Anatomy

Size, Position, and Structure

Size and Location

• Length: About 25 cm
• Diameter: Around 2 cm
• Extent: From the pharynx (C6) to the cardia of the stomach
• Position: Posterior to the trachea and heart, anterior to the spine, and traverses the diaphragm at T10

Sections of the Esophagus

• Cervical Section: From cricopharyngeus to suprasternal notch
• Thoracic Section: From suprasternal notch to diaphragm
• Abdominal Section: Final 1.25 cm segment entering the stomach

Wall Layers

• Mucosa: Non-keratinizing stratified squamous epithelium, lamina propria, and muscularis mucosae
• Submucosa: Contains glands, vessels, nerves (Meissner plexus)
• Muscularis Propria: Inner circular and outer longitudinal layers
• Adventitia: Connective tissue layer; serosa only in abdominal part

Muscle and Motility

Muscle Composition

• Upper third: Striated muscle
• Middle third: Mixed
• Lower third: Smooth muscle

Esophageal Sphincters

• UES (Upper Esophageal Sphincter): Prevents air entry during breathing
• LES (Lower Esophageal Sphincter): Prevents gastric reflux, ~20 mmHg resting tone

Peristalsis

• Primary: Initiated by swallowing
• Secondary: Reflexive due to esophageal stretch
• Tertiary: Non-propulsive, irregular contractions

Regional Anatomy

Cervical Esophagus

• Anterior: Trachea
• Posterior: Spine
• Lateral: Common carotid arteries
• Continues from the pharynx at C6–C7 level

Thoracic Esophagus

• In superior and posterior mediastinum
• Courses behind aortic arch and left bronchus
• Related anteriorly to pericardium and diaphragm, posteriorly to thoracic duct, azygos system

Abdominal Esophagus

• Lies in liver’s esophageal groove
• Peritoneal only on front and left sides
• Ends in stomach at antrum cardiacum

Anatomical Constrictions

• Cervical: ~15 cm from incisors (cricopharyngeal level, C6)
• Thoracic: ~23 cm from incisors (aortic arch/left bronchus)
• Diaphragmatic: ~40 cm from incisors (at diaphragm, T10)

Blood Supply and Drainage

Arterial Supply

• Cervical: Inferior thyroid artery
• Thoracic: Esophageal branches from thoracic aorta
• Abdominal: Left gastric and left inferior phrenic arteries

Venous Drainage

• Cervical: Inferior thyroid veins
• Thoracic: Azygos, hemiazygos, bronchial veins
• Abdominal: Left gastric vein → portal vein

Lymphatic Drainage

Cervical

• Deep cervical lymph nodes → thoracic duct

Thoracic

• Superior/posterior mediastinal nodes
• Mucosal/submucosal lymphatics drain bidirectionally
• Right paratracheal and subcarinal nodes significant

Abdominal

• Left gastric and paracardial nodes
• Posterior surface drains to upper para-aortic nodes

System Features

• Dense lymphatic networks with longitudinal drainage
• Lymphatic interconnections enable spread from lower to upper esophagus

Innervation

Parasympathetic

• Vagus nerve (CN X)
  • Nucleus ambiguus: striated muscle innervation
  • Dorsal motor nucleus: smooth muscle and LES
  • Regulates peristalsis and glandular secretion

Sympathetic

• Cervical and thoracic sympathetic trunks
• Cervical ganglia, stellate ganglion, splanchnic nerves
• Thoracic portions connect via coeliac plexus

Esophageal Plexus

• Autonomic plexus from vagus and sympathetic trunks
• Dense network around thoracic esophagus
• Vagal fibers also end in Auerbach’s (myenteric) plexus

Special Muscular Features

• Kilian Triangle: Weak dorsal spot prone to Zenker’s diverticulum
• LES: Not anatomically distinct but functionally vital
• UES: Formed by cricopharyngeus and adjacent constrictor fibers