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| [[Image:LH Monocyte Histology.jpg|right|thumb|150px|<p>'''Monocyte'''</p><sup>©RVC 2008</sup>]] | | [[Image:LH Monocyte Histology.jpg|right|thumb|150px|<p>'''Monocyte'''</p><sup>©RVC 2008</sup>]] |
− | <p>Monocytes are the largest [[Leukocytes|leukocytes]]. They have a large indented nucleus, few granules and constitute about 5% of circulating [[Leukocytes|leukocytes]]. Monocytes are precursors to a number of cells that make up the [[Lymphoreticular System - Anatomy & Physiology|mononuclear phagocytic system]]. Developing in the [[Bone Marrow - Anatomy & Physiology|bone marrow]], monocytes migrate into the circulation where, after approximately three days, they migrate into tissues and differentiate.</p>
| + | ==Introduction== |
| + | Monocytes are the largest [[Leukocytes|leukocytes]]. They have a large indented nucleus, few granules and constitute about 5% of circulating leukocytes. Monocytes are precursors to a number of cells that make up the [[Lymphoreticular System - Anatomy & Physiology|mononuclear phagocytic system]]. Developing in the [[Bone Marrow - Anatomy & Physiology|bone marrow]], monocytes migrate into the circulation where, after approximately three days, they migrate into tissues and differentiate. |
| + | |
| ==Development== | | ==Development== |
− | <p>Monocytes develop from the bi-potential [[Haematopoiesis - Overview#Colony Forming Units|CFU-GM]] stem cell. Further details of this process ([[Leukopoiesis|leukopoiesis]]) can be found [[Leukopoiesis#Monocyte development|here]].</p> | + | <p>Monocytes develop from the bi-potential [[Haematopoiesis - Overview#Colony Forming Units|CFU-GM]] stem cell during [[Leukopoiesis|leukopoiesis]].</p> |
− | <p>When monocytes leave the blood stream they then differentiate into a number of cells (all are [[Macrophages|macrophages]]): | + | <p>When monocytes leave the blood stream they then differentiate into a number of cells (all are classified as [[Macrophages|macrophages]]): |
| * Connective tissue histiocyte | | * Connective tissue histiocyte |
| * [[Respiratory System General Introduction - Pathology#Alveolar macrophages|Alveolar macrophage]] | | * [[Respiratory System General Introduction - Pathology#Alveolar macrophages|Alveolar macrophage]] |
| * Peritoneal macrophage | | * Peritoneal macrophage |
− | * Kupffer cell of [[Liver - Anatomy & Physiology|liver]] | + | * Liver Kupffer cell |
| * Melanophage of skin | | * Melanophage of skin |
| * Lipophage | | * Lipophage |
| * [[Bones - Anatomy & Physiology#Osteoclasts|Osteoclasts]] in bone | | * [[Bones - Anatomy & Physiology#Osteoclasts|Osteoclasts]] in bone |
− | * Microglial cell in bone & brain | + | * [[Neurons_- Anatomy & Physiology#Microglial_Cells|Microglial cell]] in bone & brain |
| * Specialised histiocytes | | * Specialised histiocytes |
| ** Epithelioid cell | | ** Epithelioid cell |
| * Histiocytic giant cell | | * Histiocytic giant cell |
− | ** Langhan’s cell | + | ** Langerhans cell |
− | ** Foreign body
| + | ** Touton giant cell</p> |
− | ** Touton</p> | |
| [[Image:Monocyte Picture.jpg|thumb|right|150px|Monocyte Picture - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]] | | [[Image:Monocyte Picture.jpg|thumb|right|150px|Monocyte Picture - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]] |
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| <p>Monocytes can live for months to years in the circulation.</p> | | <p>Monocytes can live for months to years in the circulation.</p> |
| <p>Monocytes are referred to as macrophages once they enter a tissue by '''diapedesis'''.</p> | | <p>Monocytes are referred to as macrophages once they enter a tissue by '''diapedesis'''.</p> |
− | <p>Monocytes/macrophages act as phagocytes, removing particular antigens. They also act as antigen presenting cells to take up, process and present antigen to [[Lymphocytes#T cells|T cells]].</p> | + | <p>Monocytes/macrophages act as phagocytes, removing particular antigens. They also act as antigen presenting cells to take up, process and present antigen to [[T cells]].</p> |
− | ===In pathology=== | + | ==Monocytosis== |
− | *[[Monocytosis|Monocytosis]]
| + | An increase in the number of monocytes (haematogenous macrophages) in the blood is known as a [[Monocytosis|monocytosis]]. It occurs in conjunction with other changes inidicative of a [[Stress Leucogram|stress leucogram]] or it may occur independently. Monocytes in the blood represent a brief transitional stage as they quickly move into tissues and differentiate further to tissue macrophages; they rarely perform any notable functions whilst in the bloodstream but they have been found to phagocytose red blood cells in cases of immune-mediated haemolytic anaemia. The major causes of monocytosis are: |
− | <br>
| + | *Stress leucogram mediated by the production or administration of glucocorticoids (plus a neutrophilia, eosinopenia and lymphopenia). |
− | ----
| + | *Chronic inflammatory processes, including chronic bacterial infections and chronic inflammatory diseases of the liver (chronic hepatitis and cholangitis) and pancreas (chronic pancreatitis). |
− | <center><b><sup>Blood cells: [[Erythrocytes|Erythrocytes]] |
| + | *Granulomatous disease results in monocytosis as monocytes are recruited to contain certain types of bacteria (namely Mycobacteria spp., Nocardia spp., Actinomyces and Rhodococcus equi) or foreign bodies. |
− | [[Basophils|Basophils]], [[Eosinophils|Eosinophils]], [[Lymphocytes|Lymphocytes]], [[Macrophages|Macrophages]], [[Mast Cells|Mast cells]], [[Monocytes|Monocytes]] & [[Neutrophils|Neutrophils]] | [[Thrombocytes|Thrombocytes]] & [[Thrombopoiesis#Megakaryocyte|Megakaryocytes]]</sup></b></center>
| + | *Certain types of monocytic or myelomonocytic chronic myeloid leukaemia may result in the presence of large numbers of monocytes in the blood. |
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− | [[Category:Blood_Cells]] | + | [[Category:Blood_Cells]] [[Category:Kate English reviewing]] |