promptme-f-sifi said: In response to your recent post about what is a dinosaur and what isn't, how do you tell the difference? This is something that's always perplexed me.
The problem with a word like “dinosaur” is that it’s really not very precise or descriptive. Scientists use much more precise terms when classifying and describing the species and groups under the general term “dinosaur” but most people just point at anything reptilian that lived a long time ago and call it a dinosaur.
pyranova said: Could you direct me to some blogs about human anatomy? I'm curious about the purpose of the cupid's bow in lips, but my searches are only coming up with cosmetics discussions or people critiquing if they love or hate them.
Hey followers, lhelp out pyranova and leave your favorite human anatomy blogs (not the NSFW kind, the science kind) in the reblogs/notes! The hive mind is always much smarter than me when it comes to matters like these :)
I’d rather talk about “Cupid’s bow”:
Named for its resemblance of a particular winged cherub’s amorous armament, the pinched curve of the upper lip is sometimes referred to as “Cupid’s bow.” It’s formed by the meeting of the upper lip with that little dimple that nearly all of us have beneath our nose, known as the philtrum.
So what does the philtrum do, besides look cute?
Nothing. Not for humans anyway.
The philtrum, our lip dimple (limple?), is just a byproduct of how your face formed. Early in your development, just a few weeks after you were put in the uterine oven to cook, your face began to take shape. Cells and tissues from the outer and middle layers of your still-formless body migrated and folded like sheets of embryonic origami. Two of those early tissues, called the nasomedial prominence and maxillary prominence, respectively, folded up like a cellular cinch-sack, with the tiny dimple beneath your nose being the seam where all that dermal dough was pinched together to make your face pastry. Follow me? It happened like so:
When this seam fails to fuse, it results in malformations like cleft lip.
The philtrum has a function in other animals, though. Let’s use my dog Oliver as an example, captured here in a particularly derpy moment this evening while we were playing fetch:
See that groove in the center of his nose? That’s his philtrum. Every time he licks his lips, a bit of saliva hangs there, drawn upwards from his mouth thanks to capillary action, keeping his big, dumb, adorable nose nice and wet. Animals like Oliver, who apparently depends highly on his sense of smell to navigate the world despite his uncanny ability not to be disgusted by his incredibly potent, but thankfully occasional, flatulence, rely on a wet nose to capture scent particles from the air. Dry nose? Less sniffs to sniff.
Since humans and higher primates rely mainly on eyesight to do our primate stuff, we are no longer under evolutionary selection to have a functioning, deeply grooved philtrum, so it’s faded over time into the dimple we know and (most of us) love today. Stephen Jay Gould might even have called it a spandrel.
Come to think of it, it may have an evolutionary function after all: It’s where you rest your finger when you say “Shh, Joe… be quiet. You’ve written enough.”
giantpredatorymollusk said: If every cell in our bodies is replaced in seven years, how do tattoos stay on?
RIGHT!? Isn’t that FREAKING COOL! Your skin cells only last for a few weeks, and yet your tattoo lasts YOUR WHOLE LIFE!
WELL! The outer layer of our skin is made of collagen, a flexible but durable protein. This is constantly sloughing off and being replaced from below as cells die leaving only their collagen-filled shells behind.
But when you get a tattoo, the needle punches past the outer layers of skin, doing quite a bit of damage. The result is that scar collagen forms around the dye that’s been placed in the dermis. Scar collagen, unlike skin collagen, doesn’t replace (which is why scars last forever.) The particles of ink are too large for white blood cells to surround them and carry them off to lymph nodes so they just sit there, surrounded by small amounts of scar collagen outside of your skin cells…pretty much forever.
This is the key to tattoo removal, by the way. Lasers are used to break the ink into smaller bits, so your white blood cells can take care of them.