Embrio 1.1: Intro

Question 1

How do sperms get to an egg?

Answer 1

Sperms pass through the col uterin and will get caught in the isthme. They will remain in the isthme for up to a week. From there they are released in small groups to migrate towrads the trome to feconder (fertilize) an egg

Question 2

How can you distinguish between 55 and 56 day?

Answer 2

The fingers of the fetus are still connected via skin on day 55

On day 56 there is no longer the connection between the fingers

Question 3

What is the difference between «Hox» and «HOX»

Answer 3

«Hox» désigne le gène hox de la souris, alors que «HOX» désigne la protéine HOX chez l’humain.

Question 4

Why are day 9 to 15 most important in the menstrual cycle in terms of egg fertilization?

Answer 4

Days 9 to 15 are crucial in the menstrual cycle for egg fertilization because this period encompasses the time of ovulation and the lifespan of both the egg and sperm. Here’s a breakdown:

Ovulation: This is when the ovary releases an egg for fertilization. If you have a 28-day cycle, ovulation usually happens around day 14.

Egg Lifespan: After ovulation, the egg stays in the fallopian tubes. The egg can be fertilized in a 12- to 24-hour window.

Sperm Lifespan: Sperm can survive in the female reproductive tract for up to five days. So, if you have unprotected sex and ovulate within five days, you can become pregnant.

Fertilization: If sperm and an egg meet in the fallopian tube, conception is likely to occur.

Question 5

Age gestationelle vs age post conception?

Answer 5

Age post conception: Age following the fertilization
Age gestationelle : most used in medicine. referes to the day of last menstruations. This can then be used to calculate the age of the fetus (this - 2weeks)

Question 6

What do sperms follow to travel?

Answer 6

They follow a thermal gradient

They go from col uterin into the trompe fallopienne because that is where it is the warmest

This gradient is what orients the sperms one direction or another

Question 7

What is the advantage of the sperms staying in the isthme?

Answer 7

It increases the chances of fertilization as the sperms can survive for up to 5 days waiting for the egg

Question 8

Why is capacitation important?

Answer 8

This is the process of acrosome activation and maturation.

Acrosome is the head of the sperm that can get inside the egg

This also allows sperms to sense chemical and thermal gradients

Question 9

What needs to happen for a sperm cell to fertilize?

Answer 9

Must pass the corona radiatta

The head of the sperm must touch and go through the zona pellucida

The zona pellucida has receptors (ZP) that can recognize the sperm ligands

When this ligand receptor binding occurs, it triggers acrosomal reaction -> head opens->enzymes go out -> digestion of zone pellucide

However, one sperm is not sufficient to digest all of the zona pellucida. Therefore, one sperm will begin and then die and if another lucky sperm is around it can continue this until one gets through

If the membranes touch, the membranes fuse and the nucleus with the DNA material in the sperm is injected inside the egg -> fecondation

Question 10

Where does fecondation occur?

Answer 10

La fécondation se produit normalement dans la trompe de Fallope

Question 11

Why can a cat not have children with a human?

Answer 11

The ZP2 receptor of the human egg will not recognize the sperm ligand (or vice versa)

Question 12

granules corticaux and membrane de fécondation

also what this is dependend on

Answer 12

Dès que la fécondation a lieu, des mécanismes sont mis en place pour bloquer les autres
spermatozoïdes, afin d’éviter une double fécondation qui résulterait en une grossesse
triploïde (à 69 chromosomes). Dans les secondes qui suivent, les «granules corticaux»
qui sont localisés immédiatement sous la membrane cytoplasmique fusionnent avec
celle-ci, occasionnant très rapidement un renflement entre cette membrane et la zone
pellucide, la «membrane de fécondation», que les spermatozoïdes ne peuvent franchir;
de plus, les granules corticaux contiennent des enzymes qui digèrent ZP2, empêchant
la liaison d’autres spermatozoïdes à la zone pellucide.

**This is dependend on intracytoplasmique de calcium **

Question 13

What is the importance of calcium for an ovocyte during fecondation?

Answer 13

Other than creating the membrane de fécondation to prevent 2 sperms fertilizing the same egg, calcium gradients in the egg can activate processes that otherwise would be silenced in the egg

libération par le réticulum endoplasmique qui est responsable de l’augmentation de la concentration du calcium dans le cytoplasme.

For example enzymes that are innactive will be activated after calcium release

Question 14

What is Capacitation:

Answer 14

Capacitation: Fluids in the female reproductive tract prepare the sperm for fertilization through a process called capacitation.

This process improves the motility of the spermatozoa and thins the membrane of the head of the sperm, facilitating the release of the enzymes needed for the sperm to penetrate the oocyte’s exterior.

Question 15

Méiose féminine goal?

Answer 15

La méiose est séparée en 2 phases: la division réductionnelle, où le nombre de chromosomes passe de 46 à 23, etla division équationnelle,
où le nombre de chromosomes reste à 23, mais avec une
chromatide unique plutôt que double.

