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# Embryology **2) Morula Formation** * Solid ball of 16-32 blastomeres. * Formed by the 3rd day. * Enter the uterus. **3) Blastocyst Formation** * Outer layer → trophoblast → gives placenta → fetal part * Inner cell mass → embryoblast → gives embryo * Blastocyst attaches to endometrial epitheliu...

# Embryology **2) Morula Formation** * Solid ball of 16-32 blastomeres. * Formed by the 3rd day. * Enter the uterus. **3) Blastocyst Formation** * Outer layer → trophoblast → gives placenta → fetal part * Inner cell mass → embryoblast → gives embryo * Blastocyst attaches to endometrial epithelium on the 6th day (implantation). **Second Week** **Formation of bilaminar embryonic disk** 1. Differentiation of embryoblast into 2 germ layers (ectoderm & endoderm). 2. Formation of two cavities: * a) Amniotic cavity - epiblast forms the floor. * b) Secondary yolk sac - hypoblast forms the roof. 3. Development of Prochordal plate. **Prochordal plate** * Region of slight enlargement of ectodermal and endodermal cells at the cephalic end of the embryo, where there is a firm union between ectodermal and endodermal cells. * Represents the future buccopharyngeal membrane. * Establishes the axis of the embryo (cephalic & caudal ends). **Cecal plate** * Linear thickening of epiblast with firm attachment to hypoblast. **Prochordal plate** * Circular thickening of hypoblast with firm attachment to epiblast. **Summary of Important Points** * Zygote is protected by zonula pellucida which is disintegrated with proliferation and implantation. * There are special types of blastomeres with projections that are responsible for zygote attachment. **Diagram Details**(Note: Image descriptions below attempt to convey the key features based on the image quality as a simplified description to avoid misunderstandings/incompleteness): The image presents diagrams and text that describe the stages of embryo development. Diagrams show different stages of the embryo development process (morula, blastocyst, etc.). There are annotations and arrows to describe the formations of cavities, layers and parts involved in these stages. Specific regions like the amniotic cavity, hypoblast, epiblast, trophoblast, and the prochordal plate are labeled in the diagrams. The text provides detailed information about each stage including the time frame, components, and structural features involved during each stage in embryological development. The image includes labels identifying specific structures and phases of development relevant to embryonic formation.