The term 'environment' is defined as physical surroundings and conditions, especially those affecting the living organisms in the biosphere. Living organisms interact with their physical and biotic environment and sometimes are able to partly modify their environment. However, all the activities of humans are not environmentally friendly and our synthetic methodologies generate substances that are highly toxic to human health [...]
B and T cells contain membrane receptors that react with specific antigenic determinants. B cells are activated by interaction with the antigen either in its dissolved form or while it is still a part of the surface of a pathogen. In contrast, the T cells of an animal are only activated when the antigen is displayed on the surface of [...]
The development of a complex, multicellular organism such as a human being is accompanied by changes in which a single, unspecialized cell (the fertilized egg or zygote) ultimately gives rise to cells and tissues that are highly specialized in structure and function. This progressive transition is characterized by four component processes: determination, differentiation, growth, and morphogenesis. New cells are usually [...]