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This article states:

Once the neural tube closes, at around week 6 or week 7 of pregnancy, it curves and bulges into three sections, commonly known as the forebrain, midbrain and hindbrain. Just to the rear of the hindbrain sits the part that will soon turn into your baby's spinal cord. Soon, these areas bubble into those five different regions of the brain that we're most familiar with: the cerebrum, cerebellum, brain stem, pituitary gland and the hypothalamus.

How "soon" after 6 - 7 weeks is this soon the article talks about? When does the brain stem appear in humans?

Fetal Brain Development

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To correct the article you referenced the neural tube closure normally occurs by the fourth week of pregnancy (28th day after conception). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3279093/

The Brainstem is comprised of three parts:

  • Medulla (Melincephalon)
  • The Pons (Metincephalon)
  • The Midbrain (Mesencephalon)

enter image description here

During fetal development the brainstem is formed by:

  • the myelencephalon (fifth vesicle) which will develop into the medulla (Melincephalon)
  • the metencephalon (fourth vesicle) which will differentiate into the pons and cerebellum
  • and the mesencephalon (midbrain)(third vesicle)

An outline of the development of the brain stem is depicted in the image below:

enter image description here

Pansky, B. 146. Introduction to Brainstem Development. Retrieved from https://discovery.lifemapsc.com/library/review-of-medical-embryology/chapter-146-introduction-to-brainstem-development

enter image description here

By the end of the sixth week the rudimentary development of the five brain vesicles is complete. The cerebral hemispheres have grown and now cover the diencephalon, the mesencephalon and the cerebellum, which has only just begun development.

enter image description here

Montfort, G. J., & Boon, R. Stages of Brain Development. Retrieved from https://www.bondingandbirth.org/uploads/5/4/1/5/5415260/06_stages_of_brain_development.pdf

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  • $\begingroup$ I'm not sure that gives the answer, it jumps from day 39 to day 90 where the parts which eventually will turn into the brainstem parts to the part where they are named as the brainstem parts. Which day do you get from the chart? $\endgroup$
    – Pablo
    May 16, 2019 at 10:49
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    $\begingroup$ @Pablo There is no 'day.' Development is a continuous process. $\endgroup$
    – Bryan Krause ♦
    May 16, 2019 at 13:49
  • $\begingroup$ @BryanKrause days are stated for many other organs/parts. Ie, heart when it starts beating. I'm assuming here when it starts to fullfill the function is meant to. $\endgroup$
    – Pablo
    May 16, 2019 at 13:53
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    $\begingroup$ @pablo the definitions of the 3 different regions that comprise the brain stem should help because they aren't necessarily defined by function but rather structure and/or location with reference to adult brain. $\endgroup$
    – user50144
    May 16, 2019 at 14:21
  • $\begingroup$ @Pablo Even the "heartbeat" day has nothing to do with a heart beat. It's just when the electrical activity of what will become the heart is detectable from the outside. There is no functioning circulatory system at that time. $\endgroup$
    – Bryan Krause ♦
    May 16, 2019 at 14:26

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