Questions tagged [embryology]

The study of the development of an embryo from fertilisation through to description as a foetus.

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Is human zygote unicellular or multicellular [closed]

Is the human zygote which is formed by fusion of sperm and egg a unicellular structure? Bcz at some places the 2 celled stage which is formed due to cleavage has been labelled as the zygote. So is the ...
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What is tissue patterning?

This term gets thrown around sometimes in biology articles, and I have a rough idea of what it is: during embryonic development, the tissue differentiates in a certain spatial configuration. Wikipedia ...
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Do primitive streak cells remain with us?

Is there any evidence or experiments to show, that cells from the primitive streak in humans remain in us in a super low quantity? For example I've read of teratomas https://www.healthline.com/health/...
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What causes midcycle FSH surge in the menstrual cycle?

I have encountered contradictory attributions to the causal factor of midcycle FSH surge. Whereas some sources attribute it to the relatively high estrogen levels (1), others say it is because of ...
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What is meant by pro-acinar cell?

What is meant by "pro-acinar cell" in the following sentence? progenitors/precursors? A transient decline in Neurog3 expression from E11 to E12 coincides with peak segregation of MPCs into ...
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For which animals, can we make iPS-derived reproductive chimeras?

If I'm right, there are two types of pluripotent stem cells: naïve and prime. The naïve form is more undifferentiated. It would seem to me that it would be easier to make genetically engineered ...
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Flexor/extensor group in lower arm and limb bud rotation

Have the flexor and extensor groups in the lower arm have rotated laterally 90° towards the humerus epicondyles independently of the rest of the lower arm? The pre-axial and post-axial veins are still ...
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Development of radial symmetry in starfishes and other animals

How does nearly perfect radial symmetry arise in an animal like the starfish? My confusion lies in the fact that cells are fluid & amorphous, & that these characteristics seem to make it ...
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Difference between haemocoel and coelom

I am looking for an embryological perspective on the following question. I know about coelom derivation, but I want to know how haemocoel is derived and how it is fundamentally different from coelom. ...
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Why can human viruses that can't infect chickens be grown in embryonic chicken cells?

Embryonic chicken cells are commonly used in vaccine production. The viruses are grown in chicken eggs, or in embryonic cells taken from those eggs, and then inactivated or attenuated to produce the ...
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How do mothers handle acid from embryo bone mineralization?

This is a relatively trivial question, but, I have not seen it discussed much. It could be one factor in the "acidosis of pregnancy" (JAMA, 1929). Are the compensatory mechanisms measurable, ...
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Where does Embryo Implantation occur? [closed]

Where does the embryo get implanted? If it is in the uterus side wall, why is the embryo shown hanging from top in some pictures?
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What fraction of embryos fail to be born? And why that high?

In the book Developmental Biology by Scott F. Gilbert and Michael J. Barresi, it says: Most human embryos die before being born. You survived. So how come is that true??? And what percentage of ...
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When does the vertebral column finish chondrifying and begin to ossify?

I have read many articles on vertebral column development in embryos on the internet. Different articles give different time periods for the end of chondrification of the vertebral column and the ...
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Primitive streak being only present in caudal half of embryo affecting gastrulation?

It is my understanding that in gastrulation epiblast cells migrate to the primitive streak where they start to form the three germ layers; does this mean that gastrulation only occurs at the caudal ...
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Embryonic cells, when can you detect them in vivo? (In order to do whole genome sequencing)

I was wondering, when is it possible to extract cells (humans or mice) in order to sequence them and detect diseases. Extra: Urine of the embryo in humans is excreted in the 16th week, so I guess that ...
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Is SCNT possible with only the nucleus of a somatic cell (rather than a whole somatic cell)?

The following figure from Life: The Science of Biology (11th edition) explains how SCNT (somatic cell nuclear transfer) was used in the cloning of Dolly: (The original paper about cloning Dolly - ...
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Why can early embryos survive freezing?

According to this Blastocyst & Embryo Freezing in IVF Embryos can be frozen at the pronuclear stage (one cell), or at any stage after that up to and including the blastocyst stage (5-7 days ...
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How does a cell distinguish left from right?

Although the human body is mostly left-right symmetrical, it consistently has asymetries. The heart is consistently slightly to the left side of the body. The liver is consistently on the right side. ...
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Modern views on the correspondence of moles

In his Memoirs, Casanova wrote: In the midst of the dimple which added such a charm to her chin Esther had a little dark mole, garnished with three or four extremely fine hairs. These moles, which we ...
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Schizocoely and Enterocoely [closed]

In terms of phyla, mollusca, annelida and arthropoda are schizocoelic, whereas echinodermata and chordata are enterocoelic. I know that their difference lies in the formation of the coelom but how ...
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When do the first neurons appear in humans?

According to this Neural Plate The neural plate appears in day 18 in humans (very specific). and according to this Neural Plate (wiki) The progenitor cells that make up the precursors to neural ...
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What is the outer boundary of oligodendrocyte myelination?

The sensory and motor neurons comprising the spinal cord and brain stem have the interesting property that different structural components belonging to the same neuron can occupy both the PNS and CNS. ...
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How does the zygote divide much faster than other cells?

Normally a cell has a mechanism that controls its division. As far as I know, it checks surface area and stuff like that to decide to go for mitosis or not. However, this is not the case for a zygote....
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Do birds require cilia for left/right symmetry during their embryological stages?

