98

Blood is not a good source of water. 1 liter of blood contains about 800 mL of water, 170 grams of protein and 2 grams of sodium (calculated from the composition of lamb blood). When metabolized, 170 grams of protein yields the amount of urea that requires 1,360 mL of water to be excreted in urine (calculated from here); 2 grams of sodium requires about ...


38

A single molecule of rhodopsin (actually the cis-retinal bound to it) can and actually does react to one photon (Purves et al. Chapter: Phototransduction in Neuroscience). It has been estimated that a single light-activated rhodopsin molecule can activate 800 transducin molecules, roughly eight percent of the molecules on the disk surface. Although ...


36

Can a cancer cells from someone else's body cause cancer in a healthy person? No. Cancer cells from another person cannot cause cancer in a healthy person. The rare cases of transmissible tumors all involve unhealthy or not yet developed persons. Transmission of tumor cells from one individual to another happens, but is quite rare, and in all cases ...


28

Before OP edited his/her question, it was a little unclear whether the question was only about humans. The following answer is more general than asked as it also considers cancers in non-humans Most cancers are not transmissible but some are. We call them (clonally) transmissible cancers. Transmissible cancers The most famous case of transmissible cancer ...


28

A recent study published in Nature by Tinsley et al. Direct detection of a single photon by humans found that it is possible for dark-adapted humans to respond to a single-photon stimulus, but only rarely. They used a source which created pairs of photons, and used one of the pair to determine whether the subject may have been exposed to a single photon. The ...


23

Your best bet is the Terminologia Anatomica, which is the international standard for anatomical terminology. The 1998 edition is freely available. It lists only a few named tendons though, which is consistent with my experience as an anatomist: very few tendons are named separately from the muscles to which they are connected. Central tendon of the ...


22

You're talking about long-wave UV, or UV-A radiation. In the 80s, experts claimed that this was a safe wavelength. Protection against UV-A was not part of sunscreen in the early days. Consequently, UV-A was (and still is) used in tanning beds due to its perceived safety over UV-B. However, a lot of research has been done since. UV-A is well understood now ...


20

(my comment reiterating the answer seemed useful, so I've reproduced it here) There are "NMDA receptors" in our body. There is not NMDA naturally in our body*. "NMDA receptor" is just a name people gave to one of the receptors that normally binds glutamate. They could have called it something else, like the "slow glu receptor", or "Glutamate Receptor A", ...


19

You can drink blood of course to a minimalistic amount (eg- a few teaspoons ) and also if blood is free from pathogens. But it should always be in very small amounts and from suitable donor. Here's why The strange fact is, blood, when drank, is toxic. When confined to places where blood is supposed to be — such as the heart, vessels, and so on — it is ...


16

Our immune system does react to horse antibodies, but as with any adaptive immune response it takes some time for the response to develop. In the weeks before our immune response fully responds to the horse antibodies, the infused antibodies can have their effect. If you then have a second infusion of horse antibodies, the immune response would not only ...


13

The FMA lists 705 tendons, but note that it includes separate terms for left and right instances. As @kmm says, many of these simply shadow the list of skeletal muscles (and is likely incomplete). You can browse the list on OLS, or if you want to extract a table you can query this SPARQL endpoint, just type in the query here: SELECT DISTINCT ?x ?v0 WHERE { ...


12

The topic is reviewed in a freely available Nature article, from which the figure below (I have added the labels ‘Hominid’ and ‘Human’) is taken. As can be seen it is thought that the lines leading to the ancestor of Neanderthals/Denisovans and that leading to modern humans diverged before humans had left Africa; and that the lines leading to Neanderthals ...


10

Here is a specific account of a person surviving at sea drinking turtle blood, while eating some fish and drinking some rain water. Several peoples have a habit of drinking raw animal blood, at least for ritual purposes; here is a recent account. They probably drink more than a few spoons full so that the Lifescience article quoted by Ishi appears alarmist.


9

No, the human brain does not produce nicotine. The brain has nicotinic acetylcholine receptors, but the endogenous agonist for these receptors is acetylcholine, not nicotine; they aren't named "nicotinic" because they are for nicotine but just because nicotine happens to act on them. Many other human receptors are named similarly, based on discovering the ...


8

They ran out of samples Their test is destructive, they can't test the same sample twice. They planned out a number of samples to test for each time period and tested them. At the end of six weeks, they were done. It doesn't really matter The point of the paper is that HCV is infectious long-term on surfaces when not cleaned properly, indicating there is ...


