Thoracic Anatomy – Esophagus, Trachea, Pleura, Diaphragm & Thoracic Cage

Flashcards cover essential vocabulary from extensive lecture notes on thoracic anatomy, including the esophagus, trachea, pleura, diaphragm, thoracic cage, and related clinical conditions.

Esophagus

25-cm fibromuscular tube extending from C6 (pharynx) to T11 (stomach); part of the digestive tract.

Cervical Esophagus

Upper esophageal segment that traverses the neck.

Thoracic Esophagus

Middle segment located in the mediastinum between trachea and vertebral bodies T1-T4.

Abdominal Esophagus

1.25-cm terminal segment that passes the diaphragm to join the stomach at T11.

Upper Esophageal Sphincter (UES)

Pharyngoesophageal junction formed largely by the cricopharyngeus muscle; prevents air entry into esophagus.

Lower Esophageal Sphincter (LES)

Physiologic gastroesophageal sphincter at T11 that prevents reflux into esophagus.

LES Closure Factors

Acute angle of entry, compression by intra-abdominal pressure, mucosal folds, and pinch-cock effect of right diaphragmatic crus.

Esophageal Constrictions (ABCD)

Sites where lumen narrows: Arch of aorta, Bronchus (left main), Cricoid cartilage, Diaphragm.

Esophageal Mucosa

Non-keratinized stratified squamous epithelium with lamina propria and muscularis mucosae.

Esophageal Submucosa

Layer containing esophageal glands and papillae.

Esophageal Muscularis Externa

Striated muscle upper third, mixed middle third, smooth muscle lower third.

Esophageal Adventitia

Outermost fibro-areolar connective tissue layer of esophagus.

Esophageal Blood Supply – Cervical

Esophageal branches of the inferior thyroid artery (thyrocervical trunk).

Esophageal Blood Supply – Thoracic

Esophageal branches from the thoracic aorta.

Esophageal Blood Supply – Abdominal

Branches from left gastric and left inferior phrenic arteries.

Esophageal Venous Drainage – Cervical

Into inferior thyroid veins.

Esophageal Venous Drainage – Thoracic

Into azygos, hemiazygos, intercostal and bronchial veins.

Porto-Systemic Anastomosis (Esophageal)

Connection between left gastric (portal) veins and systemic veins of azygos system in abdominal esophagus.

Barrett’s Esophagus

Metaplasia of lower esophageal squamous epithelium to gastric columnar epithelium due to chronic acid reflux.

Esophageal Varices

Dilated submucosal veins in lower esophagus from portal hypertension; risk of haematemesis.

Esophageal Innervation – Cervical

Parasympathetic via recurrent laryngeal nerve; sympathetic via cervical sympathetic trunk.

Esophageal Innervation – Thoracic

Esophageal plexus (vagus parasympathetic, sympathetic trunk fibers).

Esophageal Innervation – Abdominal

Parasympathetic from vagal fibers of thoracic plexus; sympathetic from thoracic sympathetic trunk.

Esophageal Lymph Drainage

Upper third to deep cervical nodes; middle third to superior & posterior mediastinal nodes; lower third to left gastric & celiac nodes.

Esophageal Carcinoma – Squamous Cell

Most common type; may occur at any esophageal level.

Esophageal Carcinoma – Adenocarcinoma

Arises from distal third; often associated with Barrett’s change.

Trachea

10–11-cm fibrocartilaginous airway from C6 (cricoid) to T5 (sternal angle) where it bifurcates.

Tracheal Cartilages

16-20 C-shaped hyaline rings supporting anterolateral wall.

Trachealis Muscle

Smooth muscle forming posterior wall of trachea between cartilage ends.

Carina

Sagittal cartilaginous ridge at tracheal bifurcation.

Right Main Bronchus

Shorter, wider, more vertical; divides into 3 lobar bronchi.

Left Main Bronchus

Longer, narrower, more oblique; divides into 2 lobar bronchi.

Tracheal Mucosa

Pseudostratified ciliated columnar epithelium with goblet cells.

Tracheal Submucosa

Connective tissue with mucus glands, vessels, nerves and lymphatics.

Tracheomalacia

Congenital softening of tracheal cartilages causing airway collapse during respiration.

Tracheal Blood Supply

Arterial branches from inferior thyroid artery; venous drainage to inferior thyroid plexus.

Tracheal Innervation

Pulmonary plexus; parasympathetic via recurrent laryngeal (vagus), sympathetic via sympathetic trunks.

Pleura

Double-layered serous membrane covering lungs (visceral) and lining thoracic wall (parietal).

Pleural Cavity

Potential space between visceral and parietal pleura containing serous fluid.

Parietal Pleura Subdivisions

Costal, Mediastinal, Diaphragmatic (plus cervical cupula).

Pleural Recess

Potential pleural space where lung does not fully occupy cavity (costodiaphragmatic, costomediastinal).

Costodiaphragmatic Recess

Largest recess between costal and diaphragmatic pleurae; common site for fluid collection.

Costomediastinal Recess

Anterior recess between costal and mediastinal pleura behind sternum.

Pleural Reflections

Lines where pleura changes direction: sternal, costal, vertebral lines.

