49

What do you mean by siblings? If by siblings, you accept cases of individuals having the same father but not the same mother, then of course, it is possible! Below, I will assume you are referring to full siblings (eventually twins). Age gap between twins According to the huffingtonpost, there is a case of two twins that were born 87 days apart. On ...


28

The extra volume of fluid is due to the fluid retaining effects of high oestrogen secretion in a pregnant human female. After this high level of oestrogen subsides the extra fluid is mainly eliminated as: urination some is lost during parturition (labour) lactation to some extent as well Reference:A Textbook of Medical Physiology (South Asian Edition) ...


27

Yes, this can happen in non-twins. There is a rare phenomenon that can occur in humans (and some other animals), called 'Superfetation'. This is when some time during pregnancy, a woman has a second oocyte fertilized and implanted. This event is an entirely separate conception, and results in two fetuses of slightly different ages in the womb simultaneously. ...


21

The actual blood cells just get circulated out over time (e.g. broken down in the spleen). Eliminating the fluid is the easy part - consider how easy it is to drink a liter of water, absorb it and add to your plasma volume, and then filter it straight back out through the kidneys in a matter of an hour or so.


20

Pregnancy test, just like any test, has some non-zero false positive rate. So yes, of course a test could be positive when a man pees on it. Pregnancy tests work by detecting the presence of a hormone called Beta-HCG. This hormone is produced by both genders but is produced in much higher dose during early pregnancy. Teenagers also produce a relatively high ...


19

I have known kids who were 7 months apart in age - the younger one was a premature birth. No human intervention or other special circumstances required.


14

It's quite possible. Consider a couple who has problems conceiving children, so they get a surrogate mother who carries the couple's child. And six months later, with the psychological pressure gone, the couple conceives a child naturally. So you can have natural siblings, almost any time apart.


13

If there has been an ejaculation by the male, and semen is present, there is a chance of getting pregnant. Period. Teens really need to know that. I think you may have your terms confused - semen is the overall fluid released during an ejaculation, sperm are the cells with tails that are produced in the testes and fertilize the egg. At any rate, according ...


13

Women with uterus didelphys have two different uteruses, and hence can be pregnant with two sons at the same time. The time of fertilization for the two uteruses can be different. The wikipedia page also mentions cases of different birth dates for the children. There was a case where the births were 72 days apart.


8

Labor is typically divided into 3 stages: Stage 1: From the onset of contractions (true labor pains) to full dilatation of the cervix (which is about 10 cm) - this takes about 12 to 18 hours Stage 2: From full dilatation of cervix to expulsion of fetus - This takes about ~ 30 minutes Stage 3. From expulsion of fetus to expulsion of placenta - this takes ...


7

How do you define the biological limit? It very much depends on how you define a biological limit. If you prefer, it very much depends on how you define a human! Some women are completely sterile while others are highly fertile and there is genetic predisposition to that. How much "perfect" should the genotype of an individual be so that it is still ...


7

Medical science has reached the point where it is able to consider performing uterine transplants in genetically female (cis-female) patients born without a uterus. In the MedlinePlus report, First Uterus Transplant Planned in U.S. doctors at The Cleveland Clinic have plans to perform the first uterus transplant in the US sometime in 2016. The article ...


7

In short, sugars are absorbed quicker than proteins and fats because they pass through the stomach quicker and their digestion is simpler. Sugar can be absorbed through the mouth mucosa when applied as a sublingual gel, as discussed here on Biology SE: Is sugar absorbed into the bloodstream through the walls of the mouth?, but probably in much smaller ...


6

This is generally done by checking for the vaginal plug in the female after you have set up the breeding. If the plug is visible then it means that copulation has happened. However, this is not a foolproof test because the vaginal plug just indicates copulation and not pregnancy. This, nonetheless works in most cases and helps you in timing the pregnancy (...


6

Identical twins Twinning occurring at the two cell stage or afterwards, up to and including the 16 cell stage, which translates to days 1 to 3 after fertilization, results in diamniotic, dichorionic twins. Twinning at the 32 cell stage (day 4), up to and including day 6 results in diamniotic, monochorionic twins. The majority of identical twins split at ...


6

So I've dug a bit into how a 'normal morphological' form is defined and characterised, since assessing morphology into 'normal' and 'not normal' is always a very tricky thing. Looking into the method section of the source you cited, we get: All laboratories generating the data analysed here used standardized methods for semen analysis [...] The ...


