Embryology Animated - the First Three Weeks

Embryology animation in 3D is essential, because embryology is a difficult topic to get your head around. I've tried to make it as easy as possible. In this video I try to answer questions like: What is embryology? What happens in the first three weeks? What is gastrulation and neurulation?

#3D_Embryology

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Video Script

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In this video, we take a simplified tour through the first three weeks of embryology. Each day finishes with some etymology, because understanding of the language behind embryology is crucial to comprehending the topic well.

Week 1

Day 1
The egg is invaded by a sperm, together forming the zygote. It contains male and female pronuclei. It’s cytoplasm is surrounded by a tough glycoprotein shell.

Zygote means ‘two things joined in a close relationship’, because sperm and egg have joined to become one cell.

Day 2
First mitotic division of the zygote occurs around 30 hours post-conception, producing two blastomeres.

Blastomere means sprout-segment, because one blastomere is one segment of the developing human-sprout.

Day 3
Division continues, and once 16 blastomeres are present they are together known as the morula, which means ‘mulberry’, because this bunch of cells visually resembles a mulberry.

Day 4
Fluid enters the morula, forming an internal cavity. The morula is now known as blastocyst. From now on, we will stop drawing individual cells, and will just show the overall shapes of structures.

Blastocyst ’sprout, again, and cyst just means ‘small fluid-filled sac’, because the human-sprout now has fluid within it.

Day 5
By day 5, the blastocyst has shed its outer shell. Cells have separated into two distinct areas: the trophoblast, which develops into the placenta and will feed the embryo, and the inner cell mass, which develops into the embryo proper.

Trophoblast comes from trephein, meaning ‘to feed’, because the trophoblast becomes the placenta which feeds the developing embryo.

Day 6
Trophoblast cells break down barriers in the uterine epithelium, allowing entry of the blastocyst.

Day 7
Meanwhile, the trophoblast begins to transform into two separate parts: cytotrophoblast on the inside, syncytiotrophoblast on the outside. The latter is one cell with many nuclei.

Syncytiotrophoblast is appropriate because it is not many separate cells, it is one ‘together-cell’.

Week 2

To simplify things, and match the imagery in most textbooks, we'll remove the endometrium now, and rotate our view like so.

Day 8
The inner cell mass differentiates into hypoblast and epiblast. A space develops in the epiblast - the amniotic cavity.

Hypoblast: meaning lower ‘sprout’
Epiblast: meaning upper sprout’
Amniotic: comes from amnion, Latin for “membrane around a foetus”.

Day 9
Meanwhile, cells of the hypoblast have migrated to replace the blastocyst cavity with the primitive yolk sac. Hypoblast and epiblast together are here known as the bilaminar disc.

Bilaminar: means 'two-layered'

Day 10
By day 10, the blastocyst is now firmly implanted in the endometrium. The syncytiotrophoblast breaks into maternal capillaries known as sinusoids, effectively co-opting their blood for the developing embryo.

Day 11
On the inner surface of the cytotrophoblast, tissue known as extra-embryonic mesoderm has developed. This eventually develops cavities which form the extra-embryonic coelom. The result is extra-embryonic mesoderm adhering to cytotrophoblast and amniotic sac, where it is known as somatopleuric, and to the yolk sac, where it is known as splanchnopleuric.

Splanchnopleuric basically means ‘on the side of the visceral organs’, because this mesoderm adheres to the viscera-side (the yolk sac becomes the gastrointestinal system).
Somatopleuric means on the side of the body.

Day 13
The space known as the extra-embryonic coelom has expanded, and is now known as the chorionic cavity. The extra embryonic mesoderm linking the cytotrophoblast to the embryo is known as the connecting stalk, which will eventually become the umbilical cord.

Chorionic: from chorion, meaning ‘outer membrane of the foetus’.

Day 14
Taking a closer look at the bilaminar disc now.

Cells in the epiblast begin to differentiate and burrow underneath. This looks like a burrow down the caudal end of the epiblast. It’s known as the primitive streak, and seeing that marks the beginning of gastrulation.

Gastrulation: means ‘becoming a gastrula (a trilaminar embryonic disc - more on that in week 3)

[sametiskpnar]

This is exactly what students need. Explanation to weird words and visualization, by not complicated but so simple yet so effective, the weird structures and their movements. Really helpful. Really good!

[tomato]

You did in 11 minutes what my professor failed to do in 6 hours

[stefanlange]

best video I've seen so far dealing with that topic - exactly the right amount of knowledge + you get a 3d understanding what kind of cells do what and are connected to which cavity and what not, finally. thank you so much.

[karten]

(Quran: Surah Az-zumar, 39:Ayah 6). “He makes you in the wombs of your mothers in stages, one after another, in three veils of darkness..” ... With grace and elegance it has been described in the Holy Quran! This interpretation seems to be the most logical from an embryological point of view.

[ashleylee]

holy crap this is the best thing i've ever seen thank you!!

[nukeani]

The blocky polygonal 3-D models are honestly WAY better than life-like models for understanding the topic

[boozy]

the simplistic visual representation makes it so much easier to visualize and understand this topic
thank you so much <3

[sametsengul]

Best animation in YouTube about a very hard topic to understand.As a Medical student, i have to say, thank you so much

[sidra-tul-muntaha]

This video is very helpful, these geometric figures makes embryology much simpler and easier.

[RashaYuki]

Thank God my country changed the language of studying into English, so I could find you 😭✨
Thank you so much!!

[prisce]

wow you have no idea of easy it is to study this in Thank you sooo much for your effort and dedication

[francescasilviamansueto]

Weird 3D models, but the video is actually very easy to remember. Thanks! (explaining the meaning of every term helps A LOT)

[zheelandara]

Best ever created content I have seen dealing with embryology. This 3D model is a blessing. Thank you.

[Mukesh-pbuv]

The Best One... We Can Ownly Imagine without much effort with the outline you provide... Which even 3d animations of events occurring can't... Weird models but very Effective...

[thaerabubaker]

Its fascinating how a random person on youtube explains topics better than uni professors

[deepanshug]

It is so difficult to understand these concepts in 2D you made it simple by making it in 3D.

[RĐØR-zn]

I checked and saw last video was 3yrs ago. We need more videos like this😭

[abijeyarajan]

Thank you for the amazing 3D visual representation of a developing embryo. Finally understood the process without any confusions. 😄😄

[hanch]

your hard work is much appreciated, this is as clear as it gets, thank you

[pakxo.]

You just decrypted my textbook with this video.
it was so difficult trying to understand what was happening in a black and white 2d small pictures