The Human Body: 35 Astonishing Human Body Facts – Part 6

11Antibiotic Side Effects

Antibiotic Side Effects

Indigestion, diarrhea, and other stomach issues are common side-effects of strong/broad-spectrum antibiotics because they kill nearly all of the healthy gut bacteria. Some bacteria though can escape due to a combination of factors, some are replenished from the appendix (turns out it is now thought to be a reservoir), and food. Probiotics have been found to be entirely useless in these cases.

In some extreme cases, doctors might recommend stool transplants, where a stool sample is brought in from a “stool bank” which is then transplanted into the patient via enema or an oral capsule.

12Olfactory Fingerprint

Olfactory Fingerprint

Armpit sweat glands are known as apocrine sweat glands, and instead of producing just sweat, they also produce a mix of proteins and lipids. The bacteria on your skin love that stuff and eat it up, producing waste products in the process. It's those waste products that cause pungent armpit odor.

There’s a reason why we secrete these oils and proteins in the first place. Hair under our arms and between our legs acts as a dry lubricant. When it isn’t enough (during intense exercise or prolonged walking/running), these secretions help reduce the friction and damage to the skin.

Each person has a unique combination of bacteria on their skin which in turn makes them have a unique smell, kind of like an olfactory fingerprint. Humans still use it to recognize family and friends from everybody else on a subconscious level.

13Travel Tiredness

Travel Tiredness

There’s a reason you feel tired by just traveling in a vehicle and doing nothing else. There is lots of data on the “stressors of flight” (many of these stressors are also present in automobiles). As the vehicle moves, the sway and direction change causes you to make micro-adjustments to keep yourself upright. These micro-movements cause your muscles to be continuously working (even if you don't realize it).

Studies done by the US Airforce reports that consistent exposure to aircraft vibrations can lead to fatigue and an increased chance of health problems.

14Skin Tensile Strength

Skin Tensile Strength

Human skin is amazingly resilient and has a shockingly high tensile strength, which is roughly 27 MPa (MegaPascals), whereas High-Density Polyethylene (milk jug plastic) is only around 15 MPa and ABS (LEGO plastic) is only about 50% stronger at 40 MPa. When someone gets big rapidly like during puberty, muscle growth, or pregnancy; the skin won’t tear but this will only result in stretch marks.

15Breast Health

Breast Health

Estrogen alone is not solely responsible for breast development and size. It is a complex interaction between genetics and several different hormones which includes steroid hormones, estrogen and progesterone, growth hormone, insulin-like growth factor 1, and prolactin.

The best (but not the only) predictor of your breast size will be your other female relatives. Having high estrogen, just like having high testosterone, is not even necessarily a good thing. It’s associated with an increased risk of depression, anxiety, hair loss, thyroid disease, heart attack, stroke, blood clots, breast cancer, and ovarian cancer. It also doesn’t make you more likely to conceive as it causes decreased sex drive and irregular periods.

16Food Preferences

Food Preferences

Children tend to be more sensitive to bitterness, which is apparent in foods like broccoli and Brussels sprouts. This is an evolved defense mechanism because poisons are often bitter-tasting. As we grow, we learn which foods are poisonous and which aren't, so we don't need the same sensitivity and through evolutionary pressure, we lose the sensitivity over time.

17Blood Taste

Blood Taste

When you complete a quick, strenuous exercise, some excess hemoglobin is released from your blood cells into the lungs due to increased heart rate and the resulting increased blood pressure, which is then carried to your mouth during an exhale. Hemoglobin is made up of iron. This is why you get a metallic blood-like taste when you thoroughly exhaust yourself.

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18Viruses & Autoimmunity

Viruses & Autoimmunity

Some viruses are structured in a way that when antibodies necessary to disable them are activated, they also become harmful to the human body itself. Many forms of kidney failure in the young are triggered by the immune reaction to streptococcus. Many forms of type I juvenile diabetes are thought to be caused by the body’s immune response to a viral infection. This is in fact the mechanism presumed for a number of autoimmune diseases that appear to be precipitated by a viral illness.

19Reduced Immunity in Old Age

Reduced Immunity in Old Age

The thymus is an important immunological gland located in your upper chest that produces T cells. These are important white blood cells of the immune system. This gland begins to deteriorate after you hit puberty, though it doesn't fully degrade until old age at which point it essentially becomes non-existent. This is the reason why with aging it becomes harder to heal from illnesses and why young kids tend to bounce back faster after illnesses.

Basically, our immune system starts to shut down as we get older because we’re simply not meant to live so long. There's no biological reason to live very long, just sentimental reason.

20Gut Feeling

Gut Feeling

When you have a “gut feeling” it’s the subconscious part of your brain triggering a mild fight or flight response. This happens when the always watching and listening subconscious part of your brain notices something that the conscious part of the brain was too distracted to notice. The hypothalamus then signals your adrenal glands to release adrenaline to give your body some extra strength, so that you can either run faster or fight harder.

Among other things, adrenaline will cause your bowels to contract and your blood vessels to expand. This is what that stomach sensation basically is and why some people will literally sh*t themselves during a high-stress situation.

It is also worthwhile to point out that the gut feeling can be sometimes completely wrong and you can see extreme examples of this in people with anxiety disorders, who experience way more “false positive” alarms.

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