Constrictions of the Oesophagus
Overview
The oesophagus is not of uniform calibre throughout its length. It is narrowed at four sites (physiological constrictions) where adjacent structures compress it, and at one functional site (lower oesophageal sphincter).
Some sources describe three main constrictions (excluding the cricopharyngeal and physiological LOS), but the complete list includes four anatomical compressions.
The Four Constrictions
| Constriction | Cause | Level | Distance from Upper Incisor Teeth |
|---|---|---|---|
| 1st — Cricopharyngeal | Junction of pharynx and oesophagus; cricopharyngeus muscle (upper oesophageal sphincter) | C5–C6 | ~15 cm |
| 2nd — Aortic | Arch of the aorta crosses the left side of the oesophagus | T4 | ~22.5 cm |
| 3rd — Bronchial (Left bronchial) | Left principal bronchus crosses anterior to the oesophagus | T4–T5 | ~27 cm |
| 4th — Diaphragmatic | Oesophagus passes through the right crus of the diaphragm at the oesophageal hiatus | T10 | ~40 cm |
Note: Some sources combine the aortic and bronchial constrictions as they occur at closely adjacent levels (both at T4–T5). Others describe a 5th constriction — the lower oesophageal sphincter (LOS) — at the gastro-oesophageal junction (T10–T11).
Distances from Upper Incisor Teeth (Clinically Important)
These distances are memorised for endoscopy — when passing a scope from the mouth:
| Constriction | Distance |
|---|---|
| Cricopharyngeal (upper oesophageal sphincter) | 15 cm |
| Aortic arch | 22.5 cm |
| Left bronchus | 27 cm |
| Diaphragm (oesophageal hiatus) | 40 cm |
Clinical Significance of Constrictions
- Foreign bodies lodge most commonly at the cricopharyngeal constriction (narrowest point), followed by the diaphragmatic constriction
- Carcinoma of the oesophagus is most common at the constriction sites — particularly the bronchial (middle third) and diaphragmatic (lower third) constrictions
- Strictures following ingestion of corrosive liquids most commonly form at constriction sites
- Barium swallow identifies these constrictions as indentations on the barium column:
- Aortic arch produces a smooth, oblique indentation on the left anterior aspect
- Left bronchus produces a horizontal indentation on the anterior aspect
- Dilated left atrium produces an additional indentation below the left bronchial indentation
Narrowest Point
The cricopharyngeal constriction (at the junction of pharynx and oesophagus — Killian’s dehiscence area) is the narrowest point of the entire oesophagus and the most common site where a foreign body or food bolus lodges.
Physiological Lower Oesophageal Sphincter (LOS)
Although there is no distinct anatomical sphincter at the gastro-oesophageal junction, a functional sphincter exists due to:
- The right crus of the diaphragm encircling the oesophagus (crural sphincter)
- The angle of His (the oblique angle of entry of the oesophagus into the stomach)
- The positive intra-abdominal pressure acting on the abdominal segment of the oesophagus
- The mucosal folds (rosette) at the gastro-oesophageal junction
Failure of the LOS → gastro-oesophageal reflux disease (GORD/GERD)