Introduction to pathology

GENERAL PATHOLOGY

INTRODUCTION TO PATHOLOGY

• By the end of this session, students are expected to be able to:
• Define pathology
• Understand evolution of pathology
• Identify subdivisions of pathology
• Explain disease development
• Classify categories of diseases

Explain cell injury and cell death

Pathological terminologies (100+ terms)

• Pathogenesis = course of disease = start–> end or terminal stage
• Necrosis = Irreversible abnormal cell death
• Apoptosis = programmed cell death
• Aetiology = cause of disease
• Ischemia= decreased blood flow to body tissue
• Hypoxia/hypoxemia= low oxygen content in blood

Oxidative stress= imbalance between free radicals and antioxidants in the body

Terms cont.

Hypoxia= low oxygen supply in bodily tissue ROS= Reactive oxygen species are derivatives of oxygen that result from aerobic respiration eg peroxides, superoxide, hydroxyl radical OR

Free radicals= oxygen containing molecules with uneven number of electrons (unstable) Antioxidant= any chemical substance that protects a cell from the damage caused by free radicals eg vitamins (A,C,E & K) , Uric acid, Glutathione, Enzymes ( Catalase) Lesion= an area of abnormal tissue

FREE RADICALS V ANTIOXIDANTS

EVOLUTION OF PATHOLOGY

• Evolution of Pathology began with the following concepts from different era :

Religious and superstitious beliefs to rational approach (Antiquity to AD 1500).

The earliest concepts of disease were the religious and superstitious beliefs that affliction or disease was the outcome of curse or evil eye of spirits.

The real practice of medicine began in the 460 to 377 BC (Before Christ).

Hippocrates introduced ethical concepts in the practice of medicine and admired/respected by the medical profession by taking Hippocratic oaths at the time of entry into practice of medicine.

PATHOLOGY

• The word pathology is derived from Greek words Pathos=suffering and logos= the study

Definitions:

It is a branch of medicine which deals with the study of the nature (aetiology) and the course (mechanisms) of disease.

It is a scientific study of structure and function of the body in disease.

During this era Papanicolaou in 1930s developed the use of exfoliative cytology for early detection of cervical cancer.

Era of modern pathology (1960s to dawn of 21st century) The major advances in molecular biology in the field of diagnosis and treatment of genetic disorders, immunology and in cancer. These includes:- The description of the structure of DNA Identification of chromosomes and their numbers Recombinant DNA technique

Mammalian cloning

Infarction= cellular/tissue death as a result of ischemia/hypoxia

Inflammation= local response of vascularized tissue to noxious stimuli that causes cellular injury Inflammatory mediators= chemical substances released by cells in response to stimuli causing inflammation [proteins , peptides, glycoprotein ,cytokines ,prostaglandins(Histamine, ]

Era of gross pathology (AD 1500 to 1800).

In this era the discovery of science in diagnosis involved studies by dissection of human body, autopsy, and the use of microscope in examining the diseased tissues.

Era of technology development and cellular pathology (AD 1800 to 1950s).

This era the technology of microscopy was advanced to involve, different staining methods or techniques, the use of electron microscope to examine and view ultra structure of the cell and its organelles

SUBDIVISIONS OF PATHOLOGY

• (1)Human pathology is the largest branch of pathology

It is conventionally divided into

(a)General pathology Which deals with general principles of disease i.e. is concerned with the basic reaction of cells and tissue to abnormal stimuli that underlies all diseases (b)Systemic pathology Includes study of diseases pertaining to the specific organs and body systems. This examine the specific responses of specialized organs and tissue to more or less well defined stimuli (2) Histopathology used synonymously with anatomic pathology (pathologic) anatomy, or morbid anatomy, is the classic method of study and still the most useful one which has stood the test of time.

…….

• Histopathology is divided into:-

(a) Surgical pathology which deals with study of tissues removed from the living body.

(b) Forensic pathology and autopsy work includes the study of organs and tissues removed at post-mortem.

(3) Cytopathology includes study of cells shade off from lesions (exfoliative cytology and fine needle aspiration cytology of superficial and deep seated lesions for diagnosis).

DISEASE DEVELOPMENT

• This is loss of ease of body
• Any harmful deviation from the normal structural or functional state of an organism.
• It is the opposite of health, what is not healthy is diseased
• The four aspects of a disease process that form the core of pathology are
• Its cause or aetiology

The mechanisms of its development, pathogenesis The structural alterations induced in the cells and organs of the body, morphologic changes The functional consequences of the morphologic changes, clinical significance

Introduction to pathology

Knowledge or discovery of the primary cause remains the backbone on which a diagnosis can be made, a disease understood or a treatment developed There are two major classes of aetiologic factors o Intrinsic or genetic o Acquired/Environmental factor Genetic factors are clearly involved in some of the common environmentally induced maladies, such as cancers and atherosclerosis The environment may also have profound influences on certain genetic diseases

ENVIRONMENTAL FACTORS

Are many and are classified as follows :

Physical agents, among these are trauma, radiations (UV, X-RAYS, GAMMA RAYS) extreme heat and cold, electrical power, i.e. the application to the body of an excess of physical energy in any form.

Chemical poisoning ( CYANIDE, MERCURY, LEAD) these are increasing with the advances in industrial processing, some act in general manner i.e. the toxic effect is to all cells. Some act locally example acids and caustics on the skin and mucous membrane and some affect certain organs such as lungs, kidneys, liver and pancreas

Introduction to pathology

Nutritional deficiency and excess, these arise as a result of poor supply, interference with absorption, inefficient transport within the body or defective utilisation.

