Neurogenesis

While I'm definitely not prepared to discuss the definition of life, I do want to start today's blogpost with one of the earliest stages we start at- the zygote.  Most high school students are comfortable with the notion of a zygote multiplying and becoming a hollow ball of cells called a blastula.  And the jump to diversifying cells follows that step with a vague conception that this leads to all the types of cells composing our bodies.

But how exactly do nerve cells, which are my primary interest, form?  What types of cells are they composed of?  This is where I hope to be of some assistance for understanding the neurogenesis of most known life.

So let's take it up from the blastula.  This hollow ball of cells undergoes a process called gastrulation during which the ball collapses in on itself and forms a double layer of cells.  This is the first step of cell differentiation between ectoderm, endoderm, and mesoderm.  Just for a general crash course, here's the end results of these primary tissue types:
ectoderm: epidermis and nervous system
endoderm: gut structures/internal organs
mesoderm: muscle, bone, and the circulatory system.

But what we want to focus on is the formation of the neural tube from the ectoderm.  The process is rather difficult to explain via text when a movie is much more descriptive.  But essentially a groove forms in the outside of the cell ball (called the neural plate) and the sides create neural crests which rise up and meet each other to create the neural tube.  Here's a video to help display the process.

The accuracy and consistency of this process is beyond impressive.  Have you ever considered yourself as a collection of cellular processes?  Just think how many functions and changes our bodies perform everyday simply to keep us alive!  It's amazing that through all our development and lives, we only suffer a limited number of medical problems.

Though google images had many more graphic pictures of
meningomycelocele, I thought it best to stick with some-
thing like this.

But they do happen every once a while, and the problems don't always have surgical solutions.  In the case of the formation of the neural tube, the most common human affliction is called spina bifida.  This occurs when there's incomplete closure of the spinal cord.  In particular, meningomycelocele is a form in which the spinal cord actually protrudes from the back.  The meninges fibers are exposed with none of the usual protective coverings, hence the name.  If the exposed tissue is low enough down the spinal cord, corrective surgery can be used to fix the problem.  But otherwise, the life expectancies for such a child aren't very good.'

If talk of this kind of physical abnormality makes you concerned, fear not.  Spina bifida is not a common occurrence and can easily be avoided by ingesting plenty of B9 folic acid.