Ch15: Head, Neck & Thorax — Summary & High-Yield（头颈胸总结）

# Ch15: Head, Neck & Thorax — Summary & High-Yield

Preparatory Mindset

This chapter consolidates the head, neck & thorax through the clinical scenarios the 100-Concepts deck and exam test: thyroidectomy anatomy (the single most important surgical theme), mediastinum subdivisions & contents, breast & its lymphatic drainage (concept 21), lung segments & aspiration (concepts 26-27), open pneumothorax (concept 28), diaphragm & hiatus hernias (concepts 22, 33-34), heart auscultation & blood supply (concepts 23-25), and the skull base foramina / epidural hematoma (concepts 68-74).

Exam mindset: the summary lectures emphasize thyroid blood supply & nerves in relation to the gland, mediastinum subdivision & contents, and inguinal canal (abdomen) — the "capstone" structures that tie regions together.

Core Concepts

1. Thyroid gland — surgical anatomy (MUST KNOW — from lectures 13/15)

- Superior thyroid artery (from ECA) — runs with the external laryngeal nerve (to cricothyroid) - Inferior thyroid artery (from thyrocervical trunk) — related to the recurrent laryngeal nerve - Thyroid ima artery (inconstant, from brachiocephalic)

- External laryngeal nerve: injury → weak/hoarse voice (cricothyroid paralysis) - Recurrent laryngeal nerve: injury → unilateral: hoarseness/paramedian cord; bilateral: stridor/airway obstruction - Parathyroids (4): behind the thyroid, supplied by inferior thyroid artery; injury → hypocalcemia → tetany (Chvostek/Trousseau signs)

• Position: below the larynx, isthmus at tracheal rings 2-3, lobes dorsolateral to the trachea
• Arteries:
• Nerves:
• Surgical principles: ligate the superior thyroid artery close to the gland (protect external laryngeal nerve); ligate the inferior thyroid artery away from the gland (protect recurrent laryngeal nerve); preserve the parathyroid glands

2. Mediastinum — subdivisions & contents (MUST KNOW)

• Superior mediastinum (above sternal angle): thymus, brachiocephalic veins & upper SVC, arch of aorta + 3 branches (BCS), trachea, esophagus, thoracic duct, phrenic & vagus nerves, sympathetic trunks
• Anterior mediastinum (in front of pericardium): thymus remnant, lymph nodes, fat
• Middle mediastinum (pericardium): heart, ascending aorta, pulmonary trunk, SVC, IVC, phrenic nerves
• Posterior mediastinum (behind pericardium): esophagus, descending thoracic aorta, azygos/hemiazygos veins, thoracic duct, sympathetic trunks, vagus nerves
• Sternal angle (Louis angle): the key landmark — T4/5 posteriorly, arch of aorta begins/ends, tracheal bifurcation, 2nd costal cartilage

3. Breast (concept 21) — recap with exam focus

• 15-20 lactiferous lobes; Cooper's ligaments; tail of Spence → axilla
• Lymphatic drainage: ~75% → axillary nodes (anterior/pectoral → central → apical → supraclavicular); medial → internal thoracic; contralateral cross-drainage
• Clinical: breast cancer → axillary nodes; sentinel node biopsy; peau d'orange; nipple retraction

4. Lung segments & aspiration (concepts 26-27)

• Right lung segments (10): upper lobe 3 (apical, anterior, posterior), middle 2 (lateral, medial), lower 5 (superior, anterior basal, posterior basal, lateral basal, medial basal)
• Left lung segments (9): upper 4 (apicoposterior, anterior, superior lingular, inferior lingular), lower 5 (superior, anterior basal, posterior basal, lateral basal, medial basal)
• Aspiration: right main bronchus more vertical → right lower lobe (superior segment in supine, posterior basal in upright)
• Lung diseases (concept 27): consolidation (air bronchogram), collapse (atelectasis — silhouette sign), effusion, cavitation (TB), nodules

5. Open pneumothorax (concept 28)

• Mechanism: penetrating wound → air enters the pleural cavity through the chest wall (sucking wound) → lung collapses, mediastinum flutters with respiration
• Clinical: cyanosis, dyspnea, "sucking" wound; treatment: seal the wound (occlusive dressing), then chest drain
• Tension pneumothorax: one-way valve → air accumulates → mediastinal shift away, hypotension, distended neck veins → immediate needle decompression (2nd ICS midclavicular)

6. Diaphragm & hernias (concepts 22, 33-34)

• Openings: IVC T8, esophagus T10, aorta T12 ("I ate at 12"); phrenic C3-C5
• Congenital diaphragmatic hernia (concept 33): Bochdalek (posterolateral, left > right) — bowel herniates into the chest → respiratory distress in newborn
• Sliding hiatal hernia (concept 34): GE junction + stomach slide above the diaphragm through the esophageal hiatus → GERD, retrosternal burning, worse supine

