Embryology | Fertilization, Cleavage, Blastulation

Summary

Este vídeo comienza una serie sobre embriología, explicando desde el final de la fertilización hasta el desarrollo del primer día. Se detallan las etapas clave como la ovulación, fertilización, cleavage y blastocystisación. Se discuten los cambios en la anatomía femenina, la liberación de hormonas y el proceso de capacitación del espermatozoide. Además, se explora la transformación del zygote en un blastocystis y la diferenciación de las células en la masa embrionaria y la trophoblasto, esenciales para el desarrollo del embrión y la placenta.

Takeaways

• 📅 La serie de embriología comienza después de la fertilización, que se discute en una lista de reproducción.
• 🌱 Se abordan los desarrollos desde la fertilización hasta la segunda semana, incluyendo la gastrulación.
• 🔎 Se conecta la anatomía uterina con la fisiología, destacando la importancia de la ovulación y la fertilización.
• 🧪 Se describe el ciclo menstrual femenino, con énfasis en la liberación de hormonas como la gonadotropina luteinizante (LH).
• 🤝 La ovulación ocurre alrededor del día 14 o 15 del ciclo menstrual, desencadenando la liberación de un óvulo.
• 🏋️‍♂️ La fertilización se produce en la ampolla del trompo de Falopio, donde el óvulo y el espermatozoide se encuentran.
• 🌟 La fusión del espermatozoide y el óvulo da lugar a un cigoto, que contiene 46 cromosomas (23 de cada progenitor).
• 📈 El cigoto comienza a proliferarse rápidamente a través de la cleavage, formando dos, cuatro, ocho y dieciséis células.
• 🌐 Se forma la morula, una bola hueca de células, a medida que el número de células aumenta.
• 🌱 La morula se convierte en un blastocisto a través del proceso de blastulación, diferenciando las células en masa embrionaria y tropoblástica.

Q & A

¿Cuál es el objetivo de la serie de videos de embriología que se menciona en el guion?

El objetivo de la serie es comenzar desde el final de la fertilización y seguir el desarrollo del embrión hasta su completitud.

¿Cuál es el primer evento que se discute en la serie de embriología?

El primer evento discutido es la fertilización, que se menciona que se puede encontrar en un playlist de reproducción.

¿Cuál es la secuencia de desarrollo que se abordará en el primer video de la serie?

El primer video cubre el desarrollo desde la fertilización hasta la primera semana, incluyendo la gastrulación.

¿Qué hormona se libera alrededor del día 14 o 15 del ciclo menstrual femenino y qué desencadena?

Se libera la hormona luteinizante, que desencadena la ovulación y la producción de fluidos en el ovario.

¿Qué es el graafian follicle y qué contiene?

El graafian follicle es una bolsa que contiene el óvulo y se prepara para la ovulación, listo para liberar un óvulo secundario.

¿Qué fase del meiosis está atrapado el óvulo secundario después de la ovulación?

El óvulo secundario está atrapado en la fase de metaphase del meiosis II después de la ovulación.

¿Qué proceso debe pasar el espermatozoide antes de poder fecundar el óvulo?

El espermatozoide debe pasar por la capacitación, un proceso en el cual se eliminan ciertas moléculas de colesterol de su cabeza.

¿Qué sucede cuando el espermatozoide toca el óvulo durante la fertilización?

Cuando el espermatozoide toca el óvulo, se activa y comienza a liberar enzimas que lo ayudan a perforar la membrana del óvulo y fusionar sus núcleos.

¿Cuál es la secuencia de divisiones celulares que sigue el zygote después de la fertilización?

El zygote pasa por la cleavage, dividiéndose en dos, cuatro, ocho y luego dieciséis células, formando una morula.

¿Qué proceso transforma la morula en un blastocisto?

El proceso de blastulación transforma la morula en un blastocisto, donde se forman la cavidad fluida y los grupos de células que eventualmente se convertirán en la tropoblasta y el embrioblasto.

¿Qué se denomina a la masa celular interna del blastocisto y qué papel desempeña?

La masa celular interna se denomina embrioblasto y es la que eventualmente dará lugar al embrión humano.

