Changes

[[Image:Lymph Node positions.jpg|thumb|right|250px|Positions of the lymph nodes (dog) - Copyright B.Catchpole RVC]]

[[Image:Aspinall Slide11.JPG|thumb|right|250px|<small>Image from [http://www.elsevierhealth.co.uk/veterinary-nursing/spe-60136/ Aspinall, The Complete Textbook of Veterinary Nursing], Elsevier Health Sciences, ''All rights reserved''</small>]]

[[Image:Lymph Node positions.jpg|thumb|right|150px|Positions of the lymph nodes (dog) - Copyright B.Catchpole RVC]]

==Introduction==

==Introduction==

''For haemolymph nodes click [[Haemolymph Nodes - Anatomy & Physiology|here]]''

''For haemolymph nodes click [[Haemolymph Nodes - Anatomy & Physiology|here]]''

[[Image:LH Lymph Node Diagram.jpg|thumb|150px|right|<p>'''Diagram'''</p>]]

[[Image:LH Lymph Node Diagram.jpg|thumb|250px|right|<p>'''Diagram'''</p>]]

<p>Part of the [[Lymphatic System - Anatomy & Physiology|lymphatic system]], the body contains hundreds of lymph nodes of varying size (1-20mm) and these are located along the routes of [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]]. They are found throughout the body but are more concentrated in the axilla, groin and mesenteries. Lymph nodes act as a filter for the lymph removing antigens and releasing immune-competent cells and immunoglobulins.</p>

<p>Part of the [[Lymphatic System Overview - Anatomy & Physiology|lymphatic system]], the body contains hundreds of lymph nodes of varying size (1-20mm) and these are located along the routes of [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]]. They are found throughout the body but are more concentrated in the axilla, groin and mesenteries. Lymph nodes act as a filter for the lymph removing antigens and releasing immune-competent cells and immunoglobulins.</p>

==Development==

==Development==

<p>Lymph nodes develop from lateral plate mesoderm in paired sacs from [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]]. These sacs undergo remodelling, and endothelial and mesenchymal outgrowths form the meshwork of channels and spaces that produces the cortex-medulla structure. Lymphocytes then populate the cortex and medulla. The subcapular sinus is a remainder of the [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessel]].</p>

<p>Lymph nodes develop from lateral plate mesoderm in paired sacs from [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]]. These sacs undergo remodelling, and endothelial and mesenchymal outgrowths form the meshwork of channels and spaces that produces the cortex-medulla structure. Lymphocytes then populate the cortex and medulla. The subcapular sinus is a remainder of the [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessel]].</p>

==Structure==

==Structure==

[[Image:LH_Lymph_Node_Follicles_Histology.jpg|thumb|150px|right|<p>'''Primary & secondary follicles'''</p>^{©Nottingham Uni 2008}]]

[[Image:LH_Lymph_Node_Follicle_Histology.jpg|thumb|150px|right|<p>'''Secondary Follicle'''</p>^{©RVC 2008}]]

[[Image:LH_Lymph_Node_Follicles_Histology.jpg|thumb|250px|right|<p>'''Primary & secondary follicles'''</p>^{©Nottingham Uni 2008}]]

[[Image:LH_Lymph_Node_Follicle_Histology.jpg|thumb|250px|right|<p>'''Secondary Follicle'''</p>^{©RVC 2008}]]

===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 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]]. 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 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]]. Afferent vessels enter the node on its convex side and efferent vessels exit on its concave side.</p>

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

==[[High Endothelial Venules]]==

==High Endothelial Venules==

[[High Endothelial Venules|High endothelial venules (HEV)]] are composed of cuboidal/columnar epithelium and are the major route for lymphocytes to enter the lymph 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 then returned directly to the bloodstream. The venules are the source of most of the node's [[:Category:Lymphocytes|T cells and B cells]] and express selectins (receptors for lymphocytes primed with antigens).

HEV express CD34 and GlyCAM-1 which bind to L-selectin on naive lymphocytes. This allows circulating lymphocytes to recognise when they have reached a secondary lymphoid organ stimulating them to leave the bloodstream and enter the lymphatic tissue.

See [[Adaptive Immune System - Overview#Antigen Processing and Presentation|here]]

==Pig Lymph Node==

==Pig Lymph Node==

<p>The lymph nodes are [[:Category:Secondary Lymphoid Tissue|secondary lymphoid tissue]], and as the [[Spleen - Anatomy & Physiology|spleen]] removes antigens from the blood, lymph nodes remove antigens from tissue/lymph. Antigen presenting cells ([[Lymphocytes#B cells|B cells]] and [[Lymphocytes#T cells|T cells]]) migrate from peripheral tissue via afferent [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] to the lymph nodes where they present their antigen to lymphocytes. [[Lymphocytes#B cells|B cells]] and [[Lymphocytes#T cells|T cells]] enter via the high endothelial venules by diapedesis and [[Lymphocytes#B cells|B cells]] migrate to the cortex while [[Lymphocytes#T cells|T cells]] to the deep cortex.</p>

<p>The lymph nodes are [[:Category:Secondary Lymphoid Tissue|secondary lymphoid tissue]], and as the [[Spleen - Anatomy & Physiology|spleen]] removes antigens from the blood, lymph nodes remove antigens from tissue/lymph. Antigen presenting cells ([[Lymphocytes#B cells|B cells]] and [[Lymphocytes#T cells|T cells]]) migrate from peripheral tissue via afferent [[Lymphatic Vessels - Anatomy & Physiology|lymphatic vessels]] to the lymph nodes where they present their antigen to lymphocytes. [[Lymphocytes#B cells|B cells]] and [[Lymphocytes#T cells|T cells]] enter via the high endothelial venules by diapedesis and [[Lymphocytes#B cells|B cells]] migrate to the cortex while [[Lymphocytes#T cells|T cells]] to the deep cortex.</p>

<p>Antibodies and immunologically competent cells leave the lymph nodes via the efferent lymphatics.</p>

<p>Antibodies and immunologically competent cells leave the lymph nodes via the efferent lymphatics.</p>

 

[[Category:Lymph Nodes|A]]

[[Category:Lymph Nodes|A]]