Embryonic Development Stages Quiz

Embryonic Development

• Embryonic development is the process by which a fertilized egg develops into a fetus.
• It consists of three stages: zygote, embryo, and fetus.

Week 1-2: Zygote Stage

• Fertilization: sperm penetrates egg, resulting in a single cell called a zygote.
• Cleavage: zygote undergoes rapid cell division without significant growth.
• Morula: solid ball of cells formed during cleavage.
• Blastula: fluid-filled cavity forms within the morula.

Week 3-4: Blastulation Stage

• Gastrulation: blastula undergoes complex cellular movements, resulting in three primary germ layers:
  • Ectoderm: outer layer, gives rise to skin, nervous system, and sensory organs.
  • Mesoderm: middle layer, gives rise to muscles, bones, and connective tissue.
  • Endoderm: inner layer, gives rise to lining of digestive system and respiratory tract.

Week 5-8: Organogenesis Stage

• Embryonic folding: embryo undergoes rapid growth and folding, forming the body plan.
• Organ formation: germ layers differentiate into specific organs and tissues.

Fetal Development (Week 9-38)

• Growth and maturation of organs and tissues.
• Development of limbs, digits, and facial features.
• Sensory organ development: eyes, ears, and nervous system.

Embryonic Period (Week 3-8)

• Critical period for embryonic development, during which major organ systems form.
• Most susceptible to teratogenic effects (e.g., thalidomide).

Fetal Period (Week 9-38)

• Fetus grows and develops rapidly, but is less susceptible to teratogenic effects.
• Fetal development is influenced by maternal and environmental factors.

Clinical Correlations

• Understanding embryonic development is essential for understanding birth defects and congenital anomalies.
• Knowledge of embryology informs medical and surgical interventions, such as in vitro fertilization and organ transplantation.