Inflammation and Infection

Nonspecific Skin

650,000 microbes/square inch; 100 trillion/ person (acts as a place holder)

Sebaceous (oil) and odoriferous (sweat) secrete antibacterial acids and enzymes

Mucous membranes trap invaders

Defense Mechanisms

Nonspecific Inflammatory response- isolate

invader, destroy it, and clean up debris

Specific much slower All cells have protein or saccharide

markers called ANTIGENS

Defense Mechanisms

Specific when an antigen of the invader

is identified, lymphocytes produce ANTIBODIES

This defense has ability to remember the invader and to produce more antibodies if the invader returns

Defense Mechanisms

Nonspecific cellular and vascular response to tissue TRAUMA

Only occurs where blood supply exists (no gangrene)

May be so intense that it harms the tissues Anaphylactic shock Autoimmune diseases

Inflammation

When any trauma happens, including injury, microbial infection, ischemia (decreased oxygen in cells), freezing, burning, electrocution, radiation, and chemical irritation

Inflammatory Process

MAST CELLS (histocytes) are in all cells When injured, they produce HISTAMINE

that causes blood vessels to dilate and increase blood flow

HYPEREMIA causes increased redness and heat in area

Hyperemia brings increased white blood cells (neutrophils also called polymorphonuclear cells- PMNs)

Inflammatory Process

These cells also line the endothelium of the vessels (capillaries become permeable)

Blood fluid called EXCUDATE leaks into tissue

Leaking causes swelling (edema) With edema, pressure is put on nerve

endings causing pain

Inflammatory Process

Inflammatory Process

5 Cardinal Signs of Inflammation

Vascular permeability also allows neutrophils to escape into tissues (DIAPEDESIS)

Neutrophils arrive in great numbers and readily move into action by a process called CHEMOTAXIS

Neutrophils detect chemicals released by bacteria, injured tissue, and proteins and they are then drawn to the area

Inflammatory Process

Begin phagocytosis (cell eating) Neutrophils life is short and they die

and then are mixed with blood fluid to make PUS

Inflammatory Process

In 3-4 days, large numbers of monocytes (large eater) arrive

More killing power and are on clean up crew This INFLAMMATION is considered acute

Inflammatory Process

After 7-10 days if the inflammation is still present, then the lymphocytes are brought in

They use a slower, more specific attack

Inflammatory Process

Last mare than 2 weeks Microscope shows large amounts of macrophages

and fewer neutrophils If macrophage cannot help, a granuloma might be

formed These are fibrous deposits of collagen and may

calcify Ex: Tuberculosis or foreign object like a splinter

Chronic Inflammation

LEISIONS can be external or internal They can often be identified from fluid

Serous exudate- clear, serum-like (Ex: blisters) Fibrinous exudate- fluid and large amounts of

fibrinogen (Ex: strep throat or if dried, a scab) Purulent exudate- full of dead neutrophils,

tissue debris, and pyogenic (pus forming) bacteria. If localized, it is called an abscess. If in a body cavity, it is called an empyema

Inflammatory Exudates

Include wounds, ulcers, wheals, blisters, vesicles, pustules, tumors, etc. Abscesses

Caused by streptococcal or staphylococcal bacteria

Body tries to keep it contained If a large abscess ruptures, it forms a tract or

opening in skin called a sinus If the tract connects two organs, it is called a

fistula

Inflammatory Lesions

Ulcers Deep loss of tissue, crater-like lesion Pressure sores or decubitus ulcers are common

problems in health care

Inflammatory Lesions

Cellulitis widespread, acute inflammatory process General edema and redness Caused by streptococcus or staphylococcus

Inflammatory Lesions

http://www.youtube.com/watch?v=FXSuEIMrPQk (Khan Academy)

http://www.youtube.com/watch?v=IuAfs970rjs

http://www.youtube.com/watch?v=IWMJIMzsEMg (animated)

http://www.youtube.com/watch?v=WJEc2GDEfz8 (cartoon)

Inflammation Videos

Tissue Repair*Cellular proliferation or division categories * mitotic- continually divide (Ex: skin and

mucosa of internal organs) * facultative mitotic- cells do not divide regularly but can be stimulated to

do so when needed (Ex: liver and kidney, but some tissue needs to be there)

* non-dividing cells- don’t divide EVER! (Ex: brain cells, heart muscle cells- repair is only scarring)

Tissue Repair and Healing

Methods of repair Regeneration

Involves mitotic cell division (bone, skin, bone marrow)

Fibrous Connective Tissue Repair Scar formation – bridge between

normal tissue and the wound, but DOES NOT restore function

Examples: brain tissue, heart muscle

Tissue Repair

http://www.youtube.com/watch?v=IYL6vg89uds

Primary Union (First Intention)*Wound edges are clean* Steps 1. line fills with serum, forming a scab 2. in 1-2 days, new capillaries bridge the gap

between the edges3. in a few days fibroblasts grow across the

deeper wound layers and begin to deposit collagen in fibrous network (granulation tissue)

4. collagen begins to contract pulling edges together and forming a scar**In a few weeks, incision will look healed but deep layers may not be for a month or more

Tissue Healing

Secondary Union (Secondary Intention) When dirty, or deeper degree of tissue damage

or cannot be pulled together Same process but with much more

inflammation to resolve Large numbers of capillaries, fibroblasts, and

collagen must be produced After a week, new soft tissue called granulation

tissue is formed and later replaced with collagen

Collagen contracts, pulling the wound edges together

Healing depends on size of wound- may need skin graph

Tissue Healing

Increased levels of dirt, bacteria, dead leukocytes, etc might make the body take months to eat up.

Wounds must be cleaned or DEBRIDED Other factors effecting healing time

Age, size of wound, location of wound, nutrition, immobility, and circulation

Organism virulence (strength) steroids

Delayed Wound Healing

Prolonged wound healing Poor or excessive scar formation

DEHISCENSE- scar does not have enough strength and separates at margin

Excessive collagen formation results in a raised scar called a keloid (more common in African- Americans)

ADHESIONS form scar tissue that adheres to a nearby organ (often after surgery)

Complications of Wound Healing

Complications or Wound Healing

Symptoms Fever Tachycardia Malaise Leukocytosis Septicemia

Tests Cutures- organism grown in agar, often with

sheep’s blood Culture and sensitivity tests- microorganisms

smeared on agar and small antibiotic-permeated disks are placed on the agar- killing zones are identified

Antigen-antibody (reactive tests or serologic tests) Skin testing (TB- Mantoux test) for induration

(positive test) Xpert test for MRSA- DNA testing

 

Testing for Infection