I know that in humans ciliary dyskenisia can lead to a Situs inversus, is this also the case for birds and reptilians?
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Does the yolk sac for Danio rerio form at the vegetal pole?

Does the yolk sac in general form always at the vegetal pole? If so, is this the case for Danio rerio (the zebrafish)?
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When does the brain stem appear in humans?

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. ...
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How does a cell identify itself?

In embryological development, undifferentiated cells developed into specific types. As far as I understand, a key differentiating factor is the regulation of gene expression via transcription factors....
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If DNA methylation inactivates genes, does DNA demethylation activate them?

DNA demethylation can be passive or active. The passive process takes place in the absence of methylation of newly synthesized DNA strands by DNMT1 during several replication rounds – for example, ...
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Has an ectopic pregnancy's blastocyst ever been made to implant?

Has an ectopic pregnancy's blastocyst ever been successfully extracted from the Fallopian tube and made to implant in the uterus?
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How to supply oxygen to a culture vessel?

I'm reading this paper: https://www.jstage.jst.go.jp/article/jpsa/51/3/51_0130043/_pdf From day 17 of the culture period until hatching, pure oxygen was supplied at a flow rate of approximately 500 ...
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Ploidy of Central cell in embroidery sac

In the unfertilized embryo sac in angiosperms, is the central cell considered to be haploid or diploid? though it has two polar nuclei but both of them are haploid, so I don't think it can be ...
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Archenteron vs Gastrocoele

What is Difference between “Archenteron” and “Gastrocoele”. Are they same or different? Gastrula is characterized by Archenteron or Gastrocoele or Both?
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Why is cartilage replaced by bones in a vertebrate adult?

Why is cartilage present in a vertebrate embryo replaced by bones in an vertebrate adult even though cartilage can also provide me the structural framework like as in Chondrichthyes and they seem to ...
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What type of movement is “spontaneous movement” if it isnt reflex movement and it isnt purposive movement?

According to Spontaneous and induced fetal activity Spontaneous motor activity of the foetus depends significantly ot the foetal age; during the period between the 12th and 16th week it was ...
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Could bone marrow transplants help make xenotransplants viable?

So the immune system doesn't calibrate (for want of a better euphemism) to recognize it's own cells until fairly well along in fetal development & the major components of the immune system (...
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Real embryo pictures: How different zones(speeman organizer, marginal zones…) are known?

In many textbook, figures of embryo are drawn,but in reality how biologist know which zone is this one of an embryo in gastrulation stade? Except the dorsal lip here i can't localize other thing.
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Fertilization of the human egg- where does our centrosome come from? [closed]

Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can ...
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How does axon guidance system precisely targets specific axons?

Axons find their way to the terminus by responding to axon guidance molecules (AGMs) that attract and repel growth cones or make them stir. This I understand. Through a very specific combination of ...
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Can a brain process auditory signals at 18 weeks of human development?

According to When a fetus hear , When a baby can hear in the womb and several other similar articles, a baby starts to hear sounds at week 18. And according to How hearing works. Hearing involves ...
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Dynamic of the number of cells over time as the embryo grows

I would like to investigate the dynamic of the number of cells over time as the embryo grows. I am interested in any multicellular animal species for which we can have some data. How does the number ...
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Can a viable embryo develop from the fusion of two egg cells?

For a zygote to form, two haploid gametes undergo meiosis and fuse during fertilisation. Since two egg cells (or even two sperm cells) are both haploid, is it theoretically possible for them to make ...
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How can there not be purpose movement in the fetus until week 18, when a fetus can open its mouth and suck its fingers at week 11?

According to Fetal Movement According to an overview produced by the Royal College of Physicians of Edinburgh, purposive movement begins at about 18 weeks, gradually replacing reflex movements ...
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difference between blastula and blastocyst

What is the difference between these 2 terms. I believe that blastocyst is for animals, but structurally is there any difference? And how would you be able to identify each?
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How does gene affect organs development in eukaryotic cells? [closed]

I'm totally new to biology and apologies if you find this basic. The central dogma insists that genetic information flows in this direction: DNA -> RNA -> proteins So far so good, it is very clear ...
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What are limitations of giving birth to a baby from a frozen embryo?

Recently the story of a woman giving birth to baby girl from an embryo frozen 24 years ago hit the news. After an in vitro fertilization the embryo was frozen on 14 October 1992( Article in the ...
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Does the mesoderm evolve from the ectoderm or the endoderm?

I know the embryos of most animals develop into 3 germ layers. However primitive animals, such as Cnidarians, only have 2 germ layers - they lack a mesoderm. Therefore the 3rd germ layer must have ...
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Cell differentiation by non-identical copies

There are in principle two ways that two cells with the same mother cell can differentiate/specialize/diverge: Because they are not perfect identical copies (= different internal influencing factors)....
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Why does cell differentiation start with the morula?

I suppose that cell differentation has to start by some external symmetry breaking. The first time there are two different types of cells is the morula with roughly 16 cells: there are some 12-15 ...
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Shell-less Chick development - Incorporation of Calcium carbonate instead of Calcium lactate pentahydrate powder?

I'm a college undergrad biology student and currently studying developmental biology as part of my curriculum. I've read a research journal titled, A Novel Shell-less culture system for chick embryo ...