Study 2c Embryogenesis Germ Layers in MCAT Biological and Biochemical Foundations of Living Systems with focused flashcards that help you recognize the idea, recall the key rule, and apply it in practice-style prompts.
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Flashcard 1: What process forms the blastocoel during blastulation?
Answer: Fluid accumulation creates a central cavity. Occurs as trophoblast cells secrete fluid, transforming the morula into a blastocyst.
Flashcard 2: What is the zygote in human development?
Answer: A diploid cell formed by fusion of sperm and oocyte. Results from fertilization, combining genetic material to initiate embryonic development.
Flashcard 3: What is the primitive streak in mammals?
Answer: A groove where epiblast cells ingress during gastrulation. Defines the embryonic axis and site for mesoderm and endoderm formation in amniotes.
Flashcard 4: Identify the germ layer that forms the adrenal cortex.
Answer: Mesoderm. Intermediate mesoderm gives rise to urogenital structures including the steroid-producing adrenal cortex.
Flashcard 5: Which structure in the human blastocyst becomes the embryo proper?
Answer: Inner cell mass (embryoblast). Contains pluripotent cells that differentiate into all embryonic tissues during development.
Flashcard 6: What is cleavage in early embryogenesis?
Answer: Rapid mitotic divisions without overall embryo growth. Divides the zygote into smaller blastomeres while maintaining constant volume until blastula formation.
Flashcard 7: What is invagination during gastrulation?
Answer: Inward folding of a cell sheet into the embryo. Creates internal cavities like the archenteron by bending epithelial sheets during layer formation.
Flashcard 8: What is the blastopore?
Answer: The opening of the archenteron to the exterior. Becomes the anus in deuterostomes or mouth in protostomes, connecting archenteron externally.
Flashcard 9: Which embryonic structure induces overlying ectoderm to form neural tissue?
Answer: Notochord. Mesodermal structure secretes signaling molecules like Shh to pattern neural plate formation.
Flashcard 10: What is neurulation?
Answer: Formation of the neural tube from the neural plate. Involves ectodermal thickening, folding, and closure induced by notochord for CNS development.
Flashcard 11: Which germ layer gives rise to the epithelial lining of the GI and respiratory tracts?
Answer: Endoderm. Innermost layer develops into internal linings and glands via epithelial folding.
Flashcard 12: What is the morula stage of embryonic development?
Answer: A solid ball of cells formed after cleavage. Represents compaction of blastomeres before fluid accumulation leads to blastocyst stage.
Flashcard 13: Which germ layer gives rise to muscle, bone, blood, and kidneys?
Answer: Mesoderm. Middle layer forms supportive and connective tissues through segmentation and differentiation.
Flashcard 14: What is implantation?
Answer: Embedding of the blastocyst into the endometrium. Occurs around day 6-7 post-fertilization, establishing maternal-fetal interface for nutrient exchange.
Flashcard 15: Identify the germ layer that forms the adrenal medulla.
Answer: Ectoderm (neural crest). Neural crest cells migrate to form chromaffin cells of the medulla, producing catecholamines.
Flashcard 16: What is gastrulation?
Answer: Reorganization forming ectoderm, mesoderm, and endoderm. Establishes the three primary germ layers essential for organogenesis in triploblastic animals.
Flashcard 17: Which option correctly matches germ layer to derivative: liver parenchyma?
Answer: Endoderm. Hepatocytes derive from endodermal foregut diverticulum during organogenesis.
Flashcard 18: Which germ layer gives rise to the epidermis and nervous system?
Answer: Ectoderm. Outermost layer differentiates into external and neural tissues via inductive signals.
Flashcard 19: What is the blastula (blastocyst in humans)?
Answer: A hollow ball of cells surrounding a fluid-filled cavity. Forms after cleavage and cavitation, preparing for implantation and gastrulation.
Flashcard 20: Which structure in the human blastocyst primarily contributes to the placenta?
Answer: Trophoblast (outer cell layer). Differentiates into syncytiotrophoblast and cytotrophoblast, facilitating implantation and placental formation.
Flashcard 21: What is the archenteron?
Answer: The primitive gut formed during gastrulation. Develops into the digestive tract lining through gastrulation movements in deuterostomes.
Flashcard 22: What is a blastomere?
Answer: A cell produced by cleavage divisions of the zygote. Each is totipotent initially, contributing to the morula through successive cleavages.
Flashcard 23: What is involution during gastrulation?
Answer: Rolling of a cell sheet inward over an internal surface. Allows cells to move interiorly along an internal surface, contributing to mesoderm formation.
Flashcard 24: What is delamination in early embryonic development?
Answer: Splitting of one cell sheet into two parallel sheets. Separates cell layers without migration, often forming endoderm from hypoblast in some species.
Flashcard 25: What is ingression during gastrulation?
Answer: Individual cells migrate inward from the surface layer. Facilitates individual cell migration to form new layers, as seen in primitive streak gastrulation.