Introduction to Pathology

DR:Gehan mohamed

It is the It is the ““Scientific study of disease" . "scientific study of the molecular,

cellular, tissue, or organ system response to injurious agents."

Definition of pathology

Pathology serves as a Pathology serves as a ""bridgebridge"" or or ""linklink" " between between the preclinical sthe preclinical sciencesciences ( (anatomy, physiology, anatomy, physiology, …………etcetc.) and the courses in clinical medicine..) and the courses in clinical medicine.

2. Classification:(1) Human pathology (2) Experimental pathology

AutopsyBiopsyCytology

Seven Seven Branches of PathologyBranches of PathologyGeneral PathologyGeneral PathologySystemic PathologySystemic PathologySurgical PathologySurgical PathologyGross PathologyGross PathologyCellular PathologyCellular PathologyClinical Pathology Clinical Pathology ImmunopathologyImmunopathology

General PathologyGeneral Pathology Common changes in all tissues. e.g.. Inflammation, Common changes in all tissues. e.g.. Inflammation,

cancer, ageing, edema, hemorrhage ….etc.cancer, ageing, edema, hemorrhage ….etc. Systemic Pathology Systemic Pathology

Discussing the pathologic mechanisms in relation to Discussing the pathologic mechanisms in relation to various organ systems e.g. CVS, CNS, GIT…..etc.various organ systems e.g. CVS, CNS, GIT…..etc.

Techniques of Pathology1. Human pathology

(1) Autopsy (2) Biopsy (3) Cytology: smear, fine needle

aspiration2. Experimental pathology

(1) Animal experiment: animal model (2) Tissue and cell culture

Necropsy: Gross examination of the animal cadaver by systematic dissection in order to evaluate any abnormal changes (lesions) that may be present.

Autopsy: Synonymous to necropsy in human medicine

Biopsy: Removal and examination of tissue obtained from the living body

What is the Disease?It is the It is the ““State in which an individual

exhibits an anatomical, physiological, or biochemical deviation from the normal”

•Disease may be defined as :Disease may be defined as :

an abnormal alteration of structure or function in any part of

the body.

Classification of Diseases: (A)Developmental(A)Developmental – genetic, congenital. – genetic, congenital. (B)Acquired:(B)Acquired:(1)Inflammatory(1)Inflammatory – Trauma, infections, immune, etc. – Trauma, infections, immune, etc. (2)Neoplastic(2)Neoplastic – tumors cancers – tumors cancers(3)Degenerative(3)Degenerative – ageing. – ageing.(4)Metabolic(4)Metabolic..(5)Iatrogenic: Drug induced(5)Iatrogenic: Drug induced..

• Definition.• Epidemiology – Where & When.• Etiology – What is the cause?• Pathogenesis - Evolution of dis.• Morphology - Structural Changes• Functional consequences• Management • Prognosis• Prevention

Pathology

What should we Know About A Disease

Knowledge of Knowledge of etiologyetiology remains the remains the backbone of:backbone of: Disease Disease diagnosisdiagnosis Understanding Understanding the nature of diseasesthe nature of diseases Treatment Treatment of diseases.of diseases.

Etiology Etiology “Study of the cause of a disease"“Study of the cause of a disease"

Etiology Etiology “Study of the cause of a disease"“Study of the cause of a disease"

An etiologic agentAn etiologic agent : :

is the factor (bacterium, virus, etc.) responsible for lesions or a is the factor (bacterium, virus, etc.) responsible for lesions or a

disease state.disease state.

Predisposing Causes of Disease:Predisposing Causes of Disease:

Factors which make an individual more susceptible to a Factors which make an individual more susceptible to a

disease (damp weather, poor ventilation, etc.)disease (damp weather, poor ventilation, etc.)

Exciting Causes of Disease:Exciting Causes of Disease:

Factors which are directly responsible for a disease (hypoxia, Factors which are directly responsible for a disease (hypoxia,

chemical agentschemical agents , virus, bacteria …. , virus, bacteria …. etc.).  etc.). 

•One One etiologic agent etiologic agent several several diseases, as diseases, as smoking.smoking.

Disease

• Several etiologic Several etiologic agents one agents one disease, as cancer .disease, as cancer .

Disease DiseaseDiseaseDisease

One etiologic One etiologic agent agent - - one disease, as one disease, as Malaria.Malaria.

EtiologyEtiology

PathogenesisPathogenesis

The sequence of events in the response of the cells or tissues to the etiologic agent, from the initial stimulus to the ultimate expression of the disease.

CELLS Response to injurious CELLS Response to injurious agentagent

Either :Either :ADAPTINGADAPTINGSUSTAINING REVERSIBLE INJURYSUSTAINING REVERSIBLE INJURYSUFFERING IRREVERSIBLE SUFFERING IRREVERSIBLE INJURY AND DYINGINJURY AND DYING

Clinical Symptoms & SignsClinical Symptoms & Signs

Clinical signs are seen only in the living Clinical signs are seen only in the living

individualindividual as organomegaly as organomegaly..

Clinical sClinical symptoms ymptoms are are the patient’s the patient’s

complain usually by its own words as pain.complain usually by its own words as pain.

Morphologic changeMorphologic change Characteristic of the diseaseCharacteristic of the disease Diagnostic of the etiologic Diagnostic of the etiologic

processprocessFunctional Functional

derangementsderangements

MORPHOLOGYMORPHOLOGY

Morphology remains at the Morphology remains at the heart of diagnostic heart of diagnostic pathology.pathology.

Morphology

(1)Gross appearance: size, shape weight color consistency surface edge, section

(2)Microscopic examination for tissue sections fixed in formalin then stained by

HE (hematoxylin and eosin) to be examined by light microscope for Histologic and cytologic changes.

Hemangioma

Histochemistry using PAS stain

PAS→BM

Immunohistochemistry

1. Ag-Ab specific reaction2. Applications : in diagnosis of

tumor histogenesis

Leiomyosarcoma Actin (+)

(3)Ultrastructural observationBy using electron microscope)

Filtering membrane

SEM (scanning electron microscope)

Podocyte

(4)Flow cytometry (FCM) In neoplastic diseases Can

determine :1- If there is One kind of

cells→quantitative assesment2. DNA ploidy analysis (amount of

DNA)

（ 5 ） Image analysis (IA) it can determine Nuclear diameter;

circumference; area; volume; morphology

（ 6 ） Molecular biology technique

1. Polymerase chain reaction (PCR)

2. DNA sequencing

Polymerase chain reaction (PCR)

prognosisprognosis

Expected outcome of the disease, Expected outcome of the disease, It is the It is the clinician's estimate of the severity and clinician's estimate of the severity and possible result of a disease. possible result of a disease.