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Lymphatic

System

Lymphatic System

 Assists the cardiovascular system by transporting excess interstitial fluid (lymph) through lymphatic vessels.  Lymph is filtered and checked for foreign or pathologic material, such as cancer cells and bacteria.  Lymphatic structures contain certain cells that initiate an immune response to abnormal materials and perform other functions essential to homeostasis and survival.  Without the primary immune response by the lymphatic system, the body would be unable to fight infection and keep itself healthy.

Immune Response

 Some cells (B lymphocytes) produce soluble proteins called antibodies.  bind to and immobilize the foreign or abnormal agent  damaging it or identifying it to other elements of the immune system  Other cells (T lymphocytes) attack and destroy the antigen directly.  Other cells become memory cells (B and T):  remember the past antigen encounters  initiate an even faster and more powerful response should the same antigen appear again

Components of the Lymphatic

System

 Lymph

 Lymphatic Vessels

 Lymphatic Capillaries  Lymphatic Vessels  Lymphatic Trunks  Lymphatic Ducts

 Lymphatic Organs

 Thymus  Lymph Nodes  Spleen

Lymphatic Capillaries

 The lymphatic network begins with

microscopic vessels called lymphatic

capillaries.

 closed-ended tubes that are found in most blood capillary networks  similar to a blood capillary in that its wall is an endothelium  tend to be larger in diameter, lack a basement membrane, and have overlapping endothelial cells  anchoring filaments help hold these endothelial cells to the nearby tissues

Lymphatic Capillaries

 Act as one-way valves.

 when interstitial fluid pressure rises, the margins of the endothelial cell walls push into the lymphatic capillary lumen and allow interstitial fluid to enter  when the pressure increases in the lymphatic capillary, the cell wall margin pushes back into place next to the adjacent endothelial cell  fluid “trapped” in the lymph capillary cannot be released back into the tissues

Lymphatic Vessels

 Lymphatic capillaries merge to form larger structures.  Lymphatic vessels resemble small veins.  both contain three tunics and both have valves  Some vessels connect directly to lymphatic organs called lymph nodes.  Afferent lymphatic vessels bring lymph to a lymph node where it is examined for foreign on pathogenic material.  Once filtered, the lymph exits the lymph node via efferent lymphatic vessels.  Lymph nodes are often found in clusters.  lymph is repeatedly examined for the presence of foreign or pathogenic materials

Trunks and Ducts

 Trunks:  Jugular  Subclavian  Bronchomediastinal  Intestinal  Lumbar  Ducts:  Right Lymphatic Duct  Into right subclavian vein/right internal jugular junction  Thoracic Duct:  Into left subclavian vein/left internal jugular junction  Cisterna chyli  Drains most of the body

Lymphatic Cells

 Also called lymphoid cells.  Located in both the lymphatic system and the cardiovascular system.  Work together to elicit an immune response.  Types of lymphatic cells are:  macrophages  epithelial cells  dendritic cells  lymphocytes

Types and Functions of

Lymphocytes

 T-lymphocytes (also called T-cells).

 B-lymphocytes (also called B-cells).

 NK cells.

 Migrate through the lymphatic tissues and

monitor them for the presence of antigens.

 Identified according to the tissue or organ

where they mature:

 T -lymphocytes mature in the Thymus  B -lymphocytes mature in the Bone marrow

B-Lymphocytes

 Make up about 15–30% of the lymphocytes in the body.  Contain antigen receptors that respond to one particular antigen and cause the production of immunoglobulins (Ig), or antibodies, that respond to that particular antigen.  the five main classes of immunoglobulins are called IgG, IgA, IgD, IgM, and IgE.  these immunoglobulins are released by the specific B- lymphocytes to immobilize or neutralize specific antigens