Parts of the Small Intestine

The small intestine, shown in figures 17.33 and 17.34 and in reference plates 51, 58, 74, and 75, consists of three portions: the duodenum, the jejunum, and the ileum.

The duodenum, which is about 25 centimeters long and 5 centimeters in diameter, lies posterior to the parietal peritoneum (retroperitoneal). It is the shortest and most fixed portion of the small intestine. The duodenum follows a C-shaped path as it passes anterior to the right kidney and the upper three lumbar vertebrae.

The remainder of the small intestine is mobile and lies free in the peritoneal cavity. The proximal two-fifths of this portion is the jejunum, and the remainder is the

Gallbladder

Small Intestine Hormones

Figure 17.32

Fatty chyme entering the duodenum stimulates the gallbladder to release bile.

1. Chyme with fat enters small intestine

2. Cells of intestinal mucosa secrete the hormone cholecystokinin (CCK) into the bloodstream

Figure 17.32

Fatty chyme entering the duodenum stimulates the gallbladder to release bile.

¡»■111 Hormones of

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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