General Histology Lec 5 Lymphatic System PDF

‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ lymphatic system lec 5 Lymph node: The L.N are encapsulated bear or kidney shaped organs composed of lymphoid tissue. distributed...

‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ lymphatic system lec 5 Lymph node: The L.N are encapsulated bear or kidney shaped organs composed of lymphoid tissue. distributed throughout the body along the coarse of the lymphatic vessels. each L.N characterized by a Convex & concave Side. the afferent lymphatic vessels enter through the convex side while on the concave side there is identation called hilum through which the arteries & nerves penetrate & the veins with the efferent lymphatic vessels leave.  ‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ Lymph: Is an exudates from the capillaries to the tissue space, it is similar to the blood (formed of plasma + cells) but some differences are: 1. Lymph contains lymphocytes & monocytes cells. 2. No granular leukocytes. 3. No RBC"s. 4. Platelets are absent. 5. Albumin and globulin proteins are higher than that of the blood. 6. Fibrinogen is less. 7. Coagulation is slower than blood. 8. Oxygen level is less than blood. 9. Carbonic acid is higher than blood. 10. Fats are seen in the lymphatics of the intestine & appear milky (chyle) due to the presence of fat globules. Histological structure: It is surrounded with a C.T. capsule formed of collagen, elastic fibers, & smooth muscle cells, which send C.T. trabeculae that divide the lymph nodes into compartments called cortical třabeculae which extend to the medulla & called medullary trabeculae. Each lymph node has 3 regions: 1-Cortical zone: lies at the periphery below the capsule. 2-Medullary zone: lies in the central part of the lymph node. 3-paracortical or juxtamedullary or deep cortex: lies between the outer cortex & inner medulla.  ‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ Cortical zone: It is formed of reticular tissue infiltrated with lymphocytes, it contain 3 components: 1- Lymphatic nodules 2- Marginal sinuses (or subcapsular sinuses). 3- Cortical trabeculae, Lymphatic nodules are spherical aggregation of lymphocytes, they could be: - Primary nodules containing inactive or naïve B-lymphocytes distributed uniformly throughout the nodule. secondary nodules containing a peripheral dark-stained area crowded with small B-lymphocytes with a central light area called germinal centre containing lymphoblasts which give rise to the plasmoblasts (immunoblasts) this cells divide to give rise to plasma cells which are immunoglobuline-producing cells. The germinal center also contains follicular dendretic cells characterized by long processes with large basophilic nuclei, its function is to trap the antigen - antibody complex on their surface for a long period of time then the antigens are recognized by the B-cell.  ‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ the marginal (subcapsular) sinus lies below the capsule is continuous with the cortical (trabecular) sinuses which extend between the trabeculae & the aggregations of the cortical nodules. the cortical sinuses are lined with fenestrated endothelial cells (with gaps in between them) associated with reticular cells macrophages which are more in the side of the sinus facing the cortical nodule. The "cortica abecula" are C.T. septa arise from the C.T capsule & run in the cortex surrounded by the cortical trabecular sinus.