lorganogenesi

Organogenesis, or organ formation, is the stage of embryonic development during which the rudiments of all major organs are established from the three germ layers: ectoderm, mesoderm, and endoderm. It follows gastrulation and neurulation and, in humans, spans roughly from week 3 to week 8 of gestation. During this period developing tissues undergo patterning, cell differentiation, and morphogenesis to produce organ primordia that will grow and mature later in fetal life.

Mechanisms guiding organogenesis involve signaling pathways and tissue interactions that regulate spatial patterning and differentiation. Key pathways include Wnt, BMP, FGF, Hedgehog, and Notch, along with transcription factors from the Hox, Sox, Pax, and Nkx families. Interactions among endodermal, mesodermal, and ectodermal tissues drive morphogenetic movements such as budding, invagination, branching morphogenesis (as seen in the lungs and glands), elongation, and tubulogenesis, which shape organ architecture.

Examples of organ primordia formed during organogenesis include the neural tube, heart, limbs, lungs, liver, pancreas, and kidneys. The neural tube gives rise to the brain and spinal cord; the heart forms from early mesodermal fields; the lungs develop through airway branching; the liver and pancreas originate from foregut endoderm; and the kidneys arise from intermediate mesoderm.

Disruptions of organogenesis, due to genetic mutations, teratogenic exposure, or nutritional deficiencies, can lead to congenital anomalies. Organogenesis is followed by maturation and growth of organs during fetal development and continuing postnatally in many tissues.