Embryology: Blastocyst & Bilaminar Disc
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Questions and Answers

What structure differentiates first in the inner cell mass during embryonic development?

  • Hypoblast (correct)
  • Trophoblast
  • Epiblast
  • Chorionic villi

Which of the following accurately describes the function of chorionic villi?

  • They are responsible for the differentiation of epiblasts.
  • They facilitate nutrient and gas exchange between the mother and embryo. (correct)
  • They assist in the development of the primary yolk sac.
  • They primarily contribute to the formation of the amniotic cavity.

Which extraembryonic structure develops into the amniotic cavity?

  • Embryotroph
  • Epiblast (correct)
  • Chorionic cavity
  • Blastocyst cavity

What is the primary role of the endometrial glands during early embryonic development?

<p>They produce nutrients for the developing embryo. (A)</p> Signup and view all the answers

At what stage does the primary yolk sac begin to develop?

<p>After the formation of the chorionic cavity. (A)</p> Signup and view all the answers

What structure forms from the hypoblast during the early stages of embryonic development?

<p>Primary yolk sac (B)</p> Signup and view all the answers

Which component is primarily responsible for eroding the endometrium during implantation?

<p>Syncytiotrophoblasts (C)</p> Signup and view all the answers

What is the primary function of HCG secreted by the syncytiotrophoblast?

<p>Sustains the corpus luteum (A)</p> Signup and view all the answers

The development of which structure indicates the formation of the bilaminar embryonic disc?

<p>Epiblast and hypoblast (B)</p> Signup and view all the answers

Which structure develops from extraembryonic mesoderm during early embryonic growth?

<p>Chorionic cavity (C)</p> Signup and view all the answers

What is the significance of the lacunar spaces found within syncytiotrophoblasts during implantation?

<p>They allow for nutrient and gas exchange. (D)</p> Signup and view all the answers

What is the sequence of development starting from the morula to the formation of the blastocyst?

<p>Morula → Blastocyst → Bilaminar disc → Epiblast (C)</p> Signup and view all the answers

Which embryonic layer is responsible for forming structures like the heart and muscles in the developing embryo?

<p>Mesoderm (C)</p> Signup and view all the answers

What is formed during the second week of embryonic development?

<p>Primary villi (D)</p> Signup and view all the answers

Which structure is responsible for the formation of the chorionic cavity?

<p>Extraembryonic mesoderm clefts (A)</p> Signup and view all the answers

Which layer forms the interface between maternal blood and embryonic tissues?

<p>Cytotrophoblast (C)</p> Signup and view all the answers

What splits to form somatic and splanchnic layers of mesoderm?

<p>Extraembryonic coelom (D)</p> Signup and view all the answers

What primarily forms the yolk sac endoderm?

<p>Extraembryonic endodermal lining of yolk sac (B)</p> Signup and view all the answers

Which of the following statements about the development of the amniotic cavity is correct?

<p>It develops during the second week. (B)</p> Signup and view all the answers

What happens to the primary yolk sac by the end of the third week?

<p>It starts to shrink. (D)</p> Signup and view all the answers

The bilaminar embryonic disc consists of which two primary layers?

<p>Epiblast and hypoblast (B)</p> Signup and view all the answers

What is the primary function of the chorion during early development?

<p>Gas exchange (D)</p> Signup and view all the answers

What structure fills the space between the cytotrophoblast and the primary yolk sac?

<p>Extraembryonic mesoderm (A)</p> Signup and view all the answers

Study Notes

Blastocyst & Bilaminar Disc

  • The blastocyst forms from the morula
  • The inner cell mass differentiates into hypoblasts (primary endoderm) and epiblasts (ectoderm)
  • Appearance of body stalk and prochordal plate
  • The hypoblasts differentiate by day 7
  • The epiblasts appear next and form the amniotic cavity by enlarging
  • The bilaminar embryonic disc is formed by the hypoblast and epiblast
  • The primary yolk sac is formed by the hypoblast
  • Extraembryonic mesoderm fills the space between cytotrophoblast and amnion
  • Extraembryonic mesoderm is derived from the yolk sac endoderm
  • The extraembryonic coelom (chorionic cavity) is formed by the fusion of clefts in the extraembryonic mesoderm
  • The chorionic cavity splits the extraembryonic mesoderm into somatic and splanchnic layers
  • The primary yolk sac shrinks to form the secondary (definitive) yolk sac
  • The chorionic sac is formed during the second week

Chorionic Villi & Embryotroph

  • The syncytiotrophoblast shows villous projections and lacunar spaces
  • The syncytiotrophoblast secretes proteolytic enzymes to erode the endometrium and human chorionic gonadotropin (HCG) to sustain the corpus luteum

Endometrial Gland

  • The syncytiotrophoblast erodes the endometrium to allow the blastocyst to burrow into the compact layer of endometrium
  • This process begins on the 5th day and finishes on the 10th day
  • This is part of the implantation process

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2nd Week of Development (2024)

Description

Test your knowledge on the formation of the blastocyst and the development of the bilaminar embryonic disc. This quiz covers key concepts such as the differentiation of hypoblasts and epiblasts, the appearance of the amniotic cavity, and the formation of extraembryonic structures. Perfect for students studying embryology!

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