General Embryology - Detailed Animation On Second Week Of Development
Summary
TLDRThe script details the early stages of human development post-fertilization, focusing on the implantation of the blastocyst into the uterine wall. It describes the differentiation of the trophoblast and embryoblast, the formation of the amniotic cavity, and the establishment of uteroplacental circulation. By the end of the second week, the bilaminar embryonic disc is connected to the trophoblast, laying the groundwork for the future umbilical cord.
Takeaways
- 🌱 Implantation of the blastocyst typically happens 6 to 8 days post-fertilization.
- 🌼 By day 8, the blastocyst has implanted into the uterine endometrium, consisting of the Trophoblast and the Inner Cell Mass (Embryoblast).
- 🔍 The Trophoblast differentiates into the cytotrophoblast and syncytiotrophoblast upon contact with the endometrium.
- 🌿 The Embryoblast forms a bilaminar embryonic disc made up of the hypoblast and epiblast.
- 🌌 An amniotic cavity starts to form between the epiblast and cytotrophoblast.
- 🕸️ The hypoblast cells migrate to form the exosomic membrane, contributing to the primitive yolk sac's walls.
- 📅 By day 12, the syncytiotrophoblast forms lacunae which later merge into a lacuna network for maternal blood flow.
- 🌐 Maternal sinusoids dilate, and the syncytiotrophoblast's expansion allows for uteroplacental circulation.
- 🔬 Extraembryonic mesoderm appears, leading to the formation of the chorionic cavity.
- 🔗 Around day 13, the secondary yolk sac forms, and by the end of the second week, the connecting stalk (future umbilical cord) links the bilaminar embryonic disc to the Trophoblast.
Q & A
When does the implantation of the blastocyst typically occur after fertilization?
-Implantation of the blastocyst usually occurs 6 to 8 days after fertilization.
What are the two main components of the blastocyst at the time of implantation?
-At the time of implantation, the blastocyst is composed of the outer cell mass, the trophoblast, and the inner cell mass, the embryoblast.
What differentiates from the trophoblast when it makes contact with the endometrium?
-When the trophoblast makes contact with the endometrium, it differentiates into two layers: an inner cytotrophoblast and an outer syncytiotrophoblast.
What is the amniotic cavity and how does it form?
-The amniotic cavity is a cavity that begins to appear between the epiblast and the cytotrophoblast soon after the embryonic disc has formed.
What is the exosomic membrane and how is it formed?
-The exosomic membrane is a thin membrane that covers the inner surface of the cytotrophoblast and is formed by cells originating from the hypoblast.
What is the primitive yolk sac and how is it formed?
-The primitive yolk sac is formed by the exosomic membrane and cells of the hypoblast together, which form its walls.
What are lacunae and how do they relate to the developing embryo?
-Lacunae are small holes that begin to form in the syncytiotrophoblast as it continues to expand. They later fuse to form large interconnecting spaces called lacuna networks.
How is uteroplacental circulation established during early development?
-Uteroplacental circulation is established as the syncytiotrophoblast expands, eroding the lining of the sinusoids and uterine glands, allowing maternal blood and uterine secretions to flow into the lacunar networks.
What is the extraembryonic mesoderm and when does it appear?
-The extraembryonic mesoderm is a new population of cells that appear between the inner surface of the cytotrophoblast and the outer surface of the primitive yolk sac.
What is the chorionic cavity and how does it form?
-The chorionic cavity is a single cavity that forms in the extraembryonic mesoderm as large cavities begin to appear and gradually fuse.
What is the secondary yolk sac and how is it formed?
-The secondary yolk sac is a smaller cavity that forms when a large portion of the exocoelomic cavity is pinched off around 13 days after fertilization.
What is the connecting stalk and its role in development?
-The connecting stalk is a band of extraembryonic mesoderm that joins the bilaminar embryonic disc to the trophoblast by the end of the second week of development, which will become the future umbilical cord.
Outlines
🌱 Early Development of the Blastocyst
The implantation of the blastocyst typically takes place 6 to 8 days post-fertilization. By the end of day 8, it has embedded into the uterine endometrium, consisting of the Trophoblast and the Inner Cell Mass. The Trophoblast differentiates into the cytotrophoblast and syncytiotrophoblast upon contact with the endometrium. Meanwhile, the Inner Cell Mass evolves into a bilaminar embryonic disc composed of the hypoblast and epiblast. A cavity, the amniotic cavity, emerges between the epiblast and the cytotrophoblast. Cells from the hypoblast migrate to form the exosomatic membrane, which, along with the hypoblast, constitutes the primitive yolk sac's walls. By Day N, the blastocyst is fully embedded, with the cytotrophoblast and syncytiotrophoblast growing faster than the embryonic disc. Lacunae form in the syncytiotrophoblast and by day 12, these fuse into lacuna networks. Maternal sinusoids form around the embryo as the syncytiotrophoblast expands, and enzymes erode the sinusoids' lining, allowing maternal blood and uterine secretions to flow into the lacunae, establishing uteroplacental circulation. The extraembryonic mesoderm appears, and the exocoelomic cavity eventually forms the secondary yolk sac. By the end of the second week, the chorionic cavity enlarges, and the bilaminar embryonic disc is connected to the Trophoblast by the connecting stalk, which will become the umbilical cord.
