The intestines, an integral part of the digestive system, are remarkable organs responsible for processing food and absorbing nutrients. Understanding their physical characteristics offers insight into their complex role. These tubular structures are organized to maximize efficiency in a confined space.
Overall Appearance and Role
The intestines are soft, tubular structures with a pinkish-red coloration in a living body. This color comes from the rich blood supply needed for their metabolic activity. They form a long, coiled pathway that extends through the abdominal cavity, acting as a continuous channel for the movement of digested material. This pathway is a primary component of the digestive tract, facilitating breakdown and absorption.
The Small Intestine’s Form
Despite its name, the small intestine is the longest section of the digestive tube, typically measuring between 10 to 16 feet (3 to 5 meters) in a living person. Its “small” designation refers to its narrower diameter, which is approximately 1 inch (2.5 to 3 centimeters) across.
This organ is highly convoluted and tightly coiled, allowing its length to fit within the abdomen. The small intestine is divided into three distinct segments: the duodenum, jejunum, and ileum. The duodenum, an initial C-shaped section, measures 8 to 10 inches (20 to 25 centimeters) and wraps around the pancreas. The jejunum extends for about 8 feet (2.5 meters), followed by the ileum, which is about 9.8 feet (3 meters) long. Its inner surface features circular folds, microscopic finger-like projections called villi, and even smaller microvilli, all of which dramatically increase its surface area for absorption.
The Large Intestine’s Form
In contrast to the small intestine, the large intestine is shorter but wider. It measures about 5 feet (1.5 meters) long and has a diameter of 3 inches (7.6 to 8 centimeters). This broader tube forms a distinctive frame-like shape that encircles the coiled small intestine within the abdominal cavity.
The large intestine comprises several segments:
- The cecum
- The colon (including ascending, transverse, descending, and sigmoid colon)
- The rectum
- The anal canal
The colon features sacculations, or pouches, called haustra. These haustra give the large intestine a segmented or “baggy” appearance, formed by the contraction of three longitudinal muscle bands called taenia coli.
Fitting Inside the Body
The lengths of both the small and large intestines are packed within the abdominal cavity. The tightly coiled small intestine typically occupies the central region, while the large intestine forms a perimeter around it. Their inherent flexibility allows these organs to fold and bend, enabling their compact arrangement within the limited space. This organized placement is maintained by the mesentery, a continuous fold of tissue that anchors the intestines to the back wall of the abdomen. The mesentery holds the intestines in position and contains blood vessels, nerves, and lymphatic tissue that supply these digestive organs.