The Inferior Constrictor Muscle is Located at 15 cm from Incisor Teeth
The structure located approximately 15 cm from the incisor teeth is the inferior constrictor muscle, specifically the cricopharyngeal part (option A).
Anatomical Landmarks and Measurements
The British Society of Gastroenterology guidelines clearly identify that the distal end of the palisade vessels penetrate the submucosal layer at the level of the gastroesophageal junction (GOJ), which lies approximately 15 cm from the incisor teeth 1. This anatomical landmark is crucial for endoscopists when delineating the GOJ during procedures.
The inferior constrictor muscle, particularly its cricopharyngeal part, forms the upper esophageal sphincter (UES) and is located at this distance. The cricopharyngeal muscle is situated at the level of the cricoid cartilage (C6 vertebral level) and forms a sphincter approximately 1.4-1.5 cm in length 2.
Distinguishing from Other Options
Let's examine why the other options are incorrect:
Diaphragm (Option B): Located approximately 40 cm from the incisor teeth at the T11 vertebral level, much deeper than the structure in question 1.
Aortic and bronchial constriction (Option C): Located 22.5-25 cm from the incisor teeth at the T4 vertebral level, where the aortic arch and left main bronchus create an impression on the esophagus 1.
Lower esophageal sphincter (Option D): Located at the distal end of the esophagus, approximately 40 cm from the incisor teeth, where it joins the stomach 1.
Functional Significance of the Inferior Constrictor
The inferior constrictor muscle, particularly its cricopharyngeal part, serves important physiological functions:
- Controls flow between the pharynx and esophagus 3
- Remains tonically contracted at rest to prevent air entry into the digestive tract 2
- Relaxes during swallowing, belching, and vomiting 3
- Protects against reflux of food into the airways 2
The cricopharyngeus has unique characteristics including high elasticity and a mixture of slow and fast-twitch fibers (with slow-twitch predominating), enabling it to maintain resting tone while still being able to stretch open during swallowing 2.
Clinical Relevance
Understanding the location of the inferior constrictor muscle at 15 cm from the incisor teeth is important for:
- Endoscopic procedures where accurate identification of anatomical landmarks is essential 1
- Diagnosis and management of oropharyngeal dysphagia, which has neurological causes in 80% of cases 3
- Assessment of cricopharyngeal dysfunction, which can present as a "cricopharyngeal bar" when the sphincter fails to relax properly 2
This anatomical knowledge is crucial for clinicians performing upper gastrointestinal endoscopy, as it helps in proper documentation and assessment of findings according to standardized protocols like the Prague classification 1.