Chapter 16: Innate Nonspecific Host Defenses Flashcards
Skin Barrier
Composed of three layers of closely packed cells; one of the body’s most important physical barriers.
Epidermis
Consists of cells that are tightly packed with keratin; makes the skin’s surface mechanically tough and resistant to degradation by bacterial enzymes.
Mucous Membranes
Line the nose, mouth, lungs, and urinary and digestive tracts provide another nonspecific barrier against potential pathogens.
Epithelial Cells
Secrete a moist, sticky substance called mucus.
Mucus
Covers and protects the more fragile cell layers beneath it and traps debris and particulate matter, including microbes; also contains antimicrobial peptides.
Ciliated Epithelial Cells
Have hair-like appendages known as cilia.
Cilia
Movement of the cilia propels debris-laden mucus out and away from the lungs.
Mucociliary Escalator
Moves debris-ridden mucus out of the body.
Goblet Cells
Secrete mucus.
Peristalsis
A series of muscular contractions in the digestive tract.
Endothelia
The epithelial cells lining the urogenital tract, blood vessels, lymphatic vessels, and certain other tissues.
Mechanical Defenses
Physically remove pathogens from the body, preventing them from taking up residence.
Resident Microbiota
Serves as an important first-line defense against invading pathogens; prevents the critical early steps of pathogen attachment and proliferation required for the establishment of an infection.
Chemical Mediators
Encompasses a wide array of substances found in various body fluids and tissues throughout the body.
Lactoferrin
Inhibits microbial growth by chemically binding and sequestering iron; starves many microbes.
Cerumen
Earwax; exhibits antimicrobial properties due to the presence of fatty acids, which lower the pH to between 3 and 5.
Antimicrobial Peptides
A special class of nonspecific mediators with broad-spectrum antimicrobial properties.
Defensins
Produced by epithelial cells throughout the body as well as by cellular defenses such as macrophages and neutrophils; they combat microorganisms by damaging their plasma membranes.
Bacteriocins
Produced exogenously by certain members of the resident microbiota within the GI tract; disrupt cell membranes.
Serum
The fluid portion of blood left over after coagulation (blood cell clotting) has taken place is serum.
Acute-Phase Proteins
Another class of antimicrobial mediators; primarily produced by the liver and secreted into the blood in response to inflammatory molecules from the immune system.
Complement System
A group of plasma protein mediators that can act as an innate nonspecific defense while also serving to connect innate and adaptive immunity.
Complement Activation
The process by which circulating precursors become functional.
Alternative Pathway
Initiated by the spontaneous activation of the complement protein C3; C3 attaches to the surface of these microbes and recruit other complement proteins in a cascade.
Classical Pathway
Provides a more efficient mechanism of activating the complement cascade, but it depends upon the production of antibodies by the specific adaptive immune defenses.
Lectin Activation Pathway
Similar to the classical pathway, but is triggered by the binding of mannose-binding lectin, an acute-phase protein, to carbohydrates on the microbial surface.
Opsonization
Refers to the coating of a pathogen by a chemical substance (called an opsonin) that allows phagocytic cells to recognize, engulf, and destroy it more easily.
Cytokines
Soluble proteins that act as communication signals between cells.
Autocrine Function
The same cell that releases the cytokine is the recipient of the signal.