Embryology question

[Pdentalstudent]

I just came across a problem that I am not to sure of
Which of the following developmental stages has the greatest nuclear-to-cytoplasmic material ratio?

a) 4 celled zygote
b) 8 celled zygote
c) Morula
d) Blastula

the answer they give in the book is D but I thought blastula's are hallow balls of cells surrounding fluid?
My answer was C, the morula because its a solid ball of embryonic cells without having the fluid.
Is the book wrong?
Also do you guys have any tips on how to memorize which parts belong in the ecto, meso and endoderms?

Thanks in advance😀

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[UCSD1984]

I just came across a problem that I am not to sure of
Which of the following developmental stages has the greatest nuclear-to-cytoplasmic material ratio?

a) 4 celled zygote
b) 8 celled zygote
c) Morula
d) Blastula

the answer they give in the book is D but I thought blastula's are hallow balls of cells surrounding fluid?
My answer was C, the morula because its a solid ball of embryonic cells without having the fluid.
Is the book wrong?
Also do you guys have any tips on how to memorize which parts belong in the ecto, meso and endoderms?

Thanks in advance😀

The way I remembered Cytoplasm decreasing is simply the fact that the more cell divisions that occur, the less Cytoplasmic material there is in comparison to the original zygote. Since the Blastula results from even more cell divisions past the Morula stage, I would assume the Blastula cells contain less Cytoplasm than those contained in the Morula. Therefore, there would be a greater Nuclear Material to Cytoplasm ratio because of it.

At least that's how I look at it.

 

[Demps]

The book is correct.

In order for nucleus to cytoplasm ratio to increase, let's call it N/C, simple math suggest that you want to increase N while decreasing C (or just stay constant).

During cleavage, the cell does not increase in size but it keeps dividing. As a result, nucleus number increases but the size of the cell remained constant. This means cytoplasmic content decreased as well.

So if you want greater N/C ratio, you want it to be later steps of early embryonic cell division.

Clearly, blastula is the latest stage. So the answer is D.

 

[predental89]

I just came across a problem that I am not to sure of
Which of the following developmental stages has the greatest nuclear-to-cytoplasmic material ratio?

a) 4 celled zygote
b) 8 celled zygote
c) Morula
d) Blastula

the answer they give in the book is D but I thought blastula's are hallow balls of cells surrounding fluid?
My answer was C, the morula because its a solid ball of embryonic cells without having the fluid.
Is the book wrong?
Also do you guys have any tips on how to memorize which parts belong in the ecto, meso and endoderms?

Thanks in advance😀

It simply means that the nuclei surrounding the hollow space is proportionally larger then the actually cytoplasm its surrounding. Its confusing but if you think about it hopefully you'll see what I mean. But no the book is right and as far as your second question. heres how I remember it.

Ecto derm = "Attractoderm" 😍 ex. things we are attracted too in other males/females. (nervous system, lens of the eye, skin(epidermis))

Endoderm = "Endernal organs" ex. lining of the digestive tract, circulatory system etc.

Mesoderm = "meansoderm" your bodies means of doing stuff ex. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks.

Hope this helps.

 

[UCSD1984]

The book is correct.

In order for nucleus to cytoplasm ratio to increase, let's call it N/C, simple math suggest that you want to increase N while decreasing C (or just stay constant).

During cleavage, the cell does not increase in size but it keeps dividing. As a result, nucleus number increases but the size of the cell remained constant. This means cytoplasmic content decreased as well.

So if you want greater N/C ratio, you want it to be later steps of early embryonic cell division.

Clearly, blastula is the latest stage. So the answer is D.

Yea, read his explanation. Way better than mine. Lol.

 

[UCSD1984]

It simply means that the nuclei surrounding the hollow space is proportionally larger then the actually cytoplasm its surrounding. Its confusing but if you think about it hopefully you'll see what I mean. But no the book is right and as far as your second question. heres how I remember it.

Ecto derm = "Attractoderm" 😍 ex. things we are attracted too in other males/females. (nervous system, lens of the eye, skin(epidermis))

Endoderm = "Endernal organs" ex. lining of the digestive tract, circulatory system etc.

Mesoderm = "meansoderm" your bodies means of doing stuff ex. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks.

Hope this helps.

Dude that "Attractoderm" idea is awesome. I like that.👍

 

[Pdentalstudent]

WOW! okay thanks guys!

thanks for the tips too!