General Pathology Overview

General Pathology

• Pathology is the study of disease causes and associated changes in cells, tissues, and organs
• Rudolf Virchow is considered the "Father of Modern Pathology"
• Aulus Cornelius Celsus studied the four signs of inflammation.
• Etiology refers to the origin or cause of a disease
• Pathogenesis describes the development of disease.

Morphologic Changes

• Morphologic changes refer to structural alterations in cells or tissues that are characteristic of a disease or diagnostic of an etiologic process. These are physical changes.

Functional Derangements and Clinical Manifestations

• Functional changes are the result of genetic, biochemical and structural alterations. These lead to clinical manifestations (signs and symptoms) of a disease and its clinical course and outcome.
• Signs are observable changes; symptoms are subjective.

Tissue Changes

• Retrogressive changes: Organs or tissue are smaller than normal.
  • Aplasia: incomplete or defective development (often in paired organs like kidneys, gonads, and adrenals).
  • Atresia: failure to form an opening.
  • Agenesia: complete non-appearance of an organ
  • Hypoplasia: failure of an organ to reach its mature size.
  • Atrophy: partial or complete wasting away of a body part. This is the shrinkage in size of the cell.
    • Physiologic atrophy: occurs naturally
    • Pathologic atrophy: occurs due to disease or lack of use
    • Endocrine atrophy: occurs due to lack of trophic hormones.
    • Vascular atrophy: occurs due to interruption or diminished blood supply
    • Starvation atrophy: lack of nutrition
    • Disuse atrophy: lack of nutrition

Other Changes

• Progressive changes: Organs or tissues are larger than normal.
  • Hypertrophy: an increase in tissue size due to increased cell size (often due to increased workload or endocrine stimulus). Examples are hypertension (pathological hypertrophy), increased workload on the heart.
  • Hyperplasia: an increase in tissue size due to increased cell number (like fitting dentures for ex.)
    • Physiologic hyperplasia: occurs naturally.
    • Pathologic hyperplasia: associated with disease.

Degenerative Changes

• Metaplasia: transformation of one adult cell type to another (reversible).
• Dysplasia: disordered growth (enlargement); abnormal cells (reversible). Example: Cervical Dysplasia.
• Anaplasia: transformation of adult cells into a more primitive type (irreversible); often used as a criterion for malignancy.
• Neoplasia: Continuous abnormal proliferation of cells without control. (Oncology - the study of neoplasms).

Inflammation

• Inflammation is the body's response to injury or invasion by an infectious agent.
• It involves a series of biochemical and cellular changes leading to phagocytosis. Inflammation can be acute or chronic. The cardinal signs of inflammation include rubor, tumor, calor, dolor, and function laesa.

Ulcers

• A defect on an organ or tissue surface caused by the sloughing (shedding) of necrotic tissue. commonly seen in the mucosa of various organs.

Tissue Repair/Healing

• Regeneration: The replacement of damaged tissues with the same type of tissue.
• Scar formation: The laying down of fibrous tissue

Cell Death

• Apoptosis: programmed cell death.
• Necrosis: pathologic cell death.
• Necrobiosis: physiological (normal) cell death.
• Pyknosis: reduction and condensation of the nucleus
• Karyorrhexis: fragmentation of the nucleus.
• Karyolysis: dissolution of the nucleus
• Autophagy: lysosomal digestion of a cell's own components; self-eating.

Other Important Changes

• Hypoxia: oxygen deficiency resulting from diminished arterial flow, venous drainage or defects in respiration
• Lipid deposition
• Protein deposition
• Pigment deposition.
• Deposition of Calcium (Dystrophic & Metastatic Calcification)
• Types of necrosis (coagulative, liquefactive, caseous, gangrenous, fat, fibrinoid)
• Cardinal signs of inflammation

Diseases

• Examples: Coagulative necrosis, Liquefactive necrosis, Caseous necrosis, Gangrenous necrosis, Fat necrosis, Fibrinoid necrosis, Cloudy swelling.

Tumor Grading and Classification

• Differentiated cells are mature cells (less malignant)
• Undifferentiated cells are younger cells (more malignant)

Death

• Somatic death: cessation of all functions in the human body.
• Clinical death: cessation of the heartbeat and respiration.
• Brain death: irreversible cessation of brain function. Primary signs of death include circulatory, respiratory, and central nervous system failure. Secondary signs of death include algor mortis, rigor mortis, and livor mortis.

Autopsy

• An autopsy is a post-mortem examination performed on a dead body. The purpose of an autopsy is to determine the cause of death and to document the extent or presence of any disease. Different methods for performing an autopsy.