| 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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Colon (Large Intestines) |
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# 123 - Colon, monkey, c.s., h - e # 124 - Colon, human, l.s., h - e (If needed, # 216 - Colon, c. s., h - e) |
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Although the same four layers of the wall exist here as elsewhere in the alimentary canal, there are no plicae circulares or villi present in the large intestine. The submucosal folds of the large intestine are semicircular in shape and are known as plicae semilunaris. The colon mucosa is thicker than that of the small intestine, and its crypts of Lieberkuhn are longer. The lumen of the intestinal gland is wider in this region of the intestine. Paneth cells are rarely seen in the glands of the normal large intestine. Compare the number of goblet cells at this level with those found elsewhere in the intestine. Look for mitotic figures in the epithelial tissue. Locate neuronal cells of the submucosal plexuses. Are taenia coli found in either of these specimens? What is the taenia coli? Lymphatic nodules are often present in colonic mucosa, as are eosinophils and plasma cells. REFERENCES: Gartner, p. 291, Figs. 1 - 2 Ross, pp. 466, 490 - 491 DiFiore, p. 203 - 205, Fig. 13.6 - 13-7 Wheater, p. 268, Fig. 14.28 - 14.29 |
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This is an image taken from the Colon. The red arrows are pointing to the thick Mucosa present in the colon. The blue arrow is pointing to the Submucosa, while the green arrow is pointing to the Muscularis externa. Beyond that the black arrow is pointing to a cross section of one of the three Taenia Coli, which are three straps of muscle that run parallel to each other, and run the whole length of the Large intestines to aide in mobility. Red arrow - Mucosa Blue arrow - Submucosa Green arrow - Muscularis Externa Black arrow - Taenia coli
Some important identification characteristics of the colon are, 1) the mucosal surface is very flat as seen in this image. There are NO VILLI PRESENT in the colon. 2) Is a very thick mucosa, lined with many GOBLET CELLS. By the time the digested food gets to the large intestine it is very dry and rough, so the need for goblet cell secretions is high, and that is why there are so many goblet cells. 3) Is the presence of many "circular profiles" (blue arrows), due to the presence of long crypt's of Lieberkuhn. These are a give away that you are in the colon. Blue arrows - Circular Profiles of Crypts
This is a high power image of the epithelium of the colon. Remember that the majority of the cells in the epithelium now are Goblet Cells, (red arrows) because of the need of the lubrication of the food passing through the colon. Red arrows - Goblet Cells |
Colon (taenia coli)
Colon
Colon Epithelium |
