Overview
The esophagus is a muscular tube approximately 25 cm long connecting the pharynx to the stomach. It passes through the neck, thoracic cavity, and abdominal cavity with distinct anatomical features including curvatures, constrictions, and layered wall structure.
Anatomical Parts of the Esophagus
Cervical Part
- Located in the neck region
- Starts at the pharyngeal opening (ostium esophageum) where pharynx ends
- Ends at the superior thoracic aperture (upper opening of ribcage)
Thoracic Part
- Begins at superior thoracic aperture
- Travels through thoracic cavity vertically at midline
- Ends at esophageal hiatus where it pierces diaphragm
Abdominal Part
- Shortest segment starting at esophageal hiatus
- Terminates at cardiac orifice where esophagus meets stomach
Curvatures
- Initial curve slightly to the left at beginning
- Middle thoracic region curves slightly to the right
- Lower thoracic region curves left again before entering stomach through diaphragm
Constrictions of the Esophagus
Anatomical Constrictors (present due to anatomical development, persist after death)
- Composed of skeletal muscle that closes during breathing
- Remain present even in non-living organisms
Physiological Constrictions (function only in living body)
- Made of smooth muscle controlled by autonomic nervous system
- Relax and disappear after loss of body functions
| Constriction | Type | Location | Vertebral Level |
|---|
| Pharyngoesophageal | Anatomical | Border between pharynx and esophagus (ostium esophageum) | C6-C7 |
| Bronchioaortic | Anatomical | Behind left principal bronchus | T4 |
| Phrenic (Diaphragmatic) | Anatomical | At esophageal hiatus | T10 |
| Aortic crossing | Physiological | Where esophagus crosses aorta | T8-T9 |
| Lower esophageal sphincter | Physiological | Esophagus terminates into stomach | T11 |
Layers of the Esophageal Wall
Tunica Mucosa (innermost layer)
- Stratified squamous non-keratinized epithelium lining lumen
- Contains mucus glands for lubrication
- Includes vasculature (blood vessels, nerves, lymphoid nodules)
- Supported by lamina muscularis mucosae
Tela Submucosa
- Loose connective tissue layer beneath mucosa
- Contains esophageal glands producing mucin for lubrication
- Esophageal cardiac glands produce neutral mucin protecting against acidic gastric reflux
- Neutralizes hydrochloric acid from stomach if reflux occurs
Tunica Muscularis
- Inner circular muscle layer with circularly arranged fibers
- Outer longitudinal muscle layer with lengthwise fibers
- Upper third: striated skeletal muscle
- Middle third: gradual transition to smooth muscle
- Lower third: entirely smooth muscle
Outer Protective Layer
- Cervical and thoracic regions: thick connective tissue (tunica adventitia)
- Abdominal region: serous coat (tunica serosa) formed by peritoneum
- Peritoneum allows organs to slide without friction in abdomen
Key Terms & Definitions
- Lumen: hollow space inside a tube (inner cavity of esophagus)
- Ostium esophageum: pharyngeal opening into esophagus
- Esophageal hiatus: opening in diaphragm where esophagus passes through
- Phrenic: anatomical term describing structures related to diaphragm
- Tunica: layer of tissue
- Tela: web-like or loose tissue structure
- Cardiac orifice: junction where esophagus meets stomach