Changes

==Follicles==

==Follicles==

<p>Lymph nodes have two types of follicles primary and secondary. Secondary follicles contain germinal centres (sites of B-cell proliferation) and have three layers.  

<p>Lymph nodes have two types of follicles, primary and secondary. Secondary follicles contain germinal centres (sites of B-cell proliferation) and have three layers.  

*The central dark zone contains a high density of dividing centroblasts, [[Lymphocytes - WikiBlood#B cells|B cells]] without surface Ig. These centroblasts migrate to the Basal light zone.

*The central dark zone contains a high density of dividing centroblasts, [[Lymphocytes - WikiBlood#B cells|B cells]] without surface Ig. These centroblasts migrate to the Basal light zone.

*In the basal light zone the [[Lymphocytes - WikiBlood#B cells|B cells]] express surface Ig and become exposed to the follicular dendritic cells.

*In the basal light zone the [[Lymphocytes - WikiBlood#B cells|B cells]] express surface Ig and become exposed to the follicular dendritic cells.

*Apical light zone (mantle zone) which contains cells which are destined to become B memory (lymphoblasts) or plasma cells (plasmablasts). </p>

*Apical light zone (mantle zone) which contains cells which are destined to become B memory (lymphoblasts) or plasma cells (plasmablasts). </p>

<p>Follicles in the cortex of a stimulated node are larger and have a pale germinal centre. Activated [[Lymphocytes - WikiBlood#B cells|B cells]] differentiate into plasma and memory cells and plasma cells migrate migrate to the medullary cords and produce immunoglobulins.</p>

<p>Follicles in the cortex of a stimulated node are larger and have a pale germinal centre. Activated [[Lymphocytes - WikiBlood#B cells|B cells]] differentiate into plasma and memory cells and plasma cells migrate migrate to the medullary cords and produce immunoglobulins.</p>

==High endothelial venules==

==High endothelial venules==

<p> High endothelial venules (HEV)are composed of cuboidal/columnar epithelium and are the major route for lymphocytes to enter the node. HEV contain a large number of aquaporin-1 channels allowing for a large uptake of water which in turn drives lymph flow through the cortex, this fluid is returned direct to the bloodstream. The venules are the source of most of the nodes [[Lymphocytes - WikiBlood#T cells|T cells]] and [[Lymphocytes - WikiBlood#B cells|B cells]] and express selectins (receptors for lymphocytes primed with antigens).</p>

<p> High endothelial venules (HEV)are composed of cuboidal/columnar epithelium and are the major route for lymphocytes to enter the node. HEV contain a large number of aquaporin-1 channels allowing for a large uptake of water which in turn drives lymph flow through the cortex, this fluid is returned direct to the bloodstream. The venules are the source of most of the nodes [[Lymphocytes - WikiBlood#T cells|T cells]] and [[Lymphocytes - WikiBlood#B cells|B cells]] and express selectins (receptors for lymphocytes primed with antigens).</p>