Anatomic Considerations

The mesentery (Fig. 14-1) suspends the jejunum and ileum from the posterior abdominal wall. It is composed of fatty extraperitoneal connective tissue, blood vessels, nerves, lymphatics, and an investment of peritoneum that reflects from the posterior parietal peritoneum. Features associated with the fan-shaped dimensions of the mesentery make it a unique suspensory ligament and contribute to the characteristic nature of small bowel loops.

The attached border, the root of the mesentery, extends obliquely from the point of termination of the duodenum, at the lower border of the pancreas on the left side of the second lumbar vertebra, to the cecum in the right iliac fossa near the right sacroiliac articulation. In that course, the line of attachment passes from the duode-nojejunal flexure down over the front of the third part of the duodenum, then obliquely across the aorta, the inferior vena cava, the right ureter, and the psoas major

Mesenteric Root Attachment

Fig. 14—1. The small bowel mesentery.

It extends from its line of attachment, or root, in a series of fanlike ruffles to suspend the jejunum and ileum. The undulating course of its intestinal edge constitutes a series of convexities and concavities. Peritoneal recesses extend between the mesenteric reflections. (Reproduced from Meyers.1)

Fig. 14—1. The small bowel mesentery.

It extends from its line of attachment, or root, in a series of fanlike ruffles to suspend the jejunum and ileum. The undulating course of its intestinal edge constitutes a series of convexities and concavities. Peritoneal recesses extend between the mesenteric reflections. (Reproduced from Meyers.1)

muscle, to the right iliac region. From the root, the mesentery extends in a series offanlike ruffles to suspend the jejunum and ileum. There are usually six main folds, from the margins of which secondary folds project in all directions, and from those again even a third series may be formed. A series of peritoneal recesses are formed between the ruffles of the small bowel mesentery. The root of the mesentery is only about 15 cm (6 in.) long and is fixed in position. It is much thicker than the part near the gut, since it contains between its layers a considerable amount of fatty fibroareolar extraperitoneal tissue and the large vascular trunks that supply the intestine (Fig. 14-2).

The base, or unattached border, of the mesentery is frilled out to an enormous degree so that, while the root measures only 6-7 in., the free border is extended to 20-22 ft (Fig. 14-3). The great length of the intestinal border is produced by plication of the mesentery along its edge for a depth of from 6-8 cm (2^-3^ in.).

The length ofthe mesentery (Fig. 14-3), measured from its root to the attached edge of the intestine directly opposite, is usually 20-22 cm (8-9 in.). It is greater at that part that suspends the coils of the intestine lying between 2 and 3 m (6 and 11 ft) from the duodenum, where it may reach a length of 25 cm (10 in.). It tends to increase in length as age advances.

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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