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105

Apparently you're not the first person to notice this; in 1895, a German nose specialist called Richard Kayser found that we have tissue called erectile tissue in our noses (yes, it is very similar to the tissue found in a penis). This tissue swells in one nostril and shrinks in the other, creating an open airway via only one nostril. What's more, he found ...


45

This is natural phenomenon called the nasal cycle. It is discussed in this paper by Telles et al. (1994), among many others. The nostrils are used on an alternating cycle of about 2-3 hours, controlled by the autonomic nervous system. If you notice alternating congestion, that also seems to be coupled to the nasal cycle (Hasegawa and Kern 1977, 1978). ...


34

Humans can, to some extent, be scaled: While most humans are two meters tall; the human body essentially works throughout the entire range from around a meter to around two and a half meters, although you tend to run into problems at the extremes. However, outside of that range you run into the tyranny of the square-cube law: As you scale a creature (or, ...


14

Hemoglobin molecules used to manufacture these products are not contained by a red cell membrane, and when released into the vasculature, these molecules rapidly scavenge nitric oxide.This can result in systemic vasoconstriction, decreased blood flow, increased release of proinflammatory mediators and potent vasoconstrictors, and a loss of ...


12

As others have said, this phenomena is called the nasal cycle, a process controlled by the autonomic nervous system that alternants congestion between your nostrils. Mentalfloss of all places has an article about this that explains: ...it makes our sense of smell more complete. Different scent molecules degrade at different rates, and our scent ...


10

The female breast is composed primarily of fat and connective tissue plus lobules and ducts for milk production and delivery. The pectoralis muscles form a thin layer beneath the breast, as seen in the figure in the link. An athletic female can enlarge the size of the pectoralis muscle and the laterals muscles, just as male athletes can enlarge their "pecs" ...


8

Fracture healing occurrs in several steps: haemorrhage: blood and surrounding cells fill the space created by the fracture. fibrous callus: chondrocytes colonize the fracture space, with neovascularization. bony callus: osteocytes colonize the fracture space and rearrange in woven bone remodelling: in long bones, woven bone is remodelled into lamellar bone ...


8

Short answer: The genes that encode eye color do not change, but the pigments in the eye can change due to external factors like diseases of medication. Long answer: Yes, it is possible that the eye color of adults can change, and it can also only happen to one eye. It is then called Heterochromia. There are two possibilities for different colored eyes, ...


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

This is a well worded question. There are more reasons than the following but the most apparent is hemoglobin production and its transport. The erythrocyte is a cell whose structure is optimal for its function-the production and transport of hemoglobin. It lacks a nucleus and organelles so that it can devote almost 100% of its energy to hemoglobin ...


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 ...


6

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 ...


5

When you bend your fingers, they all arrive at the same height. I would tend to think that their lengths differ when you keep them straight because they need to have similar length when you bend them to grasp something. And I guess that there is some optimal length (when bended) for fingers to grasp things. It is nothing but a quick hypothesis. But it ...


5

Flexion: the movement that decreases the angle between two parts [1]. Examples: clenching the hand into fist, sitting down. Contraction: the property of muscle to generate tension when actin and myosin filaments are crossing. There are a few types of contractions. The isometric contraction is when the muscle generates tension but its length doesn't change ...


5

As @WYSIWYG pointed, muscular atrophy is the main cause for height decrease. A spine injury leads to neural impairment and paresis / paralysis. This affects directly muscular trophism. It also limits physical activity, this being another favoring factor for muscular atrophy and overweight issues [1]. Association of bone degenerative processes (osteoporosis, ...


5

They don’t meet. Some framework: Spinal nerves contain motor, sensory, and autonomic fibers. Each of these have different pathways. Spinal nerves don’t go to the brain. Rather, they synapse in the spinal cord with other neurons which in turn go to the brain (sometimes requiring one more synapse). In the case of motor neurons, we talk about upper and ...


5

They would die. Let's imagine that we perfectly cut a person down the middle. That would mean cutting the spinal cord in half, probably damaging the tissue so much that the remaining half wouldn't work well. The liver would be gone. The intestines and bladder would just be open. The heart would have to be adjusted to the left. The surgery would probably ...


5

Is there a visual demonstration I can see of approximately how "packed full of cells" the brain actually is? Yes. You can inject tracers in the CSF (Cerebrospinal fluid) or in the ventricles and monitor them. In this study, the authors have injected a fluorescent tracer in the CSF and used a direct imaging. We used in vivo two-photon imaging to ...


5

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 ...


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

You cannot change the oxygen concentration of inhaled air in the absence of an external source of oxygen. However, you can use your lungs at their maximum capacity doing this: breathe deeply: =increase tidal volume. Your muscles will inflate your lungs as much as they are able to, inflating parts of the lungs that were not fully inflated (atelectases) in ...


4

This looks like a misinterpretation. Because collarbone is the only horizontal long bone of the human body [1], it is the first to fracture when falling on the shoulder. Its fracture can affect many structures: The muscles involved in clavicle fractures include the deltoid, trapezius, subclavius, sternocleidomastoid, sternohyoid and pectoralis major ...


4

They are actually different. INTERVERTEBRAL FORAMINA is actually spaces between adjacent vertebrae which gives passage for spinal nerves to exit. Whereas, VERTEBRAL FORAMINA forms vertebral canal. Source: Organization of the Nervous System: An introduction for students in the Human Anatomy Course


4

Vision deteriorates for both reasons, but I'm not quite sure how to separate the effects of aging from wear and tear. Cataracts are the leading cause of blindness in the world. Ways in which environment (which falls under the category of wear and tear in my book) affects cataract formation: UV light: people living at high altitudes (e.g. Tibet) have ...


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, ...


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. ...


3

Cortisol produced from the zona fasciculata of the adrenal cortex is directly caused by stress. According to http://en.wikipedia.org/wiki/Cortisol Cortisol stimulates gastric-acid secretion. Cortisol's only direct effect on the hydrogen ion excretion of the kidneys is to stimulate the excretion of ammonium ions by deactivating the renal glutaminase ...


3

With nearly 40,000 years of natural selection on eyesight, prior to the invention of eye glasses, there needs to be a better explanation than the effects of 'modern' technology. There are two likely reasons for the persistence of "poor" eyesight in humans. First, humans are social animals and live in groups. Within groups there is frequently a division of ...


3

Remi.b and Potterbond007 have put forward excellent answers. Would like to add something.. One of the reasons that Myopia (near sightedness) happens is because of use of eye in work like reading, which requires working with close objects. I don't think there was much working with close objects in the past. So very few people with myopia might have been ...



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