¿Qué se convierte en la tropoblasta y qué función cumple?

La tropoblasta se convierte a partir de la masa celular externa y tiene la función de formar parte de la placenta.

Outlines

00:00

🌟 Introducción a la serie de embriología

El vídeo comienza con una introducción a la serie de embriología, explicando que se iniciará desde el final de la fertilización. Se recomienda ver un vídeo previo sobre fertilización antes de continuar. Se menciona que se omitirán algunos detalles y se centrarán en el desarrollo durante la primera semana, pasando por la gastrulación y la formación del sistema nervioso. Se destaca la importancia de comprender la anatomía y la fisiología antes de abordar los eventos celulares, y se describe brevemente la anatomía uterina femenina, incluyendo la vagina, el cuello uterino, el cuerpo del útero, los ovarios y las trompas de Falopio. Se menciona que la fertilización ocurre en la ampolla de la trompa de Falopio.

05:01

🔬 Proceso de ovulación y liberación de hormonas

Se describe el proceso de ovulación y la liberación de hormonas durante el ciclo menstrual femenino. Se explica que alrededor del día 14 o 15, el cuerpo libera una hormona llamada hormona luteinizante (LH), que es estimulada por el hipotalamo a través de la liberación de gonadotropina liberadora de hormonas (GnRH). La LH estimula al ovario a producir fluido y a presionar la folículo de Graaf, lo que lleva a la ovulación. Se describe cómo la ovulación ocurre y cómo el óvulo se mueve hacia la ampolla de la trompa de Falopio, listo para la fertilización.

10:04

🤝 Fertilización y formación del cigoto

El vídeo detalla el proceso de fertilización, comenzando con la unión del óvulo y el espermatozoide en la ampolla de la trompa de Falopio. Se explica que el espermatozoide debe capacitarse, eliminar ciertas moléculas de colesterol y adherirse a receptores ZP3 en la superficie del óvulo para poder penetrar. Una vez que el espermatozoide toca el óvulo, se activa y libera enzimas que le permiten perforar la membrana del óvulo. El núcleo del espermatozoide se fusiona con el del óvulo, creando un cigoto con 46 cromosomas. Se describe el proceso de clevaje, donde el cigoto se divide repetidamente formando dos, cuatro, ocho y dieciséis células, hasta llegar a la morula, que es un conjunto de células en forma de bola hueca.

15:08

🌱 Desarrollo desde la morula hasta el blastocisto

Se describe el proceso de blastulación, donde la morula se transforma en un blastocisto. Se menciona que las células de la morula comienzan a compactarse y a agruparse, formando una estructura con células en el borde y un grupo de células en el centro. El blastocisto tiene una cavidad llena de fluido y dos tipos de masas celulares: la masa celular interna, que se convertirá en el embrión, y la masa celular externa, que se convertirá en el tropoblastoplasma. Se explica que el tropoblastoplasma se especializa en el citotrofoblasto y el siniciclo tropoblastoplasma, mientras que la masa celular interna se desarrolla en el blastodisco. Se resumen los pasos clave que ocurren durante la primera semana, incluyendo la ovulación, la fertilización, el clevaje, la blastulación y la especialización de las masas celulares.

Keywords

💡Fertilización

La fertilización es el proceso por el cual un óvulo femenino y un espermatozoide masculino se unen para formar un zigoto. En el guion, se menciona que el ciclo de ovulación y la fertilización son los primeros pasos en el desarrollo embrionario. El guion describe cómo el espermatozoide y el óvulo se encuentran en la ampolla de la trompa de Falopio, donde se produce la unión.

💡Citocinesis

La citocinesis es el proceso de división celular por el cual un zigoto se divide repetidamente para formar múltiples células. En el guion, se habla de la citocinesis como el proceso por el cual el zigoto pasa por varias etapas, desde el estádio de dos células hasta el de dieciséis células, formando una estructura llamada morula.

💡Morula

La morula es una etapa temprana del desarrollo embrionario en la cual el número de células aumenta hasta alrededor de 16, formando una estructura que es básicamente un grupo de células que rodean un espacio central vacío. En el guion, se describe cómo el zigoto se convierte en una morula a través de la citocinesis.