5

The African bush elephant and the African savannah elephant are the same species (i.e., they are just different names for Loxodonta africana). According to here and here, the African savanna/bush elephant (Loxodonta africana) has a gestation period of 22 months. The only other African species of elephant, the African forest elephant (*Loxodonta cyclotis),...


5

Yes it is possible. Pregnancy tests detect human chorionic gonadotropin (hCG), which in a healthy male can be produced by the pituitary gland. hCG consists of two subunits and the urine tests target a metabolite of the beta subunit. The levels of hCG in healthy adult males are below the sensitivity of pregnancy tests, they are similar to the hCG levels in ...


5

Little harm comes from ABO incompatibility (that would have been a major problem with reproduction.) Rh incompatibility is more dangerous, though. If a fetus is Rh+ and the mother is Rh-, when there is mixing of maternal-fetal blood (at birth, but sometimes before that), the mother will form antibodies to the blood cell surface antigen. It doesn't usually ...


5

But many women (and doctors) still call it a period. It is not a period: Pregnant women can have some light irregular bleeding during pregnancy, but it should not be like a “normal” period. Some women can confuse this for their period because often it can come right around the time she was expecting her normal period. [...] It should not be enough ...


4

So it turns out it can occur. It's called Hemolytic Disease of the Newborn (ABO), and according to the article (the relevant citations are a book and some journals to which I do not have access), it is very rare, and severe cases are even more rare. Apparently anti-A and anti-B antibodies are typically of the IgM isotype, which cannot cross the placental ...


3

human gestation period According to the link gestation period doesn't vary much between great apes. I don't see any signs that human are becoming "more complex". In fact human babies are uniquely underdeveloped compared with other mammals (large brain size, upright posture)


3

Pregnancy is a biological process that has been very well studied by medicine. As a result, modern medicine helps a lot to prevent miscarriages and to prevent death of pregnant women. While the latter clause is correct (maternal - and infant - mortality is reduced with medical care), the former is not. Miscarriages have been a problem as far back as ...


3

Ovulation and menstruation don’t happen in normally cycling women at the same time. A basic outline of the hormonal cycle that triggers these events will make this clear. Proliferative (a.k.a follicular*) phase Beginning after menses (when the endometrium is thinned), the hypothalamus produces GnRH which stimulates the anterior pituitary to produce LH and ...


3

if mother is O- That means: group O in ABO system: anti-A and anti-B antibodies group Rh- in Rh system: no D antigen and no ant-D antibodies unless previously senzitized baby is any +ve blood group other than O+ ABO system: A, B or both antigens present Rh system: D antigen present So, the mother has anti-A and anti-B antibodies and her immune ...


3

After childbirth, the umbilical cord is either tied (similar to a tourniquet - the cord itself is not tied into a knot) or clamped to cut off the blood supply. It is then cut distal to the clamp/tie, separating the child from the rest of the cord and the attached placenta. The remaining cells die and dessicate, and the stump eventually falls off, forming the ...


3

"However if the sperm has X chromosome the embryo will survive to have the 46 XX karyotype and will start to grow as molar pregnancy." Complete molar pregnancy is diploid, and there is no fetal tissue identifiable. It is a disease of the placenta, a uterine tumor (cancerous in some cases, non-cancerous in others); fetuses do not develop from such ...


3

No. Making of cloth is only perhaps 30,000 to 40,000 year old (History of clothing and textiles), and body coverings of any form, e.g. animal skins, only around 100,000 years old (based on body lice). Females being smaller than males is much, much older than this. Chimpanzees, our closest relatives, similarly have smaller females (and don't dress in cloth);...


2

Basal metabolic rate for a particular organism is determined by the amount of calories that the organism needs for basal metabolic processes (i.e. basal energy demands). Since pregnant and breastfeeding women have increased caloric requirements (i.e. increased energy demands), then that means by definition their basal metabolic rate is increased.


2

Pregnenolone -the precursor of progesterone is principally converted to estradiol instead of progesterone.Thus the oestrogen:progesterone ratio increases prior to parturition. Fetal cortisol stimulates activity of placental 17 α hydroxylase/17, 20 lyase (CYP 17) enzyme, which catalyzes the conversion of pregnenolone to estradiol. Confinement of the ...


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