20 The Lymphatic System and Lymphoid Organs and Tissues

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1 20 The Lymphatic System and Lymphoid Organs and Tissues 2 Lymphatic System Consists of three parts 1. A network of (lymphatics) lymphatic and 3 Lymphatic System: Functions Returns and leaked back to the Once interstitial fluid enters, it is called Together with and, provide the structural basis of the system 4. Figure # Lymphatic system, lymph flows toward the Lymph vessels ) include: Lymphatic Lymphatic Lymphatic Lymphatic 6 Lymphatic Capillaries Similar to, except Very (take up cell debris, pathogens, and cancer cells) cells to form, and are by filaments, preventing of capillaries 1

2 7 Lymphatic Capillaries Absent from,, bone and the : specialized lymph capillaries present in Absorb digestedand deliver fatty lymph () to the Digestion chapter 23 8 Figure # 20.1b 9 Lymphatic Vessels Similar to, except Have walls, with valves more frequently Collecting vessels in the travel with travel with _ are supplied from branching 10 Lymphatic Trunks (9) Formed by the of the largest ducts Paired Paired Paired Paired _ trunks A single i_ trunk 11 Lymphatic Ducts is into one of large Right l drains the right upper and the right side of the and duct arises from the and drains the of the Each empties lymph into circulation at the junction of the and veins on its own side of the body (left and right) 12. Figure # 20.2a pg: 755 2

3 13. Figure # 20.2b pg: Lymph Transport Lymph is propelled by: 1. Active 2. _of nearby - travel with arteries (veins and nerves) 3. Contractions of in the of the lymphatics 4. of dumped back into stream same amount as lost as 15 Lymphoid Cells the main of the system Two main varieties T cells ( ) B cells ( ) 16 Lymphocytes cells and cells against _ the body perceives as _ and their ; Mismatched or cells 17 _ Manage the Attack and destroy _ cells _ T s _ antigens while _ T s the _ antigens Produce _ cells provide, by producing 18 Other Lymphoid Cells foreign substances and help _ T cells _ cells_ antigens and deliver them to _ nodes _ cells produce _ that _ other cells in lymphoid _ 3

4 19. Figure # Lymphoid Tissue Houses and provides a site for lymphocytes Furnishes a _ vantage point Two main types tissue Lymphatic _ 21 Lymphoid Tissue _ lymphatic tissue comprises tissue elements in _ body _ Larger collections in the of _ membranes and lymphoid _ 22 Lymphoid Tissue Lymphatic, (nodules) (not same as - no ) are solid, spherical of tightly packed elements and center composed of and May form part of larger lymphoid organs 23 Lymph Nodes _ lymphoid organs of the body Embedded in, in clusters along lymphatic Near the body surface in,, and regions of the body shaped w/ fibrous 24. Fig. 20.2a; pg Lymph Nodes Functions 1. lymph destroy and s 2. system are and mount an attack against 4

5 26 Structure of a Lymph Node External extend inward and the into Two histologically distinct regions 27 Structure of a Lymph Node Cortex contains follicles with germinal centers, heavy with dividing cells nearly encapsulate the follicles (bring antigens into node) Deep cortex houses in transit T cells continuously among the, l, and stream 28 Fig pg Structure of a Lymph Node Medullary cords extend inward from the cortex and contain B cells, T cells, and plasma cells Lymph sinuses contain macrophages 30. Fig. 20.4b; pg Circulation in the Lymph Nodes Lymph via* lymphatic vessels Travels through large sinus and sinuses the node at the via **vessels Fewer ** vessels, causing flow of lymph to, allowing and time to carry out *carry to or towards ** carry away from 5

6 32 Fig. 20.4; pg Spleen lymphoid organ Served by and vein, which at the Functions lymphocyte_ and immune and the blood of and and 34 Fig. 20.6c; pg products of (e.g., ) for later blood Site of erythrocyte (normally ceases after birth) Has a capsule andcontains,, and huge numbers of 36 Structure of the Spleen Two distinct areas pulp Mostly lymphocytes on reticular fibers and involved in immune functions pulp Rich in macrophages for disposal of worn-out RBCs and bloodborne pathogens 37 Fig a&b; pg

7 38 Thymus Size with age In, it is found in the inferior and extends into the, where it partially overlies the Increases in and is most active during during and then gradually 39 Thymus Thymic lobes contain an outer and inner Cortex contains densely packed and scattered Medulla contains fewer lymphocytes and (Hassall s) involved in development 40. Figure # Thymus Differs from other lymphoid organs in important ways It functions strictly in maturation It does not antigens The of the thymus consists of -shapedcells (not fibers - CT) These thymocytes provide the in which become 42 lymphoid organs Form a of lymphatic tissue around the tonsils at posterior end of the cavity tonsils grouped at the base of the tonsils () in posterior wall of the tonsils surrounding the openings of the into the 7

8 43 Tonsils Contain with germinal centers Are not fully overlying tonsil masses i, forming tonsillar Crypts and and particulate matter Antigens in or lymphatic /vessels 44 Fig. 20.8b pg of Lymphoid Follicles of lymphoid follicles In the of the distal portion of the Similar structures are also found in the Peyer s patches and the appendix bacteria, preventing them from the intestinal Generate Antigens not in blood/lymph vessels 46 Fig. 20.8; pg MALT, including patches,, and the (digestive tract) Lymphoid in the walls of the (respiratory tract) Protects the and systems from foreign matter 8

The Lymphatic System. Dr. Naim Kittana, PhD

The Lymphatic System. Dr. Naim Kittana, PhD The Lymphatic System Dr. Naim Kittana, PhD 1 Disclosure The material and the illustrations are adopted from the textbook Human Anatomy and Physiology / Ninth edition/ Eliane N. Marieb 2013 Dr. Naim Kittana,