Après la 2ème division méiotique, le noyau de l’ovocyte contient 23
chromosomes:

I.e., go from 46 chromosomes to 23 chromosomes

Question 16

What is Morula? What key thing happens here?

Answer 16

It is the human embrio (up to day 4ish) when there are only up to 32 cells or blastomeres.

Morula humaine aux stades 4, 16 et 32 blastomères (correspondant aux 2°, 3° et 4° jours p.c. respectivement).

Key thing:
La déméthylation globale de l’ADN se fait au stade morula

Question 17

What is blastomères?

Answer 17

une cellule qui dérive des premières divisions ou segmentation du zygote durant le développement embryonnaire

Les blastomères sont totipotents:
In simpler terms, each blastomere in the early stages of embryo development has the potential to develop into a complete organism

4->16->32

Question 18

What is Blastocoel?

Answer 18

Liquid secreted by the embrio once 64 cells have been reached

fluid-filled or yolk-filled cavity that forms in the blastula during very early embryonic development

Cavite liquide de l’embryon

Question 19

What is the difference of 32 cells inside teh zona pellucida vs 64 cells Blastocoel?

Answer 19

At 32 cells, you can take any of the cells and they have the capacity of forming their own baby. Thus, all those cells remain PLURIPOTENT

However, by the time we have Blastocoel -> 64 cells -> CELLS ARE NOW DIFFERENTIATED!!!!

For example, the exterior cells are differentiated to form the placenta

These are called : Trophoblast->
the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the placenta.

Question 20

What is a Trophoblast?

Answer 20

the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the placenta.

Question 21

What is Bouton Embryonnaire ?

Answer 21

“Bouton Embryonnaire” is a term used in embryology to refer to a cluster of cells within the trophoblast, a part of a blastocyst, during embryogenesis. This internal cellular mass is the source of the embryo’s birth

The cells of the internal cellular mass of a “Bouton Embryonnaire” are pluripotent, which means they can potentially transform into cells of any body tissue (muscle, brain, bone, etc.).

The “Bouton Embryonnaire” is located in the blastocoel, and is entirely surrounded by the single layer of cells called the trophoblast.

Question 22

Would a cell of Bouton Embryonnaire be able to form a baby on its own if isolated?

Answer 22

No, because although these cells are pluripotent and can divide into virually any cell in the body, they cannot form placenta. And so they would likely die.

Question 23

What is L’extrusion?

Answer 23

During the late blastocyst stage (5th day, 64 cells), there is an extrusion of the blastocyst. This likely happens due to the action of enzymes in the liquid cacity, causing the pellucid zone (a thin outer layer) to break, and the embryo actively migrates outside of its envelope.

It’s probable that the blastocyst can split during this extrusion, thus forming two blastocysts, i.e., two monozygotic (identical) twins.

Extrusion is thus simply the blasting of the zona pellucida. Cells are no logner covered by jello but in contact with other cells

Question 24

What is nidation?

Answer 24

l’implantation du blastocyste dans l’endomètre qui est au stade sécrétoire

Après l’extrusion, les molécules d’adhérence cellulaires du blastocyste peuvent interagir avec celles de l’endomètre.

Question 25

What is Syncytiotrophoblaste?

Answer 25

A Syncytiotrophoblast, derived from the Greek words ‘syn’- “together”, ‘cytio’- “of cells”, ‘tropho’- “nutrition”, and ‘blast’- “bud”, is the epithelial covering of the highly vascular embryonic placental villi1. It actively invades the wall of the uterus to establish nutrient circulation between the embryo and the mother.

The cells of the tropoblast will touch the inner Linings of the mother’s and don’t mitrium and use cell adhesion molecules in order to get stuck on the walls

This leads to a signaling Cascades that triggers proliferation of cells in contact with the mothers uterus

The house will release enzymes that can digest the inner linings of the endometrium and will eventually enter inside the endometrium

The endometrium lining cells will themselves proliferate and angle the new structure

This means that the cells that once were exposed to the environment in the uterus are now enclosed and protected from any bacteria

Question 26

What is the first issue with the endometrium sourrounding the embryo cells?

Answer 26

Need to make sure that there is not an immune response against the embryo cells

this is why the embryo cells will release factors that will control the immune cell activity in the environment as well as release angriotrophic factors to recruit local blood vessels for oxygen and nutrient transport

sorta the same as cancer cells?
so cool!

Question 27

What produces the beta hcg?

Answer 27

Syncytiotrophoblaste

Cannot habe bHCG without Syncytiotrophoblaste

Question 28

Placenta praevia. What it is and why this is an emergency

Answer 28

placenta est implanté au dessus du col utérin instead of the endometrium

embryo implanted too low

dilatation du col peut déchirer les vaisseaux de l’endomètre, provoquant une hémorragie maternelle et embryoenne