Gastrulazione

Gastrulazione, or gastrulation, is a phase of early embryonic development in which a simple blastula reorganizes into a multilayered structure called the gastrula, establishing the three primary germ layers: ectoderm, mesoderm, and endoderm. In Italian, gastrulazione is the term used for this process, which lays the groundwork for the body plan and tissue specification.

Mechanisms of gastrulation vary among species but share common morphogenetic movements. These include invagination (folding inward of a cell sheet), involution (inward migration of cells), delamination (splitting into distinct layers), ingression (individual cells migrating through an opening), and epiboly (expansion of one cell sheet to envelop others). In many amniotes (reptiles, birds, mammals), gastrulation initiates at the primitive streak, where epiblast cells migrate inward to form mesoderm and endoderm, while ectoderm covers the outside. In amphibians, the movement occurs around the vegetal pole via the blastopore, and in fish the process is coordinated with the spreading of the blastoderm over the yolk.

Germ layer derivatives include ectoderm, which forms the epidermis and nervous system; mesoderm, which gives rise to the musculoskeletal, circulatory, excretory, and reproductive systems; and endoderm, which lines the gut and contributes to the organs of the digestive and respiratory systems.

Regulation involves signaling pathways and transcription factors that pattern the embryo. Key pathways include Nodal and Wnt signaling for mesendoderm induction, and BMP signaling for ectodermal fate, with downstream genes such as Brachyury (mesoderm) and Goosecoid (gastro-endoderm/notochord) influencing cell fate and morphogenesis.

Significance: proper gastrulation is essential for correct body axis formation and organ development. Failures in this process can lead to congenital anomalies or pregnancy loss. The process is highly conserved, though the timing and movements differ across taxa.