1- Introduction of Pathology. Objectives of the lecture To learn some terms used in pathology To learn about cell injury To know about cell adaptation.

1- Introduction of

Pathology

Objectives of the lecture

• To learn some terms used in pathology

• To learn about cell injury

• To know about cell adaptation

• To know about causes of cell atrophy

• Pathology is "Scientific study of disease “ Study of

structural and functional changes in disease.

• You need to have a basic knowledge of normal

Anatomy (structure) and Physiology (function) to

understand Pathology.

Diseases is an expression of "discomfort" due to

structural or functional abnormality.

This abnormality can be caused by various agents

Eg. Bacteria, virus, heat, radiation etc. collectively

called 'etiology'.

• Factors causing disease are mainly two types.

Environmental (or external) factors and Genetic

(or Internal) factors.

• Diseases which present since birth are called

Congenital diseases and all other diseases are

known as Acquired diseases.

• Diseases which occur in families are known as

Familial diseases.

Pathology of a disease is formally studied under four

subdivisions.

- Etiology - Study of cause / causative agent of disease

- Pathogenesis- Study of disease progression or

evolution.

- Morphology - Study of structural changes in disease

(Gross & microscopic)

- Clinical Significance - Study of how clinical features

are related to changes.

Major groups of diseases are Inflammatory, Degenerative

& Neoplastic.

Inflammatory disorders are due to damage to tissues by

various injuries (physical, chemical, infections etc.)

Degenerative disorders are due to lack of growth or

ageing.

Neoplastic disorders are due to excess cell division

forming tumours.

Cell & Tissue Injury

Cell InjuryDamage or alteration of one or more cellular components

Many types of injury are tissue-specific because of

anatomic relationships and tissue response to chemical

and infectious agents.

Cell injury disrupt cell physiology; so the cell does not

function at full capacity.

Stages in the cellular response to stress and

injurious stimuli

Cell Injury Produces:

Signs: abnormal physical findings – Objective.

Symptoms : complaints experienced by the

patient – Subjective.

Causes of Cell and Tissue Injury

1. Physical agents

2. Chemicals and drugs

3. Infectious pathogens

4. Immunologic reactions

5. Genetic mutations

6. Nutritional imbalances

7. Hypoxia and Ischemia: cell injury resulting

from inadequate levels of oxygen.

Causes:

A. Inadequate blood supply

B. Lung disease

C. Heart failure

D. Shock

hypoxia and ischemia- why so important?

All cells in the body require a continuous supply of

oxygen in order to produce ATP via oxidative

phosphorylation in mitochondria.

ATP is absolutely critical for life.

Susceptibility of specific cells to ischemic injury

• Neurons: 3 to 5 min.

• Myocytes, hepatocytes, renal epithelium: 30

min. to 2 hr.

• Cells of soft tissue, skin, skeletal muscle:

many hours

Outcomes from cell injury depend upon:

• Type of injury

• Severity of the injury

• Duration of the injury

• Type of cell being injured- Some cell types sustain

injury better than others; some tissues (e.g. liver)

have a capacity to regenerate.

Vulnerable Sites of the Cell

1. Cell membranes

2. Mitochondria

3. Endoplasmic reticulum

4. Nucleus

Consequences of Injury

1. (Reversible): No long term effects- the cell damage is repaired, the effects of the injury are reversible.

2. The cell “adapts” to the mild damaging stimulus.

3. (Irreversible): The cell dies, undergoing necrosis. The damage is irreversible.

Adaptation to injury

1. Atrophy: decrease in the size and functional capacity

of the cell, after normal growth has been attained .

( O2, blood, nerve supply)

2. Hypertrophy: an increase in the size of the cell

secondary to an increase in cell function.

Increase in the number of mitochondria and ER, etc.

Causes of Cell Atrophy

1. Loss of blood supply or innervations

2. Loss of Hormones (eg. TSH)

3. Decrease in the workload

4. Aging, chronic illness

3. Hyperplasia: an increase in the number of

cells of a tissue in response to a stimulus or

injury.

4. Metaplasia: replacement of one type of

tissue with another in response to an injury.

5. Hypoplasia: incomplete development or

underdevelopment of an organ / tissue (less

severe in degree than aplasia).

6. Aplasia: lack of development of an organ or

tissue (may have a rudimentary organ). can

also refer to lack of production of cells from an

organ or tissue (e.g. aplastic anemia).

Hypertrophy versus Necrosis

Muscular hypertrophy

Metaplasia