8

Are all genetic disorders inherited? Not all individuals with a genetic disorder inherited that disorder. Some genetic disorders are caused by spontaneous mutations. Is cancer a genetic disorder? Yes. The seminal paper by Hanahan and Weinberg, the Hallmarks of Cancer, is a good place to go to get a sense of what we understand cancer to be. This paper is ...


8

Tarrare Tarrare was a showman who was renowned for his insatiable appetite including eating cats, dogs, and snakes sometimes raw. He is also said to have eaten many inedible items. At the time, he was alleged to have committed cannibalism of a 14-month-old baby and was caught in the act of cannibalising cadavers by hospital staff. He was given away as a ...


8

Short Answer: As the comments mention, this is a hot topic for pseudoscientists to use as a selling point for their supplements. There is limited evidence that dietary acid intake significantly alters bone resorption, especially in the setting of normal renal function. This paper should answer all of your questions (emphasis mine): Frassetto, Banerjee, ...


8

Technically, we can sense the individual photons. Here is an quote from a cellular biology textbook: "Absorption of a single photon of light induces a conformational change in the rhodopsin molecule, which transmits a signal to a heterotrimeric G protein (called transducin ), which activates a coupled effector." (Karp's Cell and Molecular Biology 8e, 603). ...


7

The endometrium changes throughout the menstrual cycle in response to hormones. During the first part of the cycle, the hormone estrogen is made by the ovaries. Estrogen causes the lining to grow and thicken to prepare the uterus for pregnancy. In the middle of the cycle, an egg is released from one of the ovaries (ovulation). Following ovulation, levels of ...


7

A lot of sexually active adults carry one or another strain of HPV but most do not develop cancer. You can carry HPV — and spread it to others — without showing any symptoms yourself: HPV infections are so common that nearly all men and women will get at least one type of HPV at some point in their lives. Most people never know that they have been ...


6

When the mother eat beans, the fiber (oligosaccharides) from them is not digested in the small intestine, so it travels to the large intestine, where normal intestinal bacteria break it down to some absorbable nutrients (like short-chain fatty acids) and gas that is largerly expelled (fao.org). Some gas can be absorbed into the blood and then removed by the ...


6

How are the lung and chest wall coupled? You have your answer in the text: the surface tension between the lungs and the chest wall And as you say, it is very much like there is a physical-contact adhesion force between the lungs and the chest wall A good, medical school level anatomy textbook will walk you through this. Moore's Clinically Oriented ...


6

It's well known that obese patients have slower wound healing, but the specific cause isn't known; most likely there are multiple causes acting together. The correlation between obesity and deficient wound healing has long been established. ... Substantial evidence exists demonstrating that obesity is associated with a number of postoperative ...


6

Preamble The question suggests unfamiliarity with the nature of biochemical oxidations and their relation to energy transfer in biology. The naïve reader is recommended to consult a text for a coverage of this subject: all I feel is appropriate here is a general summary followed by a brief indication of the key reactions. General principles of energetic ...


5

I suggest you read this excellent review by Luca, Perry and DiRienzo: Evolutionary Adaptations to Dietary Changes, Annu Rev Nutr. (2010) 30: 291–314. I quote: The evolutionary history of hominins has been characterized by significant dietary changes, which include the introduction of meat eating, cooking, and the changes associated with plant and animal ...


5

There are many people worldwide who are exposed to rabies and don't die (they get treatment), but there are very few of these cases where people don't die after rabies has entered the central nervous system, and even fewer who didn't receive post exposure prophylaxis before the virus reached the CNS. Rabies isn't as rare as many would like to believe, ...


5

Viruses, in general, are obligately pathogenic i.e. they don't usually co-exist (as commensals or symbionts) with our body cells. Their mechanism of survival involves usurping of the host cell machinery to produce their own proteins and genetic material. However, as pointed out in the comments, there are some viruses such as the GBV-C which can infect the ...


5

Spinal nerves are mixed nerves containing afferent and efferent neurons of various types. Anatomically, they protrude from the spinal column bilaterally at each vertebral level. They contain both myelinated fibers (e.g., A fibers) and unmyelinated fibers (e.g., C fibers). The answer is (c): both myelinated and unmyelinated. Please note that spinal nerves ...


5

The histogram you show isn't a distribution of age-at-death for individuals, it's a distribution of life expectancies for different countries. The post you link takes data from a table on this page. Interpreting the histogram you posted, we see average life expectancy seems to hit a wall around 85. This does not mean that individual human life span is not ...


Only top voted, non community-wiki answers of a minimum length are eligible