Gastrulation patterns are therefore also affected by the amount and distribution of yolks. Movements in gastrulation starts when cells are arranged after establishment during cleavage and blastulation. The oval-shaped gastrula is transformed into an elongated embryo with a distinct head and an ovoid body while other events are taking place in the interior of the embryo such as the formation of somites and the transformation of the lateral plate mesoderm into somatic and splanchnic mesoderm. The gastrula becomes a neurula when the neural plate is formed. This is later transformed into neural folds, creating a groove, and then into neural tube from which the brain and spinal cord are formed. The future notochord tissue (chordamesoderm) acts on the overlapping ectoderm in order to transform the cells into a plate of thickened cells, the neural plate. It is initiated during late gastrulation. In vertebrates, the first phase of organogenesis is neurulation. The splanchnic mesoderm gives rise to the smooth muscles and connective tissues of the digestive tract. Somatic mesoderm gives rise to connective tissues and blood vessels of the body wall. The intermediate mesoderm gives rise to kidney tubules and their ducts. The dorsal mesoderm gives rise to vertebrae and skeletal muscles. The endoderm gives rise to the epithelium of the alimentary canal, the oral glands, and the epitheloid components of evaginations from the foregut, midgut, and hindgut. The ectoderm gives rise to structures such as the epidermis and its derivatives and glands, the nervous system, the lens, retina, and sensory epithelium if sensory organs, and the lining and derivatives of the stomodeum and proctodeum. ![]() It commences with involution in microlecithal eggs, epiboly in mesolecithal eggs, and delamination in macrolecithal eggs. The gastrulation process is based on morphogenetic movements if undifferentiated cells to form the germ layers (ectoderm, endoderm, and mesoderm). It transforms the blastula into an embryo with the germ layers, ectoderm, and endoderm for diploblastic animals, plus a third layer, the mesoderm, in triploblastic animals. ![]() Introduction Gastrulation is a highly complicated process in early development. To understand the mechanisms of neural tube formation. To compare gastrulation in vertebrates and invertebrates. To distinguish between early and late stages. Objectives At the end of this exercise, the student should be able: a. ACTIVITY #5 Gastrulation and Neurulation I.
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