💡Blastocisto

El blastocisto es una etapa del desarrollo embrionario que sigue a la morula, donde las células se organizan en un patrón específico, con un grupo de células en el centro (masa interna de células) y otro grupo de células alrededor del borde (masa externa de células). En el guion, se menciona cómo la morula se transforma en un blastocisto a través del proceso de blastulación.

💡Masa interna de células

La masa interna de células es un grupo de células dentro del blastocisto que se va a convertir en el embrión. En el guion, se destaca la importancia de la masa interna de células, ya que es la que eventualmente dará lugar al embrión y, por ende, al organismo desarrollado.

💡Masa externa de células

La masa externa de células es otro grupo de células en el blastocisto que se especializa para formar parte de la placenta. En el guion, se menciona cómo la masa externa de células se convierte en el tropoblas激, que es esencial para el desarrollo y la nutrición del embrión.

💡Tropoblas激

El tropoblas激 es una capa de células que rodea al embrión y que se especializa para formar parte de la placenta. En el guion, se describe cómo la masa externa de células del blastocisto se convierte en tropoblas激, que es crucial para la implantación y el suministro de nutrientes al embrión.

💡Discos bi y trilaminar

Los discos bi y trilaminar son etapas en el desarrollo embrionario donde el disco blastodérmico se organiza en capas que eventualmente dará lugar a los tejidos y órganos del embrión. En el guion, se menciona cómo el desarrollo continúa desde el blastocisto hacia la formación de estos discos, que son esenciales para el desarrollo del embrión.

💡Implantación

La implantación es el proceso por el cual el blastocisto se adhiere y se integra en la endometrio del útero, preparándose para el desarrollo embrionario. Aunque no se menciona directamente en el guion, es un concepto clave en la reproducción que sigue a la fertilización y la formación del blastocisto.

💡Ciclo menstrual

El ciclo menstrual es el período regular de cambios hormonales y cambios en el endometrio del útero que preparan el cuerpo de una mujer para la concepción. En el guion, se menciona el ciclo menstrual en relación con la liberación de un óvulo y la fertilización.

Highlights

Embryology series begins with the end of fertilization.

Development within the first week starts post-fertilization.

Anatomy correlation is crucial for understanding embryology.

Luteinizing hormone triggers ovulation around day 14 or 15 of the menstrual cycle.

Estrogen levels play a role in the release of luteinizing hormone.

Ovulation involves the release of a secondary oocyte from the ovary.

The secondary oocyte is in metaphase of meiosis II, awaiting fertilization.

Sperm cells undergo capacitation to prepare for fertilization.

Fertilization occurs in the ampulla of the fallopian tube.

The zygote is formed by the fusion of 23 maternal and 23 paternal chromosomes.

Cleavage is the process of cell division from zygote to morula.

The morula is a hollow ball of cells with no internal structure.

Blastulation is the transformation of the morula into a blastocyst.

The blastocyst has an inner cell mass and an outer cell mass.

The inner cell mass will develop into the embryo, while the outer cell mass will form the placenta.

The embryoblast will further develop into the bilaminar disk.

The trophoblast will differentiate into the cytotrophoblast and syncytiotrophoblast.

