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Lymphoid Organs (lymph nodes,thymus, spleen):
- diffuse lymphatic tissue and lymphatic follicles or nodules
- enclosed by a connective tissue capsule
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Lymph Nodes:
- location
- function
- structure:
- shape and size
- cortex: follicles (nodules) with germinal centers
- medulla: diffuse tissue continuation of the cortex, contains B cells and plasma cells
- sinuses:
- subcapsular sinus: reticular connective tissue, macrophages, dendritic cells
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lecture notes
- between 1-25mm
- covered in a fibrous capsule that projects inwards forming trabeculae
- all out going vessels connect at the hilum of the lymph node
- subcapsular space: mesh work of reticular fibres macrophages and dendritic cells (contain antigens)
- outer cortex: contains b cells with geminal centers
- deep cortex: where lymphocytes enter (dominated by t cells)
- medulla: contains b cells and plasmocytes aranges in lines call medullary cords
- 99% of antigens removed
- fixed macrophages line the walls of lymphatic sinuses
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circulation within and through a lymph node:
- afferent lymphatics
- efferent lymphatics
- hilus
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Thymus:
- location: posterior to the manubrium of the sternum (also in superior pleural cavity)
- function
- structure: divided into 2 lobes via the septa formed by the capsule
- thymic lobules: (2mm in width)
- cortex (stem cells, T cells)
- medulla (T cells)
- Hassall’s corpuscles
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lecture notes
- involution: the degeneration of the thymus with age
- cortex: stem cells develop and divide into t cells that then migrate into the medulla
- Medulla: thymic hormones differentiate t cells
- hassals corpuscle: clumps of t cells
- thymic capillaries: like in the CNS they dont permit crossing thus making a blood thymus barrier
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Spleen:
- location
- function
- structure:
- surfaces: diaphragmatic (smooth and convex), visceral (large bumpy surface), gastric (contains indentations), renal (long and flat edge)
- hilus: in the middle, entrance of all efferent vessels
- white pulp: T and B cells
- red pulp: reticular connective tissue , red blood cells, macrophages, lymphocytes, venous sinuses, splenic cords
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lecture notes
- 12 cm and 160 g
- location: curving lateral border of tomach, between 9 and 11th rib on the left side and is attatched to the stomach by the gastrosplenic ligament
- Function: removes abnormal cells via phagocytosis, stores iron from broken down red blood cells, initiates immune response from antigens
- red pulp: lots of RBCs
- white pulp: lymphoid nodules formed in the spleen
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