PRACTICAL WORKSHOP ON HISTOLOGY, CYTOLOGY AND EMBRYOLOGY - 2016

Chapter 3. GENERAL EMBRYOLOGY. HUMAN EMBRYOLOGY.

Slide 20. Cross-section of a chick embryo at the stage of formation of body and amniotic folds.

Staining: Heidenhain's iron hematoxylin.

Magnification: x80.

The section was prepared from a chick embryo on the second day of incubation. The cutaneous ectoderm (1) covers the entire embryo. A deep body fold (2) forms laterally, separating the embryo from the extraembryonic space. Dorsally, amniotic folds (3), formed by the extraembryonic ectoderm and parietal mesoderm, rise above the body folds. The right and left folds subsequently fuse above the embryo, forming the amniotic raphe along the midline, from which the amniotic folds transition into the serous membrane. The amniotic cavity (4) forms above the body of the embryo and is filled with Amniotic Fluid, in which the further Development of the embryo takes place. On the dorsal surface of the embryo, a cross-section of the Spinal Cord (5) is visible, with a neurocoel wider than in the previous slide. The notochord (6) lies directly beneath the spinal cord. More ventrally to the notochord are the paired dorsal aortas (7). In the somites, distinct clusters of mesenchyme can be distinguished around the neural tube and notochord—the sclerotome (8), which subsequently forms the cartilaginous and bony Tissues of the spine. The remaining Cells of the somite divide into a dorsal group—the dermatome (9)—and a ventral group—the myotome (10). A coelomic cavity (11) has formed between the parietal and visceral leaves of the splanchnotome, extending laterally into the extraembryonic coelomic space. Ventrally, the embryo is bounded by the endoderm (12). Along the body axis, it forms the intestinal groove (13).

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Slide 20. Cross-section of a chick embryo at the stage of formation of body and amniotic folds.