| Lab 12 Immune System: 1) Index 2) Introduction 3) Things to Identify 4) Diffuse Lymphoid Tissue 5)Solitary and Aggregated Lymphoid Nodules 6) Tonsils 7) Lymph Node 8) Spleen 9) Thymus 10)Comparison 11) Practical |
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Solitary
and Aggregated Lymphoid Nodules
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# 117 - Peyer's patches, ileum, monkey, c.s., H & E # 120 - Appendix, human, c.s., H & E # 123 - Colon, monkey, c. s., monkey, H & E If needed, # 124 - Colon, human, l. s., H & E |
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Lymphoid nodules are lymphoid structures common along the gastrointestinal tract, reaching their highest development in the appendix and ileum. Lymphoid nodules and lymphocytic infiltrations commonly occur together in the lamina propria and may merge imperceptibly into each other in many areas. The nodule may appear as a homogenous mass of lymphocytes (primary nodule) or may be a secondary nodule with a germinal center containing large pale cells surrounded by a dense cortex of small lymphocytes (forming a dark corona or mantle). Observe both solitary nodules and the larger and more extensive aggregated nodules (Peyer's patches). In what type of nodule are germinal centers present? On slide 120, view the nodules first with medium power and identify the large reticular cells lying in the open spaces among the lymphocytes. Compare the pale staining and larger size of the reticular cell nuclei to that of the adjacent lymphocytes. References: Gartner, p. 180 - 181, Fig. 3 (lymphatic nodule in lymph node) Ross, p. 341 (lymphatic nodule) and p. 342 (Peyer's patches) Wheater, p. 213, Fig. 11.20a (ileum) p. 213, Fig. 11.20b (colon) p. 214, Fig. 11.21 (appendix) p. 270, Fig. 14.31 (appendix) DiFiore, p. 199, (jejunum - ileum) p. 201, Fig. 13-4 (ileum) p. 203. Fig. 13-6 p. 205, Fig 13-7(colon) p. 207, Fig. 13-8 (appendix) |
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This is an image taken from the Duodenum. It is there where prominent lymphatic nodules can be found known as Peyer's Pacthes. Both colored dotted lines are outlining just a few of the Lymph nodules located there. The blue dotted lines are outlining Primary Lymph Nodules. These represent lymphocytes that haven't encountered antigen yet. The red dotted line is outlining a Secondary Nodule. In a secondary nodule the lymphocytes have encountered antigen and are rapidly dividing. This rapid division is taking place with in the Germinal Center, shown by the red arrows. This is what determines the difference between a primary and a secondary nodule. If there is a germinal center present it is a secondary nodule, if not than it is a primary nodule. Blue dotted line - Primary Lymph Nodule Red dotted line - Secondary Lymph Nodule Red arrow - Germinal Center of Secondary Nodule
This is a closer image of a Secondary Lymph Nodule (white dotted lines) taken from Peyer's Patches in the duodenum. Here you can see the two part of the Secondary Nodule. First is the Corona or Mantle, shown by the yellow arrows. Can you see it has a darker staining pattern than the Germinal Center, which is lighter, indicated by the red arrows. White dotted line - Secondary Lymph Nodule Red arrows - Germinal Center Yellow arrows - Corona or Mantle
This is another Image of a Secondary Lymph Nodule. Be careful when looking for these structures because they are very easily missed. The blue arrows are pointing to the Corona of the secondary nodule while the white arrow is pointing to the Germinal Center. Blue arrow - Carona or Mantle White arrow - Germinal Center |
Duodenum (Peyer's Patches)
Secondary Nodule
Secondary Lymph Nodule |
