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Brain Development: Neural Tube Formation

Brain Development: Neural Tube Formation

The brain, in all its complexity started out from the fertilization of a follicle.

It will take a long and delicate process for the baby’s brain to form.
Let’s look at the process a little closer.

As the morula developed, the complex of cells start differentiating until we are left with a trophoblast containing the future ectoderm and entoderm.

Formation of the Neural Tube

At around 16 days, we start seeing the differentiation of cells. We have the future ectoderm, the future endorderm, and the future mesoderm. From the mesoderm develops a sort of tube that is called the notochord.

At the beginning of the 3rd week, the midline mesoderm starts releasing a chemical signal that triggers the ectoderm to thicken and create a sort of plate: the neural plate. This tiny neural plate is responsible for the creation of the entire nervous system!!

Neural Tube Formation

Neural Tube Formation. Credit: Abitua

The neural plate then starts to cave in forming what we call the neural groove.
By the end of the 3rd week, the neural groove is so pronounced that the sides (the two folds) start to fuse together; this is the creation of the neural tube.

Let’s pause for a minute here. If you look at the pick picture, the neural plate, the neural groove and the neural tube all refer to the “same” thing, at different times. It’s just as if we were taking a look at you at different points in time. At some point it’s the “young” you, then the “adult” you, then the “old” you. While each stage might look slightly different, they all refer to you.

Here, think of “neural” as being a name, and “plate,” “groove,” and “tube” as being different points in time. Don’t let yourself be confused because there are to many words to remember.

As the neural tube closes (a process called neurulation) it pinches off from the overlaying layer.

This overlaying layer (right below the ectoderm layer) is now called the neural crest cells. They will become the sensory neurons of the spinal ganglia, as well as some of the cranial nerves.

Let’s go back to the neural groove. The un-fused ends are called neuropores. If either end is not able to fuse completely, the individual will have a malformed nervous system.

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  • Total failure of the neural tube to fuse (craniorachischisis) is fatal.

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  • If the anterior neuropore (the rostral end/ the “head” end) is not able to fully fuse, we call this condition: anencephaly (“a” stands for “lack off,” and “encephaly” stands for “brain”). The baby will lack most of its cerebral hemispheres (hence “no brain”) and will not survive.
Anencephaly

Anencephaly. Image Credit: Ed Uthman, MD

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  • If the posterior neuropore does not fully fuse this can result in a condition called “spina bifida, ” where part of the spinal cord is exposed to the external environment.

 

As you can see, the complete closure of the neural tube is extremely important. Unfortunately this type of nervous system malformation occurs in about 1 per 1000 births.

Causes Of Neural Tube Malformation

While we don’t know all the causes leading to such malformations, we know that the majority of these malformation could be prevented if the mother had ingested sufficient amounts of folic acid during the first month of pregnancy. (Remember, the neural tube starts fusing by the end of the 3rd week, all through to the 4th week).

Folic acid is mostly found in green, leafy vegetables. If you are a woman, and you are expecting to be pregnant, it is very important that you eat a lot of green leafy vegetables. If you can’t eat them as part of your regular diet, you can buy some folic acid supplement.

The difficulty lies in the fact that many women are not aware of the fact that they are pregnant by the end of the 1st month. That’s one of the reason doctors tend to recommend women to constantly eat a healthy, balanced diet rich in fibers and green vegetables.

Minimum To Remember:

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  • The notochord induces the creation of a thick neural plate
  • The neural plate starts folding. We call this folding the neural groove.
  • Once the neural groove forms, it’s called the neural tube.
  • Folic acid deficiency can lead to fatal nervous system malformations.
  • Women who are planning on having children should eat a diet rich in green leafy vegetables.

 

If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.


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