MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedonyuk 2010

BIOLOGY

SECTION 1. BIOLOGICAL FOUNDATIONS OF HUMAN VITAL ACTIVITY

1.4. ONTOGENETIC LEVEL OF LIFE ORGANIZATION

1.4.3. Biology of Individual Development

Embryonic Induction

Embryonic induction refers to the influence exerted by an earlier-developing part of an embryo on the directed development of a later-developing part. The foundation of embryonic induction lies in the interaction between different embryonic regions. The Study of this phenomenon was pioneered by the classical experiment of H. Spemann and H. Mangold (1924). In normal newt development, the ectoderm located on the DORSAL SIDE OF the embryo gives rise to the neural tube. However, if the region of the dorsal blastopore lip adjacent to the dorsal ectoderm is removed at a later gastrula stage, the neural tube fails to form. Conversely, when the dorsal blastopore lip is transplanted beneath the ventral ectoderm, it induces The formation of a neural tube, other axial Organs (notochord, somites), and ultimately leads to The Development of a secondary embryo. Observations using pigmented and non-pigmented Cells demonstrated that these Tissues are formed exclusively from the recipient's cellular material. The region of the embryo that directs the development of another region along a specific pathway was designated as the organizing center (organizer, inductor). The dorsal lip of the blastopore serves as the primary inductor (organizer) in amphibians. In fish, its equivalent is the dorsal margin of the blastodisc, while in birds, it is Hensen's node (the primitive node). The dorsal lip possesses the unique capacity to organize and trigger embryonic development; no other cells share this property. In the absence of the dorsal lip, development cannot proceed. The lip induces the Development of the neural tube while differentiating itself into the notochord and somites. Primary embryonic induction represents the initial step in a chain of successive (secondary, tertiary) induction processes during subsequent development.

development. The primordium of almost any organ undergoes two phases in its development. During the dependent differentiation phase, its developmental fate relies on METABOLISM/18.html">The Influence of an inductor and the external environment—a transplantation to a new Location results in transdifferentiation (e.g., transplanting the blastopore lip anywhere else triggers neural tube development at that site). During the independent differentiation phase, such transplantation no longer alters the developmental pathway. Subsequent research into embryonic induction focused on determining the Chemical Nature of these inductors. In 1970, H. Tiedemann isolated protein-based inductors from chick embryos. One of these induces the formation of Nervous system structures and Sense Organs, while the other induces The Muscular System. These inductors enter The Nucleus and activate the expression of the corresponding genes.