Transcripts

iein engineers what we're gonna do in

this video is we're gonna begin our

embryology series okay so if you guys

haven't already we're gonna start from

the end of fertilization which is on a

reproductive playlist if you guys

haven't seen that already go watch that

first we're not going to go into a ton

of detail on that we're kind of just

going to skip over pieces and begin the

development within the first week then

after that what we'll do is we'll go

into the next video which is going to be

the development up until the second week

right so we're gonna go for gastrulation

then we'll have another video what we're

going to the development during up to

week three which is gonna involve dinner

elation process and then we'll discuss

the the formation of the nervous system

and we'll just continue to keep going

from there until the development of the

entire embryo alright so let's go ahead

and get started I'm user so let's go

ahead and get started then so first off

we have to talk about before we kind of

get into all the cellular events I want

us to really kind of correlate our

Anatomy with kind of the bigger picture

then we'll get down to the cellular

events so if you guys remember from the

fertilization video just a little bit

about your uterine anatomy right so very

simple here there's gonna be the vagina

they also call it the sheath right then

you're gonna have this portion right

here right which is called the cervix of

the uterus then we'll kind of get into

the body of the uterus right here up

this top like portion here which is kind

of rounded out like that that's gonna be

the fundus of the uterus and then here

you're gonna have your fallopian tubes

right and then at the end of the

fallopian tube you kind of have this

little dilated region right there that's

called the ampulla of the fallopian

tubes that's where fertilization is

supposed to occur right then you got

your little fingers little same brain

right and then after that you got the

ovaries right so what's important is

that an order for us to really kind of

talk about the cellular events we have

to understand the physiology going into

this so what happens usually around day

14 or day 15 of a female's menstrual

cycle right I'm sorry

they start to release a specific type of

hormone right called luteinizing hormone

so if you guys remember here let's draw

like a little diagram here we're gonna

have this guy but you guys remember this

diagram it's pine grain into your brain

right now we're gonna have

the hypothalamus with the poster

pituitary and anti pituitary that's not

nutsacks okay so just remember that now

what happens the hypothalamus starts

releasing specific types of neuro

peptides what are these neuro peptides

called they're called ganado tropen

releasing hormone and then what is gonna

a - open releasing woman do lots of it -

it stimulates the anterior pituitary

what does it tell the anterior pituitary

to do it tells it to start secreting

large amounts of luteinizing hormone

alright and this is also kind of playing

a role not just with the GnRH but if you

guys remember a little bit back from

you're kind of the dimensional

physiology

there's also another very big trigger

here and that's going to be a sturgeon

if you guys remember that positive

feedback cycle when estrogen levels

increase again right during the second

time that's also a big stimulator of

luteinizing hormone as well all right

anyway luteinizing hormone it's released

it gets into the blood goes down to the

over what does it do

well if you guys remember it tells the

ovary to kind of start producing a lot

of fluid alright so it tells the ovary

start making a lot of fluid but

pressurize that follicle because

remember we have that graafian follicle

which is the guy who's gonna have that

secondary oocytes what does he do he

triggers the release of certain types of

prostaglandins to dilate the vessels to

increase a lot of the leakiness out of

the capillaries around that graafian

follicle and activate certain types of

enzymes metalloproteinase is to break

down the connective tissue around it and

guess what that helps helps to pop that

little OA site out and then what happens

is the fimbriae they get all kinds of

cool and they start kind of moving that

actual oh a site towards what the

ampulla then this little oh a site here

we're going to draw it right here and

here is going to be the corona radiata

around it it gets popped out here right

so now that's our secondary oocytes I

think eyes remember I talked about it

and the kind of the whole ovulation

cycle that this is the secondary oocyte

what that means is if it's are

undergoing meiosis one and it's getting

ready to go into meiosis

- right it's getting ready to finish

meiosis - but it hasn't yet what stage

is it particularly in well if you guys

remember we said that once it's ovulates

it's stuck in a specific phase it's a

secondary Oh a site in metaphase -

that's an important thing to remember

secondary oocytes stuck in metaphase -

the reason why is it's waiting for a

sperm cell to touch it and then once it

does it says oh what I need is here I'm

gonna go ahead and finish meiosis to get

myself prepared for this nucleus from

the sperm cell and then I'm gonna fuse

with it so it's waiting and waiting and

who is awaiting on it's waiting on the

lucky son of a gun

right who gets the sperm cells where

they need to go and what happens is the

