Q: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, help 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.”
What does a 375 million-year-old fish have to do with Sonic the Hedgehog?
I’ll give you a hint: It has to do with the evolution of thumbs! To know the rest, you’ll have to watch this week’s It’s Okay To Be Smart. Do it. Do it now.
Joining me this week is none other than Dr. Neil Shubin, discoverer of the famous Tiktaalik fossil. He’s got a three-part series called Your Inner Fish premiering this Wednesday at 10 PM Eastern on PBS. It’s basically just like this video, only with fewer Sega Genesis references and more Arctic paleontology expeditions.
I’m 100% not sorry for all the thumb puns this week :)
This is a fish.
Well, a fish embryo. Zebrafish (Danio rerio), a model of vertebrate developmental biology, to be exact.
This video shows the intricate migration of all 16,000 cells in an 18-hour-old fish embryo, and I promise you, it is the coolest thing you will see all day.
From nose to toes to brain to bones, the development of complex multicellular creatures from the humble beginnings of a single cell is the result of nature’s most delicate and gorgeous chemical ballet. There are so many waves of signals, so many interacting gradients, in order to define up from down and left from right and front from back, using only proteins and RNA. It’s a wonder that it works at all.
A wonder, indeed.
Bonus: If this tickles your mitotic fancy, you’re going to want to check out these 3D fruit fly development GIFs.
In 1905, E. G. Conklin published a remarkable fate map of the ascidian embryo. He showed that “all the principle organs of the larva in their definitive positions and proportions are here marked out in the 2-cell stage by distinct kinds of protoplasm.” This study of cell lineage has been the basis for all subsequent research on the autonomous specification of tunicates. The color plates of this study are considered to be some of the best examples of embryological illustration and descriptive anatomy.
It takes so much division in order to come together.
A Wrinkle In Time
A developing fruit fly embryo, one of the workhorse organisms of developmental genetics, captured in four dimensions using an amazing new microscopy technique called lightsheet fluorescence microscopy. Fluorescent microscopy has allowed us to decipher the inner workings of biological machinery for decades, but observing those glowing labels over periods of hours or days at a time has been difficult.
A fluorescent label, the chemical beacons that give off light when excited by certain wavelengths, can only shine for so long before running out of quantum juice. This new technique uses a thin, sheet-like laser beam to gently illuminate only a thin slice of a specimen at a time, it can be used on living organisms over a period of many hours.
Computers assemble gigabytes worth of 2D images into 3D structures, and those are laced together on a timeline to make movies of cellular dynamics. The random dots in the foreground and background are reference beads to orient the images.
Now for the good stuff! Watch this fly embryo evolve before your eyes from a blobby grain of rice to a ridged worm, sculpted only by the power of overlapping chemical gradients.
(more lightsheet goodies at Cell Picture Show)
Dance of Development
I enjoyed the fruit fly embryonic development video from this post so much, I decided to animate it. Grow, little alien … grow like the wind!!!
My short ode to development, inspired by the image above, (via biocanvas):
Epithelial cells line surfaces and cavities throughout the body, forming skin, glands, and tracts. This mouse embryo has been genetically engineered to allow for the visualization of epithelial cells, showing the pattern of whisker placement on the face.
Image by Evan Heller, Rockefeller University.
The dance of biological development tops our best ballet or even our most magnificent marches. And it is truly a dance, as this video of a developing fruit fly embryo makes beautifully clear:
Those cells, darting to and fro! They are pulled in and out of furrows, sensing the position and identity of their neighbors, migrating and multiplying at the whim of invisibly overlapping chemical gradients. It’s a journey in both space and time, the emergence of greater form from a horde of interconnected individuals.
The whisker patterns of the mouse above are just one of the many awe-inspiring end results of developmental organization. While only a few of those nodes will sprout whiskers, the larger pattern drawn by development can be seen radiating outward toward the tail like rays from the sun.
These relics of organization often remain invisible in adult animals, although sometimes they do show through (like when humans have “stripes”). Jason Silva has said that “to understand is to perceive patterns.” I offer this as an accompanying idea: To exist at all is to emerge from the sum of patterns.
Animal Eye Close-Ups
Jeepers creepers, where’d you get them peepers?
Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point.
That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this:
Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from.
And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began.
Hello, Little Fishy!
Enjoy this virtual microscope, and explore a zebrafish embryo down to the individual cell! All without leaving your computer or spending those pesky hours preparing it in a lab.
This species of fish, Danio rerio, is used in labs around the world to study development. Especially eye development, because … well. it has a huge eye.