organogenesis
Summary
Organogenesis is the process of organ formation during embryonic development, occurring primarily during weeks 3-8 of human gestation. This critical period involves the differentiation of the three primary germ layers into specific organ systems. It represents the most teratogen-sensitive period of development.
Detail
Organogenesis is the fundamental developmental process where the three primary germ layers (ectoderm, mesoderm, and endoderm) differentiate into specific organ systems during the embryonic period. In humans, this occurs primarily between weeks 3-8 of gestation, following gastrulation. The ectoderm gives rise to the nervous system, skin, and sensory organs; the mesoderm forms the musculoskeletal, cardiovascular, and genitourinary systems; and the endoderm develops into the gastrointestinal tract, lungs, and associated glands. This period is characterized by rapid cell division, migration, differentiation, and programmed cell death (apoptosis). Critical signaling pathways including Wnt, Hedgehog, and TGF-β coordinate these complex processes. Organogenesis is the most vulnerable period to teratogenic influences, as disruption during this time can cause major structural birth defects. Understanding organogenesis is essential for recognizing congenital anomalies, timing of teratogen exposure effects, and normal versus abnormal development patterns.
Sources
- Langman's Medical Embryology
- Moore's The Developing Human
- First Aid for the USMLE Step 1
- Robbins Basic Pathology
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