Changes

===General===

===General===

<p>Grossly the lymph nodes are round or bean shaped and have an outer cortex and an inner medulla. Microscopically the nodes have a follicles, paracortical zones and medullary cords and sinuses. At the hilum the medulla is present on the outer part of the node. Lymph nodes are located in series with [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] and afferent vessels enter the node on its convex side and efferent vessels exit on its concave side.</p>

<p>Grossly the lymph nodes are round or bean shaped and have an outer cortex and an inner medulla. Microscopically the nodes have a follicles, paracortical zones and medullary cords and sinuses. At the hilum the medulla is present on the outer part of the node. Lymph nodes are located in series with [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] and afferent vessels enter the node on its convex side and efferent vessels exit on its concave side.</p>

====Capsule and reticular framework====

===Capsule and reticular framework===

<p> The nodes are surrounded in a fibrous capsule that extends into the node as trabeculae, which provide an overall framework. Below the capsule is the sub-capsular sinus. The nodes parenchyma contain a fine network of reticular fibres and reticular cells. Reticular cells provide "scaffolding" for other cells as well as expressing surface complexes and substance to attract T,B and dendritic cells.  

<p> The nodes are surrounded in a fibrous capsule that extends into the node as trabeculae, which provide an overall framework. Below the capsule is the sub-capsular sinus. The nodes parenchyma contain a fine network of reticular fibres and reticular cells. Reticular cells provide "scaffolding" for other cells as well as expressing surface complexes and substance to attract T,B and dendritic cells.  

The cortex has aggregations of B cells (follicles) in its outer region and a paracortex consisting of a rim of T cells surrounding these follicles. Dendritic cells are also found in close association with the T cells.  The medulla contains medullary cords of cells (B cells, plasma cells and some macrophages) and between these cords is the medullary sinus lined with endothelial cells and macrophages.</p>

The cortex has aggregations of B cells (follicles) in its outer region and a paracortex consisting of a rim of T cells surrounding these follicles. Dendritic cells are also found in close association with the T cells.  The medulla contains medullary cords of cells (B cells, plasma cells and some macrophages) and between these cords is the medullary sinus lined with endothelial cells and macrophages.</p>

====Sinuses====

===Sinuses===

<p>Three sinuses are present:

<p>Three sinuses are present:

*Subcapsular/cortical

*Subcapsular/cortical

*Medullary

*Medullary

Antigens and transformed cells that pass through the sinuses are filtered by macrophages and removed from the lymph.</p>

Antigens and transformed cells that pass through the sinuses are filtered by macrophages and removed from the lymph.</p>

====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, B cells without surface Ig. These centroblasts migrate to the Basal light zone.

*The central dark zone contains a high density of dividing centroblasts, B cells without surface Ig. These centroblasts migrate to the Basal light zone.

*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 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 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 T and 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 T and B cells and express selectins (receptors for lymphocytes primed with antigens).</p>

===Pig Lymph Node===

==Pig Lymph Node==

''As well as dolphins, hippopotamuses and rhinoceroses''

''As well as dolphins, hippopotamuses and rhinoceroses''

<p> The structure of the pig lymph node is inverted compared with that of most mammals.

<p> The structure of the pig lymph node is inverted compared with that of most mammals.

** Connect with para-trabecular sinuses and exit from efferent lymphatics on the node surface.

** Connect with para-trabecular sinuses and exit from efferent lymphatics on the node surface.

* Blood vessels enter and leave at the hilus</p>

* Blood vessels enter and leave at the hilus</p>

===Histology===

==Histology==

<gallery perrow="4" >

<gallery perrow="4" >

Image:LH Lymph Node Gross Histology.jpg|<p>'''Gross view'''</p>^{©Nottingham Uni 2008}

Image:LH Lymph Node Gross Histology.jpg|<p>'''Gross view'''</p>^{©Nottingham Uni 2008}