Mindmap
Keywords
💡Implantation
💡Blastocyst
💡Trophoblast
💡Embryoblast
💡Cytotrophoblast
💡Syncytiotrophoblast
💡Amniotic Cavity
💡Exocoelomic Membrane
💡Extraembryonic Mesoderm
💡Connecting Stalk
💡Uteroplacental Circulation
Highlights
Implantation of the blastocyst occurs 6 to 8 days after fertilization.
By the end of day 8, the blastocyst has embedded into the endometrium of the uterus.
The blastocyst is composed of the Trophoblast and the Inner Cell Mass.
The Trophoblast differentiates into an inner cytotrophoblast and an outer syncytiotrophoblast upon contact with the endometrium.
The Inner Cell Mass differentiates into a bilaminar embryonic disc composed of the hypoblast and the epiblast.
A cavity begins to form between the epiblast and the cytotrophoblast known as the amniotic cavity.
Cells from the hypoblast form a thin membrane called the exosomic membrane.
The exosomic membrane and hypoblast cells form the walls of the primitive yolk sac.
By Day N, the blastocyst is completely embedded in the uterus wall.
The growth of the syncytiotrophoblast and cytotrophoblast is much quicker than the bilaminar embryonic disc.
Small holes called lacunae form in the syncytiotrophoblast as it continues to expand.
By day 12, the lacunae stop growing and fuse to form large interconnecting spaces called lacunae networks.
Capillaries in the endometrium dilate, forming maternal sinusoids.
Syncytiotrophoblast enzymes erode the lining of the sinusoids and uterine glands, allowing maternal blood and uterine secretions to flow into the lacunar networks.
A uteroplacental circulation is established, facilitating the exchange of gases and metabolites.
A new population of cells, the extraembryonic mesoderm, appears between the cytotrophoblast and the primitive yolk sac.
Large cavities in the extraembryonic mesoderm fuse to form the chorionic cavity.
Around 13 days after fertilization, a portion of the exocoelomic cavity is pinched off to form the secondary yolk sac.
By the end of the second week, the chorionic cavity enlarges, and the bilaminar embryonic disc is joined to the Trophoblast by the connecting stalk.
The connecting stalk is the precursor to the future umbilical cord.
Transcripts
implantation of the blastocyst usually
occurs 6 to 8 days after fertilization
by the end of day 8 the blastocyst has
borrowed into the endometrium of the
uterus at this time it is composed of
two main components the outer cell Mass
the Tropa blast and the Inner Cell Mass
the embrya blast as the Tropa blast
makes contact with the endometrium it
differentiates into two layers an inner
cytotrophoblast and an outer sinot Tropa
blast the embryoblast differentiates
into a bilaminar embryonic dis composed
of two cell layers the
hypoblast and the
epiblast soon after the embryonic disc
has formed a cavity begins to appear
between the epiblast and the
cytotrophoblast known as the amniotic
cavity cells originating from the
hypoblast begin to migrate forming a
thin membrane which covers the inner
surface of the cyot Tropa blast this is
called the exosomic membrane the
exosomic membrane and cells of the
hypoblast together form the walls of the
primitive yoke sack by Day N the
blastocyst is completely embedded in the
uterus wall at this stage of development
the growth of the ciot Tropa blast and
cytotrophoblast is much quicker than the
bamer embryonic disc small holes called
launi begin to form in the cciio Tropa
blast as it continues to
expand by day 12 the lacuni stop growing
and fuse to form large interconnecting
spaces called Lacuna networks
capillaries in the endometrium
surrounding the developing embryo dilate
forming maternal sinusoids as the sinot
Tropa blast continues to expand enzymes
begin to erode the lining of the
sinusoids and uterine glands allowing
maternal blood and uterine secretions to
flow into the luner neck networks
establishing a uteroplacental
circulation the blood and uterine
secretions only come into close
proximity to the embryo allowing the
exchange of gases and
metabolites around the same time a new
population of cells appear between the
inner surface of the cyot Tropa blast
and the outer surface of the Primitive
yolk Sac known as the extra embryonic
mesoderm large cavities begin to appear
in the extraembryonic
mesoderm these gradually fuse to form
one single cavity called the chonic
cavity around 13 days after
fertilization a large portion of the
exosomic cavity is pinched off forming a
smaller cavity the secondary yolk sack
by the end of the second week of
development the chonic cavity enlarges
and the bilaminar embryonic disc is
joined to the Tropa Blast by a band of
extraembryonic mesoderm called the
connecting stock the future umbilical
cord
5.0 / 5 (0 votes)