• The effect may be of a general nature as in starvation or lack of oxygen.
• They may cause specific damage e.g. in vitamin deficiencies.

Dietary excess can the cause of many systemic diseases such as cardiac diseases.

Infections and infestations, viruses, bacteria, fungi, protozoa and metazoan all cause diseases.

Dietary excess can the cause of many systemic diseases such as cardiac diseases.

Infections and infestations, viruses, bacteria, fungi, protozoa and metazoan(worms all cause diseases.

They may do so by causing destruction directly to the tissue or damage can be due to toxins produced by these microorganisms.

Abnormal immunological reactions, the immune process is normally protective but in certain circumstances the reaction may become deranged.

Hypersensitivity to various substances can lead to alarming shock-like conditions- anaphylaxis.

• Immune process may act against the body cells – autoimmunity.
• Psychological factors cause and influence disease process in several ways.
• Psychological stress may lead to mental illness.
• Their influence on the individual symptoms and reaction to established somatic disease is apparent.

-They are important components in disease caused by addiction, e.g. alcohol and tobacco.

• Psychogenic factors are causally related to diseases such as hypertension, peptic ulcers, coronary artery thrombosis and ulcerative colitis.

Introduction to pathology

Essentially are the results of activities of single genes and groups of genes. Both normal and abnormal gene influence susceptibility and resistance to disease Normal genes

Susceptibility of light skin to damage e.g. skin cancer by the ultraviolet rays in sunlight. This is due to lack of protective pigment – melanin.

The blood group A is associated with increased incidence of pernicious anaemia and gastric cancer. Blood group B is associated with duodenal ulcer.

The human leucocytes antigen (HLA) is associated with susceptibility (eg. Rheumatoid arthritis and T1D) and resistance to infections and also to the occurrence of autoimmune disorders.

The blood group Duffy negative confers resistance to infection by Plasmodium vivax.

Abnormal genes

Mutation give rise to abnormalities of chromosomes and component genes, the majority occur spontaneously without known cause, in some cases radiation, chemical or infective agents are incriminated.

There are hereditary diseases where genetic abnormality directly determines a disease, but most of the diseases are multifactorial having elements of both genetic and environmental.

There is acquired specific genetic abnormality in stem cells, which potentiate the development of malignant tumour.

PATHOGENESIS

Refers to the sequence of events in the response of cells or tissues to the aetiologic agent, from the initial stimulus to the ultimate expression of the disease The study of pathogenesis remains on of the main domain of pathology Morphological changes:

Refers to the structural alterations in cells or tissue that are either characteristic of the disease or diagnostic of the aetiologic process

Functional derangement and clinical importance

The nature of the morphologic changes and their distribution in different organs or tissues influence normal function and determine the clinical features, course and prognosis of the disease.

All forms of organ injury start with molecular or structural alterations in cells.

Cell-cell and cell-matrix interactions contribute significantly to the response to injury, leading collectively to tissue and organ injury which are as important as cell injury in defining the morphologic and clinical patterns of disease.

The failure of adaptation as seen in pathology may be due to o Inability to respond adequately i.e. in overwhelming infections for which the body has no answer

Introduction to pathology

A disease is partly the result of an adaptive mechanism being turned against the host instead of working to his benefit. " For example antibodies which aid to destruct harmful parasites such as bacteria, they can cause disease because of host’s tissue become in anyway altered they may themselves be mistaken as alien and invoke a destructive antibody response ( Autoimmune diseases), and various allergic disorders.

CLASSIFICATIONS OF DISEASES

A disease often originates from a perversion of a survival mechanism. Failure of adaptation tends to be self reinforcing and progressive once a pathological process has started one damn event leads to another.

This is best seen in long-lasting (chronic) illness and is often due to the inappropriate triggering of homeostatic mechanisms.

When the body responds quickly to unfavourable environmental events the response is often overdone.

In normal circumstance if more leukocytes are needed the bone marrow produces the appropriate amount in pathological circumstances a great excess released from the marrow.

Disease usually development following failure of cellular or tissue adaptation after injury or damage by various agents

Basing on body response disease can be classified into 4 categories namely :-

• Congenital = born with

Examples: Sickle cell disease, Cerebral palsy,Down syndrome, Cleft-lip and Cleft-palate, Congenital heart defect, (Neural tube defect/Spina bifida), Hydrocephalus, Gastroschisis, Omphalocoele etc

• Inflammatory = local tissue/ cellular response to injurious agent

Example: All infections, Rheumatoid arthritis (RA),Type1diabetes mellitus, Multiple sclerosis,

3) Degenerative = disease due to aging

• Examples: Osteoarthritis, Osteoporosis,Spondylosis, Parkinson's disease
• Neoplastic = tumour(s)=abnormal growth or swelling

Examples:

Benign tumours: Osteoid osteoma, Benign prostate hyperplasia(BPH),Lipoma, Fibroma,uterine myoma, Polyp, ovarian cyst, Warts, Malignant tumours: All forms of cancer e.g Osteosarcoma, Prostate cancer,Liposarcoma, Fibrosarcoma, Myosarcoma, Endometrial cancer,Breast cancer, Lung cancer,Liver cancer (Hepatoma), Seminoma (cancer of seminal vesicles),