Patho Week 1 Part 1

Biological Parameters and Variation

• "Normal" biological parameters exist as a distribution within populations, with no singular value applicable to all.
• Variation in biological parameters influenced by factors such as genetics, age, gender, situational context, time, and laboratory conditions.
• Example: Heart rates differ significantly between children and adults, reflecting age-related norms.
• Hormone levels, influenced by gender and time of day, show variability; testosterone peaks in the morning, female hormones fluctuate with the menstrual cycle.
• Environmental conditions, like living at sea level versus high altitude, affect red blood cell counts.

Race in Medicine

• Race has historically been used to categorize biological variations, but this approach is problematic.
• Race is a social construct, not a biological category, lacking a direct correlation with genetic ancestry.
• Misconceptions exist that equate race with significant genetic differences, while actual variance due to ancestry-related genes is minimal (approximately 0.1%).
• The misuse of race in medical settings has led to racial stereotypes, biased treatments, and inadequate healthcare for diverse populations.
• Disparities in health outcomes often relate to social determinants rather than genetic differences.

Biology of Skin Color

• Skin color is primarily determined by the type and amount of melanin produced by melanocytes.
• Two melanin types: pheomelanin (reddish) and eumelanin (black/brown), packed into melanosomes above skin cell nuclei.
• Melanin functions to absorb harmful UV radiation, reducing DNA damage risks.
• Indigenous populations in high UV regions typically produce more melanin to reduce UV damage, which correlates with regional sunlight exposure.
• Excessive UV exposure can break down folic acid, while insufficient UV can lead to vitamin D deficiency, impacting bone health.

Key Concepts: Etiology, Pathogenesis, Clinical Manifestations

• Etiology: Refers to the cause of a disease.
• Pathogenesis: Describes how a disease develops and its effects on body functions, including factors like injury duration and quantity.
• Clinical Manifestations: Observable signs and subjective symptoms resulting from the disease, including phases like latent, prodromal, and acute periods.

Clinical Manifestations of Disease

• Signs are objective and measurable, while symptoms are subjective and reported by patients.
• Examples include:
  • Sign: Elevated blood pressure (objective measurement).
  • Symptom: Patient reports headaches (subjective experience).

Disease Time Course Terms

• Latent period: Time until disease signs/symptoms appear.
• Prodromal period: Initial emergence of nonspecific signs/symptoms.
• Acute period: Time when disease manifestations are most severe.
• Examples:
  • Latent: A tumor not showing symptoms.
  • Prodromal: Flu symptoms appearing before diagnosis.
  • Acute: Severe chest pain during a heart attack.

Differential Diagnosis

• A systematic process of identifying potential diagnoses based on clinical evidence.
• Methods include assessing signs/symptoms, laboratory tests, tissue diagnosis, and imaging studies.

Interdependence of Cells and Systems

• Organism function is reliant on cellular health, while cells depend on larger systems (e.g., circulatory system providing oxygen).
• Hierarchical structure: Cells → Tissues → Organs → Organ Systems → Organism.

Total Body Water Composition

• Total body water is composed of intracellular fluid (40% of body weight) and extracellular fluid, which includes plasma (5%) and interstitial fluid (15%).
• Approximately 60% of body weight is made up of total body water, which decreases with increased adipose tissue since fat contains less water.

Body Water Differences by Age and Gender

• Aging results in muscle mass loss and increased fat, reducing total body water.
• Biological males typically have higher total body water due to greater lean muscle mass compared to biological females.

Cell Volume Regulation

• Cell volume is controlled through water and osmolyte balance, notably sodium and potassium.
• Water regulation occurs via the ADH/thirst system; osmolyte balance is managed by the renin-angiotensin system and sodium-potassium ATPase pumps.

Distribution of Fluids

• The distribution of fluids between intracellular fluid (ICF) and extracellular fluid (ECF) is determined by osmolarity.
• Distribution between intravascular and interstitial spaces is controlled by Starling forces, particularly hydrostatic pressure.

Capillary Bulk Flow and Starling Forces

• Capillary bulk flow describes fluid movement between intravascular and interstitial spaces, primarily driven by Starling forces that balance pressures.

Causes of Edema and Third Space Fluid Accumulation

• Edema can arise from diminished plasma oncotic pressure, increased capillary permeability, elevated capillary blood pressure, or lymphatic obstruction.
• Third space fluid accumulation occurs in body cavities due to Starling force imbalances (e.g., ascites, pleural effusion).

Isotonicity, Hypertonicity, Hypotonicity

• Isotonic: ECF alterations maintain osmolarity balance; causes include hemorrhage or excessive IV fluids.
• Hypertonic: Elevated ECF osmolarity; leads to hypernatremia.
• Hypotonic: Decreased ECF osmolarity; often caused by conditions like hyponatremia or excessive water retention.

Potassium Shift Between ICF and ECF

• pH changes affect potassium levels: acidosis increases ECF potassium, while alkalosis decreases it.
• Insulin moves potassium into cells as a cofactor for glucose conversion to glycogen; low insulin keeps potassium outside.
• Catecholamines can also influence potassium distribution, affecting overall cellular function.