Department of Pathology,

Faculty of Veterinary Medicine,

Zagazig University, Egypt

Introduction of PathologyBY

Professor Dr. Mohamed Hamed Mohamedmohamedelariny@yahoo.com

+20124067373

2011

Introduction of PathologyDisease: It is any departure from healthy state. (Disease=Dis+ease, away

from comfort).

Health: It is normal condition of body and mind.

Pathology: (pathos = suffering or disease + logos = study of) It is a branch

of science which deals with study of structural and functional changes

occurring in the body as a result of disease (abnormal biology).

Pathology is divided into:

1-General Pathology: It deals with basic reactions of the body to an

injurious stimulus.

2-Systemic Pathology: It deals with application of basic pathological

reactions to various systems.

3-Special pathology: It deals with application of basic pathological

reactions to specific disease.

4-Nutritional Pathology: Study the disease resulting from either excess or

deficiency of essential nutrients.

5-Chemical pathology: It is biochemical alteration of body fluids and

tissue that results from disease.

6-Toxico-pathology: It deals with the changes related with toxicological

substances.

7-Gross/Macroscopic Pathology: It is the examination of a tissue with

naked eye.

8-Microscopic/Histopathology: It the examination of a tissue with the

help of microscope.

9-Clinical Pathology: It is a branch of pathology that is applied at the bed

sides of a patient and it includes diagnosis of diseases using laboratory

methods. It includes examination of blood, urine, feces, etc.

10-Experimental pathology: Study of diseases artificially produced in

animals.

11-Comparative Pathology: It is the study of animals and comparing them

occurring in man.

Pathological Terms:

Post mortem: It is the systemic and scientific examination of body after

death to know the cause of death (Cadaver = dead body).

Biopsy: Study of tissue collected from live animal.

Autopsy: It means post mortem examination related to man.

Necropsy: It means post mortem examination related to veterinary field.

Oncology: Study of the tumor and neoplasm.

Pathogenesis: Developmental process of a disease or it is the mechanism

by which causes produce disease.

Clinical Signs: They are physical manifestation that we can see (objective).

Symptoms: It is subjective evidence of disease that the patient felt and tells us

Syndrome: (Syn means together, drome means run) so, It reflects a group

of signs (symptoms) that occur together and characterize a particular

disease.

Lesions: They are structural changes seen by naked eyes or microscopically.

Pathognomic Lesion: It is a lesion that is specific of a particular disease.

Diagnosis: It is the art of determination of nature of disease means its

causes, signs, lesions, etc.

Prognosis: It is the outcome or fate of disease.

Incubation Period: It means the time that elapses between the action of

cause and getting manifestation of disease.

Morbidity: It is the percentage of exposed animal that get affected.

Mortality: It is the percentage of deaths among animal affected by that

disease.

Etiology: Study of causes of disease.

Etiologic agents: It includes:

1-Physical

2-Chemical

3-Microbiological

4-Nutritional

5-Immunological

Etiology classified into:

A-Intrinsic Causes or Predisposes:

I-Genetic defects or inherited causes:

II-Non-genetic factors: They include

i-Anomalies (abnormalities): It is a disturbance of development that

involves an organ or a part of it. Anomaly may be due to

1-Disturbances from development:

a-Arrest of development called as aplasia or agenesis It includes

-Hypoplasia -atrasia (closure of lumen or duct) -Fusion

b-Excessive development: It includes

-Hyperplasia -Polydactyla

2-Persistence of fetal structure e.g. persistent urachus.

3-Displacement during development:

4-Fusion of sexual characters e.g. hermaphrodite, free martin.

ii-Monster: It is a disturbance of development that involves several organs

and causes great distortion of the individual.

III-Genus: disease specific for particular genus as Hog cholera only for swine.

IV-Breed: disease restricted to certain breed as dairy cattle are more

susceptible to disease than beef cattle.

V-Strain: disease restricted to certain strain e.g. strain of chickens are

resistant to leukosis.

VI-Age: different disease affecting different age animal e.g. strangles

(young), glanders (old).

VII-Sex:

VIII-Color: White color more resistant to photodynamic diseases.

B-Extrinsic Causes:

I-Physical Agents: by1-Radiation injury: by x or gamma- rays.

2-Excessive cold: cause frostbite which leads to necrosis due to

injury of blood vessels.

3-Electricity (electrocution):

4-Decreas atmospheric pressure (Brisket disease).

5-Increase atmospheric pressure (Caisson’s disease).

6-Heat (sunstroke disease).

7-Mechanical injury: by accident, gun shot.

NB: Definitions Related to Mechanical Injury:

i-Perforation: It is a type of deep wound with narrow inlet.

ii-Laceration: It is a type of wound produced by blunt object and

characterized by extensive tissue damage and with irregular borders.

iii-Contusion: It is subcutaneous wound characterized by intact skin

and destructed subcutaneous tissue.

iv-Concussion:It is a violent jerk or shock caused by an injury related

with head injury.

v-Dislocation: any break in continuity of bone or cartilage (fracture).

vi-Luxation: anatomical relationship between the tissues may not be

maintained and ligaments may be turned.

II-Chemical Agents: acids, alkali, insecticides, pesticides, some

deficiencies as phosphorus, zinc

III-Microbial Agents: bacteria, viruses, fungus, parasites

Portals of Infections: Entry of infections can occur through the

following paths:

i-Skin: It is the largest tissue and it harbors much kind of bacteria as

resident flora. Bacteria penetrate through skin and cause disease.

Ectoparasites (lice, tick, mites and flies) are seen.

ii-Alimentary Tract: the main sites are mouth and intestine.

1-Mouth: It has resident flora that may gain entry into the tissues

and blood through wound in the buccal mucosa as actinomycosis

disease which affects the hard tissues as bone and actinobacllosiis

affecting the soft tissue as tongue.

2-Intestine: it also acts as site of entry e.g. enterotoxaemia in sheep.

iii-Conjunctiva: Brucella and Cryptococcus infect the conjunctiva.

iv-Respiratory Tract: It is an important route through which various

infections occur as TB, glanders.

v-Urogenital Tract: as in venereal diseases Dourine in horse,

trichomoniasis, surra.

vi-Mammary gland: mastitis.

Modes of Transmission:1-Direct contact:

a-Genital tract: Dourine, Brucellosis transmitted by coitus.

b-Skin: Bites of rabid animals disseminate rabies. Anthrax as

contagious disease.

c-Infection of wounds: as Tetanus in horse.

d-By droplet infection: Infective bacteria of suspended air as minute

droplet which cause infection when inhaled as in TB, Glanders, CBPP.

2-By Congenital Transmission: through the placenta.

3-Indirect Transmission: by food, water, milk.

4-By Air-Transmission:

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