CELLULAR INJURY AND ADAPTATION

INTRODUCTION TO PATHOLOGY

Pathology is the study of suffering. It is a science concerned with the cause of much the suffering and why diseases arise and what they do. The physiologic state or "normal" is achieved by adaptive responses to the EBB and then flow of various stimuli permitting the cell to adopt and to live in harmony within their microenvironment. Homeostasis is then preserved.

Pathology deals with this study of deviations from normal structure, physiology, biochemistry, cellular, and molecular biology.

The study of pathology is divided into: General Pathology Special or Systemic Pathology

General Pathology

• the study of the basic reactions of cells and tissues to abnormal stimuli that underlie all diseases

Special or Systemic Pathology

• examines this specific responses of specialized organs and tissues to more or less will define stimuli

The four aspects of a disease process that fork the core of pathology

1. Etiology (cause)

2. Pathogenesis (mechanisms of development)

3. Morphologic changes (structural alterations induced in the cells and organs of the body

4. Clinical significance (functional consequences of the morphologic changes)

5. Etiology

The two major classes of etiologic factors are:

Genetic and Acquired

1. Etiology

Knowledge of primary etiology remains the backbone on which diagnosis can be made, disease understood, or a treatment developed. But the concept of one cause leading to one disease developed largely from the discovery of specific infectious agents as the causes of specific diseases is no longer sufficient. What it is true that there would be no Malaria without malarial parasite, no tuberculosis without tubercle bacilli, and no gout without a genetic defect on urate metabolism, not everyone infected with these organisms, or born with the metabolic abnormality, developed the disease at the same rate and with the same severity.

2. Pathogenesis

This refers to the sequence of events in the response of the cells or tissues or the whole organism to etiology from the initial stimulus to the ultimate expression of the manifestation of the disease. In the majority of diseases, the etiologic agent is still unknown or unclear.

3. Morphologic changes

This refers to the structural and associated functional changes in cells or tissues that are either characteristics of the disease or diagnostic of the etiologic process

4. Clinical significance

The nature of morphologic changes and their distribution in different organs or tissues influence normal function and determine the clinical features, symptoms, signs, and prognosis of disease. With this preamble, we can turn to the nature origin and meanings of cell damage.

CELLULAR INJURY AND ADAPTATION

A normal cell is said to be in a homeostatic, steady state, able to handle physiologic demands. External changes may bring out a number of cellular adaptation and which a new but altered study is achieved but in which the cell remains viable.

If the limits of adaptive capability exceeded, or when no adaptive response is possible, a sequence of events follows and it is cell injuries.

Necrosis This refers to the sum of the morphologic changes occurring within dead cells in a living tissue. These changes are caused by the cell's own degradative enzymes and the enzymes released by infiltrating leukocytes.

Autolysis Descriptive term traditionally used for the process of dissolution of that cells by the cells' own digestive enzymes after death of organism. When it occurs, it is referred to as post mortem autolysis.

Hypoxia (lack of oxygen) This is probably the most common cause of cell injury and may also be the ultimate mechanism of damage initiated by a variety of physical, biologic, and chemical agents.

Physical agents This include mechanical trauma, extreme temperature, sudden changes, atmospheric pressure radiation, and electric shock.

Chemical agents

Simple chemicals like glucose or salt in a hypertonic concentration may cause cell injury by deranging the fluid and electrolyte homeostasis of cells.

Biologic agents These agents range from the microscopic viruses to large tapeworms. In between or rickettsiae, bacteria, fungi, and parasites.

In general, bacteria cause cell injury by means of secreting toxin (exotoxin) or by the release of endotoxin from their cell walls when the bacteria are killed or by induction of immunological response to antigens contained within the microbiologic agent.

ALTERATIONS IN ORGANELLES AND CYTOSKELETON

1. Lysosomes: Heterophagy and Autophagy

2. Hypertrophy of Smooth Endoplasmic Reticulum

3. Mitochondrial Alterations

CELLULAR ADAPTATIONS The four most important adaptive changes in the cells will be considered here. These include atrophy, hypertrophy, and metaplasia.

ATROPHY This is the shrinkage in the size of the cell by loss of cell substance. When a sufficient number of cells are involved the entire tissue, or organ diminishes in size, or becomes atrophic.

The apparent causes of atrophy are:

1. Decreased workload

2. Loss of innervation

3. Diminished blood supply

4. Inadequate nutrition

5. Loss of endocrine stimulation

HYPERTROPHY This refers to an increase in the size of cells. Such change also increase the size of the organ.

Hypertrophied organ no longer produce new cells but has larger cells. This can be caused by increased functional demand or by specific hormonal stimulation and may occur on their both social and pathological condition.

HYPERPLASIA It constitutes an increase in the number of cells in an organ addition which may then have increased volume.

Hyperplasia has been divided into physiologic and pathologic hyperplasia

Physiologic hyperplasia Its two most common types are:

1. Hormonal hyperplasia

2. Compensatory hyperplasia

Pathologic hyperplasia Most forms of pathological hyperplasia present instances of excessive hormonal stimulation of target cells. This constitutes a fertile soil in which cancerous proliferation may eventually arise.

METAPLASIA This refers to a reversible change in which one adult type (such as epithelium) is replaced by another adult cell type

DYSPLASIA

An operation and adult cells characterized by variation in their size, shape, and organization. It is a controversial thing in pathology. Strictly speaking, it is deranged development: however in common medical usage, it is applied to either epithelial or mesenchymal cells that have undergone somewhat irregular, atypical, proliferative changes, in response to chronic irritation or inflammation.