<p>[[High Endothelial Venules|High endothelial venules (HEV)]] facilitate lymphocyte access to the [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] from the bloodstream. Once inside the lymph node, the naive lymphocytes search for antigens. If there are no antigens present, the naive lymphocytes leave via the efferent lymphatic vessel and return back to the bloodstream. Each lymphocyte can search several [[:Category:Secondary Lymphoid Tissue|secondary lymphoid organs]] each day. This process is called '''surveillance'''.</P> | <p>[[High Endothelial Venules|High endothelial venules (HEV)]] facilitate lymphocyte access to the [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] from the bloodstream. Once inside the lymph node, the naive lymphocytes search for antigens. If there are no antigens present, the naive lymphocytes leave via the efferent lymphatic vessel and return back to the bloodstream. Each lymphocyte can search several [[:Category:Secondary Lymphoid Tissue|secondary lymphoid organs]] each day. This process is called '''surveillance'''.</P> |