Pathophysiology Week 2 Review: Comprehensive Notes

Patho study tips: three key things to understand

1) What is the pathophysiology? (basic disease processes and definitions)
2) Causes and risk factors (etiology and predisposing factors)
3) Manifestations (clinical presentation and signs/symptoms)

• Use resources: NVCAS, PL, textbook, study guide, and med term workbook. Practice questions on PL and NVCAS Path of Practice Workbook.

• Strong emphasis on understanding connections between mechanisms and clinical outcomes.

Core concepts introduced in this session

• Grounded in week 2 topics: cellular regulation, inflammation, hypersensitivity, genetics, immunity, and cancer.

• Common confusions reported by students include immunity concepts, hypersensitivity, and genetic disorders; these will be revisited with practice questions.

Quick reference: key vocabulary and concepts with brief definitions

• Ischemia: ext{Decrease in oxygen delivery to tissues}

• Apoptosis: ext{Programmed cell death (controlled cellular suicide)}

• Physiological vs Psychological

  • Physiological: ext{body processes, physical/biological functions}

  • Psychological: ext{mind-related processes and mental health}

• Hyperthermia: ext{Elevated body temperature}

• Metastasis: ext{Spread of cancer cells to distant sites}

• Urticaria: ext{Hives; wheals from allergic reactions}

• Psoriasis: ext{Plaque psoriasis with well-defined plaques, often on elbows/knees}

• Macula: ext{Flat, nonpalpable discolored skin area}

• Stages of pressure injury (pressure ulcers):

  • Stage 1: ext{Erythema with intact skin}

  • Stage 2: ext{Partial-thickness loss; blister/ulceration through the epidermis into the dermis}

  • Stage 3: ext{Full-thickness loss down to the hypodermis (fat layer) with crater formation}

  • Stage 4: ext{Full-thickness tissue loss with exposure of muscle/tendons/joints; high infection risk}

• Pressure injury risk factors: edema, age, loss of sensation, excessive moisture, immobility, poor hygiene, trauma, inadequate nutrition/hydration.

• Factors promoting healing: youth, good nutrition, adequate hemoglobin, effective circulation, clean/undisturbed wounds.

• Factors delaying healing: advanced age, anemia, circulatory problems, chronic diseases (e.g., diabetes).

• Wound care and infection prevention: wound dressings, pain meds, infection prevention, and increased mobility to promote healing.

Matching activity concepts (quick recap)

• Prefixes: hyper- = increased above normal; hypo- = decreased or below normal; dys- = bad/difficult/impaired/abnormal; patho- = disease

• Ischemia: decreases oxygen delivery to tissues

• Apoptosis: programmed cell death

• Physiological vs Psychological: physical body processes vs mind/mental processes

• Hyperthermia: high body temperature

• Metastasis: spread of cancer cells to other parts of the body

Genetic disorders: inheritance patterns and categorization

• Autosome vs X-linked inheritance basics

  • Autosomal: genes on autosomes (non-sex chromosomes). Affected individuals can be either sex; inheritance patterns depend on whether the gene is dominant or recessive.

  • X-linked: genes on the X chromosome; presentation differs between males (XY) and females (XX).

• Autosomal recessive (example: Sickle Cell Disease)

  • Sickle cell disease is autosomal recessive. Cross example from the session:

  • One parent has disease (aa) and the other is a carrier (Aa).

  • Offspring: Aa (carrier) or aa (affected) with equal probability.

  • Probabilities:
    P( ext{affected})= frac{1}{2}, \ P( ext{carrier})= frac{1}{2}.

• Autosomal dominant (example: Huntington’s disease)

  • Huntington’s disease is autosomal dominant. Cross example: affected (Hh) x unaffected (hh).

  • Offspring: 50% affected (Hh), 50% unaffected (hh).

  • Note: There is no carrier state for autosomal dominant; once the dominant allele is present, the trait is expressed.

  • Probability:
    P( ext{affected})= frac{1}{2}, \ P( ext{unaffected})= frac{1}{2}.

• X-linked recessive (examples: color blindness, Duchenne muscular dystrophy, hemophilia A)

  • Duchenne muscular dystrophy (DMD): X-linked recessive.

  • Cross example from session: Carrier mother (X^A X^a) x Unaffected father (X^A Y).

