Introduction to Pathology lecture 1 Dr. Nadia Sabry Al-Ani

Definition of pathology Study of disease by Scientific method "scientific study of the molecular, cellular, tissue, or organ and system response to injurious agents."

Pathology as a word means: The study (logos) of suffering (pathos).  

Branches of Pathology General Pathology: Systemic Pathology Study of the Common changes in all tissues. e.g. Inflammation, cancer, ageing, edema, hemorrhage ….etc. Systemic Pathology Discussing the pathologic mechanisms in relation to various organ systems e.g. CVS, CNS, GIT.

What is the Disease?

Abnormal alteration of structure or function in any part of the body. What is the Disease? “State in which an individual exhibits an anatomical, physiological, or biochemical deviation from the normal” Abnormal alteration of structure or function in any part of the body.

Classification of Diseases: Genetically determined diseases: congenital , developmental Acquired diseases: *Inflammatory – Trauma, infections, immune, *Neoplastic – tumors or cancers

What should we Know About A Disease Definition. Epidemiology – Where & When. Etiology – What is the cause? Pathogenesis - Evolution of dis. Morphology - Structural Changes Functional consequences Management Prognosis Prevention Pathology

Pathology focuses on 4 aspects of disease: ETIOLOGY: Cause of disease. PATHOGENESIS: Mechanisms of development of disease. MORPHOLOGY: The structural alterations induced in cell and tissues. FUNCTIONAL CONSEQUENCES: Functional results of the morphologic changes, as observed clinically.

How can we Remember & Understand the disease

By a morphologic IMAGE This can be:- Gross appearance:- By the naked eye. Microscope :- Light microscopic Electron microscope X-ray:- Radiograph Molecular study:- Genetic, Histochemistry,… In MOST cases it is: LIGHT MICROSCOPIC

Etiology: What is the cause? Environmental agents: Physical Chemical Nutritional Infections Immunological Psychological Genetic Factors: Genes Multifactorial: As Diabetes, Hypertension Cancer

Environmental causes of diseases Physical agents: mechanical injury, heat, cold, electricity, irradiation….etc. Chemicals & drugs: cyanide, strong acids and alkalins. Deficiency diseases: e.g. iron deficiency. Infective M.O. : bacteria, protozoa, fungi and viruses. Immunological factors: Harmful effects result from the reaction of antibodies and lymphocytes with microbes and their toxic products. Pscychogenic factors: e.g. schizophrenia and depression Diseases of addiction: (Alcohol, various drugs, tobacco)

Methods used to study pathology:  1- Histopathology: Examination of the diseased tissues by light or electron microscope.   2- Cytopathology: Examination of isolated cells for diagnosis of the disease. 3- Biochemistry: Examination of the metabolic disturbances of diseases by evaluation of various compounds in body fluids. 4- Microbiology: Identification of the causative microorganism of the disease by examination of body fluids, mucosal surfaces and excised tissues using microscopical, cultural and serological techniques.

Methods used to study pathology Cont. 5- Haematology: Microscopical examination of blood.   6- Cytogenetics: Examination of chromosomal abnormality. 7- Histochemistry: Detection of cells and tissues constituents using special immunohistochemical techniques. 8- Forensic pathology: Examination of tissues taken from autopsy (dead body).

Histochemical stains used in pathology Hematoxylin & Eosin staining (H &E) : Hematoxylin:- Strong affinity for nucleus = blue color. Eosin:- Bind tissue proteins = pinkish discoloration.

Demonstrates Glycogen & mucosubstances, Outlines basement membranes. Special stains most commonly:- periodic acid Schiff stain. (PAS) It is used to :- Demonstrates Glycogen & mucosubstances, Outlines basement membranes. Makes evident most types of fungi & parasites.

Stains for micro- organisms. These include techniques for gram-positive and gram-negative bacteria, acid-fast mycobacteria, Fungi & parasites. for example Gram stain, ziehl-Neelsen ( for acid-fast organisms) Gram stain ziehl-Neelsen

Amyloid stain (congo red) to detect amyloid.

Reticulin stains:- used to demonstrate: - Reticular fiber (type III collagen presents in the connective tissue throughout the body). - Basement membranes (type IV collagen and laminin). - The main use of this stain is in tumor pathology.

Giemsa stain: It is most useful for the demonstration of various lymphoreticular elements . (Bone marrow smear)

I hear, I forget I see, I remember I do, I understand Chinese Proverb..