1.3 Primary and secondary changes
The histological changes seen in a tissue may be primary (a cause of the disease process) or secondary (a consequence of the disease). For example if blood pressure is high due to vascular disease, it may cause an increase in the volume of the heart muscle as the heart finds it more difficult to pump blood into the circulation. A further consequence may be a decrease in the volume of the heart ventricles so that less blood is pumped with each contraction. Interpreting the changes seen histologically, to identify the underlying pathology, requires a sound understanding of the disease process. It takes many years of study and observation to build up a good knowledge of the appearance of normal and diseased tissues, and many pathologists specialise in particular tissues or groups of disease. In this course, we only have space to introduce the subject and outline how it can help with diagnosis of disease.