Ch. 20 - Part 1 Flashcards
immune system
provides resistance to disease
immune system two intrinsic systems
innate (nonspecific) & adaptive (specific)
first line of defense
external body membranes (skin and mucosae)
second line of defense
antimicrobial proteins, phagocytes, and other cells (inhibit spread of invaders; inflammation most important mechanism)
third line of defense
attack particular foreign substances (takes longer to react than innate)
pathogens
disease-causing microorganisms
surface barriers are skin and mucous membranes, along with their secretions
physical barrier to most microorganisms; keratin is resistant to weak acids and bases, bacterial enzymes, and toxins; mucosae provide similar mechanical barriers
protective chemicals of the skin and mucous membranes
acid, enzymes
acid mantle
acidity of skin and some mucous secretions inhibits growth
enzymes
lysozyme of saliva, respiratory mucus, and lacrimal fluid kills many microorganism; enzymes in stomach kill many microorganisms
mucin
sticky mucus that lines digestive and respiratory tract traps microorganisms
defensins
antimicrobial peptides that inhibit microbial growth
other chemicals
lipids in sebum and dermcidin in sweat are toxic to some bacteria
respiratory system also has modifications to stop pathogens
mucus-coated hairs in nose trap inhaled particles; cilia of upper respiratory tract sweep dust-and bacteria –> laden mucus toward mouth
innate system necessary if microorganisms invade deeper tissues; includes:
phagocytes, natural killer (NK) cells, inflammatory response, antimicrobial proteins, fever
pattern recognition receptors
found in second-line cells; recognize and bind tightly to structures on microbes, disarming them before they do harm
Toll-like receptors (TLRs)
plays central role in triggering immune responses; human have 11 different ones and each recognizes a particular class of attaching microbe
phagocytes
white blood cells that ingest and digest (eat) foreign invaders
neutrophils
most abundant phagocytes, but die fighting; become phagocytic on exposure on infectious material
macropahges
develop from monocytes and are chief phagocytic cells
free macrophages
wander through tissue spaces; ex –> alveolar macrophages
fixed macrophages
permanent residents of some organs; ex –> stellate macrophages (liver) and microglia (brain)
opsonization
immune system uses antibodies or complement proteins as opsonins that coat pathogen