This is a video of zebrafish going through the most important portion of development, gastrulation, and then seemingly having a massive fit (they are probably just starting to move about, the films sped up a lot so it looks a bit odd). It’s a little bit crazy that we can see something like this happening right in front of us, but that is also essentially how humans develop.
Embryology has several distinct phases, these include:
- Cleavage- the formation of many cells from one.
- Gastrulation – The organising of these cells into different layers. (I.E. for brain and skin in the ectoderm layer, muscle and bones in the mesoderm layer and most of the other organs in the endoderm layer etc.)
- Neurulation – the formation of the nervous system.
- Organogenesis – the formation of our organs.
If you watch the video. They all start off dividing. Gastrulation starts in the bottom left at about 0.06 (when the big bulgy bit, which is all of the cells, suddenly start to move around it). In the same cell neurulation would have occured around 0.12, but you can’t see it. Organogenesis would have started after 0.20.
We go through the same process, but it takes months, not days.
In fact we’ve finished most of these processes by the end of the third month. After that most of the time is spent maturing and developing our organs to perfection, especially the brain and lungs. 2 of the biggest problems with premature births are:
1) Poor lung development (so baby can’t breathe once it’s born). We can help this by giving them a breathing tube (intubate), but this is not a perfect intervention.
2) Brain damage, not enough oxygen gets to the brain (usually due to the poorly developed lungs) and as it hasn’t fully developed yet it is more susceptible to major damage.
Most other organs are working quite well. The digestive system might need take a bit of time to acclimatise to milk, but the heart has been beating pretty well since 8 weeks.
As a testament to how important our brains are, the biggest reason as to why we stay in the womb for so long is to allow our brains to develop. Even in spite of this, causing our mother so much pain during birth because of our big heads, the brain still won’t be fully developed until over a year after birth.