Introduction to Pathology
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.
General Pathology concerns with basic alterations of tissues as a result of the disease. e.g. Fatty changes, Thrombosis, Amyloidosis, Embolism, Necrosis.
Systemic Pathology deals with alterations in tissues/ organs of a particular system. e.g. Respiratory system, Genital system, etc.
Specific Pathology is the application of the basic alterations learned in general pathology to various specific diseases. It involves the whole body or a part of the body. e.g. Tuberculosis, Rinderpest.
Experimental Pathology concerns with the production of lesions through experimental methods. e.g. Rotavirus ~ calves ~enteritis
Clinical Pathology includes certain laboratory methods which help in making the diagnosis using animal excretions/ secretions/ blood/ skin scrapings/ biopsy etc. e.g. Urine examination, Blood examination.
Post-mortem Pathology is the examination of an animal after death. Also known as Necropsy or Autopsy. It forms the base for the study of pathology.
Microscopic Pathology deals with the examination of cells/ tissues/ organs using a microscope. It is also known as histopathology / cellular pathology. e.g. Microscopy, Electron microscopy.
Humoral Pathology is the study of alterations in fluids like antibodies in serum.
Chemical Pathology is the study of chemical alterations of body fluids/ tissues. e.g. Enzymes in tissue.
Physiological Pathology deals with alteration in the functions of organs/systems. It is also known as Pathophysiology. e.g. Indigestion, Diarrhoea, Abortion.
Nutritional Pathology is the study of diseases occurred due to deficiency or excess of nutrients. e.g. Vit.-A deficiency-induced nutritional roup, rickets due to calcium deficiency.
Comparative Pathology is the study of diseases of animals with a comparative study in human beings and other animals. e.g. Zoonotic diseases such as Tuberculosis.
Oncology is the study of cancer/ tumor/ neoplasms.
Immunopathology deals with the study of diseases mediated by immune reactions. It includes Immunodeficiency diseases autoimmunity and hypersensitivity reactions.
Cytopathology is the study of cells shed off from the lesions for diagnosis.
Forensic Pathology includes careful examination and recording of pathological lesions in case of veterolegal cases.
Homeostasis is the mechanism by which the body keeps equilibrium between health and disease. e.g. Adaptation to an altered environment.
Toxopathology or Toxic Pathology deals with the study of tissue/ organ alterations due to toxins/ poisons.
Health is a state of an individual living in complete harmony, with his environment; surroundings.
A disease is a condition in which an individual shows an anatomical, chemical, or physiological deviation from the normal. (Discomfort with environment & body).
Illness is the reaction of an individual to disease in the form of illness.
Etiology is the study of the causation of disease.
Diagnosis is the art of precisely knowing the cause of a particular disease (Dia= thorough, gnosis= knowledge)
Any subjective evidence of disease of animal characterized by an indication of altered bodily or mental state as told by owner (Complaints of the patients).
Indication of the existence of something, any objective evidence of disease, perceptible to the veterinarian (Observations of the clinicians).
A combination of symptoms caused by the altered physiological process.
The lesion is a pathological alteration in structure function that can be detectable.
A biopsy is the examination of tissues received from living animals.
Infection is the invasion of the tissues of the body by pathogenic organisms resulting in the development of a disease process.
Infestation is the superficial attack of any parasite/organism on the surface of the body.
Pathogenicity is the capability of an organism for producing a disease.
Virulence is the degree of invasiveness of a pathogenic organism.
Pathogenesis is the progressive development of a disease process. It starts with the entry of cause in the body and ends either with recovery or death. It is the mechanism by which the lesions are produced in the body.
The incubation period is the time elapses between the action of a cause and the manifestation of disease.
Course of disease
Course of disease is the duration for which the disease process remains till fate either in the form of recovery or death.
Prognosis is an estimate by a clinician of probable severity/outcome of a disease.
Morbidity rate is the percentage/ proportions of affected animals out of the total population in a particular disease outbreak. e.g. Out of 100 animals, 20 are suffering from diarrhea. The morbidity rate of diarrhea will be 20%.
The mortality rate is the percentage/ proportions of animals out of the total population died due to disease in a particular disease outbreak. e.g. In a population of 100 animals, 20 falls sick and 5 died. The mortality rate will be 5%.
Case fatality rate
The case fatality rate is the percentage/ proportions of animals that died among the affected animals. In a population of 100 animals, 20 falls sick and 5 died. The case fatality rate will be 25%.