sperm once it's ejaculated it goes into

the vagina up through the cervix of the

uterus up through the body it makes its

way through the fallopian tubes and it

meets that nice little secondary oocytes

phase - at the ampulla all right and it

says hey I want to go ahead and touch

you now not in a creepy way though

alright so it goes ahead and it touches

it and then guess what starts happening

well let's go ahead and dig into that so

what we're gonna do is we're gonna

imagine that these guys are touching one

another right here in this kind of like

zone we're going to blow it up and we're

gonna take a look see so now we're

blowing it up here and here we're gonna

have that egg right so we have that

secondary oocytes stuck in metaphase -

this is the one then we got that sperm

cell and that sperm cell is coming over

here to meet this egg alright but in

order for it to be able to touch it you

guys remember it has to go through a

process called capacitation where has to

clean off a bunch of cholesterol

molecules and things off of the head of

it and then it has to attach to a

specific type of protein on the surface

and what is this protein if you remember

we have what's called zp3 receptors and

these zp3 receptors are really important

because once the actual sperm touches so

zp3 receptors once the sperm cell

touches it it activates the sperm cell

and then the head of the sperm cell whew

with the zone with the oocytes membrane

starts releasing a bunch of different

enzymes lysosomes hydrolytic enzymes

from its acrosome and it starts

burrowing its way through this then what

it does is it releases its nucleus you

see this little green guy it releases

its nucleus into the cytoplasm so here's

going to be this nucleus now in the

nucleus you know that there's

chromosomes right 23 chromosomes are

going to be in the sperm cell nucleus

and 23 chromosomes are going to be in

d.o.a sites nucleus well what happens is

let's see here 23 are gonna be paternal

and 23 of the other chromosomes are

going to be maternal these are going to

fuse when they fuse how many you gonna

get was 23 plus 23 it's 46 right so

you're gonna get 46 chromosomes now and

this is going to be a diploid cell but

we're also going to call it as I go so

again how many chromosomes 23 plus the

23 23 maternal 23 paternal 46 total

chromosomes and this is going to give us

our zygote now it's pretty amazing when

you think about it that from this one

cell this one cell we're actually gonna

be able to make an entire human body

that's pretty amazing so how does this

happen this zygote guess what

it starts undergoing lots and lots of

lots of proliferation so it starts going

through achieve one sg2 mitosis and just

starts replicating and replicating and

replicating what is that call whenever

it starts replicating and making two

cells then four cells then eight cells

then sixteen cells

that's called cleavage so it's very

simple we've already talked about

fertilization now what do we have to go

through we have to go through a bunch of

stages called cleavage so it's very

simple now now it's just a matter of

counting it up now what I'm gonna do is

I'm going to divide this cell it was

once one cell guess what I'm gonna do

now I'm gonna now have two cells now

here's the important thing to remember

remember I told you that this pink

membrane had a protein called the zona

pellucida three receptor that pink

protein is called the zona pellucida so

you're gonna have it in fertilization

you're gonna have it in the zygote and

you're

so gonna have it in this cell where it

divides what's this cell called this is

now called the two cell stage it's very

simple right so zygote you're gonna go

into the two cell stage guess what it's

then gonna do then it's then gonna

divide again it's gonna go from two

cells and you're gonna double that so

now it's going to be four cells so let

me do this now so there is going to be

four cells so this is the four cell

stage then what I bet you already

guessed it it's going to divide again

and it's going to turn into the eight

cell stage and then what do you think

it's going to go to after that it's

gonna go to the sixteen cell stage so

throughout that process now if you

imagine we're gonna have eight cells

here and then before you know we're not

gonna draw in all sixteen cells here

what you know here is that you're gonna

have tons and tons and tons of cells and

what this is gonna do is it's going to

form a kind of structure which is very

interesting what do I mean okay you're

gonna have these cells and they're going

to be surrounding the entire thing

surrounding this entire structure right

so it's entire circle you have these

cells surrounding it but inside the

center of it is hollow there's nothing

in there okay so if you were to imagine

let's imagine I took like a

cross-section here here's going to be

all the cells right forming the outer

coat

there's our cells forming the outer coat

but inside of this there's nothing it's

completely Hollow what do we call this

anything from 16 cells and up until we

get our blastocyst we call this the

marula so we call this one the marula

and this is basically going to be a

hollow ball of cells which is going to

be 16 or + cells

and what they call these they'd like to

give these cells a special name these

little circular blue cells here once

it's at the level of the marula they

