Submucosa of small intestine
Tela submucosa intestini tenuis
- Synonym: Submucosal layer of small intestine
- Related terms: Submucosa
Definition
The submucosa of small intestine is a layer of dense irregular connective tissue layer situated between the mucosa and muscularis externa. It forms the principal supporting framework of the intestinal wall and serves as a conduit for the blood vessels, lymphatic vessels, and nerves that supply the mucosa. Rich in collagen and elastic fibres, the submucosa provides the gastrointestinal wall with both strength and flexibility, allowing it to stretch and recoil as chyme passes through the intestinal lumen. This mechanical support helps maintain the structural integrity of the intestine while accommodating changes in luminal volume during digestion.
Vasculature and lymphatics
In addition to its supportive role, the submucosa contains a large network of blood vessels and lymphatics that drain the mucosal capillary beds and transport absorbed nutrients, water, electrolytes, and immune cells away from the intestine. Lymphatic vessels within the submucosa receive dietary lipids absorbed by the mucosal lacteals and convey them into the systemic circulation.
Submucosal (Meissner's) plexus
Embedded within the submucosal connective tissue is the submucosal (Meissner's) plexus, a component of the enteric nervous system that regulates glandular secretion, local blood flow, and the activity of the muscularis mucosae.
Regional variations of the submucosa
Although the submucosa has a similar basic structure throughout the small intestine, it exhibits important regional specialisations.
Segment | Distinctive submucosal characteristics |
Duodenum | In the duodenum, submucosa contains Brunner's glands (duodenal glands), which secrete a bicarbonate-rich alkaline mucus that neutralises the acidic chyme entering from the stomach, protects the intestinal mucosa, and creates an optimal environment for pancreatic enzyme activity. |
Jejunum | In the jejunum, the submucosa lacks specialised glands or significant lymphoid aggregates but forms the core of the prominent plicae circulares, permanent circular folds that increase the absorptive surface area and slow the passage of chyme to facilitate nutrient absorption. |
Ileum | In the ileum, the submucosa is characterised by extensive Peyer's patches, which are aggregated lymphoid nodules that originate in the lamina propria and extend deeply into the submucosa. These lymphoid structures play a crucial role in immune surveillance by monitoring intestinal contents and initiating immune responses against pathogenic microorganisms. |
Histological Identification
Histologically, the submucosa of small intestine appears as a relatively pale staining connective tissue layer beneath the muscularis mucosae and can be identified by the presence of larger blood vessels, lymphatics, and the submucosal plexus. The presence of Brunner's glands is diagnostic of the duodenum, whereas prominent Peyer's patches are characteristic of the ileum.
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.
