Developmental Biology

Adhesion molecules are critical for an array of biological processes. For instance, in development they play key roles in tissue morphogenesis, cell migration, and axon guidance. In the immune system, they regulate leukocyte interactions and are important for cell activation. They also mediate leukocyte contact with blood vessel endothelia and are essential for transmigration. Pathologically, adhesion molecules affect tumor cell invasiveness and metastases.Inflammatory cell recruitment requires the concerted action of at least five major sets of adhesion molecules: integrins, immunoglobulin-like molecules, selectins, carbohydrate structures serving as selectin ligands, and certain ectoenzymes.

The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.

The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.

Gastrulation, occurring during the second week after fertilization, involved the formation of the three fundamental germ layers of the embryo – the ectoderm, the mesoderm, and the endoderm. During this time, important signal-calling phenomena – called embryonic inductions – set the molecular stage for the initiation of organ formation. In addition, the fundamental asymmetry of the body is set in place.

The immune system is a complex network of cells, tissues and organs that work together to protect the body from harmful substances and organisms and defend against disease. The immune system can be classified into distinct responses, such as innate immunity and adaptive immunity, or humoral immunity and cell-mediated immunity.

Growth factors and morphogens regulate embryonic patterning, cell fate specification, cell migration, and morphogenesis. The activity and behavior of these signaling molecules are regulated in the extracellular space through interactions with proteoglycans.The formation of morphogen concentration gradients directs the biological responses of surrounding cells. Graded responses occur as a result of morphogens binding to specific cell surface receptors that subsequently activate intracellular signaling pathways and promote or repress gene expression at specific threshold concentrations. Activation or inactivation of these signaling pathways provides positional information that ultimately determines cell fate decisions, tissue organization, and morphology. Research in model organisms has revealed that morphogenetic fields are involved in many aspects of development. Research in higher organisms has demonstrated that homologues of these same signaling molecules regulate vertebrate axis formation, anterior/posterior polarity during limb development, mesoderm patterning, and numerous other processes that establish an organism’s basic body structure.