Mechanisms and processes of development

Question 1

Describe and give examples of mechanisms and processes of prenatal development.

Answer 1

The main processes of developments are growth, morphogenesis and specialisation. Growth is achieved through increase in cell number (proliferation), increase in cell size and increase in the amount of extracellular material. Morphogenesis is the creation of shapes of cells, tissues and organs and specialisation is the change of non-specialised cells and tissues to specialised cells and tissues with specific functions.

Question 2

Briefly describe three mechanisms of development that contribute to the development of a specific organ

Answer 2

For the lungs.

Cell-cell interactions: interactions (depending on signalling mediated by soluble proteins,
cell-surface proteins or ECM proteins and the receptors for the signalling molecules) between endoderm-derived epithelium of a bronchus with surrounding mesoderm-derived mesenchyme results in branching morphogenesis, in which a bronchus divides into two bronchi and this process repeats.

Specialisation (differentiation): the mesenchyme (relatively undifferentiated, primitive connective tissue) derived from mesoderm differentiates into cartilage, smooth muscle, and CT of bronchi. This requires the induction and maintenance of expression of specific sets of genes in the various differentiated cell types.

Morphogenesis: creation of cell shape when simple cuboidal epithelium of the end part of a small bronchiole tube contacts a capillary and changes shape through rearrangement of the cytoskeleton to simple squamous, forming the lining of the alveolus.