1. Mrs. Dalia Kamal Eldien MSC in Microbiology Lecture NO 12

3.  The immune and lymphatic systems are two closely related organ systems that share several organs and physiological functions.  The immune system is our body’s defense against infectious pathogenic viruses, bacteria, and fungi as well as parasite and protists.  The immune system works to keep these harmful agents out of the body and attacks those that manage to enter

7.  The lymphatic system is part of the circulatory system, comprising a network of lymphatic vessels that carry a clear fluid called lymph (from Latin lympha meaning water), lymph is a fluid containing infection- fighting white blood cells, throughout the body.  The lymph has a number of functions, including:- 1- Helps the body to get rid of toxins, waste and other unwanted materials 2-Removal of interstitial fluid ( extracellular fluid of tissue).

10. Primary lymphoid organs Secondary lymphoid organs Secondary lymphoid organs Bone marrow Thymus Lymph node Spleen Tonsils

12.  primary lymphoid organ, composed of two identical lobes, located anatomically in front of the heart and behind the sternum(is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the chest)  This small organ stores immature lymphocytes (specialized white blood cells) and prepares them to become active T cells, which help destroy infected or cancerous cells.

15. Cortex: The cortical portion is mainly composed of lymphocytes, supported by a network of finely- branched epithelial reticular cells, which is continuous with a similar network in the medullary portion. The cortex is the location of the earliest events in thymocyte development

16. Medulla : In the medullary portion, the reticulum is coarser than in the cortex, the lymphoid cells are relatively fewer in number. The medulla is the location of the latter events in thymocyte development.  Both cortex and medulla contain small lymphocyte (Called in this particular location as thymocytes.  No lymphatic nodules are present in the thymus.