title: Presence of a complete endothelial barrier between lymph and lymphoid tissue in the lumbar lymph nodes of the duck (Anas platyrhynchos).
abstract: The ultrastructure of the lumbar lymph nodes of the domestic duck is described and compared with published accounts of mammalian lymph nodes. The barrier to cell migration between lymphoid tissue and lymph is more formidable in the duck than in the mammal. In the duck the lymphatic endothelium lining the lymph spaces is continuous and bonded with desmosomes whereas in the mammal it is unbonded and fenestrated. In both types of node there are filtering zones and areas of dense lymphatic tissue but their topographical organisation differs. There is no cortex or medulla in the duck lymph node and filtration occurs in extensive lymphatic spaces traversed by numerous trabeculae to which are attached rounded phagocytic macrophages. Dense lymphoid tissue is scattered throughout the node, suspended by trabeculae or attached to the capsule and there are blood vessels analogous to the post capillary venules of mammalian nodes where lymphocytes migrate between blood and lymphoid tissue.
mesh_terms: D000818:Animals; D004372:Ducks / Q000033:anatomy & histology*; D004727:Endothelium / Q000502:physiology; D008196:Lymph / Q000502:physiology; D008198:Lymph Nodes / Q000648:ultrastructure*; D008208:Lymphatic System / Q000502:physiology*; D008322:Mammals / Q000033:anatomy & histology