Never have the immeasurably complex events of the first 4 weeks of human development been so succinctly and eloquently précised.
This is embryology.
No really. Think about it…
- We start life as two cells united during the events of fertilization.
- The cells fuse and proliferate to form a cluster.
- The cluster reorganizes to form a flat, two-layered germ disc
- This quickly transforms into a three layered disc during an event known as gastrulation.
- The three layers are the famous germ layers: ectoderm (dorsal, sky blue), mesoderm (middle, red) and endoderm (ventral, yellow). The illustration shows these layers sandwiched between some extra-embryonic structures like the yolk sac (orange) and amniotic cavity (turquoise blue).
Fact: Babies are not flat discs. This three-layered disc must undergo some incredibly complex changes in order to become much more baby-like…right?
Double Fact: Babies are not actually that complex. They are just tubes surrounded by organs, muscles, skin and bones. Parents know only too well that they have a mouth at one end for putting food in and an anus at the other end for elimination of waste.
So the question is, how do you make a tube from a flat disc?
The answer is remarkably simple really. You just roll it up.
The less sticky way to make a baby…Take three different colored sheets of paper each representing a different layer of the germ disk. One blue (ectoderm, on top), one red (mesoderm, middle) and one yellow (endoderm, bottom). Now make a tube by rolling them. Congrats! You just made a baby!
Something similar happens to the germ disc. It undergoes lateral folding (the sides of the disc roll underneath itself; not shown here) and cranio-caudal folding (where the head and tail curl ventrally; shown here).
Just like your paper baby, this process essentially ensures that the outer layer of the tube is covered in ectoderm (blue) - this becomes the baby’s skin. The inside of the tube becomes the baby’s digestive tract from mouth to anus and is lined with endoderm (yellow). And, almost all of the baby in between is formed from mesoderm (red).
When baby gets older, goes out on its first date, and has that first kiss. He/she temporarily unites his/her endoderm lined digestive tract with the endoderm lined gut tube of their partner. Thus creating a continuous tube from the butthole of kisser A to kisser B.
Ironically, if more people thought about this statement while they were actually kissing, there would actually be much fewer babies in the world.
- Quote is adapted from a statement I stumbled upon here
- Gif adapted from an animation available here