Lymphatic System Components Lymphatic vessels Lymphoid tissues and organs function in the immune system comprised of phagocytic cells and lymphocytes Lymphatic Vessels One way flow toward heart Lymphatic Capillaries Formed by loosely overlapping endothelial cells Anchored by collagen filaments helps mini valve system Lacteals Lymphatic capillaries of the intestines found in villi Lymph fluid in lymphatic vessels called chyle Lymphatic Vasculature Lymphatic capillaries drain into larger vessels called lymphatic collecting vessels which have 3 tunics Lymphatic Vasculature Lymphatic capillaries Lymphatic collecting vessels 3 tunics but thinner than veins have more valves than veins Lymphatic Vasculature Lymphatic capillaries Lymphatic collecting vessels Lymphatic trunks drain large regions of the body Major Lymphatic Trunks Bronchomediastinal Subclavian Jugular Lumbar Intestinal Lymphatic Vasculature Lymphatic capillaries Lymphatic collecting vessels Lymphatic trunks Lymphatic ducts Factors Assisting Lymphatic Flow Valves prevent backflow Muscular pump contraction of skeletal muscle pushes fluid only in one direction because of valves Respiratory pump when we change our breathing it changes thoracic pressure Arterial pumping because lymph moves near arteries then pressure of arteries moves lymph towards heart Smooth muscle contraction contracts in tunic and then helps move it toward junction Lymphoid Cells Lymphocytes specialized WBC B cells ultimately produce plasma which produces antibodies tag cells to be destroyed T cells directly destroy foreign cells Lymphoid Cells Lymphocytes B cells T cells Macrophages activates T cells phagocytizes foreign cells Lymphoid Cells Lymphocytes B cells T cells Macrophages Dendritic cells phagocytic also activates T lymphocytes Lymphoid Cells Lymphocytes B cells T cells Macrophages Dendritic cells Reticular cells produce a stroma which is network of reticular connective tissue that supports other cells Lymphoid Tissue Proliferation site for lymphocytes Allows detection of infection or damage Lymphoid Organs Lymph nodes cluster along lymphatic vessels inside there are reticular tissue combined activity of all lymph nodes and components that filter lymph Lymphoid Organs Lymph nodes Spleen largest stores breakdown products of RBCs stores platelets forms RBCs in fetus basic responsibility os to remove and aged and affected cells out of the lymph Lymphoid Organs Lymph nodes Spleen Thymus functions in early life and then degenerates make us immunocompetent gives T cell ability to interact with foreign cell interact with pathogens to destroy them Lymphoid Organs Lymph nodes Spleen Thymus Tonsils trap any foreign cells in air or food so it doesn t pass into body Lymphoid Organs Lymph nodes Spleen Thymus Tonsils Peyer s patches organs assoc with lymphatic system help create memory cells which give us long term immunity Lymph Node Histology Capsule Trabeculae Subscapular sinuses Cortex Medulla Follicles Medullary cords Medullary sinuses Lymph Node Action Lymph enters via afferent lymphatic vessels Filters through sinuses Exits through efferent lymphatic vessels at hilus Spleen Histology Capsule Trabeculae White pulp Red pulp Splenic cords Spleen Action Blood delivered via splenic artery Lymph filtered by lymphocytes in white pulp Then filtered by marcophages in red pulp Cleansed fluid returns to splenic vein Thymus Histology Cortex Medulla Hassall s corpuscles Thymus Action Action most prominent in newborns Secretes thymosin and thymopoietin Causes T lymphocytes to become immunocompetent Tonsils Palatine tonsils largest and most often infected Tonsils Palatine tonsils Lingual tonsils underneath tongue base of tongue Tonsils Palatine tonsils Lingual tonsils Pharyngeal tonsil adenoids posterior wall of nasopharynx Tonsils Palatine tonsils Lingual tonsils Pharyngeal tonsil adenoids Tubal tonsils paired openings of auditory tubes in pharynx Anatomy Joke of the Day Tonsil Histology Follicles with germinal centers Crypts dead end channels trap bacteria and foreign materials these move from crypts to epthelial lymphoid tissure then destroyed and creates memory cells Tonsil Action Crypts trap bacteria and particulates Bacteria pass through epithelium into lymphoid tissue Lymphoid tissue destroys pathogens Memory cells formed Peyer s Patches Isolated clusters of lymphoid follicles Destroy bacteria Generate memory lymphocytes Lymphatic Development Developing veins bud off lymph sacs at fifth week First to form are jugular lymph sacs Also from vena cava and iliac veins These form branching system of lymphatic vessels Connection of jugular lymph sac with jugular veins become right lymphatic duct and thoracic duct Lymphoid organs develop from mesodermal mesenchyme that become reticular tissue Except thymus first to appear outgrowith of pharnyx lymphocytes can start to occupy thymus before birth seems to have some sort of control over other lymphatic organs