Clinical Anatomy of Lungs & Mnemonics

Topic Overview

Clinical Anatomy — Lungs

1. Bronchopulmonary Segments and Surgical Importance

• Each lung consists of ten bronchopulmonary segments, functionally independent and supplied by its own segmental bronchus and artery.

• These segments are separated by connective tissue septa, allowing segmental resection in cases like localized tuberculosis, abscess, or carcinoma without affecting other regions

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2. Aspiration of Foreign Bodies

• The right principal bronchus is shorter, wider, and more vertical; hence, inhaled objects (like a coin, peanut, or seed) most often enter the right bronchial tree, especially the posterior basal segment of the lower lobe

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• Clinical effects include segmental collapse, obstructive pneumonia, or bronchiectasis.

3. Bronchogenic Carcinoma

• Smoking is the leading cause. The common sites are the hilum and upper lobes.

• Metastasis occurs via bronchomediastinal lymph nodes to the supraclavicular (sentinel) nodes, and through the bloodstream to brain, bones, and liver.

• Compression of the left recurrent laryngeal nerve by enlarged mediastinal nodes causes hoarseness of voice

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4. Pulmonary Collapse (Atelectasis)

• Caused by bronchial obstruction from mucus plugs or tumors.

• Leads to loss of air in alveoli, mediastinal shift toward the affected side, and reduced breath sounds.

5. Lung Abscess

• Usually secondary to aspiration pneumonia, especially in the posterior segment of upper lobe or superior segment of lower lobe.

• Presents with fever, cough with foul sputum, and radiographic cavity formation.

6. Emphysema and Chronic Obstructive Pulmonary Disease (COPD)

• Loss of alveolar elasticity and enlarged air spaces lead to poor ventilation.

• Commonly associated with smoking and air pollution.

• Results in barrel-shaped chest, pursed-lip breathing, and cyanosis.

7. Tuberculosis

• The apex of the lung (especially right) is the most common site for primary infection, due to high oxygen tension favoring Mycobacterium tuberculosis growth.

• May lead to fibrosis, cavitation, and spread to lymph nodes.

• Complete anti-tubercular treatment is essential to prevent drug-resistant TB

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8. Pneumothorax and Tension Pneumothorax

• Air in the pleural cavity causes collapse of the lung.

• If air entry continues without exit, it becomes tension pneumothorax, displacing the mediastinum to the opposite side.

• Immediate needle decompression followed by chest tube drainage is lifesaving.

9. Pulmonary Embolism

• Thrombus from deep veins of legs may travel to pulmonary arteries, blocking blood flow.

• Causes sudden chest pain, dyspnea, and death if large.

• CT pulmonary angiography confirms diagnosis.

10. Carina and Cough Reflex

• The carina (ridge at tracheal bifurcation) is extremely sensitive.

• Irritation triggers violent cough reflex via vagus nerve.

• Widening or distortion of carina on bronchoscopy suggests subcarinal lymphadenopathy or carcinoma.

11. Pleural Effusion Secondary to Lung Disease

• Lung infections or carcinoma may cause reactive pleural effusion.

• Fluid collects in costodiaphragmatic recess, compressing the lung.

• Aspiration is done above the upper border of a rib to avoid the neurovascular bundle.

12. Postural Drainage

• Technique used to drain bronchopulmonary segments by positioning the patient so gravity assists mucus drainage.

• Each lobe/segment has a specific position for effective drainage — crucial in bronchiectasis and cystic fibrosis.

13. Sentinel (Virchow’s) Node

• Left supraclavicular lymph node enlargement may indicate intra-thoracic or abdominal malignancy, often bronchogenic carcinoma.

14. Accessory Lobes and Fissures

• Occasionally, accessory fissures or azygos lobe may be seen — significant during surgery or radiographic interpretation to avoid misdiagnosis.

15. Neonatal Respiratory Distress Syndrome (Hyaline Membrane Disease)

• Occurs in premature infants due to deficiency of surfactant.

• Leads to alveolar collapse, hypoxia, and respiratory failure.

• Treatment: Surfactant replacement and oxygen therapy.

Summary

The lungs are clinically significant not only in respiration but also in numerous systemic diseases — from infection and cancer to vascular and developmental disorders. Understanding their segmental anatomy, vascular pattern, and pleural relations is essential for diagnosis, bronchoscopy, and thoracic surgery