Lymphatic system model 0142-00

small intestinefor teaching

Magnified hundreds of times, three of the more than 5 million villi that line the small intestine are replicated in this vinyl model depicting their essential role in digestion and nutrient absorption. The Denoyer-Geppert Intestinal Villi model accurately represents three of the five million villi that line the walls of the 27-foot small intestine in humans. Villi exist to increase the surface area available for food absorption; this area has been estimated at approximately eleven square yards. Also, under some conditions, food may pass through the small intestine rapidly; the villi make the most of the time that the digested material is in contact with the intestine. The intestinal villi (1) project from the surface of the mucous membrane over the folds and between them. They have cores of lamina propria (8), which is composed of loose connective tissue. Each villus contains a vascular capillary network (3), a central lacteal (7), and nerve fibers. Lymphatic tissue abounds in the lamina propria and may appear as solitary nodules or in groups of nodules called Peyer’s patches. The flow of lymph is controlled by valves so it can pass out of the intestine only. This lymphatic system makes up one of the two important routes that absorbed particles travel to enter the blood stream. The second consists of the vascular system; here, one arteriole (5) enters each villus splitting into capillaries and is collected by venules (4). The crypts of Lieberkühn (6) open between the villi. They produce enzymes, mucus and possibly a hormone. There are goblet cells (21) in the crypts among the columnar epithelium (20).