  • Offspring: 1/4 affected sons (X^a Y), 1/4 carrier daughters (X^A X^a), 1/4 unaffected sons (X^A Y), 1/4 unaffected daughters (X^A X^A).

  • Probabilities across all offspring:
    P( ext{affected})= frac{1}{4}, \ P( ext{carrier})= frac{1}{4}, \ P( ext{unaffected})= frac{1}{2}.

• X-linked dominant is less common in the examples here; Fragile X is cited as X-linked dominant in the session examples.

• Key clarifications included:

  • Choosing terminology: male offspring commonly show X-linked recessive disorders because they have only one X chromosome.

  • In autosomal vs X-linked patterns, X is linked to a sex chromosome; autosomal is not linked to sex chromosomes.

Punnett square practice highlights (three examples with results)

• Example 1: Sickle cell disease cross

  • Parent genotypes: aa (one parent with disease) and Aa (carrier)

  • Offspring: Aa (carrier) or aa (affected)

  • Probabilities:
    P( ext{affected})= frac{1}{2}, \ P( ext{carrier})= frac{1}{2}.

• Example 2: Duchenne muscular dystrophy cross (X-linked recessive)

  • Parent genotypes: mother X^B X^b (carrier) and father X^B Y (unaffected)

  • Offspring outcomes: 1/4 X^B X^B (unaffected), 1/4 X^B X^b (carrier female), 1/4 X^B Y (unaffected male), 1/4 X^b Y (affected male)

  • Probabilities:
    P( ext{affected})= frac{1}{4}, \ P( ext{carrier})= frac{1}{4}, \ P( ext{unaffected})= frac{1}{2}.

• Example 3: Huntington’s disease cross (Autosomal dominant)

  • Parent genotypes: Hh (affected) x hh (unaffected)

  • Offspring: 50% affected, 50% unaffected

  • Probability:
    P( ext{affected})= frac{1}{2}, \ P( ext{unaffected})= frac{1}{2}.

• Practical note: In exam settings, you may be asked probabilistic questions; use a scratch sheet to compute Punnett squares as needed.

Pressure injuries: visual staging and interpretation from the session

• Stage 1: Reddened, intact skin; warmth and possible pain; epidermis only

• Stage 2: Partial thickness loss; blister or shallow ulceration into the dermis

• Stage 3: Full thickness loss down to the hypodermis (fat layer) with crater formation

• Stage 4: Full thickness loss with exposure of muscle, tendon, or bone; high infection risk

• Example interpretation from session:

  • Some confusion occurred about stages 1 vs 2; corrected understanding: stage 1 is intact skin with redness, stage 2 shows partial thickness loss with a blister; stage 3 shows deeper tissue loss; stage 4 is large, open wound with exposure of deeper structures.

Other skin presentations reviewed

• Urticaria (hives): allergic reaction with raised welts

• Cellulitis: bacterial skin infection without abscess formation in the diagram

• Psoriasis: plaque-like, scaly skin lesions (often on elbows, behind knees, wrists, etc.)

• Macula: flat, nonpalpable, discolored skin area

Pathophysiology of tissue damage and wound healing factors

• Conditions affecting tissue integrity and healing

  • Risk factors for impaired tissue integrity: edema, age, loss of sensation, excessive moisture, immobility, poor hygiene, trauma, inadequate nutrition/hydration

  • Factors promoting healing: youth, good nutrition, adequate hemoglobin (Hb), effective circulation, clean wounds, undisturbed environment

  • Factors delaying healing: advanced age, anemia, circulatory problems, chronic diseases (e.g., diabetes mellitus)

  • Potential complications if untreated: tissue death (necrosis), infection, wound irritation

• Wound care principles to reduce infection risk

  • Appropriate wound dressings, pain medications, infection prevention strategies

  • Increase mobility and overall health to support healing

Inflammation and immune defense: a concise framework

• Three lines of defense
  1) First line: physical and chemical barriers (skin, mucous membranes, saliva, tears) – immediate barrier to entry
  2) Second line: innate (nonspecific) defenses – rapid response (phagocytosis, inflammation, interferons)
  3) Third line: adaptive (specific) immunity – antigen-specific response (B and T cells), slower to develop but more targeted

• Acute inflammatory mediators and steps

  • Damaged mast cells and platelets release chemical mediators: histamine, serotonin, prostaglandins, leukotrienes

