Basic Embryology Flashcards
What is the difference between prenatal, fetal, and gestational ages?
Prenatal refers to before birth, fetal age is from conception to birth (38 weeks), and gestational age is measured from the last menstrual period (40 weeks).
What are the key events in the embryonic period?
The first 8 weeks where all major organs are formed.
What are the key events in the fetal period?
The remaining 30 weeks where organs grow larger and become more complex.
What occurs during ovulation and fertilization?
The egg is released into the peritoneal cavity, and fertilization occurs in the fallopian tube when maternal and paternal genetic material join to form a zygote.
What are cleavage stages such as morula, blastomere, and blastocyst?
Cleavage is the process where the zygote divides, forming blastomeres, then a morula (12-16 cells), and later a blastocyst.
What are the functions of the inner cell mass and trophoblast?
The inner cell mass forms the embryo, while the trophoblast forms the placenta.
What is the difference between bilaminar and trilaminar embryonic discs?
Bilaminar consists of epiblast and hypoblast layers, while trilaminar includes three primary germ layers: ectoderm, mesoderm, and endoderm.
What are the three germ layers and their significance?
Ectoderm, mesoderm, and endoderm are the primary germ layers from which all body tissues develop.
What is gastrulation and its importance?
Gastrulation is the process where the epiblast cells invaginate to form the three germ layers.
What role does the notochord play in neurulation?
The notochord signals the ectoderm to begin forming the neural plate, leading to the development of the brain and spinal cord.
What are the stages of neurulation?
Neural plate forms the neural groove, which eventually becomes the neural tube.
Why is folic acid important for neural tube closure?
Folic acid is crucial in preventing neural tube defects by ensuring proper closure of the neural tube.
What are somites, intermediate mesoderm, and lateral plate mesoderm?
They are regions of the mesoderm that differentiate to form structures like muscles, urogenital systems, and serous cavities.
What are the derivatives of mesodermal divisions?
Somatic mesoderm forms the body wall, and splanchnic mesoderm forms internal organs.
What is embryo folding, and when does it occur?
Embryo folding begins at week 4, leading to the cylindrical body plan.
What are the major events by the end of week 4 and week 8 in embryonic development?
By week 4, the embryo begins to fold, and by week 8, all major organs are in rudimentary form.
When does the heart start pumping in embryonic development?
The heart starts pumping around day 29, which is approximately 4 weeks into development.
Why is drug avoidance important during early pregnancy?
Drugs can cause birth defects during the critical period when major organs are forming.
What is the difference between monozygotic and dizygotic twins?
Monozygotic twins come from one zygote that splits, while dizygotic twins come from two separate eggs fertilized by two sperm.
What is the significance of neural crest cells?
Neural crest cells give rise to sensory nerve cells and other structures in the peripheral nervous system.
What is the primitive streak and its role?
The primitive streak is a structure that forms on the surface of the epiblast and is crucial for gastrulation.
What is the importance of the amniotic and yolk sacs?
The amniotic sac provides a protective environment for the embryo, and the yolk sac supports nutrient supply during early development.
What are the serous cavities, and how do they form?
Serous cavities like peritoneal, pericardial, and pleural cavities form from the lateral plate mesoderm.
What structures form from the lateral plate mesoderm?
The lateral plate mesoderm splits into somatic (parietal) mesoderm and splanchnic (visceral) mesoderm, forming the serous membranes around organs.
