🌿 Barrier & Breath

A comprehension lab for the skin & respiratory system, built around the week’s review questions. For herbalism & nutrition students — every concept links back to the clinic.

Tap any term. Each one answers a review question and shows how it shows up in herbal & nutrition practice. Work through them in any order.

Skin & Body Membranes

Integumentary system — Ch. 4

Respiratory System

Airways & gas exchange — Ch. 5

Pick a term above

Each reveals the answer to one review question, plus the clinical tie-in.

Answer in your own words, rate how sure you are, then reveal the model answer and grade yourself. The point isn’t the score — it’s catching what you were confident but wrong about.

How sure are you?
Self-grade:

The questions people miss are about relationships, not definitions. Move the controls and watch the cause–effect.

1. Pressure ↔ Volume — why air moves at all

Drag the diaphragm. Boyle’s law: at constant temperature P × V is constant, so pressure and volume are inversely related. The diaphragm and intercostal muscles change thoracic volume; the lungs are passive.

Diaphragm relaxed
diaphragm
Volume — Pressure — Airflow —
🌿 Clinic: This is why a slow, diaphragmatic breath recruits more volume change than shallow chest breathing — the foundation under every breathing-practice recommendation.

2. CO₂ ↔ blood pH — the acid you exhale

Carbonic anhydrase turns CO₂ + H₂O into carbonic acid, which dissociates into bicarbonate + H⁺. More CO₂ → more H⁺ → lower pH.

Blood CO₂ normal
Reaction CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺
pH 7.40 balanced
🌿 Clinic: A client over-breathing from anxiety blows off CO₂, pH climbs (alkalosis) — tingling, lightheadedness. A slow exhale lets CO₂ rise and pH return. Dietary acid load is buffered by this same bicarbonate system.

3. What actually tells you to breathe?

Most people guess oxygen. The dominant drive is rising CO₂ (sensed as H⁺ by central chemoreceptors). Pick the strongest stimulus:

4. Ventilation ↔ Perfusion (V/Q)

Ventilation = air reaching alveoli. Perfusion = blood reaching the capillaries around them. Gas exchange needs both. Set each and see what limits exchange.

Ventilation80
Perfusion80
V
Q
Exchange
🌿 Clinic: Healthy lungs but poor circulation (or vice versa) both cap oxygenation. It’s why “support the lungs” and “support circulation” are paired goals, not separate ones.

A client walks in. Reason from the physiology — each scenario maps onto the week’s review concepts.