  • Histamine causes vasodilation and increased vascular permeability; bradykinin activates pain receptors

  • Neutrophils (and later macrophages) migrate to the site and perform phagocytosis

  • Key mediators: kinins, histamines, prostaglandins, leukotrienes

• Common inflammatory and infection markers

  • C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and complete blood count (CBC) to assess leukocytosis

• Hypersensitivity and antibodies (ACID mnemonic)

  • A: Allergic reactions (IgE-mediated)

  • C: Cytotoxic (IgM/IgG-mediated)

  • I: Immune complex (IgG/IgM-mediated)

  • D: Delayed-type (cell-mediated) hypersensitivity

  • ACID stands for Allergic, Cytotoxic, Immune complex, Delayed

• Steps of infection and modes of transmission

  • Incubation: time between organism entry and first signs/symptoms

  • Prodromal: early nonspecific symptoms (fatigue, malaise, headache, etc.)

  • Acute/illness: overt symptoms and communicability

  • Transmission modes: direct contact, indirect contact, droplet, airborne, vector-borne

• Chain of infection (pathogen lifecycle)

  • Pathogen lifecycle: reservoir and exit, mode of transmission, portal of entry, etc.

  • Example pathways include touching contaminated surfaces (indirect contact), respiratory droplets (droplet), airborne particles (airborne), and vectors like insects (vector-borne)

Immunity types and practical examples

• Naturally acquired immunity

  • Active natural: exposure to antigen (infection) leads to antibody production

  • Passive natural: antibodies transferred from mother to fetus via placenta or through breast milk

• Artificially acquired immunity

  • Active artificial: vaccines introduce antigens to stimulate antibody production

  • Passive artificial: administration of antibodies produced in another person or animal (e.g., rabies post-exposure) for immediate protection

• Practical notes from session examples

  • Flu vaccine as active artificial immunity

  • Rabies vaccine as passive artificial immunity

• AIDS (Acquired Immunodeficiency Syndrome)

  • AIDS reflects advanced HIV infection with significant defenses compromised

  • Characteristics: high risk for secondary infections and cancers; helper T cell (CD4+) depletion leads to immune suppression; precautions tailored to CD4 count

Summary of the infection and cancer themes

• Infections present with local signs (swelling, erythema, heat, pain, tenderness, lymphadenopathy, exudate) and/or systemic signs (fever, leukocytosis, malaise, fatigue, anorexia, headache, arthralgia)

• Inflammation and infection share overlapping signs; complications can lead to systemic involvement (sepsis)

• Tumor biology differentiation

  • Benign tumors: differentiated, slow-growing, encapsulated, local effects only; rare systemic effects

  • Malignant tumors: rapid growth, invasion, nonencapsulated, may metastasize; systemic effects more common; life-threatening depending on location

• Stress response physiology

  • Acute stress triggers sympathetic nervous system activation and adrenal release of epinephrine and norepinephrine, increasing heart rate, blood pressure, respiratory rate, and glucose availability

  • Cortisol release moderates inflammation but suppresses immune function with chronic exposure

  • Antidiuretic hormone (ADH) increases blood pressure and volume

  • Prolonged stress contributes to chronic disease risk (e.g., heart disease, hypertension, stroke, diabetes, ulcers, infections, cancer) and psychosocial changes (anxiety, depression, sleep issues)

• Analogy to remember immune defense and infection processes

  • Osmosis Jones-like imagery for white blood cell patrol helps conceptualize surveillance and response to pathogens

Quick practical takeaways for exam preparation

• Be comfortable with inheritance: autosomal dominant/recessive and X-linked patterns; know how to read Punnett squares and calculate probabilities

• Memorize key term distinctions (ischemia, apoptosis, inflammation mediators, hypersensitivity types, lines of defense)

• Understand pressure injury staging, risk factors, and healing processes

• Distinguish local vs systemic signs of infection and inflammation

• Recall vaccine-based immunity vs natural infection-based immunity, and when passive vs active immunity applies

• Practice with practice questions and use scratch work on Punnett squares to reinforce probability calculations

Additional resources for deeper study and practice

• NVCAS weekly videos and PowerPoints

• Personalized learning platform (practice questions)

• Path of Practice Question Workbook

• Textbook and study guide

• Med term workbook

• Coach Ally available in Canvas for additional practice questions

• Office hours: National VCAS to review tricky concepts