LOCATION:
In chains or groups. Adapted for filtering
the lymph. Drain specific regions via afferent lymph
vessels and are connected to larger lymph vessels via efferent
lymph vessels. From the the lower extremities and abdominal organs
lymph drains into the Cisterna chyli, then into the
left thoracic duct which also collects lymph from the
left arm. The thoracic duct lymph finally enters the venous system at
the junction of the internal jugular and subclavian
veins. On the right, the Right lymphatic duct drains
the right arm, shoulder, thoracic wall and head and neck regions;
2. ORGANIZATION:
More advanced organization than, in previous groups: A bean-shaped organ
(1-25 mm); Capsule; Ttrabeculae; Cortex; Medulla; Lymph sinuses;
Highly organized system of capillaries; of vasomotor
nerves;
3. STROMA:
Reticular C.T. of reticular cells and reticular fibers
(of mesodermal origin). Fibers are continuous between reticular meshwork
and trabeculae. A narrow band-like reticular lamina supports the walls
of sinuses (No basement membrane);
4. PARENCHYMA:
Cortex of small lymphocytes with lymphoid nodules
supported by the reticular CT framework. Nodules may have germinal centers
with larger lymphocytes. Medulla contains a sponge-work
of medullary cords surrounded by medullary
sinuses. The cords contain lymphocytes, plasma cells and/or
granulocytes. Medullary sinuses contain reticular cells,
macrophages and may contain other leukocytes.
5. DIAGNOSTIC FEATURES:
Cortex and medullary cords ( Fig. 1).