Lamina propria, components

The lamina propria constitutes a continuous sheet of connective tissue containing collagen, elastic fibres and cellular components in a hydrated ground substance. It also carries blood capillaries and nerve fibres that serve the mucosa. It is through the blood vessels in the lamina propria that drag moieties can gain entry to the systemic circulation. 

The epithelium is supported underneath by lamina propria and a layer of smooth muscle called muscularis mucosa (3-10 cells thick). These three layers, i.e., the epithelium, lamina propria, and muscularis mucosa, together constitute the intestinal mucosa.On the apical surface, the epithelium along with lamina propria projects to form villi. The cell membranes of epithelial cells that comprise the villi contain uniform microvilli, which give the cells a fuzzy border, collectively called a brush border. These structures, although greatly increase the absorptive surface area of the small intestine, provide an additional enzymatic barrier since the intestinal digestive enzymes are contained in the brush border. In addition, on the top of the epithelial layer lies another layer, the UWL, as previously described. The metabolic and biochemical components of the epithelial barrier will be discussed. 

Morphological studies have demonstrated the presence of cells in the GI tract that contain dopamine and express components of dopamine signaling pathways, including catecholamine biosynthetic enzymes and specific dopamine receptors and transporters. In tlie stomach, tyrosine hydroxylase is expressed in epithelial cells, including acid-secreting parietal cells. In the small intestine, cells of the lamina propria, including immune cells, also express tyro-... 

Smooth muscle is separated from the epithelium by the lamina propria, a region of connective tissue containing nerves and blood vessels. In the trachea, the smooth muscle connects the open ends of the incomplete cartilage rings and therefore constitutes only a fraction of the circumference of this component of the airways. Further down the pulmonary tree, through the bronchi and bronchioles,... 

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