Thorax Anatomy · Respiratory

Lung Lobes

Right lung has 3 lobes; left has 2 — the cardiac notch eliminates the left middle lobe equivalent. This asymmetry governs aspiration patterns, fissure anatomy, and surgical resection.

✦ The Mnemonic

"Right: Upper-Middle-Lower; Left Lacks Middle — Heart Takes The Space"

Right = 3 lobes (10 segs); Left = 2 lobes (8–10 segs)

RUL Right Upper Lobe 3 segments: Apical, Posterior, Anterior

RML Right Middle Lobe 2 segments: Lateral, Medial — separated from RUL by horizontal fissure

RLL Right Lower Lobe 5 segments: Superior + 4 basal (Medial, Anterior, Lateral, Posterior)

LUL Left Upper Lobe Apicoposterior, Anterior + Lingula (Sup + Inf lingular) — RUL + RML equivalent

LLL Left Lower Lobe 4–5 segments: Superior + 3–4 basal (anteromedial often fused)

📚 Clinical Breakdown

Right lung has oblique + horizontal (minor) fissures; left lung has oblique only. Both oblique fissures run from T4 posteriorly to the 6th rib anteriorly.

The lingula (left upper lobe) is the anatomical equivalent of the right middle lobe. It is the common site of aspiration pneumonia in patients who aspirate supine. The right lower lobe is most affected in upright patients.

Foreign body aspiration preferentially involves the right main bronchus — it is more vertical, shorter, and wider. In adults the right lower lobe posterior segment is most affected.

Right fissures Oblique + Horizontal (minor)

Left fissures Oblique only

Aspiration site (upright) Right lower lobe

Lingula equivalent Right middle lobe

⭐ Clinical Pearl

Accessory fissures are present in 30–50% of people. The most common — the azygos fissure in the right upper lobe — can mimic pathology on CXR but has no clinical significance.

Next: Bronchopulmonary Segments →