through to reach the egg? Is the ...
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1answer
77 views

How can a blood test give information about rickets?

Can we detect rickets from a blood test? What evidence pf rickets is in the blood and how is the blood treated to detect rickets?
3
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1answer
45 views

Why would growth hormone (somatotropin) cause both lipid AND glucose release?

GH increases lipolysis (lipid breakdown) and the release of fatty acids from adipocytes into the blood. Fatty acids then can be used as energy sources to drive chemical reactions, including ...
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0answers
68 views

Proteases in the blood

I’m reading on hormones and the book talks about how peptide or amine hormones are easily broken down by proteases present in the blood plasma. This has led me to question the interactions between ...
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1answer
93 views

Why are lipid-soluble substances harder to excrete?

I understand why water-soluble substances can be excreted. However, why are they easier to excrete than lipid-soluble substances? Why can’t lipid-soluble substance be excreted just as easily in the ...
2
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1answer
127 views

Why is chromatin not condensed during interphase but is in prophase [closed]

Cell cycle goes through three processes: Interphase Mitosis Cytokinesis Why are chromatins not condensed during interphase but instead condensed at prophase of mitosis? What makes them condense ...
2
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1answer
125 views

What is the difference between Amino acids from blood and urine?

I would like to understand the difference between different tests for Amino Acids. Any blood laboratory offers amino acids tests using 3-4 methods Blood serum Urine Random Urine 24 hour (all the ...
2
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2answers
148 views

Why is warm water comfortable, but warm air uncomfortable?

I friend of mine tried floating, where you lay in a bath kept at body temperature (98.6 degrees F). He said after a while you don't feel the water at all. This made me wonder why being in warm water ...
11
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2answers
646 views

Is global life expectancy normally distributed?

I am trying to find out what the world distribution of life expectancy looks like.
2
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1answer
36 views

What is the mechanism of folic acid deficiency and neural tube defects?

I am having difficulty finding the mechanism by which folic acid reduces the risk of neural tube defects. I know that it does so, but what in particular actually occurs with folic acid deficiency to ...
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1answer
19 views

Absorption of Topical Magnesium

Can Magnesium be absorbed through the skin? Some athletes believe that Homeopathic magnesium lotions can reduce muscle pain. I've tried this and it doesn't work nor can I see how it can.
3
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1answer
109 views

Why is one testicle larger than the other?

Why is one testicle generally larger in humans? Just due to asymmetric development, or is there a hypothesis as to some utility it serves? I read that the different heights may be attributed to ...
2
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3answers
77 views

Do adult humans exchange beneficial bacteria? If so, how?

Recently there has been increasing interest and research into symbiotic bacteria present in humans and human gut. I'm aware of two new discoveries: humans are surrounded by a unique cloud of ...
2
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1answer
29 views

Can specific B-cells be created in a lab? [closed]

Instead of creating protein sequences, could that stepped be skipped and just have B-cells created to manufacture a particular type of immunity?
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2answers
64 views

When did human ancestors learn to walk? [closed]

Where does our ancestor learn to walk from? How do we control our legs whenever we take a step? I confuse every time whenever I take one step.
4
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1answer
90 views

Is it easy to test human Flicker Fusion Threshold?

How would you go about testing human flicker fusion threshold? Is the testable rate consistent in humans over time or volatile?
3
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0answers
35 views

Can body temperature affect the quality of sleep?

If so, how does it influence our sleep? And what can we do to improve the quality of sleep by adjesting our body tempurature?
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0answers
26 views

What are the molecular/cellular basis of pruritus ?

Could someone please explain the cells and molecules involved in the clinical phenomenon of pruritus ? I'm interested in a general view about the subject, but detailed answers will be appreciated. ...
5
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1answer
100 views

Where in the world does blue eyed whites originate from?

I know that there were no blue eyed people until ~6000 years ago due to a mutation and all blue eyed people have a single common anchestor. But where in the world does it originate? I assume it ...
3
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2answers
86 views

How does acupuncture work?

Can anyone actually tell me how acupuncture works? There are numerous websites with little actual explanation, but assert that it works. For example the below article: ...
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1answer
2k views

How long can human tissue last without blood?

I've heard it said various times that the body's tissues will begin to necrotize after being cut off from the blood supply for only a few minutes, but that can't be true. A few years ago, I woke up ...
3
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4answers
143 views

Can general soap kill bacteria?

