MBBS PATHOLOGY NOTES
1. Definition of Pathology
Pathology is the study of diseases. It involves understanding the
causes (etiology), mechanisms of development (pathogenesis),
structural alterations in cells or tissues (morphological
changes), and the consequences of these changes (clinical
manifestations).
2. Etiology (Cause of Disease)
Diseases can be caused by a variety of factors. These are
classified as:
o Genetic causes: Mutations in genes, inherited defects
(e.g., cystic fibrosis, sickle cell anemia).
o Environmental causes: Physical, chemical, biological
factors (e.g., smoking, radiation, viruses).
o Multifactorial causes: A combination of both genetic and
environmental factors (e.g., cancer, hypertension).
3. Pathogenesis (Mechanisms of Disease)
Pathogenesis refers to the step-by-step development of the
disease after the initial cause. It includes:
o Cellular injury: When cells are exposed to stress or
harmful agents (hypoxia, toxins), they undergo various
forms of injury (reversible or irreversible).
o Inflammation: The body’s response to harmful stimuli
like infections or tissue damage. It is characterized by
redness, heat, swelling, pain, and loss of function.
o Repair: The body tries to repair the damage by
regeneration (replacing damaged cells) or fibrosis
(formation of scar tissue).
, 4. Morphological Changes (Structural Alterations)
Diseases often lead to characteristic changes in the structure of
cells or tissues. These are studied using microscopy and include:
o Hypertrophy: Increase in cell size, leading to the
enlargement of tissues or organs (e.g., muscle
hypertrophy).
o Hyperplasia: Increase in the number of cells (e.g.,
glandular hyperplasia in breast tissue during pregnancy).
o Atrophy: Decrease in cell size or number, leading to
shrinkage of tissues (e.g., muscle wasting in immobilized
patients).
o Metaplasia: A reversible change where one type of cell is
replaced by another (e.g., in smokers, the normal columnar
cells of the respiratory tract may be replaced by squamous
cells).
5. Necrosis vs. Apoptosis
Necrosis: This is unplanned cell death due to injury. It is often
associated with inflammation and leads to the loss of tissue
integrity. Types of necrosis include:
o Coagulative necrosis: Common in ischemic conditions
(e.g., myocardial infarction).
o Liquefactive necrosis: Seen in infections and brain
infarcts, where tissue becomes liquid and pus-filled.
o Caseous necrosis: A form of necrosis with a cheese-like
appearance, typical in tuberculosis.
Apoptosis: Programmed, regulated cell death that occurs
without causing inflammation. It plays a crucial role in tissue
homeostasis and development.
6. Inflammation (Acute vs. Chronic)
1. Definition of Pathology
Pathology is the study of diseases. It involves understanding the
causes (etiology), mechanisms of development (pathogenesis),
structural alterations in cells or tissues (morphological
changes), and the consequences of these changes (clinical
manifestations).
2. Etiology (Cause of Disease)
Diseases can be caused by a variety of factors. These are
classified as:
o Genetic causes: Mutations in genes, inherited defects
(e.g., cystic fibrosis, sickle cell anemia).
o Environmental causes: Physical, chemical, biological
factors (e.g., smoking, radiation, viruses).
o Multifactorial causes: A combination of both genetic and
environmental factors (e.g., cancer, hypertension).
3. Pathogenesis (Mechanisms of Disease)
Pathogenesis refers to the step-by-step development of the
disease after the initial cause. It includes:
o Cellular injury: When cells are exposed to stress or
harmful agents (hypoxia, toxins), they undergo various
forms of injury (reversible or irreversible).
o Inflammation: The body’s response to harmful stimuli
like infections or tissue damage. It is characterized by
redness, heat, swelling, pain, and loss of function.
o Repair: The body tries to repair the damage by
regeneration (replacing damaged cells) or fibrosis
(formation of scar tissue).
, 4. Morphological Changes (Structural Alterations)
Diseases often lead to characteristic changes in the structure of
cells or tissues. These are studied using microscopy and include:
o Hypertrophy: Increase in cell size, leading to the
enlargement of tissues or organs (e.g., muscle
hypertrophy).
o Hyperplasia: Increase in the number of cells (e.g.,
glandular hyperplasia in breast tissue during pregnancy).
o Atrophy: Decrease in cell size or number, leading to
shrinkage of tissues (e.g., muscle wasting in immobilized
patients).
o Metaplasia: A reversible change where one type of cell is
replaced by another (e.g., in smokers, the normal columnar
cells of the respiratory tract may be replaced by squamous
cells).
5. Necrosis vs. Apoptosis
Necrosis: This is unplanned cell death due to injury. It is often
associated with inflammation and leads to the loss of tissue
integrity. Types of necrosis include:
o Coagulative necrosis: Common in ischemic conditions
(e.g., myocardial infarction).
o Liquefactive necrosis: Seen in infections and brain
infarcts, where tissue becomes liquid and pus-filled.
o Caseous necrosis: A form of necrosis with a cheese-like
appearance, typical in tuberculosis.
Apoptosis: Programmed, regulated cell death that occurs
without causing inflammation. It plays a crucial role in tissue
homeostasis and development.
6. Inflammation (Acute vs. Chronic)
