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Part of the immune system that consists of 2 independent parts: 1.meandering network of lymphatic vessels 2.various lymphoid tissues and organs Lymphatic.

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Presentation on theme: "Part of the immune system that consists of 2 independent parts: 1.meandering network of lymphatic vessels 2.various lymphoid tissues and organs Lymphatic."— Presentation transcript:

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2 Part of the immune system that consists of 2 independent parts: 1.meandering network of lymphatic vessels 2.various lymphoid tissues and organs Lymphatic system is located within loose connective tissue systems of the body The Lymphatic System

3  Form a 1-way system in which lymph fluid flows only toward the heart  Vessels are similar to capillaries, but very permeable.  They have the same 3 tunics, but thinner.  They occur everywhere blood capillaries occur. Lymphatic vessels

4 arteriole venule lymphatic capillaries blood capillaries lymphatic vessel

5 Fig

6 Edema- swelling of lymph vessels- lymphedema Lymph Transport lacks pump for circulation relies on activity of skeletal muscles and pulsation of nearby arteries for movement of fluid 3L of lymph enters blood stream every 24 hrs proteins easily enter lymphatic system uptake of large particles such as cell debris, pathogens, and cancer cells  lymph nodes where it is cleansed of debris and examined by cells of the immune system (WBC)

7 Fig Systemic CirculationPulmonary Circulation

8 Formation of Lymph interstitial fluid blood capillary lymphatic capillary tissue cell

9 composed of: lymphoid cells lymphoid tissue Lymphoid Organs

10 Lymphoid Cells b b Lymphocytes the main warriors of the immune system b b formed in red marrow of spongy bone (leukopoeisis) b b Two main varieties T cells (T lymphocytes) B cells (B lymphocytes)

11 Lymphocytes b b T cells and B cells protect against antigens Anything the body perceives as foreign – –Bacteria and their toxins; viruses – –Mismatched RBCs or cancer cells

12 Lymphocytes b T cells Manage the immune responseManage the immune response Attack and destroy foreign cellsAttack and destroy foreign cells cells/cm3 blood b B cells Produce plasma cells, which secrete antibodiesProduce plasma cells, which secrete antibodies

13 Other Lymphoid Cells b b Macrophages phagocytize foreign substances and help activate T cells b b Dendritic cells capture antigens and deliver them to lymph nodes b b Reticular cells produce stroma that supports other cells in lymphoid organs

14 Figure 20.3 Macrophage Medullary sinus Reticular fiber Lymphocytes Reticular cells on reticular fibers

15 Lymphoid Tissue b b Houses and provides a proliferation site for lymphocytes b b Furnishes a surveillance vantage point b b Two main types Diffuse lymphatic tissue Lymphatic follicles

16 Reticular connective tissue found in all lymphoid organs except for thymus Lymphoid Tissue

17 Lymph nodes Spleen Thymus Peyer’s patches Tonsils Red Bone Marrow Appendix Lymph Organs:

18 Hundreds of small organs found imbedded in connective tissue Large clusters occur in inguinal, axillary, and cervical regions. Lymph Node

19 Figure 20.2a Cervical nodes Entrance of right lymphatic duct into vein Internal jugular vein Entrance of thoracic duct into vein Thoracic duct Cisterna chyli Lymphatic collecting vessels Axillary nodes Aorta Inguinal nodes Regional lymph nodes: (a) General distribution of lymphatic collecting vessels and regional lymph nodes. Drained by the right lymphatic duct Drained by the thoracic duct

20 Lymph Nodes b Functions 1.Filter lymph—macrophages destroy microorganisms and debris 2.Immune system—lymphocytes are activated and mount an attack against antigens

21 Structure of a Lymph Node b b Bean shaped b b External fibrous capsule b b Trabeculae extend inward and divide the node into compartments b b Two histologically distinct regions Cortex Medulla

