BackThe Small Intestine: Gross Anatomy and Glandular Structures
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The Digestive System
The Small Intestine
The small intestine is a crucial organ in the digestive system, responsible for most nutrient absorption and digestion. It is divided into three main regions: the duodenum, jejunum, and ileum. Each region has specialized structures to support its function.
Gross Anatomy of the Ileum: The ileum is the final and longest segment of the small intestine, connecting to the large intestine at the ileocecal valve. Its wall contains several specialized features to aid in digestion and absorption.
Intestinal Glands (Crypts of Lieberkühn)
Definition: Intestinal glands, also known as crypts of Lieberkühn, are tubular invaginations of the epithelial lining that extend into the lamina propria of the mucosa.
Function: These glands secrete intestinal juices containing enzymes and mucus, which aid in the final stages of digestion and protect the mucosal surface.
Location: Found throughout the small intestine, including the ileum.
Duodenal (Brunner’s) Glands
Definition: Brunner’s glands are compound tubular glands located in the submucosa of the duodenum (the first part of the small intestine).
Function: These glands secrete an alkaline mucus that helps neutralize acidic chyme entering from the stomach, protecting the duodenal lining and providing an optimal pH for enzymatic activity.
Location: Present only in the submucosa of the duodenum, not in the jejunum or ileum.
Summary Table: Glandular Structures of the Small Intestine
Gland | Location | Function |
|---|---|---|
Intestinal glands (Crypts of Lieberkühn) | Mucosa of duodenum, jejunum, and ileum | Secrete intestinal juices; contain stem cells and immune cells |
Brunner’s glands | Submucosa of duodenum | Secrete alkaline mucus to neutralize gastric acid |
Example: When acidic chyme from the stomach enters the duodenum, Brunner’s glands secrete mucus to protect the intestinal lining, while the crypts of Lieberkühn release enzymes to continue digestion.
Additional info: The small intestine also contains other specialized cells, such as Paneth cells (which secrete antimicrobial peptides) and enteroendocrine cells (which release hormones to regulate digestion).
