Ch 21 A

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immune system

A system (including the thymus and bone marrow and lymphoid tissues) that protects the body from foreign substances and pathogenic organisms by producing the immune response; Provides resistance to disease

Two intrinsic systems of the immune system

1. Innate (nonspecific) defense system (first and second lines of defense)
2. Adaptive (specific) defense system (third line of defense)

Innate (nonspecific) defense system

constitutes first and second lines of defense; First line of defense: external body membranes (skin and mucosae); Second line of defense: antimicrobial proteins, phagocytes, and other \n cells (inhibit spread of invaders; inflammation most important mechanism)

Adaptive (specific) defense system

Third line of defense attacks particular foreign substances (takes longer to react than innate)

First line of defense

external body membranes (skin and mucosae); Innate/nonspecific

Second line of defense

antimicrobial proteins, phagocytes, and other cells (inhibit spread of invaders; inflammation most important mechanism); Innate/nonspecific

Third line of defense

attacks particular foreign substances (takes longer to react than innate); Adaptive/specific

pathogens

disease causing agents (microorganisms

Surface barriers

-Skin, mucous membranes, and their secretions \n -Physical barrier to most microorganisms \n -Keratin is resistant to weak acids and bases, bacterial enzymes, and \n toxins \n -Mucosae provide similar mechanical barriers

Pattern Recognition Receptors (PRRs)

proteins on or in cells that recognize specific compounds unique to microbes or tissue damage, allowing the cells to sense the presence of invading microbes or damage

Phagocytes

A type of white blood cell that ingests invading microbes (phagocytosis)

Neutrophils

most abundant phagocytes, but die fighting; become phagocytic on \n exposure to infectious material

Macrophages

develop from monocytes and are chief phagocytic cells; most robust phagocytic cell

Natural Killer (NK) Cells

-Nonphagocytic, large granular lymphocytes that police blood and lymph \n -Can kill cancer and virus-infected cells before adaptive immune system is activated \n -Attack cells that lack "self" cell-surface receptors \n -Kill by inducing apoptosis in cancer cells and virus-infected cells \n -Secrete potent chemicals that enhance inflammatory response

Inflammation

a localized response to an injury or to the destruction of tissues; triggered whenever body tissues are injured

Cardinal signs of inflammation

redness, swelling, heat, pain, sometimes loss of function

benefits of inflammation

-Prevents spread of damaging agents \n -Disposes of cell debris and pathogens \n -Alerts adaptive immune system \n -Sets the stage for repair

stages of inflammation

1. Inflammatory chemical release
2. Vasodilation and increased vascular permeability
3. Phagocyte mobilization

histamine

Chemical stored in mast cells that triggers dilation and increased permeability of capillaries; key inflammatory chemical

kinins, prostaglandins, cytokines and complement

Inflammatory mediators; cause vasodilation of local arterioles, makes capillaries leaky; many attract phagocytes to area

Phagocyte mobilization

-Neutrophils flood area first; macrophages follow \n -If inflammation is due to pathogens, complement is activated; adaptive immunity elements arrive

Pus

creamy yellow mixture of dead neutrophils, tissue/cells, and living/dead pathogens

Abscess

Collection of pus underneath the skin bc collagen fibers are laid down; may need to be surgically drained