Pathology · Chapter 6

Environmental Pathology and Nutritional Disorders

The chapter question

A patient collapses after an exposure. How do you reason from the exposure to the molecular target, and then to the lab that confirms it?

Exposure → molecular target

  • House fireHemoglobin (CO) · cytochrome oxidase (cyanide)
  • Battery factoryALA dehydratase + ferrochelatase (lead)
  • AntifreezeADH → oxalic acid (ethylene glycol)
  • Acetaminophen overdoseGlutathione depleted → NAPQI (zone 3)
  • Chronic alcoholNADH/NAD⁺ ratio

Teaching schematic. Name the target first; the labs follow.

Each exposure points to a molecular target; name the target and the labs follow.

Make a quick prediction

A man is pulled from a house fire. His PaO₂ is normal but he has a severe lactic acidosis. Which single fact would best tell carbon monoxide from cyanide?

Study path

Follow the order or jump to the concept you need. Every topic has a Deep Learning and a High-Yield view of the same facts, and ends with a short knowledge check.

0 of 6 topics studied0 of 42 questions correct
  1. 6.130 minUp nextTobacco, alcohol and drugsEach chemical injures through a specific molecule: smoke delivers carcinogens and carbon monoxide, ethanol floods the liver with NADH, and acetaminophen becomes toxic only when glutathione runs out.Tobacco: what each constituent doesEthanol metabolism: three enzymes and one bottleneckToo much NADH: five findings from one ratioDrugs of abuse+3
  2. 6.226 minToxins, metals and venomGases, metals and toxic alcohols each hit one molecular target. Name the target and the labs follow: hemoglobin binding for CO, cytochrome oxidase for cyanide, heme enzymes for lead, and ADH-made acids for the toxic alcohols.Air pollutantsCarbon monoxide and cyanide: two ways to starve a mitochondrionLead and other heavy metalsMethanol and ethylene glycol: the gaps that name them+2
  3. 6.328 minPhysical injuryMechanical, thermal, electrical and radiation injuries each leave a recognizable pattern. Read the wound to read the force, and know why a large burn kills by fluid loss before it kills by infection.Mechanical injury: reading the woundAbusive head traumaBurns: depth, area and the fluid shiftHeat and cold+2
  4. 6.424 minMalnutrition and eating disordersProtein-energy malnutrition splits into two patterns by what is missing; eating disorders are read from their electrolytes. Edema in kwashiorkor and hypokalemic alkalosis in bulimia are predictable from first principles.Kwashiorkor versus marasmusAnorexia nervosaBulimia nervosaObesity and metabolic syndrome
  5. 6.536 minVitaminsFor each vitamin, hold the same chain: what it does, when it runs short, what the deficiency looks like, and the look-alike or toxicity that catches people out. The fat-soluble ones fail together in fat malabsorption; the water-soluble ones tie to specific enzymes.Fat-soluble versus water-solubleVitamin AVitamin DVitamin E+6
  6. 6.618 minTrace elementsEach trace metal is the cofactor of one or two enzymes, so its deficiency reads straight off the enzyme: zinc for wound healing and taste, copper for collagen cross-linking and iron transport. Use the absorption site and the exposure before you match symptoms.Read the absorption site and the exposure firstZincCopper and iron handlingChromium, selenium, iodine and fluoride

Practice

How the ideas connect

10 bridges carry one concept into the next, within this chapter and across chapters. Each is taught where you first need it.