The lymphatic and immune systemFluid, vessels, cells and tissues

Functions of the lymphatic/immune systemMaintaining balance between intracellular and extracellular fluid levelsTransport of lipids and lipid-soluble vitamins (A,D, E, K)Immune functionAntigen trappingB and T lymphocytes, antigen-presenting cells

Overview of the lymphatic system

Lymphatic vessels system parallels circulatory systemCapillaries drain into lymphatic vesselsValves keep fluids movingCirculates through lymph nodesLymphatic vessels are not present in avascular tissue, CNS, red bone marrow, parts of spleen

Structure of lymphatic capillaries

Lymphatic ducts connect lymphatic and circulatory systems

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Lymphatic ducts return lymph to bloodThoracic (left lymphatic) ductReceives blood from left side of upper body, and entire lower bodyDrains into venous blood at junction of left internal jugular and left subclavian veinsRight lymphatic ductDrains right side of head, neck, thorax, upper limb, heart, liver

Edema: excess retention of interstitial fluidHigh blood pressureHeart diseaseLiver disease

Organs and tissues of the lymphatic systemThymusLymph nodesSpleen

The thymus: T (thymus) cells mature there

Primary lymphoid tissues

Thymic educationT cells migrate from bone marrow to thymusMost are eliminated thereSurviving cells regulate immune response (helper T cells) or help control infection (cytotoxic T cells)Thymus decreases in size throughout life

Immune response protects against a diversity of infectious agents

Secondary lymphoid tissues and organsTonsils (palatine, pharyngeal, lingual)Lymph nodesSpleen

Lymph nodes: about 600 throughout bodyTends to occur in groups (esp. mammary glands, axillae and groin)EncapsulatedTrabeculae form compartmentsExchange between blood and lymph

Features of lymph nodes

Drainage of different regions of the body by lymph nodes

CervicalAxillary (mammary)PoplitealInguinalThoracicAbdominalIntestinalMesenterial

Lymph nodes filter lymph; spleen filters blood

Spleen, continuedWhite pulp (arteries)T and B cells, macrophagesRed pulp(veins)Removal of damaged cellsStorage of plateletsFormation of blood cells in fetus

Important aspects of immune functionProtection from infection (immediate and long-term)Immune surveillanceDistinguishes self from non-selfDisorders include hypersensitivity, autoimmune disease, immune deficiency