Title: The Small and Large Intestines | Anatomy and Physiology II
Headings: The Small and Large Intestines
The Small and Large Intestines
Learning Objectives
The Small Intestine
Structure
Histology
Structure versus function: the absorptive surface of the small Intestine
Circular folds
Villi
Microvilli
Intestinal Glands
Intestinal Mucosa-Associated Lymphatic Tissue (MALT)
Mechanical Digestion in the Small Intestine
Chemical Digestion in the Small Intestine
Bile salts: hydrogen bonding and emulsification
Figure 5. Emulsification of fats by bile salts
Disorders of the Small Intestine: Lactose Intolerance
The Large Intestine
Structure
Subdivisions
Cecum
Colon
Rectum
Anal Canal
Histology
Anatomy
Bacterial Flora
Digestive Functions of the Large Intestine
Mechanical Digestion
Chemical Digestion
Absorption, Feces Formation, and Defecation
Chapter Review
Self Check
23.5 Exercise 33.
Critical Thinking Questions
Glossary
References

Content: Not only is this where most digestion occurs, it is also where practically all absorption occurs. The longest part of the alimentary canal, the small intestine is about 3.05 meters (10 feet) long in a living person (but about twice as long in a cadaver due to the loss of muscle tone). 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.