lecture 2 Bloodtrans_notes

lecture 2 Bloodtrans_notes - Immunology Lecture II...

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Immunology Lecture II Lymphatic Organs: This lecture began with the lymphatic organs (except for the thymus which had been discussed in the previous lecture), beginning with the hundreds of lymph nodes found throughout the trunk of the body. The flow of the lymph fluid through the lymph node begins by the fluid entering in through the afferent lymphatic vessels. After the lymph fluid enters through the afferent lymphatic vessels it begins diffusing through the lymph node by entering an area called the cortex, which houses the B cells. Also within the cortex are the germinal centers, which are areas of rapidly dividing B cells which have been stimulated by an antigen traveling into the lymph node. After passing through the cortex, the lymph fluid enters the paracortex, which contain the T cells. The next area of the lymph node is called the medulla, which contains both B cells and T cells. After diffusing through the lymph nodes, the lymphatic fluid exits through the efferent lymphatic vessels. The organization of the lymph node is important for the interaction and communication between the B cells and the T cells. An important characteristic of the lymph node is the fact that it directly connects the circulating blood with the circulating lymphatic fluid. This is because the lymph nodes contain lymphatic arteries and veins. At the very end of the arteries are the post-capillary venules. This is where the lymphocytes circulating in the blood are able to enter the lymph node through endothelial transport. This type of cell transport is characterized by the lymphocytes passing directly into and through the endothelial cells. Larger cells must pass between the endothelial cells. After the lymph node has received the necessary lymphocytes from the blood, the rest of the blood exits out the lymphatic vein. The lymph fluid, as well as the blood will return to the circulatory system. This is accomplished the lymphatic fluid passing through the lymph nodes, entering the thoracic duct, and finally emptying into the left subclavian vein where it will then dump into the blood stream. A histological characteristic of the lymph node is the presence of a capsule surrounding the entire organ. The capsule is responsible for the swelling, which occurs during an infection. During a localized infection, only lymph nodes found in the area of infection will become swollen. On the other hand, if a systemic infection has occurred, lymph nodes throughout the body will become swollen. The spleen is another lymphatic organ, which, like the lymph nodes, contains a capsule surrounding the outer edge. This also allows for swelling to occur during infection or injury. The spleen has no direct connection with the lymphatic fluid. However, since the lymphatic fluid enters the blood stream through the subclavian vein,
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lecture 2 Bloodtrans_notes - Immunology Lecture II...

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