Title: The Small and Large Intestines | Biology of Aging
Headings: The Small and Large Intestines
The Small and Large Intestines
The Small Intestine
Structure
Mechanical Digestion in the Small Intestine
Chemical Digestion in the Small Intestine
The Large Intestine
Structure
Subdivisions
Cecum
Colon
Rectum
Anal Canal
Anatomy
Teniae Coli, Haustra, and Epiploic Appendages
Bacterial Flora
Digestive Functions of the Large Intestine
Mechanical Digestion
Chemical Digestion
Absorption, Feces Formation, and Defecation
References

Content: Since this makes it about five times longer than the large intestine, you might wonder why it is called “small.” In fact, its name derives from its relatively smaller diameter of only about 2.54 cm (1 in), compared with 7.62 cm (3 in) for the large intestine. As we’ll see shortly, in addition to its length, the folds and projections of the lining of the small intestine work to give it an enormous surface area, which is approximately 200 m 2, more than 100 times the surface area of your skin. This large surface area is necessary for complex processes of digestion and absorption that occur within it. 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. 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.