Changes

*[[Secondary Lymphoid Tissue - Anatomy & Physiology|Secondary lymphoid organ]]</p>

*[[Secondary Lymphoid Tissue - Anatomy & Physiology|Secondary lymphoid organ]]</p>

===Erythrocytes & Platelets===

===Erythrocytes & Platelets===

<p>In the foetus the spleen also has a role in [[Overview of Haematopoiesis - WikiBlood|haematopoiesis]] when it becomes the main [[Erythrocytes - WikiBlood|erythrocyte]] producing organ during the hematopoietic transitional phase.</p>

<p>In the foetus the spleen also has a role in [[Overview of Haematopoiesis - WikiBlood|haematopoiesis]] when it becomes the main [[Erythrocytes - WikiBlood|erythrocyte]] producing organ during the haematopoietic transitional phase.</p>

<p>In the developed animal the red pulp is involved in the removal of aged, damaged or abnormal [[Erythrocytes - WikiBlood|erythrocytes]] (along with the [[Liver - Anatomy & Physiology|liver]] and [[Bone Marrow - Anatomy & Physiology|bone marrow]]). As [[Erythrocytes - WikiBlood|erythrocytes]] age they become less supple and this causes them to become damaged when they pass through the very narrow capillaries of the spleen, after which they are phagocytised by splenic [[Macrophages - WikiBlood|macrophages]]. If a splenectomy is performed the number of aged [[Erythrocytes - WikiBlood|erythrocytes]] in circulation increases.</p>

<p>In the developed animal the red pulp is involved in the removal of aged, damaged or abnormal [[Erythrocytes - WikiBlood|erythrocytes]] (along with the [[Liver - Anatomy & Physiology|liver]] and [[Bone Marrow - Anatomy & Physiology|bone marrow]]). As [[Erythrocytes - WikiBlood|erythrocytes]] age they become less supple and this causes them to become damaged when they pass through the very narrow capillaries of the spleen, after which they are phagocytised by splenic [[Macrophages - WikiBlood|macrophages]]. If a splenectomy is performed the number of aged [[Erythrocytes - WikiBlood|erythrocytes]] in circulation increases.</p>

<p> The red pulp also acts as a storage site for [[Erythrocytes - WikiBlood|erythrocytes]]. The degree of storage is variable between species but is particularly notable in horses which during exercise under sympathetic activity can contract their spleen to increase the concentration of circulating [[Erythrocytes - WikiBlood|erythrocytes]]. In some species such as cats and rodents the red pulp acts as a storage site for [[Thrombocytes - WikiBlood|platelets]] and contains [[Thrombopoiesis - WikiBlood#Megakaryocyte|megakaryocytes]].</p>

<p> The red pulp also acts as a storage site for [[Erythrocytes - WikiBlood|erythrocytes]]. The degree of storage is variable between species but is particularly notable in horses which during exercise under sympathetic activity can contract their spleen to increase the concentration of circulating [[Erythrocytes - WikiBlood|erythrocytes]]. In some species such as cats and rodents the red pulp acts as a storage site for [[Thrombocytes - WikiBlood|platelets]] and contains [[Thrombopoiesis - WikiBlood#Megakaryocyte|megakaryocytes]].</p>

===Lymphoid===

===Lymphoid===

<p>Blood flows through the marginal sinus meaning that most antigens present in the blood come into contact with the [[Lymphocytes - WikiBlood#B cells|B lymphocytes]] and dendritic cells in the spleen. Dendritic cells in the marginal sinus and red pulp take up antigens from the blood and transport them to the primary follicles in the white pulp. If the antigen activates the [[Lymphocytes - WikiBlood#B cells|B lymphocytes]] then a germinal centre will form in the primary follicle and this is called a splenic nodule. Antibody producing cells then migrate to the red pulp and marginal zone.</p>

<p>Blood flows through the marginal sinus meaning that most antigens present in the blood come into contact with the [[Lymphocytes - WikiBlood#B cells|B lymphocytes]] and dendritic cells in the spleen. Dendritic cells in the marginal sinus and red pulp take up antigens from the blood and transport them to the primary follicles in the white pulp. If the antigen activates the [[Lymphocytes - WikiBlood#B cells|B lymphocytes]] then a germinal centre will form in the primary follicle and this is called a splenic nodule. Antibody producing cells then migrate to the red pulp and marginal zone.</p>