Villi structures

The surface area in the luminal side of the small intestine per unit length of the serosal (blood) side is enormous in the proximal jejunum, and steadily decreases (to about 20% of the starting value [62]) in the distal portions of the small intestine. The surface area is increased threefold [69] by ridges oriented circumferentially around the lumen. Similar folds are found in all segments of the GIT, except the mouth and esophagus [66]. Further 4—10-fold expansion [62,69] of the surface is produced by the villi structures, shown schematically in Fig. 2.4. The layer of epithelial cells lining the villi structures separate the lumen from the circulatory system. Epithelial cells are made in the crypt folds of the villi, and take about... 

The presence of folds and villi structures on the surface area is not taken into account for the in vivo effective intestinal membrane permeability (Pefr when extrapolated from a perfusion experiment, a smooth tube is usually assumed). In humans, the fold expansion (FE) of the surface area is about threefold, and villi expansion (VE) is about 10-fold [7]. In the case of high epithelial membrane permeability (Pep) absorption occurs at the top of the villi before diffusing down the villi channels, whereas low Pep compound may diffuse down the villi channels to the crypts (Figure 6.1). Therefore, accessibility (Acc) to the surface depends on Pep and diffusion coefficient [7, 8]. The effective membrane permeability can be expressed as ... 

Celiac disease is a genetically dependent disease. In people who are genetically predisposed, the consumption of cereal products containing gluten leads to atrophy of villi structure with compensational crypts hyperplasia and massive lymphocytic infiltration around the lamina propria of the mucosa. The consecutive introduction of gluten into the diet results in the recurrence of histopathological changes (Kaukinen et al., 2002). 

Ciypt and Villus Structures of the Mucosa of the Small Intestine... 

Inclusion of SDP in the diet improves food intake and food conversion efficiency over a wide range of pig types and environments, but it is particularly effective in situations where there is a high level of exposure to pathogens. SDP is a palatable ingredient and by promoting food intake at weaning it helps to maintain villus structure and function and hence efficient digestion and absorption of nutrients. As a source of nutrients, there is no difference between porcine and bovine sources of plasma. 

Martial MA, Carlson SL, and Madara JL [1987] Partitioning of paracellular conductance along the ileal crypt-villus axis a hypothesis based on structural analysis with detailed consideration of tight junction-structure function relationships. J Membr Biol 80 59-70... 

Figure 4.4 Diagram of the structure of a villus. Most of the absorbed materials enter the blood vessel, but chylomicrons enter the lymph in the lacteals.

FIGURE 2.50 Cr) ts and villus. Left) A normal crypt and villus. Two crypts are shown on either side of the villus. Malabsorptive diseases may involve degeneration of the villi. (Center) A short villus. (Right) Complete disappearance of a villus. The disease may involve an enlargement of the crypts, which is shown. The figure does not show the lacteal and other structures of the villus. (Redrawn with permission from Riecken, 1988.)... 

On the other hand, the Golgi apparatus is implicated in the synthesis of cell-wall membranes. It is possible that the alkaline phosphatase is a catalytically inactive, structural protein of such cell membranes when they are still in the cytoplasm, which may explain many failures to demonstrate its presence in the Golgi apparatus. Upon becoming part of the outer surface, say of the brush border of the intestinal villus, the enzyme may be activated by the alkaline contents of the duodenal lumen. The concept of catalytically inactive membrane enzyme proteins is developed in a recent publication with regard to 8-glucuronidase (FIO). 

Figure 2 The structure of the absorptive cell of the intestinal lining reflects its specialized function in digestion. The absorptive cell is one of the two main cell types that constitute the epithelium of the villus. The other type is the goblet cell, which secretes mucus. Cells of both types are produced by cell division in the crypts and assume their mature structure during a 2-day migration to the villus tip. Exposed in transit to the action of digestive fluids, some of the membrane covering the absorptive cell may be sloughed off. The cell is abundantly supplied with mitochondria, which provide energy for metabolic...

Brief mention is made of placental transmogrification of the lung. It occurs in association with lipomatosis and bullous emphysema and is composed of placental villus-like structures in the lung parenchyma. The epithelium surfacing the placentoid structures shows immunostaining for TTF-1 in most cases. The stromal cells express vimentin and are non-reactive for TTF-1. Mast cells are common in the stromal tissue. 

C-BRUSH VEIN BORDER ARTERY B-STRUCTURE OF VILLUS... 

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