Introduction to Pathology

Introduction to Pathology

• Pathology is derived from Greek words: pathos (disease) and logy (study)
• Pathology is a branch of biological sciences
• It studies structural and functional abnormalities in cells, tissues, organs, and body fluids
• These abnormalities result from disease

Divisions of Pathology

• In academic studies, pathology is divided into medical and comparative pathology
• In professional practice, pathology is divided into two major groups:
  • Anatomic pathology (study of disease effects on cells, tissues, and organs)
  • Clinical pathology (study of disease effects in body fluids and secretions using lab methods)

Branches of Anatomic Pathology

• General pathology: studies common basic changes in tissues caused by disease, including cell injury, necrosis, inflammation, and neoplasm.
• Systemic pathology: examines morphological changes in specific organ systems (e.g., respiratory, digestive, nervous) due to disease.
• Special pathology: applies general pathology knowledge to particular diseases (e.g., diabetes, atherosclerosis).
• Diagnostic pathology (histopathology): studies tissue abnormalities using gross and microscopic examination of biopsy samples.
• Biopsy: tissue sample from a living body to diagnose diseases.
• Cytopathology: examines cellular changes using cytological samples (e.g., vaginal swab, laryngeal swab).
• Post-mortem pathology (autopsy/necropsy): examines a deceased body to determine cause of death.

Branches of Pathology

• Forensic pathology: investigates the cause of unexpected or sudden death.
• Physiological pathology (pathophysiology): studies how organs and systems function differently due to disease.

Experimental Pathology

• Study of illnesses created or induced experimentally in animals
• Analyze structural and functional abnormalities in body tissues
• Understand mechanisms of the underlying diseases.

Disease and Disease Circumstances

• Disease: a state where an individual deviates morphologically, biochemically, and/or physiologically from a normal status.
• Etiology: the science that deals with causes and origins of diseases, and factors that contribute to the disease or disorder.
• Lesions: abnormal structural and functional changes in the body during disease; commonly used term in pathology.

Types of Lesions

• Macroscopic lesions: observable with the naked eye (location, color, size, shape, consistency, appearance of the cut surface)
• Microscopic lesions: require a microscope for observation; quantified using terms like mild, moderate, severe, or critical.

Pathogenesis and Development of Disease

• Pathogenesis: the step-by-step development of a disease process from the beginning to its end; the mechanism by which a disease develops
• Pathogenicity: describes the ability of a pathogen to cause disease; (e.g., H5N1 influenza virus versus nonpathogenic E. coli).

Symptom, Sign, Diagnosis and Prognosis

• Symptom: a disease sign felt by the patient.
• Sign: a disease sign observed by a clinician.
• Diagnosis: identifying a disease based on signs and symptoms.
• Prognosis: prediction of the probable outcome of a disease.

Cell Injury

• Cell injury: divided into reversible and irreversible
• Reversible cell injury: changes that regress and resolve if the damaging agent is removed.
• Irreversible cell injury: cell damage progresses to the point of no return, where cell death is inevitable.

Point of No Return

• Precise moment irreversible cell injury occurs, where adaptation cannot save the cell and cell death is unavoidable
• Different types of cell injury result in different changes at the cellular level or in response to stress.

Cell Death

• Characteristics of irreversibility: inability to reverse mitochondrial dysfunction, development of profound membrane disturbances.

Classification of Cell Death

• Necrosis: cell death due to catastrophic injury to cell integrity mechanisms.
• Apoptosis: genetically programmed cell death.

Summary

• Pathology involves understanding "what happened" and "how" a disease/tissue developed
• Understanding pathogenesis is crucial for rational disease management, treatment, and control.

This quiz covers the fundamental aspects of pathology, an essential branch of biological sciences that studies diseases and their impacts on cells, tissues, and organs. It also delineates the divisions and branches of both medical and comparative pathology, providing insights into anatomic and clinical pathology.