BRONCHOPULMONARY SEGMENTS — Drawable

Draw this: Branching tree + lung segments + V/Q zones + aspiration rules
AIRWAY BRANCHING — Trachea to Alveolus TRACHEA C-rings, 10-12cm CARINA (T4) R MAIN BRONCHUS Wider, shorter, vertical → ASPIRATION HERE L MAIN BRONCHUS Narrower, longer, horizontal R UPPER 3 segments R MIDDLE 2 segments R LOWER 5 segments ↑ Eparterial (above PA) Only eparterial bronchus L UPPER 4-5 seg (incl LINGULA = 2) L LOWER 4-5 segments Lingula = L "middle lobe" Cardiac notch takes space BRONCHOPULMONARY SEGMENT = Functional Surgical Unit Own segmental bronchus + segmental artery. Veins run BETWEEN segments (intersegmental). → Surgeon follows veins to resect one segment. R=10, L=8-10 segments total. V/Q ZONES — Why TB Loves the Apex West Zones: gravity determines perfusion distribution APEX BASE ZONE 1 (Apex) V/Q = 3.3 (HIGHEST) ↓↓ Perfusion · ↓ Ventilation HIGH O₂, LOW immune cells ZONE 2 (Middle) V/Q ≈ 1.0 (IDEAL) Best gas exchange ZONE 3 (Base) V/Q = 0.6 (LOWEST) ↑↑ Perfusion · ↑ Ventilation Edema starts here GRAVITY WHY TB LOVES THE APEX — Chain 1. Gravity → blood flows to bases → Apex has LOWEST perfusion 2. Low perfusion = fewer immune cells delivered 3. Ventilation still reaches apex → HIGH O₂ tension 4. M. tuberculosis = OBLIGATE AEROBE → loves O₂ → High O₂ + low immunity = REACTIVATION Miliary TB (hematogenous) = uniform distribution (not V/Q dependent) 🇮🇳 India = 28% global TB burden. Upper lobe cavity = bread-and-butter CXR. ASPIRATION — Position Determines Segment Upright → R lower lobe POSTERIOR BASAL Supine → R upper POSTERIOR / R lower SUPERIOR R lateral→ R middle lobe / Lingula ALWAYS RIGHT — R bronchus wider, shorter, more vertical CLINICAL MAP Apex → TB reactivation Base → Pulm edema first R lower → Aspiration R middle → TB node compress 🇮🇳 Middle lobe syndrome RIGHT vs LEFT — Quick Reference Table FEATURE RIGHT LUNG LEFT LUNG Lobes 3 (upper, middle, lower) 2 (upper + lingula, lower) Fissures Oblique + Horizontal Oblique only Segments 10 8-10 Special Eparterial bronchus (above PA) Cardiac notch + Lingula Aspiration YES — wider, shorter, vertical Less common Impressions SVC, azygos, IVC Aortic arch, desc aorta, cardiac
🧠 5 RETENTION ANCHORS:
1. TB → apex because: HIGH V/Q = high O₂ + low immune cells. M.tb is obligate aerobe.
2. Aspiration → always RIGHT (wider, shorter, vertical). Upright = R lower posterior basal. Supine = R upper posterior.
3. Segment = own bronchus + own artery. Veins run BETWEEN segments. That's why surgeons can remove one segment.
4. Right = 3 lobes, 10 segments, eparterial bronchus. Left = 2 lobes, 8-10 segments, lingula, cardiac notch.
5. Middle lobe syndrome = TB lymph nodes compress R middle lobe bronchus (narrow, long, surrounded by nodes). Common in India.