Understanding pH: Acidity, Alkalinity, and Its Importance in Medicine

pH (potential of hydrogen) measures acidity/basicity on a logarithmic scale 0–14.

• pH 7 = neutral (pure water at 25°C).
• pH < 7 = acidic (higher H⁺ concentration).
• pH > 7 = basic/alkaline (lower H⁺).

Physiological Relevance

Compartment	Normal pH	Clinical Significance
Arterial blood	7.35–7.45	Tight range; <7.35 = acidemia, >7.45 = alkalemia
Venous blood	7.31–7.41	Slightly lower (CO₂)
Gastric fluid	1.5–3.5	Digestion, pathogen kill
Urine	4.5–8.0	Reflects acid-base handling
CSF	7.32–7.42	CNS homeostasis

Disorders

• Acidosis: Metabolic (DKA, renal failure, lactic) or Respiratory (hypoventilation).
• Alkalosis: Metabolic (vomiting, diuretics) or Respiratory (hyperventilation).

Buffer Systems

• Bicarbonate (blood), Phosphate (cells/urine), Proteins (hemoglobin), Renal (H⁺ excretion/HCO₃⁻ reabsorption).

pH homeostasis is vital for enzyme function, protein structure, oxygen delivery, and electrolyte balance.