7. Heart — auscultation & blood supply (concepts 23-25)

- RCA: SA node (60-70%), right marginal, posterior interventricular (80-85% — right dominant); inferior MI - LCA: LAD (anterior interventricular) — anterior wall & septum ("widow maker"); circumflex — lateral wall - Coronary sinus: main venous drainage → right atrium

• Auscultation areas: aortic 2nd RICS; pulmonary 2nd LICS; tricuspid lower left sternal border; mitral = apex (5th LICS midclavicular)
• Blood supply:
• Cardiac hypertrophy (concept 23): LV hypertrophy → boot-shaped heart (aortic stenosis/HTN); RV hypertrophy → pulmonary HTN

8. Skull base & intracranial bleeding (concepts 68-74)

• Foramina of the base of skull (concept 68): optic canal (CN II, ophthalmic a.), superior orbital fissure (III, IV, V1, VI), foramen rotundum (V2), foramen ovale (V3), foramen spinosum (middle meningeal a.), internal acoustic meatus (VII, VIII), jugular foramen (IX, X, XI, IJV), hypoglossal canal (XII), foramen magnum (medulla, XI, vertebral arteries)
• Epidural hematoma (concept 74): middle meningeal artery tear at the pterion → lens/biconvex bleed, does not cross sutures → lucid interval → urgent craniotomy
• Subdural hematoma: bridging vein tear → crescentic, crosses sutures (elderly, shaking)
• Fracture of the middle cranial fossa / skull base: CSF rhinorrhea, Battle's sign, raccoon eyes

9. Key neck/head miscellany (concepts 76-100 recap)

• Scalp layers (76): SCALP — Skin, Connective tissue, Aponeurosis, Loose areolar (dangerous area), Pericranium
• Innervation of face skin (77): V1 (ophthalmic: forehead), V2 (maxillary: midface), V3 (mandibular: lower face/jaw)
• Facial nerve (78): motor face; taste ant 2/3 tongue (chorda tympani); 5 branches "Two Zebras Bit My Cat"
• Epistaxis (80): Little's area — Kiesselbach's plexus (ant ethmoidal, sphenopalatine, greater palatine, superior labial)
• Movements at TMJ (83): temporalis (elevation & retraction), masseter (elevation), medial pterygoid (elevation), lateral pterygoid (protrusion) — the only protruder
• Horner syndrome (92): sympathetic injury (stellate ganglion, lung apex tumor, carotid dissection) → ptosis, miosis, anhidrosis, enophthalmos
• Retropharyngeal space (97): between buccopharyngeal & prevertebral fascia → infection to superior mediastinum
• Carotid sheath (98): CCA/ICA, IJV, vagus
• Axillary sheath (99): prevertebral fascia extension around axillary vessels & brachial plexus
• Posterior triangle (100): CN XI, cervical plexus, brachial plexus trunks, subclavian a.

High-Yield Points

• Thyroid surgery: "superior nerve goes with superior artery (ligate close to gland); recurrent nerve goes with inferior artery (ligate away from gland)"
• RLN injury: unilateral = hoarse; bilateral = stridor/airway emergency
• Mediastinum mnemonic: "S-A-M-P" = Superior, Anterior, Middle, Posterior — posterior = esophagus, descending aorta, azygos, thoracic duct, sympathetic trunk, vagus
• Sternal angle = T4/5, arch of aorta, tracheal bifurcation, 2nd costal cartilage
• Breast: 75% → axillary; medial → internal thoracic
• Aspiration → right lower lobe (superior segment supine / posterior basal upright)
• Open pneumothorax: seal the wound; tension: needle decompression 2nd ICS midclavicular
• Diaphragm: "I ate at 12" — IVC T8, Esophagus T10, Aorta T12
• Epidural = lens, artery (pterion/middle meningeal), lucid interval; Subdural = crescent, vein
• Coronary: RCA → inferior; LAD → anterior/septum; circumflex → lateral
• Lateral pterygoid = protrudes (only one)
• Horner: ptosis, miosis, anhidrosis (remember "PMA")

Topic Summary

The head/neck/thorax capstone: thyroidectomy anatomy (superior thyroid a. + external laryngeal n.; inferior thyroid a. + recurrent laryngeal n.; parathyroids), mediastinum (superior/anterior/middle/posterior; posterior = esophagus/aorta/azygos/duct/sympathetic/vagus), breast lymphatics (75% axillary), lung segments & aspiration (right lower lobe), open & tension pneumothorax, diaphragm openings & hiatus hernias, heart auscultation/blood supply, and the skull base foramina & epidural/subdural hematomas. These are the highest-yield exam items across the head, neck & thorax.