I had a dream last night. We re-did the ultrasound and you looked bigger and happier. You even had toes! Little webbed toes, but they were there. And you stretched out your little legs and arms into your gestational sac and the doctor was happier. I was happy too. 🙂
Maybe it was a dream of things to come. I’m hoping so. I’m feeling much more optimistic today. I know you’re in there. I know your little heart is beating. So, all mommy can do is try to be patient…..and track your growth of course! Ha!
Now that we have a more precise idea of where you are in age (6w3d today!) I can track, more closely, what’s going on with you. I found an amazing educational site on human reproduction, fertilization, embryology, systems development, and fetal development. It’s mommy’s new favorite site! So, here we go!
You are at a Carnegie human stage 13/14. Carnegie stages are a standardized system of 23 stages used to chronologically define early embryonic development. It is used only for the first 60 days of life and then you technically become a fetus. Yay, graduation! Here’s a chart to show you all the stages:
And here is a scanning electron microscope close-up image of what you probably look like right now:
In your ectoderm, your neural tube is still closing, the Caudal neuropore closes (the posterior or bottom end of your neural tube), and your forebrain begins to develop!
In your mesoderm, you have continued segmentation into somite pairs (portions of bilateral segmented tissue on either side of the notochord that will give rise to your skin, muscle and vertebrae!) and you’re working on pairs 21-29 right now.
Your overall body has a heart, liver, umbilical cord and early upper limb bulges and you form the shape of a C. You’re pretty cute if you ask me!
Courtesy of UNSW Embryology:
Central Nervous System
The central nervous system develops from the neural plate, a structure which appears on day 18. It is an ectodermal structure, extending along the surface of the embryo for much of its length. During the middle of the fourth week, an indentation – the neural groove – forms down the midline of the plate. This continues to deepen until the neural folds reach the 4th somite level, at which points the folds of the neural plate begin to fuse, forming the neural tube. The neural tube forms the eventual brain and spinal cord.
Simultaneously continuing during Week 4 is growth of the neural tube rostrally as 3 dilations:
These 3 vesicles of the neural tube are called the primary brain vesicles. The cavity within the tube forms the 4 ventricles of the brain and the central canal of the spinal cord. Later, these 3 vesicles split into 5, with each forming different areas of the central nervous system.
While the neural groove descends, the embryo grows and undergoes a series of folding processes. Although the embryo and amnion grow, the yolk sac does not grow, causing the embryo to fold laterally, caudally and cranially around the yolk sac. This folding process bends the neural tube, forming 2 noticeable flexures in the Stage 13/14 embryo.
Tracking your development like this is really fun! I love you, monkey.