GENERAL MEAT PATHOLOGY.

 

ABNORMALITIES OF FOOD ANIMALS:   

The abnormalities of food animals can be classified as either physiological or pathological. Some of the physiological conditions may be detected both ante- mortem and post –mortem. The same applies to abnormalities that are as a result of Pathological conditions; some may be detected at ante-mortem inspection thou most are appreciated at postmortem.

2.2 Pathological conditions:

A pathological condition is one caused by disease, rather than occurring physiologically. As a field, pathology addresses four components of disease: cause, mechanisms of development (pathogenesis), structural alterations of cells (morphologic changes), and the consequences of changes (clinical manifestations).

2.2.1 Inflammation:

 This is the reaction of the cellular and vascular tissue to injury. It is a property of the body for self defense, whereby it reacts sharply to any stimulus received by it.

Inflammation is not a disease which enters from the outside; rather, it is a mechanism developed by the body itself, as a tool to fight outside attack. Inflammation has three basic functions;

1. To destroy;

2. To dilute or isolate the injurious agent and;

3. To repair the damaged tissues.

Without inflammation, infection would go unchecked, wounds would never heal, and injured organs would remain permanent festering sores. However inflammation can also be fatal as can be seen in hypersensitivity reactions.

Since inflammation is the most basic and the most common body response to injury, its understanding forms the very backbone of pathology.

Beneficial effects of inflammation:

• Limitation of infection;

• Healing of wounds and;

• Normalization of injured tissue.

Undesirable effects of inflammation:

• Development of crippling disease e.g. Rheumatoid arthritis;

• Life threatening sensitivity reactions;

• Fatal glomerular disease;

• Disfiguring scars;

• Joint stiffness and;

• Scar tissue hampering vital functions.

Ten generalities about the inflammatory response:

1. It is a process involving multiple participants (cellular, humoral and tissue);

2. It occurs only in living tissue;

3. It is a series of events overlapping into a continuum;

4.  It is an evoked response that requires initiation by a stimulus;

5. It can be more harmful than the initiating stimulus;

6. It is fundamentally a defense reaction;

7. It is fairly stereotyped irrespective of the initiating stimulus;

8. It has most of its reactive components in blood;

9. It is highly redundant with many promoters and regulators;

10.  It is largely a surface oriented phenomenon.

Inflammation is classified as either acute or chronic.

1. Acute Inflammation:

Acute inflammation is of a relatively short duration (minutes, several hours or a few days). Its main characteristics are exudation of fluids and plasma proteins and emigration of leukocytes (neutrophils).

1. Etiology:

1. Infectious agents; Bacteria, Viruses, Fungi, Chlamydia, Rickettsiae, Mycoplasma, Protozoa, Helminths and Arthropods.

2. Chemical agents; Toxins, Acids, Alkalis and other caustic substances.

3. Physical agents; Burns, electricity, radiation and trauma.

4. Immunological reactions; Tissue damaging Ag-Ab reactions e.g. Hypersensitivity reactions and autoimmune diseases.

5. Necrotic tissue; this can trigger inflammation. Certain stimuli like toxins, bacteria and ischemia cause cell necrosis directly, and necrotic tissues in turn can trigger the elaboration of inflammatory mediators.

6. Nutritional imbalances; these include deficiencies in specific vitamins.

2. Cardinal Signs of inflammation:

1. Rubor (redness): Due to increase of blood in an area (hyperemia);

2. Tumor (swelling): Hyperemia and increased protein rich fluid containing cells collecting in the extra-vascular tissues (exudate).

3. Calor (Heat): Due to increased blood flow and rate of metabolism at the site.

4. Dolar (pain): this is due to increased pressure on sensory nerve endings, stretching of tissues from accumulation of exudate and the release of chemical mediators following injury e.g. prostaglandins, kinins and serotonin.

5. Functio laesa (Loss of function):  Due to a combination of pain, swelling and destruction of tissues.