Lymphatic System

• Components of the lymphatic system

  • Cells
  • Tissue
  • Organs
  • Vessels
• Immunity


  • Innate
  • Adaptive
• Innate immunity


  Nonspecific, first line of defense, physical barriers, neutrophils, NK cells, HCl, defensin, lysozyme, complement, interferons
• Adaptive immunity


  Mediated by lymphocytes and APCs, gradually acquired upon exposure, B & T lymphocytes, memory lymphocytes
• Lymphoid organs


  • Primary
  • Secondary
• Primary lymphoid organs


  Bone Marrow, Thymus, differentiation (antigen-dependent)
• Secondary lymphoid organs


  Lymph node, Spleen, MALT, participate in cell mediated immunity and humoral responses, differentiation into immune effectors and memory
• Education center


  Bone marrow, thymus, Peyer's patches
• Antibodies


  • IgG
  • IgA
  • IgM
  • IgE
  • IgD
• IgG


  Fetal circulation, pregnant women, phagocytosis
• IgA


  Secretory, protect mucosae
• IgM


  First line of defense, B lymphocyte surface
• IgE


  Allergic reaction, mast cell and basophil
• IgD


  B cell activation
• T lymphocytes


  • Helper T cells
  • Killer T cells
  • Regulatory T cells
  • γδ T cells
• Helper T cells


  CD4, produce IL-2 which trigger b cells to turn to plasma cells, MHC class 2
• Killer T cells


  Trigger apoptosis to microorganism, MHC class 1
• Regulatory T cells


  Suppressor, inhibit specific immune responses
• γδ T cells


  Dermis and mucosal epithelia, intraepithelial, do not recirculate to lymphoid organs
• Peyer's patches


  Located in the wall of small intestine, macrophages capture and destroy bacteria thereby preventing them from penetrating intestinal wall
• Mucosa-associated lymphoid tissue


  Augment mechanical and chemical barriers of surface mucosal epithelia, one of the largest lymphoid organs, B cells, CD4+ helper T cells
• Thymus gland


  Production of immunocompetent T cells, maturation of t cells, regulation of t cell maturation, proliferation, function via secretion of hormones
• Thymus capsule


  Vascularized connective tissue capsule that extends into the parenchyma dividing the organ into lobules
• Thymus lobules


  Outer basophilic cortex surrounding lightly stained medulla
• Thymus cortex


  Contains T lymphoblasts (thymocytes), thymic epithelial cells
• Hassall's corpuscle


  Aggregates of TECs, sometimes keratinized, unknown purpose but they release cytokines
• Spleen


  Located on the left side of abdominal cavity, below diaphragm, curls around anterior aspect of stomach, dense connective tissue capsule, white pulp, red pulp
• Spleen white pulp


  Lymphoid nodules, periarteriolar lymphoid sheaths
• Spleen red pulp


  Blood filled sinusoids, filters blood, recycles Fe from RBC, hematopoiesis in fetus and sometimes adults, removal of abnormal blood cells and particulate matter
• Tonsils


  Trap and remove bacteria entering the throat, tonsilitis, palatine, lingual, pharyngeal
• Capsule


  Dense connective tissue from which emerge trabeculae to penetrate splenic pulp
• White pulp


  • Lymphoid nodules
  • Periarteriolar lymphoid sheaths
• Red pulp


  Blood filled sinusoids
• Functions of the spleen

  • Filters blood
  • Recycles Fe from RBC
  • Hematopoiesis in fetus and sometimes adults
  • Removal of abnormal blood cells and particulate matter
• Tonsil


  Trap and remove bacteria entering the throat
• Tonsilitis


  Tonsils become congested with bacteria and become swollen
• Types of tonsils


  • Palatine
  • Lingual
  • Pharyngeal
• Palatine tonsils


  Posteriorly on soft palate, stratified squamous with 10-20 deep invaginations or tonsillar cypts
• Lingual tonsils


  At the base of the tongue, stratified squamous with crypts
• Pharyngeal tonsils


  On the posterior wall of the nasopharynx, pseudostratified ciliated columnar with a thin underlying capsule