call these blastomeres blasto mears okay

so that's important to remember now from

here what's gonna happen then okay so

now we have this marula right the marula

guess what it starts to do it starts to

take the cells right you have the cells

right here forming the edge what's going

to happen is a bunch of the cells in the

center there's gonna be a bunch of cells

that start compacting towards one edge

alright so you're gonna have the cells

lining the edge of this cell so let's do

it like this here you're gonna have

these cells they're gonna be kind of

lining the edge and they're gonna form

one type of cell structure that's very

important because this helps to go on

and form a part of the placenta okay

then another group of the cells around

that are gonna group towards one side

and kind of clump together let's do that

in a different color so that we don't

confuse this let's do this in the screen

here now we're gonna have these other

cells and they're going to be kind of

grouping together here and now we had a

hollow ball now what we do is we have a

cell lining around the edge and we had

to have just a bunch of group of cells

just clumped together in this one edge

over here what do we call this this is

going to be our blastocyst so the

process of what we're going from the

marula into the blastocyst is your blast

chelation process so now what do we have

here we're gonna have our blast

chelation

and we're gonna form here our blastocyst

which is so darn cool now within the

blastocyst you're gonna have this fluid

filled cavity so it's going to be all

fluid in here right

but then this group right here this

bunch of cells that are going to be kind

of clumped here together

this becomes a specific thing right we

call this part here the inner cell mass

okay and then the cells around the edge

or the periphery of it this is going to

be called D and very simple outer cell

mass now what happens is these cells

they start to differentiate and become

more functional right and what happens

is they become a little bit more

differentiate a little bit more

functional and then they become a

different type of name we just like to

change names for things all the time so

now what happens they continue to

differentiate continue to develop and

now that outer cell mass becomes a

specific type of thing which we call the

trophoblast so now this outer cell mass

is now what we call a trophoblast

becomes a little bit more differentiated

a little bit more specialized and we

call this the trophoblast

then we had that inner cell mass it

starts to become more specialized and

more differentiated and it turns into a

specific thing which is going to be

important and this is going to be called

the embryo blast this is called the

embryo blast so all I want you to really

know is the outer cell mass becomes the

trophoblast and the inner cell mass

becomes the embryo blast why is that

important because guess what eventually

the trophoblast becomes which we're

going to talk about next

it didn't differentiate into two other

specialized layers one is going to be

called the Saito trophoblast which we'll

talk about and the other one is to be

going to be called the syncytium

trophoblast the embryo blast guess what

its gonna start developing into it's

gonna start developing into your by

lemon or disk so and we'll talk about

how that happens but this is going to

start converting into your bi laminar

disk so within this first week right

that we've talked about what happened we

had ovulation was the first step right

so let's go ahead and mark out down our

steps first step was ovulating right

second step was fertilization okay and

that was here this was here and then

continuing on down here this is still

fertilization right so this is still the

fertilization step then what happened

from all the way from the zygote all the

way until the sixteen cell stage this

was all called cleavage so we'll write

that down that was the third step okay

then what happened after that then the

next thing is the marula converted into

the blastocyst okay that's going to be

the fourth stage so the fourth step is

going to be blast elation then after

that the blastula became more

specialized and converted into a

trophoblast which used to be the outer

cell mass and the embryo blast which we

used to become d which used to be the

inner cell mass then they will become

even more specialized in the embryo

blast become the bilaminar disk which is

going to be the EPI blast and the hypo

blast which we'll talk about and the

trophoblast is going to become the Saito

trophoblast and this is serial blast

this is important because these help to

be able to make to your structures like

the placenta okay whereas the embryo

blast is gonna make the embryo right so

this will then go from the by laminar to

the Tri laminar and that will help us to

make our entire embryo so that's why

this is so important this is generally

occurring within the first week

what we'll do next is we'll take this

truffle blast excel with the embryo

blast and we'll talk about how it

sprouts these little things we'll talk a

little bit more about this in seetio

trophoblast with the villi and how it

breaks through the zona pellucida and

then we'll talk a little bit more about

the embryo blast and how that converts

into the bilaminar disk alright so we'll

talk about that in the next video

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