Embryogenesis and Germ Layer Formation (2C) - Bio & Biochem
- What process forms the blastocoel during blastulation?
- Fluid accumulation creates a central cavity. Occurs as trophoblast cells secrete fluid, transforming the morula into a blastocyst.
- What is the zygote in human development?
- A diploid cell formed by fusion of sperm and oocyte. Results from fertilization, combining genetic material to initiate embryonic development.
- What is the primitive streak in mammals?
- A groove where epiblast cells ingress during gastrulation. Defines the embryonic axis and site for mesoderm and endoderm formation in amniotes.
- Identify the germ layer that forms the adrenal cortex.
- Mesoderm. Intermediate mesoderm gives rise to urogenital structures including the steroid-producing adrenal cortex.
- Which structure in the human blastocyst becomes the embryo proper?
- Inner cell mass (embryoblast). Contains pluripotent cells that differentiate into all embryonic tissues during development.
- What is cleavage in early embryogenesis?
- Rapid mitotic divisions without overall embryo growth. Divides the zygote into smaller blastomeres while maintaining constant volume until blastula formation.
- What is invagination during gastrulation?
- Inward folding of a cell sheet into the embryo. Creates internal cavities like the archenteron by bending epithelial sheets during layer formation.
- What is the blastopore?
- The opening of the archenteron to the exterior. Becomes the anus in deuterostomes or mouth in protostomes, connecting archenteron externally.
- Which embryonic structure induces overlying ectoderm to form neural tissue?
- Notochord. Mesodermal structure secretes signaling molecules like Shh to pattern neural plate formation.
- What is neurulation?
- Formation of the neural tube from the neural plate. Involves ectodermal thickening, folding, and closure induced by notochord for CNS development.
- Which germ layer gives rise to the epithelial lining of the GI and respiratory tracts?
- Endoderm. Innermost layer develops into internal linings and glands via epithelial folding.
- What is the morula stage of embryonic development?
- A solid ball of cells formed after cleavage. Represents compaction of blastomeres before fluid accumulation leads to blastocyst stage.
- Which germ layer gives rise to muscle, bone, blood, and kidneys?
- Mesoderm. Middle layer forms supportive and connective tissues through segmentation and differentiation.
- What is implantation?
- Embedding of the blastocyst into the endometrium. Occurs around day 6-7 post-fertilization, establishing maternal-fetal interface for nutrient exchange.
- Identify the germ layer that forms the adrenal medulla.
- Ectoderm (neural crest). Neural crest cells migrate to form chromaffin cells of the medulla, producing catecholamines.
- What is gastrulation?
- Reorganization forming ectoderm, mesoderm, and endoderm. Establishes the three primary germ layers essential for organogenesis in triploblastic animals.
- Which option correctly matches germ layer to derivative: liver parenchyma?
- Endoderm. Hepatocytes derive from endodermal foregut diverticulum during organogenesis.
- Which germ layer gives rise to the epidermis and nervous system?
- Ectoderm. Outermost layer differentiates into external and neural tissues via inductive signals.
- What is the blastula (blastocyst in humans)?
- A hollow ball of cells surrounding a fluid-filled cavity. Forms after cleavage and cavitation, preparing for implantation and gastrulation.
- Which structure in the human blastocyst primarily contributes to the placenta?
- Trophoblast (outer cell layer). Differentiates into syncytiotrophoblast and cytotrophoblast, facilitating implantation and placental formation.
- What is the archenteron?
- The primitive gut formed during gastrulation. Develops into the digestive tract lining through gastrulation movements in deuterostomes.
- What is a blastomere?
- A cell produced by cleavage divisions of the zygote. Each is totipotent initially, contributing to the morula through successive cleavages.
- What is involution during gastrulation?
- Rolling of a cell sheet inward over an internal surface. Allows cells to move interiorly along an internal surface, contributing to mesoderm formation.
- What is delamination in early embryonic development?
- Splitting of one cell sheet into two parallel sheets. Separates cell layers without migration, often forming endoderm from hypoblast in some species.
- What is ingression during gastrulation?
- Individual cells migrate inward from the surface layer. Facilitates individual cell migration to form new layers, as seen in primitive streak gastrulation.