Cellular Adaptation and Injury

Cellular Adaptation

• Cells adapt to environmental changes by altering their size, number, and characteristics
• These changes answer to specific stimuli and are usually reversible

Definitions

• Homeostasis is the body's ability to maintain a stable internal environment
• Hyperplasia involves an increase in the number of cells, like in Benign Prostatic Hyperplasia (BPH)
• Hypertrophy means an increase in cell size due to more workload, common in cardiac and skeletal muscle tissue
• Atrophy signifies a reduction in cell size resulting from disuse, decreased blood flow, or malnutrition
• Metaplasia is the replacement of one cell type with another that can better endure stress but doesn't function as well as the original
• Dysplasia is abnormal cell growth that changes cell size, shape, or appearance and can precede cancer

Mechanisms of Cellular Injury

• Many agents can cause cell injury, including physical, chemical, biological, and nutritional factors
• Three primary mechanisms of cell injury exist

Free Radical Injury

• Free radicals are highly reactive molecules which can cause cell damage and lead to diseases like cancer

Hypoxic Cell Injury

• Hypoxic cell injury refers to cellular oxygen deprivation
• Brain, heart, and kidneys are highly susceptible
• It causes inflammatory response

Impaired Calcium Function

• Impaired calcium function involves a buildup of calcium inside the cell, damaging cell structures

Reversible Cell Injury

• Reversible cell injury impairs function but is not cell death
• The body can repair itself if the injury is reversed before permanent damage occurs
• Injured cells accumulate abnormal amounts of substances
• Sodium buildup leads to intracellular swelling, is often related to hypoxic injury
• Lipid buildup, causing fatty changes, is more ominous than swelling, but reversible with dietary changes
• Calcium buildup leads to internal cell damage through enzyme activation

Irreversible Cell Injury

• Irreversible cell injury leads to permanent cell death of two types
• Apoptosis means controlled cell death without inflammation
• Necrosis means uncontrolled cell death with inflammation

Telomeres

• Telomeres are the outermost tails of chromosome arms, shortening with each cell replication
• Too-short telomeres lead to replicative senescence, where the cell can no longer reproduce

Cellular Aging

• Cellular aging causes damage such as decreased elasticity of blood vessels causing atherosclerosis and high blood pressure
• Aging also causes loss of bowel motility, muscle mass, and subcutaneous fat

Inflammatory Process

• Inflammation is the body's response to injury, toxin, stress, or trauma
• It is necessary for tissue repair and is generally healthy unless it becomes chronic

Chronic Inflammation

• Sustained inflammation causes significant health problems

Diseases related to Inflammation

• Inflammation underlies diseases like cardiovascular issues, stroke, cancer, diabetes, autoimmune disorders, Alzheimer's, lung disease, and arthritis

Organs of the Immune System

• Bone marrow produces all blood components
• The thymus gland produces T cells
• Lymph nodes, tonsils, and the spleen also play roles

Cells of Inflammation

• Endothelial cells line blood vessels and produce chemicals that regulate blood flow and clotting
• Platelets (thrombocytes) are responsible for blood coagulation and release inflammatory mediators
• Leukocytes (white blood cells) are major components of the inflammatory response
• Leukocytosis indicates a higher than normal production of white blood cells
• Leukocytes are classified as granulocytes or agranulocytes

Signs and Symptoms of Inflammation

• SHARP: Swelling, Heat, Altered Function, Redness, Pain

Granulocytes

• "Granpa B.E.N.": Neutrophils, Eosinophils, Basophils
• Neutrophils increase in acute bacterial infections
• Eosinophils elevate with allergic reactions and parasite infections
  • Basophils elevated in allergic reactions

Agranulocytes

• Lymphocytes (B and T cells) elevate in viral and chronic infections
  • Monocytes become macrophages and phagocytize foreign particles

T Cells

• T cells: "Timely" in cell-mediated immune response
  • Produced in the thymus gland
• T memory cells remain in lymph nodes
  • Helper T-cells activate and regulate T and B cells -- Killer T-cells attack virus-infected and tumor cells using antigens/phagocytosis
  • Natural killer cells attack abnormal cells like cancer cells
    • Suppressor T-cells restore the immune system to normal after infection

B Cells

• B cells: "Back up" in humoral immune response
• A slower response than T cells
  • Produced in bone marrow
    • Releases antibodies and assist in T cell activation
    • It takes time to make antibodies

Antigens

• The body must recognize an invader
• Specialized cells present an invader with help from T-cell lymphocytes
  • The two key components of this process are the antigen and the antibody
  • Antigen is short for "antibody generator," triggering the body to make antibodies
  • Antigens are identifiers on cell surfaces to distinguish between body cells and foreign entities

Antibodies

• Antibodies are the body's complement and are specific to each cell
• Like a lock and key, when antibodies connect to antigens, the foreign cell can't reproduce

Acute Versus Chronic Inflammatory Responses

• Acute inflammation is about short-term removal or limitation of the injury
• Chronic inflammation lasts for weeks or years and promotes continuous healing - Results in permanent damage

Vascular Phase

• The vascular phase involves local vasodilation and increased capillary permeability
  • SHARP: Swelling, Heat, Altered Function, Redness, Pain --Vasodilation causes heat and redness
• Plasma brings white blood cells and proteins to the site causing swelling and pain
• Chemical mediators such as histamine, serotonin, cytokines, and kinins control response

Cellular Phase

• Leukocytes, mainly neutrophils, arrive at the injury and emigrate through blood walls
• • The leukocytes move in a gradient manner
• Leukocytes encase the microbe and digest

Acute v. Chronic Inflammation: Outcomes

Acute inflammation resolves completely, heals with scarring, or progresses to chronic inflammation.

Inflammation - CHRONIC PHASE

• Chronic inflammation can span weeks, months, or even years. -- Usually characterized by continued infections
• Also characterized by flare ups

Local vs, Systemic Inflammation

• Local inflammation is contained to a specific site, exhibiting SHARP signs
• Systemic inflammation involves the entire body
  • Is characterized by fever, increased white blood cells and inflammatory markers like C-reactive protein

Acute phase proteins

• The liver makes them and they provide function during situations of systemic inflammation
• Elevated CPR causes indication for myocardial infarction
• Fibrinogen is known to causes issues if it rises too fast
  • Serum Amyloid A protein proves cellular energy

White cell balance

Neutrophils have a time frame of about 24 - 48 hr for them to replaced and spread the infection cycle. Normal lab results will indicate normal leuko values in terms of blood and what percentage is being shown

Systemic Inflammatory Response Syndrome (SIRS)

• A potential "worst-case scenario," that may lead to multiple organ failure and circulatory shock

Fever (Hyperthermia)

• Is primarily caused by conditions of viral or bacterial nature
• It is the first symptom that indicate the inflammation is systemic and moving

Fever, the regulator

Things that elevate body state comes in various ranges depending on who, and what can be tolerated. There is a fine line between it can can be handled safely and also it has been taken care of

Pyrogens

Anything that causes and triggers fever can be caused to the body as an infection. Those things may also take place when chemicals are released for the rise in body temperatures