Gastrointestinal Nursing.pdf

60 Chapter 5Figure 5.1(1996).Structure of the villus. Reproduced with permission from Hinchliff et al.of the small intestine is known as the brush border. The presence of the mucosalfolds, the villi and the microvilli increases the surface area and therefore theabsorptive capacity of the small bowel by approximately five hundredfold.The mucosa of the small intestine is simple columnar epithelium. Four majorcell types are present:• Absorptive cells, which produce digestive enzymes and absorb nutrientsfrom digested food.• Goblet cells, which produce protective mucus that lubricates the surfaceand protects it from mechanical damage.• Granular cells, which protect the intestinal epithelium from bacteria.• Endocrine cells, which produce peptide hormones that regulate secretionand motility in the gastrointestinal tract, liver and pancreas.Two types of gland are present in the duodenum. At the base of the villi aretubular invaginations that reach almost to the muscularis layer; these are knownas the intestinal crypts or crypts of Lieberkuhn. The submucosa of the duodenumcontains coiled compound tubular mucous glands, known as the glandsof Brunner, which secrete an alkaline fluid rich in mucus. These are morenumerous in the proximal region of the duodenum.