Host Defenses. Microbiology 2314. A Healthy Host Has a Variety of Defenses to Prevent Infection. Definitions. Resistance - Ability to ward off disease. Susceptibility - Lack of resistance. Two Types of Resistance. Nonspecific Resistance / Defense Against All Invaders.
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- Ability to ward off disease.
- Lack of resistance.
2. Mucus Membranes
Structure and Composition (Waterproof Keratin) Provide Resistance to Infection.
It is not a great place for bacteria to live…
Symbiotic bacteria living on the skin decompose dead skin cells.
The process results in a strong odor as the number of bacteria increase.
Protects the eyes from irritating substances and microorganisms.
The conjunctiva has only a small number of bacteria present due to continuous blinking and lachrymal secretions which contain bactericidal substances.
Saliva Washes Microorganisms from Teeth and Gums
S. mutans Secretes Sticky Polysaccharide Plaque
Teeth in skulls from Europeans prior to the 1500’s showed remarkably well-reserved teeth. Once sugar was introduced into the European diet, teeth deteriorated quickly and tooth decay became a widespread disease.
Snotty noses are a result of the body trying to rid the system of the trapped microorganisms.
The kidney and bladder are usually sterile.
Sebum is an oily/fatty substance secreted from the sebaceous glands (unsaturated fatty acids) that inhibits the growth of pathogenic bacteria.
Constituent % by weight
Glycerides and free fatty acids 57.5
Wax esters 26.0
Cholesteryl esters 3.0
3. Nasal Secretions
We frequently see this when WBC’s engulf bacteria.
Chemotaxis is the process by which phagocytes are attracted to microorganisms.
Macrophages are Mature Monocytes that are Phagocytic in Nature
Histiocytes are a special type of macrophage fixed in a particular tissue
1. Kupffer Cells / Liver
2. Alveolar macrophages / Lungs
1. Segmented (Mature)
2. Banded (Less Mature)
Wright's stain is a technique that is used to make the differences between cells visible under light microscopy.
It is used in the examination of peripheral blood smears and bone marrow aspirates.
What does this indicate?
What is your diagnosis in this case?
What is the differential diagnosis?
This 52 year old male had gradually increasing fatigue together with discomfort in the left upper quandrant. Physical examination revealed an easily palpable spleen and liver edge. A few slightly enlarged lymph nodes were palpable in the neck.
3. Heat (Local Fever)
5. Possible Loss of
Increase in blood vessel diameter to increase blood flow
1. Histamine / Body Cells
2. Kinins / Blood Plasma
3. Prostaglandin / Damaged Cells
Adherence of phagocytes to vessel walls.
Phagocytes leaving blood vessels and
Accumulation of damaged tissue, dead
microbes, and white blood cells (phagocytes).
The complement system consists of a group of serum proteins that activate one another to destroy invading microorganisms.