Embryology Problem based question (Q1- Langman)

ANATOMY AIIMS, GROSS ANATOMY, EMBRYOLOGY, NEUROANATOMY, MICROANATOMY, APPLIED/ CLINICAL ANATOMY

What is meant by “competence to respond” as part of the process of induction? What tissues are most often involved in induction? Give two examples.

Answer:

"Competence to respond" refers to the ability of a cell or tissue to respond to a signaling molecule, which may be secreted by nearby cells or tissues, and initiate a developmental process. The competence of a cell or tissue to respond to a signal depends on the presence of receptors for that signal on the cell surface, as well as the ability of the intracellular signaling pathways to transduce the signal and initiate a response.

In embryology, induction is a process by which one group of cells or tissues influences the development of another group of cells or tissues through signaling molecules. The responding tissues must be competent to respond to the signaling molecules for induction to occur. This concept is fundamental to the understanding of the development of the body's different structures.

The tissues that are most often involved in induction are those that give rise to the major body systems and organs, such as the neural tube, limb buds, and the eye. For example, the neural tube is induced by the notochord, a structure that secretes signaling molecules such as Sonic Hedgehog (Shh) and Bone Morphogenetic Protein (BMP) to induce the development of the overlying ectoderm into the neural plate, which later folds and fuses to form the neural tube. The limb buds are induced by the underlying mesoderm, which secretes signaling molecules such as FGFs and BMPs to induce the development of the overlying ectoderm into the apical ectodermal ridge (AER). The AER plays a crucial role in limb development and is required for limb outgrowth and patterning.

Another example of induction is the development of the eye, which is induced by the optic vesicle. The optic vesicle secretes signaling molecules such as Fibroblast Growth Factors (FGFs) to induce the overlying ectoderm to form the lens placode, which later invaginates to form the lens vesicle. The optic vesicle also interacts with the surface ectoderm to induce the formation of the cornea.

In summary, competence to respond is the ability of a cell or tissue to respond to a signaling molecule and initiate a developmental process. Induction is a fundamental process in embryology, and it involves the interaction of different tissues through the secretion of signaling molecules. The responding tissues must be competent to respond to the signaling molecules for induction to occur. Examples of tissues involved in induction include the neural tube, limb buds, and the eye.

References:

Gilbert SF. Developmental Biology. 10th edition. Sunderland (MA): Sinauer Associates; 2013. Induction: The Embryological Basis of Development.

Langman J. Medical embryology. 12th ed. Baltimore: Williams & Wilkins; 1993. Induction of the neural plate.

Kengaku M, Okamoto H. Basic principles of development and differentiation of the vertebrate eye. Dev Growth Differ. 1995 Aug;37(4):549-57. doi: 10.1111/j.1440-169x.1995.tb01015.x.