Lymphatic System Overview and Components

Lymphatic System Overview

• The lymphatic system carries excess extracellular fluid back to the venous system
• Lymph is clear, colorless fluid; chyle is milky lymph from the small intestine
• Lymphatic vessels are present in most body areas except the brain, bone marrow, and avascular tissues (epithelia and cartilage)
• Lymphatic flow is unidirectional due to valves in the vessels

Lymphatic Organs and Tissues

• Lymphatic organs include lymph nodes, lymphatic vessels, and lymphatic ducts
• The lymphatic system includes primary, secondary, and diffuse lymphoid tissue
• Lymph nodes filter lymph and contain germinal centers for B cell proliferation
• The thymus is a primary lymphoid organ where T lymphocytes mature
• The thymus involutes (shrinks) after puberty
• The thymus has a cortex and medulla, with Hassall's corpuscles in the medulla
• Lymph nodes have a cortex, paracortex, and medulla
• Lymph nodes contain lymphatic nodules (primary and germinal) with B lymphocytes and macrophages
• Lymph nodes filter lymph, identify foreign antigens, and initiate an immune response
• Lymphatic vessels form a network connecting lymph nodes and ducts that drain lymph into veins

Lymphatic Circulation

• Two major lymphatic ducts: thoracic duct (drains most of the body) and right lymphatic duct (drains the upper right quadrant)
• The thoracic duct begins in the cisterna chyli and drains lymph into the junction of the left subclavian and internal jugular veins
• The right lymphatic duct is smaller and drains lymph into the junction of the right subclavian and internal jugular veins

Lymphatic System Function

• Filtration of lymph: Lymph passing through nodes allows macrophages to remove pathogens and cellular debris.
• Antigen recognition: Specialized cells in lymph nodes (dendritic cells) present antigens to T and B cells, initiating immune responses.
• Humoral immunity: B cells differentiate into plasma cells producing antibodies that target foreign antigens
• Cell-mediated immunity: T cells target and destroy infected or cancerous cells
• Lymph nodes act as sites of antigen recognition, cellular proliferation and differentiation.

Clinical Correlations

• Lymphangitis: Inflammation of lymphatic vessels, often from infection
• Lymphadenitis: Inflammation of lymph nodes, often due to infection or malignancy
• Lymphedema: Localized swelling due to impaired lymphatic drainage.
• Cancers can spread through lymphatic systems or nodes

Explore the essential functions and structures of the lymphatic system. This quiz covers lymphatic organs, the flow of lymph, and the roles of lymph nodes and the thymus. Test your knowledge on how these components work together in the immune response.