Etiology is the study of cause of disease. It gives precise causal diagnosis of any disease. Broadly, the cause of diseases can be divided into two:
a. Intrinsic causes b. Extrinsic causes
Cell death, the ultimate result of cell injury, is one of the most important events in pathology, affects every type of cell, and is the main result of ischemia (lack of blood flow), infections, toxins, and immune reactions. There are two main patterns of cell death: necrosis and apoptosis.
Pathology is the study of the anatomical, chemical and physiological alterations from normal as a result of disease in animals. It is a key subject because it forms a vital bridge between preclinical sciences (Anatomy, Physiology, Biochemistry) and clinical branches of medicine and surgery. Pathology is derived from the Greek word pathos = disease, logos= study. It has many branches.