Anatomy

The closely related techniques of histochemistry and cytochemistry are concerned with the investigation of chemical activities of tissues and cells. For example, the presence of certain colours within cells indicates that particular chemical reactions have occurred. In addition, the density of the colour reaction may serve as an index of the intensity of the reaction. Histochemical methods have been particularly successful in the study of enzymes, catalytic substances that control and direct many of the cell's activities. Much knowledge of enzymes was gained in studies carried out after removal of the enzymes from their cells of origin, but not until the advent of histochemistry could the anatomist see through the microscope which cells carry specific enzymes or gauge how active these enzymes are in different cells under various conditions.

An important technique of histochemistry involves the use of radioactive isotopes of various chemical elements that are present in cells and tissues (see Isotope; Radioimmunoassay; Isotopic Tracer). Elements or compounds “tagged” or “labelled” with radioactive isotopes are administered to living materials, permitting the investigator to trace the pathways taken by these substances through the various tissues. The degree of concentration and dilution of elements within specific cellular constituents may be estimated by measuring the radiations emanating from these tissues. The technique of labeling compounds with radioactive isotopes makes it possible to study the distribution and concentration of isotopes in tissue slices similar to those studied routinely under the microscope. This study, called autoradiography, is accomplished by bringing the radioactive tissue slices into contact with photographic films and emulsions that are sensitive to radiation.

Another technique of localizing chemical compounds within tissue slices is microincineration: the heating of microscopic sections to the point at which the organic materials present are destroyed and only the mineral skeleton remains. The remaining minerals can then be identified by special chemical and microscopic procedures. Thus, microincineration provides still another way of locating specific chemical elements within particular cell or tissue components.

Another development in the field of histochemistry is microspectrophotometry, a precise method of colour analysis. In this process the colours within a tissue slice are analysed with a spectrophotometer, an instrument that measures the intensity of each colour as a function of wavelength. Microspectrophotometry can be used to estimate the characteristics of unstained cells and tissues by measuring their absorption of particular wavelengths. Another application permits precise judgements to be made concerning the nature and intensity of colour reactions. These judgements provide, in turn, accurate information about the location and intensity of chemical reactions in the components of living organisms.

The diversity of anatomical methodologies reflects the overall trend within the discipline away from gross anatomy to the inner workings of the body’s cells at the molecular level, such that the older disciplinary boundaries of anatomy, physiology, biochemistry, developmental biology, and embryology are increasingly irrelevant. The research agenda is one of vibrancy built upon centuries of accumulated knowledge. In the field of neuroanatomy, determining the fine structure of the brain is one of the few remaining challenges, albeit immense, for structural studies.

Until recently, medical students in the Western world still routinely enjoyed or endured their rite of passage via the dissection of a human cadaver. For many, dissection is now offered as a special option rather than a part of the core curriculum. Online representations of the body and observation of preparations made by trainee surgeons have replaced personal time spent with the scalpel. A re-evaluation of the whole medical curriculum and consideration for the increasing burden of ever more detailed anatomical knowledge led to this reduced role for anatomy in the education of doctors. Where medical education has moved from separate disciplines to an integrated interdisciplinary approach, anatomy as a distinct scheduled subject has effectively disappeared and in less-integrated curricula the dominance of the subject has significantly declined. The classic advanced textbook, Gray’s Anatomy: The Anatomical Basis of Clinical Practice (1858; 39th ed. 2005), has reoriented its format so that regions of the body rather than its systems dominate, reflecting what clinicians encounter in practice, rather than an idealized presentation of knowledge, evidence of the discipline’s mutability to meet new demands.