central mesentery

hmm, i’d say mine is pretty short, but thick. sometimes textured... talkin about the hair, people. hey there, hairy humans, trace here for dnews. there are so many different types of hair– wavy, straight, fine, thin, thick, curly, bushy, wiry… some people’s hair is easy to comb, whileothers are constantly battling a tangled mess. but is there really an advantage to havinga certain type of hair? we’ve talked a bit about why we have hairat all in another dnews video, but needless

to say. we have it. fur and hair is the same thing. all mammals have hair, including us. hair is composed of keratin, a fibrous, resilientprotein that gives hair its strength. the keratin protein is made up of long chainsof amino acids bonded together, the most abundant of which is “cysteine,” which is ableto form strong bonds with itself, called disulfide bonds. that’s important because where these bondsaccumulate on the hair shaft influences the

shape of the hair! for example, in curly hair, the protein buildsup more on one side of the hair, causing it to curve, whereas in straight hair, it’sdistributed more evenly throughout. there’s even a condition called “uncombablehair syndrome” involving a gene mutation that doesn’t allow keratin to bond to thehair shaft correctly causing extremely dry, frizzy hair and endless tangles. but, keratin isn’t the only thing that changeshair type, the shape of the hair follicles --- the structures in your skin that growyour hair -- influence its shape and thickness. larger follicles produce thicker strands ofhair, smaller follicles thinner strands…

makes sense. but, if the follicles are say, oval-shaped,or asymmetrical, then the hair that comes out of them won’t be perfectly round; insteadit bends to one side, producing curls. think about it like gift-wrapping ribbon---whenyou run scissors along one side, it’ll curl. it’s a similar principle with an asymmetricalfollicle – one side is flat, the other curved, resulting in ringlets. frizz and texture are often associated withcurly hair because natural oils secreted by your scalp can’t move down the hair as easily. those oils trap moisture in the hair -- whichis why humidity makes curly hair even more

frizzy! but there’s definitely one advantage ofhaving curly hair – and it’s not what you think. curly hair actually tangles less than straighthair. yep! a study published in the american journalof physics found that the angle at which straight hairs bump into each other is most likelyto cause tangling. see, the outside of your hair -- called thecuticle -- consists of a series of overlapping keratin cells, like shingles on a roof.

if the hairs meet at a sharp angle, the cuticleshook onto each other. although straight hairs meet less often thancurly hairs overall, when they do, they tend to meet at steeper angles and thus are morelikely to hook and tangle than curly hairs. we all have different hair, but there’snot a hard evolutionary reason why. though there are a bunch of hypotheses asto how we got it. like one 2013 study in the journal cell whichfound a specific gene mutation that causes thicker hair. it emerged 30,000 years ago in central china,later spreading to africa and europe. that same gene mutation also had other effects,such as increasing the density of sweat glands.

the researchers believe that high humidityin east asia at the time may have given people with the mutation an advantage because theycould sweat more efficiently, and perhaps thicker hair simply propagated as a side effectof the gene. another study in the american journal of humangenetics identified two genes which cause curly hair in european descendents, but eventhey say the exact point when curly hair evolved is unknown. more research is needed to see what otherfactors could have been involved. but whether you’ve got stick straight strandsor corkscrew curls, hair is completely individual – so embrace what nature gave you!

and remember: it’s the size… (of the follicle)that matters… i hated my hair for a long time until i figuredout how to take care of it. it was a process, but now, i love it! or, what’s left of it… want to know more about hair? here are five weird uses for it...besidesjust keeping your head warm. also, check out this video from our friendsat seeker stories about how professional actors are teaching medical students how to interactwith patients. got any hair tips?

tell us in the comments, please subscribefor more dnews and thanks for watching.