Circular muscular layer of small intestine
Stratum musculare circulare intestini tenuis
- Latin synonym: Stratum circulare tunicae muscularis intestini tenuis; Stratum helicoideum gradus brevis
- Synonym: Circular layer of muscular coat of small intestine; Short pitch helicoidal layer
- Related terms: Circular layer; Short pitch helicoidal layer
Definition
The inner circular layer of small intestine is the inner component of the muscularis externa of the small intestine. It consists of circularly arranged smooth muscle fibres that encircle the intestinal lumen. Contraction of this layer narrows the lumen and plays a major role in segmentation and peristalsis, facilitating the mixing and propulsion of intestinal contents.
In certain regions, the circular muscle becomes thickened to form sphincters, such as the ileocaecal sphincter at the junction of the ileum and caecum. The activity of the circular muscle layer is coordinated by the myenteric (Auerbach's) plexus, which lies between the circular and longitudinal muscle layers.
References
Collins JT, Nguyen A, Omole AE, et al. Anatomy, Abdomen and Pelvis, Small Intestine. [Updated 2025 Feb 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459366/
Standring, S. (2015) Grays Anatomy: The Anatomical Basis of Clinical Practice. 41st edn. London: Churchill Livingstone Elsevier. Chapter 65, Small intestine.
