Chapter 1: Introduction to Pathology

Cellular Adaptations

Cellular adaptations are modifications that cells undergo in response to various stressors or stimuli. These adaptations help cells survive, maintain function, or prepare for increased demand. The main types include atrophy, hypertrophy, hyperplasia, dysplasia, and metaplasia.

Atrophy involves a reduction in cell size, leading to decreased tissue mass. Causes include diminished use of tissues, inadequate nutrition, reduced neurologic or hormonal stimulation, and aging. For example, prolonged immobilization may result in muscle atrophy.

Hypertrophy is the enlargement of individual cells, increasing overall tissue mass. This often occurs as an adaptive response to increased workload, such as cardiac muscle enlargement in patients with hypertension.

Hyperplasia is an increase in the number of cells within a tissue, resulting in tissue expansion. Hyperplasia can be physiological, like compensatory growth after tissue loss, or pathological, as seen in hormone-driven disorders or precancerous conditions.

Dysplasia refers to disordered cell growth characterized by variability in cell size, shape, and nuclear morphology. Chronic irritation or infection often causes dysplasia, and it can serve as a precursor to malignancy. A classic example is cervical dysplasia, which is monitored through Pap smears.

Metaplasia occurs when one mature cell type is replaced by another, often as an adaptive response to chronic irritation or nutrient deficiency. For instance, chronic smoking can induce replacement of ciliated columnar epithelium with stratified squamous epithelium in the respiratory tract, enhancing tissue resistance but compromising normal function.

Common Causes of Cellular Injury

Cellular injury occurs primarily due to ischemia, a condition where tissue oxygenation decreases because of circulatory obstruction. Hypoxia reduces cellular metabolism, impairing normal function. Other contributing factors include:

• Physical agents: Extreme heat, cold, or radiation

• Mechanical damage: Tissue pressure or tearing

• Chemical toxins

• Microorganisms: Bacteria, viruses, parasites

• Abnormal metabolite accumulation

• Nutritional deficiencies

• Fluid or electrolyte imbalances

Infection and Inflammation

Infections and inflammatory processes can induce cellular injury. Certain pathogens trigger pyroptosis, a form of cell death where lysosomal enzymes are released, causing plasma membrane rupture and inflammation. This inflammatory response manifests as redness, swelling, and pain, impairing surrounding tissue function.

Chemical Injury

Chemical injuries can originate from external (exogenous) or internal (endogenous) sources, altering membrane permeability or generating free radicals. These free radicals damage cellular components, contributing to ongoing pathological processes.

Types of Necrosis

Necrosis is cell death resulting from injury or disease. Major types include:

Apoptosis

Apoptosis is a programmed and controlled form of cell death essential for tissue homeostasis. Cells undergo self-digestion, forming apoptotic bodies that are phagocytosed without triggering inflammation. Apoptosis occurs during normal cell turnover, abnormal development, or following cellular damage.

Tissue Necrosis Types

The different tissue necrosis types relate to organ-specific patterns of injury:

Chapter 2: Fluids and Electrolytes, Acids and Bases

Fluid Compartments

The body contains two major fluid compartments:

1. Intracellular fluid (ICF): Present inside cells; constitutes the majority of body fluid.

2. Extracellular fluid (ECF): Located outside cells; includes intravascular fluid (blood plasma), interstitial fluid, cerebrospinal fluid, and transcellular fluids (e.g., synovial, peritoneal).

Water Movement

Water movement between plasma and interstitial fluid is governed by hydrostatic and osmotic pressures. At the capillary’s arteriolar end, higher hydrostatic pressure pushes fluid into tissues, while at the venous end, osmotic pressure draws fluid back into capillaries.

Edema

Edema is the excessive accumulation of fluid in the interstitial space. Causes include:

• Increased capillary hydrostatic pressure (e.g., heart failure)

• Loss of plasma proteins (e.g., hypoalbuminemia)

• Lymphatic obstruction

• Increased capillary permeability (e.g., inflammation)

Clinical manifestations include swelling, skin discoloration, weight gain, and pulmonary congestion.

Sodium and Water Balance

Sodium and water balance is regulated by:

• Antidiuretic hormone (ADH): Controls water retention and urine concentration.

• Aldosterone: Enhances sodium reabsorption and fluid retention.

• Renin-Angiotensin-Aldosterone System (RAAS): Increases blood pressure and fluid volume through angiotensin II-mediated vasoconstriction and aldosterone secretion.

Electrolyte Imbalances

Water Deficits and Excesses

• Hypovolemia: Low blood volume from fluid loss; signs include dehydration, hypotension, concentrated urine.

