| Lab 20 Small & Large Intestines: 1) Index 2) Things to Identify 3) Duodenum 4)Jejunum 5) Ileum 6) Appendix 7) Colon 8) Rectum 9) Rectal Anal Junction 10) Anus 11)Comparison of Structures 12)Practical |
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Jejunum
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# 119 - Jejunum, monkey, h-e, 1.5mm # 118 - Jejunum, monkey, h - e If needed, # 215 - Duodenum , jejunum, and ileum combination, c.s. |
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The jejunum is characterized by extensive plical folds from which rise tall, slender villi. The epithelium has the same columnar absorptive epithelium (check for the striated border) and goblet cells as found in the duodenum, but goblet cells are more numerous in the jejunum. You will not see submucosal glands, since Brunner's glands are found only in the duodenum. Observe the vascularity of the lamina propria and submucosa. Identify lacteals, lymphatic channels filled with pink-stained lymph that are found in the lamina propria core of these villi. You may see slips of smooth muscle running up into the villi from the muscularis mucosae layer. This allow movement of the villi which then enhances absorption. Slide 119 nicely demonstrates Paneth cells in the bases of these glands. What is their function of these cells and their red-staining granules? You may be able to identify the clear staining (with H&E) enteroendocrine cells in the base of the intestinal glands based on their apical nuclear position (near lumen rather than base of cell). They contain very fine cytoplasmic secretory granules whose release is directed towards the lamina propria. There may be lymphocytic infiltrates or an occasional lymphatic nodule present in some areas of the lamina propria. Try to identify the large parasympathetic ganglion cells of the myenteric plexus (Auerbach's plexus) which lie between the inner circular and the outer longitudinal layer of the muscularis externa. You may be able to identify the parasympathetic ganglion cells of the submucosal plexus of Meissner which are found in the submucosa, but these are not easy to find. If not, check Gartner to see an example of Meissner's plexus. Characterize the serosa. Compare the appearance of the jejunum with the duodenum (slide 115 and 116. REFERENCES: Gartner, p. 289 Fig. 1 - 4 Ross, pp. 459, 486 - 487 DiFiore, p. 199, Fig. 13-2 - 13-3 Wheater, p. 261 |
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This is a low power image of the second and longest part of the small intestines, the Jejunum. It is characterized it's very extensive and long Plicae circulares, which are indicated by the blue arrows. Notice how long they are. They are also characterized as having long and slender Villi indicated by the red arrows. While the black arrows are pointing to some of the many Crypt's of Lieberkuhn. Blue arrows - Plicae Circulares Red arrows - Villi Black arrows - Crypts of Lieberkuhn
Here is a another look at the Villi (blue arrows) of the Jejunum. Notice how long they are, which is a characteristic of the jejunum. The black arrows are pointing to Goblet cells, and at this magnification you can see how there numbers have increased since the duodenum and are more obvious. The red arrows are pointing to special lymphatic structures called Lacteals. These are specialized lymphatics found with in the villi which function to absorb FAT. Blue arrows - Long Villi Black arrows - Goblet cells Red arrows - Lacteals
This is a closer look at the villi. Again note the increase presence of Goblet cells (blue arrows) among the absorptive Enterocytes. You also get a closer look at a Lacteal, which the red arrow is pointing out. Blue arrows - Goblet cells Red arrow - Lacteal
This is a view at the base of the villi showing some of the Crypts of Lieberkuhn, indicated by the red arrows. The blue arrows are pointing to cells which stain lighter than the rest of the cells around them which make them stand out, these are the Enteroendocrine cells (APUD cells). Do you remember what there function was? The black arrow is pointing to a cell type with RED STAINING GRANULES, which are the Paneth cells. Do you remember the function of these cells? Blue arrows - Enteroendocrine cells Red arrows - Crypts of Lieberkuhn Black arrow - Paneth Cell
This is a high magnification shot of Paneth Cells indicated by the blue arrows. Here you get a good look at the Red granules containing the bacteriocidal lysozymes which function to kill of any unwanted bacteria. Blue arrows - Paneth Cells
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Jejunum
Jejunum Villi
Goblet cells & lacteal (jejunum)
Crypts of Lieberkuhn (jejunum)
Paneth Cells |
