Functional Anatomy of the Immune System

Abstract

Our species is constantly under threat from a large number of pathogens comprising four groups: viruses, bacteria, fungi, and parasites (protozoa and worms). At a homeostatic temperature of about 37°C, and with proteins, fat, and sugar, the body provides an optimal environment for pathogen growth and replication. However, pathogens have difficulty penetrating the barriers that divide the body from the environment. Such a protective surface is comprised of the skin (≈2 m²), the surface of the respiratory tract (≈150 m²), the gastrointestinal tract (≈300 m²), and the genitourinary tract (< 0.5 m²). One task of the immune system is to guarantee the integrity of the body against all intruders (Janeway & Travers, 1997). Another task within the body is to rapidly recognize cellular degeneration and to prevent the development of cancer. However, some aspects of the immune system are not positive. Allergies and diseases such as rheumatoid arthritis and inflammatory bowel disease are thought to develop as a result of an immune system overreaction. Additionally, transplanted cells and organs can be recognized as being foreign and consequently rejected. Therefore, the different phases of an immune response must be carefully regulated. Recently, it has become clear that other organ systems participate in the regulation of the immune system. However, many open questions regarding these interactions remain. It is possible to answer such questions only when different disciplines such as anatomy, endocrinology, immunology, neurology, and psychology come together to solve these problems that have relevance for the health of humans. Therefore, it is important for those interested in such a multidisciplinary field to have an understanding of the fundamentals of the other disciplines.