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b.
Blood vessels:
Most of the blood enters the lymph node via:
(1) Arteries
in the hilus, branches of these run within
the trabeculae;
(2) Smaller branches continue in the medullary cords and after
reaching the cortex form
(3) a capillary plexus around lymphoid nodules;
(4) Post capillary venules with "cuboidal" endothelium
arise from the plexus [These tall endothelial venules
are permeable to lymphocytes from the blood. This is the only
place where lymphocytes can leave the blood ( by diapedesis)
to migrate to the cortex.] and give rise to:
(5) venules with normal (flattened) endothelium,
which are tributary to larger veins leaving the node at the
hilus. (See Fig. 1.).
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LABORATORY
EXERCISE:
Virtual Slide 35. Lymph
node - This slide is stained with H&E. You
should be able to locate all of the features of a typical
lymph node from this sections. As usual, you should use your
syllabus for information on the morphology. Identify and study
the capsule, trabeculae,
stroma, subcapsular (marginal) sinus,
trabecular or intermediate sinus, cortex,
secondary lymphoid nodules, paracortex,
medullary cords and sinuses.
Find the lymphoid nodules in the cortex. Identify germinal
centers. Identify the mantle or crown.
Identify reticular cells forming the stroma and those spanning
sinuses! Identify, small lymphocytes, plasma cells,
granulocytes, and macrophages in the medullary cords and sinuses!
Also use your Digital Histology CD. |
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