Chapter 3 Inflammation and Repair Defense Mechanisms Defense

Chapter 3 Inflammation and Repair

Defense Mechanisms • Defense mechanisms can be – Nonspecific: • Protecting against all invaders – Specific: • Identifies specific invader before neutralizing it • Three lines of defense protect body against foreign invasion: 1. Physical or surface barriers (nonspecific) 2. Inflammation (nonspecific) 3. Immune response (specific)

Defense Mechanisms: Physical or Surface Barriers • Skin – Body’s first line of defense – Covered with “good” bacteria • Normal flora • Prevents growth of “bad” bacteria – Glands • Secrete antibacterial substances onto surface – Mucus membranes • Secrete mucus that traps invaders

Defense Mechanisms: Inflammation • Nonspecific response to anything causing cell injury – Causes can be: • Goal – Isolate & destroy invader, clean up debris, & promote healing • Characteristic signs of inflammation are:

Inflammatory Process • Chemical agents are formed & released when tissue is damaged – Called: • Cell Derived Mediators come from two sources: – Mast cells – Injured cells

Inflammatory Process: Cell derived Mediators • Mast cells – Specialized cells found in: – Release histamine in response to trauma • Histamine – Leads to:

Inflammatory Process: Cell derived Mediators • Injured cells – Plasma membranes release two mediators in response to injury: – Effect:

Inflammatory Process: plasma derived Mediators • Blood plasma contains proteins that circulate as inactive compounds • With tissue damage they leak into injured area and are activated – Called: – Leads to:

Inflammatory Process • Hyperemia: – Vasodilation: increases blood flow to the area • Causes increased redness and heat • Bring increased numbers of leukocytes (WBC’s) to the area

Inflammatory Process • Leaky blood vessels – Fluid leaks from dilated & more permeable blood vessels into tissues • Called: – Fluid containing: • Leads to: – Neutrophils escape from blood into tissues

Inflammatory Process • Neutrophils – A type of white blood cell – Use phagocytosis – Drawn to injured area by chemotaxis • Chemicals released by injured tissue or bacteria tell neutrophils where to go • Monocytes show up 3 -4 days later

Inflammatory Process • Monocytes – A type of white blood cell – Are called a macrophage after entering tissue – Use phagocytosis • Other leukocytes of inflammation release chemicals – Basophils: histamine – Eosinophils: allergic response

Defense Mechanisms: Immune response – Occurs if inflammation persists beyond 7 days – Lymphocytes will be used • A type of WBC • Specific killers • ID invaders & make antibodies that neutralize/kill – Remember invader for later

Types of Inflammation • Hard to determine exactly when acute inflammation becomes chronic • In general: – Acute: lasts less than 10 days – Chronic: lasts longer than 10 days • Will see a larger # of macrophages & less neutrophils • Can see damage to tissue • If damage is severe scar tissue may form which can disturb normal function

Defense Mechanisms: Immune response Fig. 3 -1

Tissue Repair and Healing • Final phase of inflammation – Macrophages clean up the area & stimulate the repair process – Body repairs tissue in 2 ways: • Regeneration – Damaged tissue replaced by cell division of healthy tissue – Ex. Skin tissue replaced by epithelial cell division • Fibrous connective tissue repair – Same results no matter location – A tough fibrous tissue is formed (scar) – Doesn’t restore function – Nerve, brain, & heart muscle don’t regenerate only use fibrous repair

Inflammatory Exudates • Appearance of exudate can vary • Types: – Serous – Fibrinous – Purulent – Hemorrhagic

Inflammatory Exudates • Serous exudate – E. g. • Fibrinous exudate – Coagulates to form a mesh-like lesion • On surface called: – Can cause 2 areas to stick together • Called an:

Inflammatory Exudates • Purulent exudate – Commonly called: • Hemorrhagic exudate

Lesions • Any abnormality of tissue due to physical or pathologic injury • Lesions caused by inflammation include: – Abscesses – Cellulitis

Lesions • Abscess • Usually caused by bacterial infection – Will see common signs of inflammation – Draining an abscess can help speed healing – Ex.

Lesions • Cellulitis – Characterized by: – Cause:

Infection • Invasion of pathogenic organisms causing cell or tissue injury & leading to the inflammatory response – Pathogenic • 3 conditions needed for infection to occur

Conditions Needed for Infection to Occur 1. Pathogens must successfully enter the body – Common points of entry

Conditions Needed for Infection to Occur 2. Pathogen needs to be able to survive the hosts defenses – Virulence: • High virulence: • High number of invading microorganisms • Vulnerable condition of individual or host

Conditions Needed for Infection to Occur 3. The number of invading pathogens influences risk for infection

? ? QUESTIONS? ? 27