Inferior Limit of Parietal Pleura

Rib 8 midclavicular, Rib 10 midaxillary, T12 vertebral column.

Pneumothorax

Air in pleural cavity causing lung collapse; presents with chest pain, SOB, hyper-resonance.

Thoracentesis Site

Posterolateral chest wall, mid-scapular or posterior axillary line, 1–2 interspaces below top of effusion and above 8th rib.

Triangle of Safety

Area for chest drain bounded by pectoralis major, latissimus dorsi & 5th intercostal space in axilla.

Visceral Pleura Innervation

Autonomic fibers from pulmonary plexus; insensitive to pain.

Parietal Pleura Innervation

Phrenic and intercostal nerves; sensitive to pain and temperature.

Diaphragm

Domed musculotendinous sheet separating thoracic and abdominal cavities; primary muscle of inspiration.

Diaphragmatic Domes

Right dome higher (4th IC space) than left (5th rib) in full expiration.

Crus of Diaphragm

Tendinous slips attached to lumbar vertebrae; right crus L1-L3, left crus L1-L2.

Median Arcuate Ligament

Midline tendinous arch uniting crura in front of aorta at T12.

Medial Arcuate Ligament

Thickened psoas fascia from L1 body to L1 transverse process.

Lateral Arcuate Ligament

Thickened fascia over quadratus lumborum from L1 transverse process to 12th rib.

Central Tendon

Trefoil aponeurosis into which diaphragmatic fibers insert; fused with fibrous pericardium.

Aortic Hiatus

Opening at T12 behind median arcuate ligament transmitting aorta, thoracic duct, azygos vein.

Esophageal Hiatus

Opening at T10 within right crus fibers for esophagus, vagal trunks, left gastric vessels.

Caval Opening

Foramen at T8 in central tendon for inferior vena cava and right phrenic nerve branch.

Phrenoesophageal Ligament

Fascial cone attaching diaphragm to esophagus; involved in sliding hiatal hernia.

Hiatus Hernia – Sliding

Upward displacement of gastroesophageal junction through esophageal hiatus.

Hiatus Hernia – Paraesophageal

Fundus herniates beside esophagus while junction stays abdominal.

Bochdalek Hernia

Posterolateral congenital diaphragmatic defect from failed pleuroperitoneal membrane fusion.

Morgagni Hernia

Anterior diaphragmatic defect at costosternal junction.

Diaphragmatic Blood Supply

Inferior phrenic arteries (main), plus pericardiacophrenic, musculophrenic, superior phrenic, intercostal & subcostal branches.

Diaphragmatic Nerve Supply

Motor from phrenic nerves (C3-C5); peripheral proprioception from lower intercostal nerves.

Thoracic Cage

Bony framework of 12 thoracic vertebrae, 12 pairs of ribs/costal cartilages, and sternum.

Manubrium

Superior part of sternum bearing jugular and clavicular notches; articulates with body at sternal angle.

Sternal Angle (Angle of Louis)

Manubriosternal joint at level of T4/T5; landmark for aortic arch, tracheal bifurcation, etc.

Xiphoid Process

Inferior sternum segment at T10; forms xiphisternal joint.

True Ribs

Ribs 1-7; attach directly to sternum via their own costal cartilages.

False Ribs

Ribs 8-10; costal cartilages join the cartilage above, not the sternum directly.

Floating Ribs

Ribs 11-12; no anterior attachment, end in abdominal musculature.

Typical Rib Features

Head with two facets, neck, tubercle, shaft with costal angle and costal groove.

Costal Groove

Inferior rib groove housing intercostal vein, artery, and nerve (VAN).

Atypical 1st Rib

Broad, flat, single facet, grooves for subclavian vessels separated by scalene tubercle.

Atypical 2nd Rib

Tuberosity for serratus anterior on superior surface.

Atypical 10th–12th Ribs

Single head facet; ribs 11-12 lack neck and tubercle.

Intercostal Space

Gap between adjacent ribs; contains intercostal muscles, nerves and vessels.

Costovertebral Joint

Articulation between rib head and thoracic vertebral bodies.

Costotransverse Joint

Articulation between rib tubercle and transverse process of corresponding vertebra.

Superior Thoracic Aperture

Opening bounded by T1, first ribs & manubrium; passage for thoracic inlet structures.

Inferior Thoracic Aperture

Large opening closed by diaphragm; bounded by T12, 11th–12th ribs, costal margin & xiphisternal joint.

RALS Mnemonic

Pulmonary artery positions at lung hilum: Right Anterior, Left Superior to main bronchus.

Hilum of Lung

Mediastinal surface gateway for bronchi, vessels, nerves, lymphatics at T5-T7.

Azygos Vein Arch

Venous arch over right lung hilum entering SVC.

Barrel Chest Radiograph Aortic Knuckle

Left border prominence created by arch of aorta on PA chest X-ray.

Thoracic Duct

Major lymphatic trunk ascending behind esophagus, entering venous angle at left subclavian-IJ vein junction.

Recurrent Laryngeal Nerve

Branch of vagus looping under right subclavian (right) or aortic arch ligamentum arteriosum (left).

Sympathetic Trunk

Paravertebral chain providing sympathetic fibers to thoracic viscera and body wall.