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Surface Defenses Epidermal: Chemical

PH is slightly acidic due to the breakdown of the fatty acid component of Se-bum

Surface Defenses Epidermal: Physical

(1) Many layers of closely packed cells. (2) Upper layer contains a tough protein called keratin (3) Skin is dry (4) Skin is continuously being shed along with the microbes on them

Surface Defenses Mucus Membrane: Physical

(1) Many layers of closely packed cells (2) Ciliary escalator moves mucus into a position to be coughed out along with microbes (3) mechanical washing: tears (eyes), urine (urethra), saliva (mouth), secreations (vagina)

Surface Level Defenses Mucus Membrane Chemical:

(1) Mucus (2) Lysozyme (3) PH

How does mucus prevent microbes from gaining access to our system?

Thick substance that traps microbes as they are inhaled or eaten

How does lysozyme prevent microbes from gaining acess to our system?

Lysozyme breaks down peptidoglycan and causes the Lyse of bacteria.

Where is lysozyme

Tears, perspiration, saliva, nasal tissue fluids

How does PH prevent microbes from gaining acess to our system?

Body PH and temperature is just not livable for most microbes. Gastric PH is around 2.

Describe Phagocytosis - 6 steps

(1) Chemotaxis (2) Adheres to microbe (3) Forms pseudopod that engulfs the microbe - becomes phagosome (4) Phagosome fuses c/ lysosome forming a phago-lysosome (5) chewed to pieces by lysozyme - leaving a residual body (6) exocytosis - most pieces leave as indigestable material. phagocyte can become an ANTIGEN presenting phagocyte

Which WBCs are important to phagocytosis?

Neutro-phil & monocyte

Largest percent of WBCs in the blood?


Classic signs of Inflammation

Redness/Erythema, Heat, Swelling/Edema, Pain, Loss of function

Acute Inflammation - purpose

(1) Destroy/Contain invading organism, (2) Repair/Replace Wounded Tissue


highly phagocytic, #'s increase in early infections, most abundant WBC in blood circulation


Migrates to tissues and differentiate into Macrophages


somewhat Phagocytic. Important Defense against parasitic worms

Acute Inflammation - steps

(1) bacteria invade (2) damaged cells release chemicals (3) Vasodialation - increased blood flow (4) vessels are more permeable - monocytes sqeeze through interstiatial space (diapedesis) (5) Swelling, pressure on nerves (pain) (5) blood clot forms (6) phagocytes devour bacteria (7) accumulation of wbcs form pus (8) undifferentiated stem cell repairs damaged tissue, blood clot is absorbed or falls off as scab

Chemicals in Inflammation

(1) Increase Blood Flow, Increased Fluid, Increased Plasma This causing Swelling (2) WBCs come in and destroy damaged cells and bacteria (3) Heat comes in and slows down bacteria while speeding up our enzymes (4) pain

Systemic Response

Whole body response

How does fever help our body?

Slows down bacteria growth. Speeds up our enzymes. Releases the protein, "transferrins" (which binds up Fe and keeps it away from microbes that need Fe for growth). Increased production of T-lymphocytes


These lymphocytes detect & destroy invading agents


(1) Made of proteins (2) Works as a cascade (starts off small, ends big) (3) Forms the Membrane Attack Complex (punches holes in cells)

What activates complement?

(1) Antigens (2) Proteins

Complement enhances inflammation and phagocytosis. What does enhance tells us?

Complement proteins are chemotactic to phagocytes, NK cells, and Tc cells. Complement proteins help activate inflammation.

What is the effect of the Membrane Attack Complex?

Cytoplasm leaks out through the ring of proteins causing the microbial cell to lyse. Cannot control osmotic pressure and die.

Interferons (IFNs)

Defend against viruses. Viruses trigger cells to make interferons which go to neighboring cells. They (1) warn them -- they shut down protein synthesis for 3-4 days >> Nothing for virus to hyjack (2) Recruit NKCs and cytotoxic T-cells to the area to destroy originally infected cell by triggering apoptosis


Main Phagocyte. Largest percentage of WBCs. Migrate into Tissue.


Base color - purple. Release histamine. IgE Anti-body attached. Help activate Inflammation.


Circulate blood and lymph, migrate into tissues. Purpose - Specific Immunity - become B and T cells

Monocyte --->> macrophage

Wandering macrophages migrate through tissues, fixed macrophages remain in a tissue.
Purpose - Highly phagocytic


Grandules stained with acidic stain, Red. released into blood migrate into tissues. Purpose- Somewhat Phagocytic. Important in defense of worms.

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