Ch 21 Lecture Notes a&P

Topics: Immune system, Antibody, Humoral immunity Pages: 19 (3759 words) Published: June 22, 2013
Chapter 21 The Immune System:
Innate and Adaptive Body Defenses
Innate and Adaptive Defenses (Fig. 21.1, pg. 767)

Body Defenses against Infection (Fig. 21.1, pg. 767)
* Immunity
* Resistance to disease
* Pathogen
* disease causing agent
* bacteria, viruses, etc

* Innate (nonspecific) Defenses
* responds quickly
* general defenses
* protects against many pathogens
* First line of defense
* skin and mucosae prevent entry of microorganisms
* Second line of defense
* antimicrobial proteins, phagocytes, and other cells * Inhibit spread of invaders throughout the body
* Inflammation is its most important mechanism
* Adaptive (specific) Defenses
* Third line of defense – mounts attack against specific foreign substances * Takes longer to react than the innate system
* Works in conjunction with the innate system
* carried out by lymphocytes that recognize a specific invader

* Both defenses work together to protect the body against infection

Innate (Nonspecific) Defenses
* 1. First Line of Defense – Surface Barriers: skin and mucous membranes * Skin
* Intact epidermis layer of the skin; tough physical barrier * Keratin is resistant to weak acids and bases, bacterial enzymes, and toxins * Mucosae (mucus membranes) provide similar mechanical barriers * Protective chemicals inhibit or destroy microorganisms

* Sebum, which has a pH of 3 to 5 due to the presence of unsaturated fatty acids and lactic acid * Gastric juice renders the stomach nearly sterile because its low pH (1.5-3.0) kills many bacteria and destroys most of their toxins * Saliva and lacrimal fluid contain lysozyme that also has antimicrobial properties. * Mucus traps microorganisms that enter the digestive and respiratory systems * Respiratory system modifications

* Mucus-coated hairs in the nose trap inhaled particles * Cilia & mucus trap & move microbes toward throat

* 2. Second Line of Defense – Internal Defenses: Cells & Chemicals * Necessary if microorganisms invade deeper tissues
* Phagocytes
* Natural killer (NK) cells
* Inflammatory response (macrophages, mast cells, WBCs, and inflammatory chemicals) * Antimicrobial proteins (interferons and complement proteins) * Fever

* Phagocytes: Macrophages (Fig. 21.2, pg. 769)
* Macrophages (monocytes) are the chief phagocytic cells * Free macrophages wander throughout a region in search of cellular debris * e.g., alveolar macrophages
* Fixed macrophages are permanent residents of some organs * e.g., Kupffer cells (liver) and microglia (brain) are fixed macrophages * Neutrophils become phagocytic when encountering infectious material

Phagocytosis
* 1. Chemotaxis
* attraction to chemicals from damaged tissues, complement proteins, or antibodies * 2. Adherence
* attachment to plasma membrane of phagocyte to antigen * 3. Ingestion
* engulf by pseudopods to form phagosome
* 4. Digestion
* merge with lysosome containing digestive enzymes & form lethal oxidants * 5. Indigestible and residual material is removed by exocytosis

* Natural Killer Cells
* Are a small, distinct group of large granular lymphocytes * React nonspecifically and eliminate cancerous and virus-infected cells * Target cells that lack “self” cell-surface receptors * Kill their target cells by releasing perforins and other cytolytic chemicals * Secrete potent chemicals that enhance the inflammatory response * Found in blood, spleen, lymph nodes & red marrow

* Inflammation (Fig. 21.4, pg. 771)
* Tissue response to injury
* Function is to:
* Prevents the spread of damaging agents
* Disposes of cell debris and pathogens
* Sets the stage for...
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