Title: 9.6: The Small and Large Intestines - Biology LibreTexts
Headings: 9.6: The Small and Large Intestines
9.6: The Small and Large Intestines
Learning Objectives
The Small Intestine
Structure
Histology
Circular folds
Villi
Microvilli
Intestinal Glands
Intestinal MALT
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
Self Check
Critical Thinking Questions
Glossary
References
Contributors and Attributions

Content: Compare and contrast the location and gross anatomy of the small and large intestines
Identify three main adaptations of the small intestine wall that increase its absorptive capacity
Describe the mechanical and chemical digestion of chyme upon its release into the small intestine
List three features unique to the wall of the large intestine and identify their contributions to its function
Identify the beneficial roles of the bacterial flora in digestive system functioning
Trace the pathway of food waste from its point of entry into the large intestine through its exit from the body as feces
The word intestine is derived from a Latin root meaning “internal,” and indeed, the two organs together nearly fill the interior of the abdominal cavity. In addition, called the small and large bowel, or colloquially the “guts,” they constitute the greatest mass and length of the alimentary canal and, with the exception of ingestion, perform all digestive system functions. The Small Intestine
Chyme released from the stomach enters the small intestine, which is the primary digestive organ in the body. 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.