N245: Inflammation, Tissue Repair, and Wound Healing

What is the first line of defense?

Skin, mucous membranes (and their secretions)

What is the second line of defense?

Includes the inflammatory process and immune system response

What is the third line of defense?

The production of specific antibodies

What happens to capillaries during an inflammatory response?

They dilate and the spaces between cells widens

-itis

inflammation

Inflammation

A normal defense response to injury, irritation, or infection

What are some causes of inflammation?

Physical damage, chemical irritation, ischemia, allergic reactions, temp changes, infection

What chemicals are released during inflammation?

1. Injured cells release bradykinin

2. Bradykinin activates pain receptors

3. Mast cells/basophils release histamine

Bradykinin

A chemical mediator that is released during inflammation --> causes vasodilation

Histamine

Chemical stored in mast cells --> causes dilation and increased permeability of capillaries

What causes capillary dilation?

Bradykinin and histamine increase blood flow and capillary permeability

What do neutrophils do?

During the inflammatory response, neutrophils phagocytize bacteria

What do monocytes do?

During the inflammatory response, monocytes become macrophages and eat the microbes

Vascular phase of inflammation

Overall vasodilation and increased capillary permeability

Cellular phase of inflammation

Involves white blood cells leaving the circulatory system, moving to the site of injury, and becoming activated

What are the outcomes of inflammation?

RASP:

Resolution

Abscess

Scar

Persistent inflammation

Does inflammation change depending on the cause?

No, the steps of inflammation are the same regardless of the cause

Steps of inflammation

1. Vasodilation

2. Hyperemia

3. Increase in capillary permeability

4. Chemotaxis to attract cells of the immune system

Arachidonic acid

A pro-inflammatory chemical messenger released by injured cell membranes

5 signs of inflammation

Heat, redness, swelling, pain, loss of function

Rubor

Redness

Tumor

Swelling

Calor

Heat

Dolor

Pain

Functio laesa

Loss of function

What causes redness?

increased blood flow and vasodilation

What causes swelling?

Increased capillary permeability --> causes a shift of protein and fluid into the interstitial space

What causes pain?

Swelling puts pressure on nerves, release of chemical mediators (e.g., bradykinins)

What causes loss of function?

Pain and swelling impair function

Exudate

Inflammatory fluid that leaks out of cells (high in protein, blood, and immune cells)

Serous exudate

Watery: contains fluid, some proteins, and white blood cells

Hemorrhagic exudate

Exudate that contains blood

hemorrhage = bleeding

Fibrinous exudates

Exudate that contains a large amounts of fibrinogen --> forms a thick and sticky clot

Membranous/Pseudomembranous Exudates

Exudate that develops on mucous membrane surfaces and are composed of necrotic cells

Purulent/Suppurative Exudates

Exudate that contains pus; composed of white blood cells, proteins, and tissue

I'm so sorry this picture is literally vile... but i guess it will help with the desensitization

Abscess

A localized collection of pus underneath the skin

Pyrogens

Substances that cause fever

Interleukins

Proteins (cytokines) that stimulate the growth of B and T lymphocytes

Tumor necrosis factor

A chemical that causes inflammation and triggers apoptosis

Systemic affects of inflammation

1. Fever (pyrexia)

2. Headache/fatigue

3. Anorexia

What time of the day is fever highest?

At night

Leukocytosis

An increase in the number of white blood cells

How does leukocytosis change with inflammation?

The amount of WBCs increases during periods of inflammation

What is the expected erythrocyte sedimentation rate during inflammation?

This test measures how quickly red blood cells settle in a test tube

Inflammation causes RBCs to clump together --> the more inflammation, the higher/faster your ESR

How could a differential count determine the cause of inflammation?

A differential count determines the amount of each type of white blood cell in the blood --> helps determine whether infection is bacterial or viral

How can circulating plasma proteins determine the presence of infection?

Normally, C-reactive protein (CRP) is not found in blood

When there is an infection, CRP will attach to bacteria to prepare them for phagocytosis

Chronic inflammation

Long-lasting, out-of-control inflammatory response that continues for more than a few weeks

Which WBCs are present during chronic inflammation

Presence of more lymphocytes and macrophages

Which WBCs are present during acute inflammation?

There is an increased presence of neutrophils

Epithelioid cells

Macrophages that have differentiated so that they specialize in taking up debris and other small particles

Granuloma

A small area of inflammation (contains epithelioid cells)

How can foreign bodies cause granulomas?

Splinters, sutures, asbestos can cause granulomas

Granulomas associated with microorganisms include...

Tuberculosis, syphilis, fungal infections, brucellosis

How can inflammation lead to infection?

1. Microbes can penetrate tissues more easily when they are swollen

2. The exudate creates a hospitable environment for microbes

How does inflammation lead to skeletal muscle spasm?

Inflammation --> pain --> muscle spasm

How can inflammation lead to ulcers?

Prolonged inflammation can cause cell death and necrosis --> leading to ulcer formation

Labile cells

Cells that undergo mitosis regularly and quickly

Stable cells

Cells that stop dividing when growth is complete (they can divide if they are injured)

Permanent Cells

Cells that cannot undergo mitosis

Resolution

Healing that leaves the body with limited damage

Regeneration

The damaged cells are replaced with functional cells

Replacement/Fibrosis

The damaged tissue is replaced by scar tissue (non functional)

Scar tissue

Tissue that forms at the site of healing wounds; made mostly of collagen

What happens if scar tissue forms in an area with permanent cells?

Since permanent cells cannot regenerate, the area containing scar tissue will be non-functional

Example: myocardial infarction

What is the goal of wound healing?

To restore the structural and functional integrity of injured tissue

Primary intention healing

Small, clean wounds that heal with little tissue loss

Secondary intention healing

Large, contaminated wounds that heal with major tissue loss

What are the stages of wound healing?

1. Inflammatory

2. Proliferation

3. Maturation

Inflammatory phase

The initial phase of wound healing; includes blood clotting and invasion of WBCs

Proliferation phase

The second phase of wound healing; new tissue forms, fibroblasts produce fibrin

Maturation phase

The third phase of wound healing; scar tissue forms, cells differentiate

How can scar tissue cause loss of function?

Scar tissue may replace nerves, muscles, and glands

How can scar tissue limit range of motion?

Scar tissue is not elastic --> ROM may be decreased

Adhesions

Bands of scar tissue that link two surfaces that are normally separated

Hypertrophic scar tissue

Overgrowth of fibrous tissue during scare formation --> leads to keloid formation

How can scar tissue cause ulceration?

Scar tissue can limit bloodflow --> leading to tissue death