The Body’s Defenses - Antibodies and the Lymphatic System

Learning Outcomes

C6 describe the components of blood• explain the roles of antigens and antibodies

C7 describe the inter-relationships of the structures of the lymphatic system

• describe the functions of the lymphatic system • q identify and give functions of lymph

capillaries, veins, and nodes

Antibodies and Antigens

• Antigens are foreign substances that are recognized by the immune system

• They are usually proteins or polysaccharides (such as those found on cell membranes or the outer coat of a virus)

• Antibodies are proteins produced by lymphocytes, to react with a specific antigen

Antibody Structure• Contains 4

polypeptide chains - 2 heavy and 2 light chains

• Has specific sites that recognizes and binds to its particular antigen (variable region)

• Antibody structure

Antibody production

• B-lymphocyte recognizes a foreign antigen• B cell is activated to divide rapidly• B cells in plasma produce and release

antibodies

Antibody Function• Bind to antigens of invading

cells causing them to clump together

• Phagocytic w.b.c’s (macrophages) then destroy them

• Memory B-cells remain in the bloodstream providing lasting immunity – these will reproduce quickly next time that specific antigen is encountered

Antibody video

The Lymphatic System

• A system closely associated with the circulatory system

• Consists of lymph vessels (veins and capillaries), lymph nodes, and organs including the spleen and thymus gland

• A one-way system, from tissues to blood• Empties into the bloodstream at lymphatic

ducts

Fig. 14.1

Lymph Vessels

• Lymph veins – similar in structures to circulatory veins; carry fluid from capillaries to ducts

• Lymph capillaries – found in all tissues, along with blood capillaries

Lymph Nodes

• Located along lymph vessels• Contain large numbers of lymphocytes• Function in fighting infection and antibody

production

Functions of the lymphatic system:

①Immunity / fighting infection②Absorption of glycerol and fatty acids in the

lacteals③Return of excess tissue fluid to the blood

(capillary exchange)