First Line of Defense

• non specific defense
• mechanical barrier
  • such as: unbroken skin or mucous membrane
• blocks the entry of bacteria and other harmful substances into the tissues
• body secretions such as tears and saliva that contain enzymes that destroy potentially damaging material

Second Line of Defense

• includes the non specific processes of phagocytosis and inflammation

Phagocytosis

• process by which neutrophils and macrophages engulf and destroy bacteria, cell debris, or foreign matter

Neutrophils

• a leukocyte
• phagocytosis of microorganisms

Inflammation

suffix: -itis

• a sequence of events intended to limit the effects of injury or a dangerous agent in the body
• is intended to localize and remove an injurious agent
• the general signs and symptoms serve as a warning of a problem which may be hidden within the body
• non specific response
• results in redness, swelling, warmth, and pain

Interferons

• nonspecific agents
• protect uninfected cells against viruses

Third Line of Defense

• specific defense
• provides protection by stimulating the production of specific antibodies and sensitized lymphocytes

Normal Capillary Exchange

• usually not all capillaries in a particular capillary bed are open
  • unless the cells' metabolic needs are not being met by the blood supply to the area
  • or an accumulation of wastes occurs

Arterial End of Capillary

• movement of fluid, electrolytes, oxygen, and nutrients
• based on net hydrostatic pressure (pushes things out)

Venous End of Capillary

• hydrostatic pressure is decreased
• osmotic pressure (pulls things in)- relatively high
  • b/c plasma proteins remain within the vessels

Glucocorticoids

• acts as an anti-inflammatory by decreasing capillary permeability

Causes of Inflammation

• direct physical damage
  • such as: cuts or sprains
• caustic chemicals
  • such as: acids or drain cleaner
• ischemia or infarction
  • local deficiency of blood
• allergic reactions
• extremes of heat and cold
• foreign bodies
  • ex: splinter or glass
• infection

Steps of Inflammation

• An injury to capillaries and tissue cells will result in the following reactions:
  1. Bradykinin is released from injured cells
  2. Bradykinin activates pain receptors
  3. Sensation of pain stimulates mast cells and basophils to release histamine
  4. Bradykinin and Histamine cause capillary dilation
     • results in an increase in blood flow and increased capillary permeability
  5. Break in skin allows bacteria to enter the tissue
     • results in migration of neutrophils and monocytes to the site of injury
  6. Neutrophils phagocytize bacteria
  7. Macrophages (mature monocytes) leave the bloodstream and phagocytose microbes

Acute Inflammation

• When tissue injury occurs, the damaged mast cells and platelets release chemical mediators into the interstitial fluid and blood.
• examples of chemical mediators:
  • histamine
  • serotonin
  • prostaglandins
  • leukotrienes
• Chemical mediators affect blood vessels and nerves in the damaged area
• Cytokines
  • serve as communication in the tissue fluids sending messages to induce fever

Histamine

• released immediately from granules in mast cells and exert their effects at once
• immediate vasodilation and increase capillary permeability to form exudate

Leukotrienes

• synthesized from arachidonic acid in mast cells
• responsible for the later effects
• prolongs inflammation
• vasodilation
• increased capillary permeability
• chemotaxis

Hyperemia

• increased blood flow to a particular area

Increase in Capillary Permeability

• allows plasma proteins to move into interstitial space along with fluid.
• Increased fluid dilutes any toxic material, while globulins serve as antibodies, and fibrinogen forms fibrin mesh around the area to localize the injurious agent

Chemotaxis

• attract cells of the immune system
• first Neutrophils and later monocytes and macrophages

Vasodilation

• relaxation of smooth muscles causing an increase in the diameter of arterioles

Basophils

• release of histamine, leading to inflammation

Eosinophils

• numbers are increased in allergic responses

T Lymphocytes

• active in cell-mediated immune response

B Lymphocytes

• produce antibodies

Monocytes

• phagocytosis

Macrophages

• active in phagocytosis
• mature monocytes that have migrated into tissues from the blood

Diapedesis

• The movement or passage of blood cells, especially white blood cells, through intact capillary walls into surrounding body tissue.

Redness and Warmth

(inflammation symptom)

• caused by increased blood flow into the damaged area

Swelling or Edema

(inflammation symptom)

• caused by the shift of protein and fluid into the interstitial space

Pain

(inflammation symptom)

• results from increased pressure of fluids on the nerves; release of chemical mediators (ex: Bradykinin & prostaglandins)

Loss of Function

(inflammation symptom)

• may develop if cells lack nutrients
• edema may interfere with movement

Exudate

• a collection of interstitial fluid formed in an inflamed area

Serous/Watery Exudate

• watery
• consists primarily of:
  • fluid
  • some proteins
  • and some white blood cells
• occurs with allergic reactions and burns

Fibrinous Exudate

• thick and sticky
• high cell and fibrin content
• increases the risk of scar tissue in the area