I have read that general soap can kill bacteria by opening holes in the bacterial membrane. http://questions.sci-toys.com/node/90 However, I found some articles as well saying that it cannot. ...
3
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1answer
114 views

What causes the pain when a bone fracture is healing?

Why does a fracture still hurts when it is healing? I understand the pain at the beginning - the bone is not in its place, there is a pressure against the nerves, also the swelling pushes the nerves ...
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1answer
71 views

Transmission of HIV from Mother-to-Child Through Breastfeeding

If a mother is HIV+ and was on medications which would help her deliver a HIV negative baby, can the baby contract the HIV through her breast milk?
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1answer
63 views

Is there a blood panel lab test that measures all the hormone-producing glands?

I understand that there are gland-specific hormone tests, such as: Secretin: for the pancreas; and Prolactin/ACTH: for the pituitary; and PTH: for the payathyroid, etc. However, are there any ...
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1answer
70 views

What if there are no bacteria such as Streptococcus mutans

If someone removed all bacteria such Streptococcus mutans in her mouth by starving long time, or by some chemical method, would she never have such bacteria? In my thought, because S.mutans only ...
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0answers
12 views

Why do I wake up with morning wood? [duplicate]

According to this answer on a question about the brain, the answer implies that based on certain activities the human body is undergoing, the brain then diverts the appropriate needed resources to ...
8
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1answer
103 views

What happens to the food you accidentally aspire?

I'm well aware of health effects of aspiration of solid food and liquids, but I'm interested on what is the reaction of the body on the biological level to the strange body on our lungs. I ask this ...
2
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1answer
221 views

What is the global average BMI?

I have been looking for hours trying to find this number, and can't seem to get a straight answer. I've seen some studies that calculate the change in BMI, but for some reason they don't give you the ...
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1answer
36 views

Does exercising increase the rate at which UV rays are absorbed and cause affects?

Does exercising while in sunlight affect the rate at which the human body absorbs and reacts to UV rays? As sunburn is the secretion of fluids, increased dilation of blood vessels and inflammation of ...
1
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1answer
89 views

Is intelligence (or mental ability) genetically transferred (inherited characteristic) from the parent to the offspring or is it an acquired trait?

The question is simple- whether our mental ability i.e. ability to acquire and store knowledge and comprehend and analyse the stored bits, an inherited trait (i.e. genetically transmitted from the ...
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0answers
57 views

Are lines (wrinkles) on the human forehead skin related to science of (often worried) thinking?

It is the common observation that when we tend to think about anything, most often, we tend to make the conformation of raising the skin of forehead; from my observation this is the most common ...
2
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1answer
33 views

Why does mud therapy work by some pain related diseases?

Apparently, some users here agree there is no ion exchange through the skin. Mud therapy has some therapeutic effect for pain related diseases. As an anecdotal example, I experienced pain relief by ...
0
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1answer
38 views

How can rapid growth cancer get nutrients in vivo?

When I was little, before I get into biological studying, I read a news talking about cancer would be totally cured after decades. I still remember that researchers had a theory to claim if they could ...
32
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3answers
3k views

How could humans have interbred with Neanderthals if we're a different species?

To be clear, I'm not doubting that homo sapiens and homo neanderthalensis did interbreed: of that much I'm convinced. Within the past few years I've seen an upcropping of pop-sci articles discussing ...
2
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2answers
191 views

What makes diffculty to make a human bio-tooth compare to a mouse's? [closed]

Some time ago I read a news article that said a bio-engineered tooth based on a mouse's would be available around 2015. There was some research about it at King's College in the UK, and many other ...
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2answers
47 views

Rampant low Vitamin D

Why have people inadequate vitamin D status? Is it just (the lack of) sun exposure, or is it related to hormone and thyroid function?
2
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1answer
28 views

ATP to disassembly of nucleotide ratio

DNA Helicase, the enzyme that is responsible for tearing apart the strands before DNA replication, requires ATP to rip apart nucleotides. I have asked this question to several professors and they ...
0
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1answer
58 views

Are progenies factually half-clones of the parents?

Given that a "clone" (if anything, in the context of human cloning) is taken to be, as far as I have understood, a specimen possessing the same genome as his "father/mother", aren't all "non-cloned" ...
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1answer
60 views

Is it possible for a person to eat so many carrots that one turns orange?

I once read that Jerry Rubin (a famous 1960s activist) ate so many carrots that he turned orange. (This was in the East Bay Express, around twenty years ago.) I assumed it could be true, though he ...