blastoporen

The blastopore is the opening formed during gastrulation in animal embryos that will become part of the digestive tract. It arises as cells of the blastula move inward to form the archenteron, the early gut cavity. The opening at the tip of the archenteron is the blastopore, and its fate varies among major animal groups.

During gastrulation, different cell movements establish the germ layers and rearrange tissues. The blastopore's position and fate are closely linked to the mode of gastrulation in a species. In protostomes, the blastopore typically develops into the mouth, with the anus formed later from a secondary region. In deuterostomes, the blastopore generally becomes the anus, while the mouth forms later from another ectodermal structure (stomodeum).

In amphibians and some other vertebrates, the blastopore lies on the dorsal lip region; this dorsal lip serves as an organizer center that can induce surrounding tissues to form neural structures, a phenomenon demonstrated by Spemann and Mangold in transplantation experiments.

In many species the blastopore eventually closes as the gut forms, and the archenteron differentiates into the internal gut and surrounding tissues. The term blastopore is central to the study of gastrulation and early axis formation in embryology.