Purulent

• thick, yellow-green
• contains more leukocytes, cell debris, and microorganisms
• indicates bacterial infection
• aka "pus"

Abscess

• localized pocket of purulent exudate in a solid tissue

Other General Manifestations of Inflammation

• mild fever (pyrexia)
  • if inflammation is extensive
• malaise
  • feeling unwell
• fatigue
• headache
• anorexia
  • loss of appetite

Pyrogens

• fever-producing substances
• circulate in the blood and cause the body temperature control system in the hypothalamus to be reset at a higher level

Leukocytosis

• increased white blood cells in the blood
• especially neutrophils

Differential Count

• the proportion of each type of WBC
• may be helpful in distinguishing viral from bacterial infection

Cell Enzymes in blood

• may be elevated in the blood in the presence of severe inflammation and necrosis
• helpful in locating the site of necrotic cells

Ulcers

• erosion of tissue

Infection & Inflammation

• infection may develop in an inflamed tissue b/c microorganisms can more easily penetrate when the skin is damaged and blood supply is impaired
• some microbes resist phagocytosis
• inflammatory exudate provides an excellent medium for microorganisms to reproduce and colonize the inflamed area

Chronic Inflammation

• may develop following an acute inflammation, when causative agent is not completely eradicated

Characteristics of Chronic Inflammation

• less swelling and exudate
• presence of more lymphocytes, macrophages, and fibroblasts than acute inflam
• more tissue destruction occurs
• more collagen is produced resulting in more fibrous scar tissue

Granuloma

• small mass of cells with a necrotic center covered by connective tissue
• may develop around foreign objects such as splinter

Acetylsalicylic Acid (ASA)

• an anti-inflammatory agent
• decrease prostaglandin synthesis, reducing the inflammatory response
• decrease pain and fever
• DO NOT GIVE TO CHILDREN WITH VIRAL INFECTIONS DUE TO RISK OF LEADING TO REYES SYNDROME
• aspirin

Acetaminophen

• decreases fever and pain
• does not diminish the inflammatory response
• TYLENOL or PARACETAMOL

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

• has anti-inflammatory, analgesic, antipyretic activities
• act by reducing production of prostaglandins
• used to treat inflammation in musculoskeletal system

Anti-Inflammatory Effects of Glucocorticoids

• act as an anti-inflammatory by decreasing capillary permeability
• enhance effectiveness of epinephrine and norepinephrine
• reduced number of leukocytes and mast cells, decreasing the release of histamine and prostaglandins
• reduces immune response

RICE Therapy for Injuries

• Rest
• Ice
  • cold causes vasoconstriction, decreasing edema and pain
• Compression
  • reduces the accumulation of fluid
• Elevation
  • improve fluid flow away from damaged area

Resolution

• the process that occurs when there is minimal tissue damage
• the damage cells recover and tissue returns to normal within a short period
• ex: sunburn

Regeneration

• the healing process that occurs in damaged tissue in which the cells are capable of mitosis
• the damaged tissue is replaced by identical tissue from the proliferation of nearby cells

Replacement

• takes place when there is extensive tissue damage
• cells are incapable or mitosis
• functional tissue replaced by scar tissue
• loss of function

The Healing Process

• the process of tissue repair begins following injury when a blood clot forms and seals the area
• after 3 to 4 days foreign material and cell debris has been removed granulation tissue grows into the gap

Complication due to Scar Formation

• loss of function
  • results from the loss of normal cells and lack of specialized structures or normal organization in scar tissue
    • ex: hair follicles, nerves, receptors

Contractures and Obstructions

• scar tissue is nonelastic
• shrinks over time
• contracture
  • An abnormal, often permanent shortening, as of muscle or scar tissue, that results in distortion or deformity, especially of a joint of the body

Adhesions

• bands of scar tissue joining two surfaces that are normally separated

Hypertrophic Scar Tissue

• overgrowth of fibrous tissue
• leads to hard ridges of scar tissue or keloid formation

Ulceration

• blood supply may be impaired around scar
• results in further tissue breakdown and ulceration at future time

Burn

• a thermal (heat) or nonthermal (electrical or chemical) injury to the body, causing acute inflammation and tissue destruction
• may be mild or severe
• classified by the depth of skin damage and the percentage of body surface area involved

Superficial Partial-Thickness Burns (First Degree)

• involves epidermis and may involve upper part of dermis
• little, if any, blister formation
• usually appears red and painful but readily healed without scar tissue

Deep Partial-Thickness Burn (second degree)

• involve the destruction of the epidermis and part of the dermis
• area is red, edematous, blistered, and often hypersensitive
• easily infected

Full Thickness Burns (third and fourth degree)

• destruction of all skin layers and underlying tissues
• burn area may be painless b/c of destruction of the nerves

Effects of Burn Injury

• both local and systemic
• shock
• dehydration and edema
• respiratory problems
• pain
• infection

Hematocrit

• the percentage of RBCs in a volume of blood