Body Defenses Innate Defenses Page 403 410 Part

Body Defenses: Innate Defenses Page 403 -410

Part II: Body Defenses � The body has two defense systems foreign materials that form the immune system � Immunity—specific resistance to disease (such as bacteria, virus, fungus) ◦ Provided for by the adaptive defenses © 2015 Pearson Education, Inc.

Body Defenses � Innate (nonspecific) defense system ◦ Mechanisms protect against a variety of invaders ◦ Responds immediately to protect body from foreign materials � Adaptive (specific) defense system ◦ Specific defense is required for each type of invader © 2015 Pearson Education, Inc.

Innate (Nonspecific) Body Defenses � mechanical barriers that include: ◦ Body surface coverings ◦ Specialized cells ◦ Chemicals produced by the body � See Table 12. 1 for a more detailed summary © 2015 Pearson Education, Inc.

Surface Membrane Barriers �first line of defense: ◦ Skin and mucous membranes 1. 2. 3. 4. Acidic p. H of the skin inhibits bacterial growth Stomach mucosal secretions kill pathogens (HCl) Saliva and lacrimal (eyes) fluid contain lysozyme Mucus traps microogranisms © 2015 Pearson Education, Inc.

Internal Defenses: Cells and Chemicals �second line of defense: ◦ ◦ ◦ Natural killer (NK) cells Inflammatory response Phagocytes Antimicrobial proteins Fever © 2015 Pearson Education, Inc.

Natural Killer (NK) Cells � Found in blood and lymph � Release perforin (lytic chemicals) ◦ Does not discriminate ◦ targets abnormal cell’s membrane and nucleus ◦ causes disintegration of cancer or virus-infected cells � http: //biology-animations. blogspot. com/2010/04/nk-cellanimation. html © 2015 Pearson Education, Inc.

Inflammatory Response � Takes place when tissues are injured/damaged � Functions: ◦ Prevent spread of damaging agents ◦ Phagocytosis eliminates cell debris and pathogens ◦ Sets the stage for tissue repair � Begins with redness, heat, swelling, pain © 2015 Pearson Education, Inc.

Steps of the Inflammatory Response Release of inflammatory chemicals causes: 1. Blood vessels dilate and leak 2. Pain receptors to be activated 3. Influx of neutrophils and macrophages ◦ ◦ Neutrophils devour foreign materials Macrophages replace spent neutrophils and dispose of cell debris © 2015 Pearson Education, Inc.

Figure 12. 8 Phagocyte mobilization. 3 Positive Inflammatory chemicals diffusing from the inflamed site act as chemotactic agents Neutrophils 1 Enter blood from bone marrow and roll along the vessel wall Capillary wall chemotaxis 2 Diapedesis Endothelium Basement membrane

Phagocytes/Phagocytosis � Implored when pathogens get through the first line of defense � Macrophages or neutrophils will: 1. Engulf foreign material into a vacuole 2. Vacuole fuses with a lysosome 3. Enzymes from lysosomes digest the material © 2015 Pearson Education, Inc.

Figure 12. 9 a Phagocytosis by a macrophage. (a) A macrophage (purple) uses its cytoplasmic extensions to pull spherical bacteria (green) toward it. Scanning electron micrograph (10, 800×).

Figure 12. 9 b Phagocytosis by a macrophage. 1 Phagocyte adheres to pathogens. 2 Phagocyte Phagosome engulfs the (phagocytic particles, forming a phagosome. vesicle) Lysosome Acid hydrolase enzymes (b) Events of phagocytosis 3 Lysosome fuses with the phagocytic vesicle, forming a phagolysosome. 4 Lysosomal enzymes digest the pathogens or debris, leaving a residual body. 5 Exocytosis of the vesicle removes indigestible and residual material. Slide 1

Antimicrobial Proteins: Complement proteins and Interferons � Complement proteins ◦ Complement Fixation: proteins become fixed to sugars/proteins (antibodies) on a foreign cell’s surface ◦ Membrane Attack Complexes (MAC): lesions produced by fixation �Creates holes in the cell’s surface �Water enters and cell bursts © 2015 Pearson Education, Inc.

Figure 12. 10 Activation of complement, resulting in lysis of a target cell. Membrane attack complex forming Antibodies attached to pathogen’s membrane Pore Activated complement proteins attach to pathogen’s membrane in step-by-step sequence, forming a membrane attack complex (a MAC attack). MAC pores in the membrane lead to fluid flows that cause cell lysis.

Interferons � Virus infects cell � Cell secretes proteins called interferons � Interferons bind to receptors on healthy cell surfaces ◦ Interfere with the ability of viruses to replicate DNA http: //highered. mheducation. com/sites/0072556781/student_view 0/chapter 31/anim ation_quiz_2. html © 2015 Pearson Education, Inc.

Fever � Abnormally high body temperature ◦ Up to 104°-106° - depends on the individual ◦ systemic response to invasion by microorganisms � Regulated by hypothalamus � Inhibits reproduction of bacteria � Increases speed of repair processes © 2015 Pearson Education, Inc.