• Hypervolemia: Excess fluid volume from kidney failure or overhydration; signs include edema, weight gain, hypertension.

Acid-Base Balance

Acid-base homeostasis is vital for cellular function. The lungs regulate carbon dioxide levels, while the kidneys control bicarbonate and hydrogen ion concentrations.

Chapter 5: Inflammation

Physiology of Inflammation

Inflammation is a protective response to injury, infection, or chemical exposure. It aims to remove harmful agents and initiate tissue repair. Classic signs include redness, swelling, warmth, pain, and functional loss.

Acute vs. Chronic Inflammation

• Acute inflammation: Rapid onset, short duration, neutrophil infiltration, plasma protein exudation.

• Chronic inflammation: Long-lasting, macrophage and lymphocyte presence, fibrosis, and tissue remodeling.

Inflammatory Mediators

• Histamine: Released by mast cells; causes vasodilation and capillary permeability.

• Cytokines: Coordinate immune responses and recruit cells to the injury site.

Wound Healing Phases

1. Hemostasis: Clot formation and vasoconstriction.

2. Inflammation: Debris removal and pathogen control.

3. Proliferation: New tissue formation via angiogenesis and collagen deposition.

4. Remodeling: Tissue maturation, functional recovery over months to years.

Complications: Infection, wound dehiscence, hypertrophic scars.

The Burn Wound and Its Consequences

Burn Wound Characteristics

Burns result in eschar formation, which exerts pressure on surrounding edematous tissues. Escharotomy may be required in circumferential burns to restore circulation. Initial burns may be painless, but inflammation causes delayed pain. Full-thickness burns require skin grafts. Mixed burns often contain partial- and full-thickness areas.

Fluid Shifts and Cardiovascular Compromise

Burns cause fluid and protein leakage, hemoconcentration, hypotension, and risk of hypovolemic shock. Fluid resuscitation includes IV fluids and plasma expanders to restore volume and protein balance.

Immunologic Alterations

Burn patients are at high risk of infection. Common pathogens include Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella, and Candida. Severe infections can lead to sepsis, requiring antimicrobial therapy, tissue excision, and skin grafting.

Types of Infectious Microorganisms

Lymph Node Treatment and Cancer Spread

• Lymph nodes may be removed to prevent micrometastases.

• Cancer dissemination occurs via lymphatics, veins, or “seeding” within body cavities.

TNM Staging System

Effects of Cancer and Its Treatment

• Warning Signs: Unexplained bleeding, sores, lumps, weight loss, fatigue, chronic cough.

• Local Effects: Pain, obstruction, necrosis, infection.

• Systemic Effects: Weight loss, anemia, paraneoplastic syndromes.

• Treatment Side Effects: Bone marrow suppression, epithelial cell damage, GI mucosa injury, sterility risk, organ-specific toxicity.

Environmental Hazards and Cancer Risk Factors

• Smoking: Increases risk of lung and bladder cancer, cardiovascular diseases, fertility issues, and fetal complications.

• Radiation: Damages rapidly dividing cells; can cause mutations, cancer, or radiation sickness.

• Lead: Causes anemia, kidney injury, neurological deficits, especially harmful in children.

• Asbestos: Leads to asbestosis, pleural thickening, and mesothelioma.

• Ionizing Radiation: Alters cell structure and function; contributes to cancer development.

Skin Structure and Functions

• Skin Functions: Barrier against pathogens, prevents fluid loss, regulates temperature.

• Layers: Epidermis (stratum basale, spinosum, granulosum, corneum), dermis (connective tissue, blood vessels, sensory receptors), hypodermis (subcutaneous fat).

Pruritus and Dermatitis

• Pruritus (itching): Triggered by allergic reactions, irritants, or parasites.

• Dermatitis types: Contact dermatitis, urticaria, atopic dermatitis, psoriasis.

Skin Cancer

• Keratoses: Benign age-related lesions.

• Squamous cell carcinoma: Malignant, sun-exposure related, treatable.

• Melanoma: Aggressive, high metastatic risk.

• Kaposi sarcoma: Associated with immunocompromised states.

References

American Association of Critical-Care Nurses. (n.d.). Clinical considerations for burn care. Retrieved from https://www.aacn.org

Burke, J. F., & K. J. (2015). Burn care: Pathophysiology and management. Journal of Trauma and Acute Care Surgery, 78(2), 307-317.

NR 283 Exam 1

Davis, A. J., & H. L. (2020). Burn injury: Understanding the complications. Journal of Burn Care & Research, 41(2), 295-302.

Miller, K. C., & H. A. (2018). The immunologic response to burn injury. Clinics in Plastic Surgery, 45(1), 57-63.