22 Figure 20.4 Afferent lymphatic vessels Efferent lymphatic vessels Capsule Trabeculae Hilum Cortex Lymphoid follicle Germinal center Subcapsular sinus Medulla: Medullary cord Medullary sinus Follicles Trabecula Subcapsular sinus Capsule Medullary cords Medullary sinuses (b) Photomicrograph of part of a lymph node (72x) (a) Longitudinal view of the internal structure of a lymph node and associated lymphatics

23 lymphatic capillaries blood capillaries lymphatic vessels lymphatic node one- way valves

24 Spleen b b Largest lymphoid organ b b Served by splenic artery and vein, which enter and exit at the hilus b b Functions Site of lymphocyte proliferation and immune surveillance and response Cleanses the blood of aged cells and platelets, foreign matter, bacteria, viruses and debris Stores breakdown products of RBC – –e.g. iron Erythrocyte production in fetus (normally ceases after birth)

25 Figure 20.6c (c) Photograph of the spleen in its normal position in the abdominal cavity, anterior view. Diaphragm Spleen Adrenal gland Splenic artery Pancreas Left kidney

26 Structure of the Spleen b b Two distinct areas White pulp around central arteries Mostly lymphocytes on reticular fibers and involved in immune functions Red pulp in venous sinuses and splenic cords – –Rich in macrophages for disposal of worn-out RBCs and bloodborne pathogens

27 Figure 20.6a,b Arterioles and capillaries Capsule Trabecula Venous sinuses Red pulp Splenic cords White pulp Central artery Splenic artery Splenic vein (b) Diagram of spleen histology Splenic artery Splenic vein Hilum (a) Diagram of the spleen, anterior view

28 Thymus Located: on top of heart Secretes hormones thymosin and thymopoeitin Causes T-lymphocytes to function against specific pathogens in the immune response (called immunocompetent) Most active during youth; it  in size during childhood, by old age, it's mostly been replaced by fibrous and fatty connective tissue

29 Fig

30 Thymus b Thymic lobes contain an outer cortex and inner medulla b Cortex contains densely packed lymphocytes and scattered macrophages b Medulla contains fewer lymphocytes and thymic (Hassall’s) corpuscles involved in regulatory T cell development

31 Figure 20.7 Cortex Medulla Thymic (Hassall’s) corpuscle

32 Thymus b b Differs from other lymphoid organs in important ways It functions strictly in T lymphocyte maturation It does not directly fight antigens b b The stroma of the thymus consists of star-shaped epithelial cells (not reticular fibers) b b These thymocytes provide the environment in which T lymphocytes become immunocompetent

33 Tonsils Prevent pathogens in respiratory tract and digestive tracts from penetrating mucous membrane lining

34 Tonsils b b Simplest lymphoid organs b b Form a ring of lymphatic tissue around the pharynx Palatine tonsils—at posterior end of the oral cavity Lingual tonsils—grouped at the base of the tongue Pharyngeal tonsil—in posterior wall of the nasopharynx Tubal tonsils—surrounding the openings of the auditory tubes into the pharynx

35 Tonsils b b Contain follicles with germinal centers b b Are not fully encapsulated b b Epithelial tissue overlying tonsil masses invaginates, forming tonsillar crypts b b Crypts trap and destroy bacteria and particulate matter

36 Figure 20.8 Tonsil Tonsillar crypt Germinal centers in lymphoid follicles Pharyngeal tonsil Palatine tonsil Lingual tonsil

37 Aggregates of Lymphoid Follicles b b Peyer’s patches Clusters of lymphoid follicles In the wall of the distal portion of the small intestine Similar structures are also found in the appendix b b Peyer’s patches and the appendix Destroy bacteria, preventing them from breaching the intestinal wall Generate “memory” lymphocytes

38 Figure 20.9 Smooth muscle in the intestinal wall Lymphoid nodules (follicles) of Peyer’s patch

39 MALT b b Mucosa-associated lymphatic tissue, including Peyer’s patches, tonsils, and the appendix (digestive tract) Lymphoid nodules in the walls of the bronchi (respiratory tract) b b Protects the digestive and respiratory systems from foreign matter


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