Title: 23.6 The Small and Large Intestines – Anatomy & Physiology
Headings: 23.6 The Small and Large Intestines
23.6 The Small and Large Intestines
Learning Objectives
The Small Intestine
Structure
Histology
Circular folds
Villi
Microvilli
Intestinal Glands
Intestinal MALT
External Website
Mechanical Digestion in the Small Intestine
Chemical Digestion in the Small Intestine
Disorders of the…Small Intestine: Lactose Intolerance
The Large Intestine
Structure
Subdivisions
Cecum
Colon
Homeostatic Imbalances – Colorectal Cancer
Rectum
Anal Canal
Histology
Anatomy
Bacterial Flora
Digestive Functions of the Large Intestine
Mechanical Digestion
Chemical Digestion
Absorption, Feces Formation, and Defecation
External Website
Interactive Link Questions

Content: Structure
The coiled tube of the small intestine is subdivided into three regions. From proximal (at the stomach) to distal, these are the duodenum, jejunum, and ileum ( Figure 23.6.1 ). The shortest region is the 25.4-cm (10-in) duodenum, which begins at the pyloric sphincter. Just past the pyloric sphincter, it bends posteriorly behind the peritoneum, becoming retroperitoneal, and then makes a C-shaped curve around the head of the pancreas before ascending anteriorly again to return to the peritoneal cavity and join the jejunum. The duodenum can therefore be subdivided into four segments: the superior, descending, horizontal, and ascending duodenum. Of particular interest is the hepatopancreatic ampulla (ampulla of Vater). Located in the duodenal wall, the ampulla marks the transition from the anterior portion of the alimentary canal to the mid-region, and is where the bile duct (through which bile passes from the liver) and the main pancreatic duct (through which pancreatic juice passes from the pancreas) join. This ampulla opens into the duodenum at a tiny volcano-shaped structure called the major duodenal papilla. The hepatopancreatic sphincter (sphincter of Oddi) regulates the flow of both bile and pancreatic juice from the ampulla into the duodenum.