Recent comments in /f/askscience

UrbanSpartan t1_j50d44r wrote

Reply to comment by L0cked4fun in Is there any difference in efficacy when a vaccine is administered somewhere other than the upper arm (e.g. on the foot)? by MercurioLeCher

The deltoid is the shoulder muscle. Anything 2ml and less can be appropriately administered in the deltoid. It would be highly unusual if not impossible for them to enter into the joint space with the needles used for a IM injection. Additionally, even if they did it would have no effect on your rotator cuff, which is just a group of 4 muscles. Its not one physical structure like most people tend to assume. You need at least a 1.5 inch needle to enter into the glenohumeral space, the needles in IM injections are usually 1 inch or less and they are not going all the way through l. I'm 6'5" and I've never had an issue getting an IM shoulder injection. I also do joint space injections all the time and you have to be very specific in where you aim and how to even enter into the space as the acromion blocks most of the joint off.

44

SloeMoe t1_j50bvdg wrote

Reply to comment by fruticosa in Given that reproduction is difficult or impossible when both animals have different numbers of chromosomes, how did so many species evolve to have so many different numbers of them? by MercurioLeCher

Sounds kind of like forking in software development. So let's say it's a sexually reproducing species. At gametogenesis, the chromosomes are doubled, how does that sperm with double chromosomes sync up with non-doubled eggs from any other individual in the population? Beyond that, how would any offspring find a suitable mate, seeing as they have dissimilar chromosome counts now?

3

ceelo71 t1_j50ahuf wrote

Reply to comment by LiquidPizza in Is there any difference in efficacy when a vaccine is administered somewhere other than the upper arm (e.g. on the foot)? by MercurioLeCher

Agreed, physicians are definitely capable of giving an IM shot, but rarely do. This may have been a thing a long time ago, but is not done (at least in the US) currently. Source - have been a practicing physician for twenty years.

It’s like starting an IV - the only docs that are good at that are anesthesiologists. They even know how to set up the pumps, mix IV meds, etc. if someone were crashing and needed an IV and infusion started, and I was the only one there to do it, the prognosis would be poor.

8

ikefalcon t1_j508nej wrote

Reply to comment by VictoriousEgret in Given that reproduction is difficult or impossible when both animals have different numbers of chromosomes, how did so many species evolve to have so many different numbers of them? by MercurioLeCher

As the previous commenter said, human chromosome 2 has nearly identical sequences to chromosomes 2a and 2b in the other great apes. It’s believed that human ancestors like Neanderthals had 23 chromosome pairs like humans.

Also, chromosomes usually have 1 centromere (center link between pairs of chromatids) and 2 telomeres (basically end caps of the chromosome). Human chromosome 2 has a vestigial (unused due to no longer being needed) extra centromere and 2 vestigial telomeres found inside the chromosome sequence.

This is pretty good evidence that there used to be 2 chromosomes before they fused together.

55

LiquidPizza t1_j507jdq wrote

Reply to comment by ceelo71 in Is there any difference in efficacy when a vaccine is administered somewhere other than the upper arm (e.g. on the foot)? by MercurioLeCher

Doctors are perfectly capable of giving an intramuscular injection. It doesn't take longer than an hour to learn how to administer them and even that is being generous.

But you're definitely correct in that it does not happen often that doctors give shots especially in a hospital setting.

EDIT: for intravenous injections I would agree with you as nurses (depending on which specialty) are a lot more experienced and do this much more regularly than doctors.

10

dkysh t1_j506qis wrote

Reply to comment by fruticosa in Given that reproduction is difficult or impossible when both animals have different numbers of chromosomes, how did so many species evolve to have so many different numbers of them? by MercurioLeCher

Another (close) example: Human's chromosome 2 is the result of the fusion of other 2 smaller chromosomes present in all other great apes, chromosomes 2a and 2b.

The content of chr2a+2b is almost identical to human's chr2, even with genes following the same order. This makes them much more compatible and probable to recombine and produce viable offspring.

68