The lymphatic system consists of structures inherently involved in the functions of the immune system, so the anatomy of both these systems is covered in this chapter. The lymphatic system includes tissues and organs that support the body in a variety of ways beyond their roles in the immune system. The immune system includes tissues, cells, and soluble factors that remove debris from the body and defend it from infection. (Thumbnail image credit: "Anatomy of the Lymphatic System" by OpenStax is licensed under CC BY 3.0)
- 19.1: Introduction to the Lymphatic and Immune Systems
- Rather than being made up of a distinct set of organs like most body systems, the immune system is integrated within each of the body's systems to prevent or slow infection, fight sickness, and promote healing following tissue damage. The lymphatic system is comprised of a distinct set of organs whose primary functions support the immune system.
- 19.2: Functions of the Lymphatic and Immune Systems
- The immune system is a dynamic set of anatomical and physiological barriers, cells, and soluble factors that work together to prevent and fight infection and rid the body of debris and abnormal cells. The immune system can be temporally organized into three lines of defense. The lymphatic system functions to facilitate aspects of immune system function, while it is also integrated into vital functions for other body systems.
- 19.3: Anatomy of Lymphatic Vessels
- The lymphatic system includes a network of unidirectional lymphatic vessels with lymph nodes at intervals along each vessel. Flow through lymphatic vessels originates in lymphatic capillaries that are interwoven into blood capillary beds and drains through larger and larger lymphatic vessels, merging into lymphatic trunks that drain into lymphatic ducts that drain lymph into the subclavian veins of the bloodstream.
- 19.4: Anatomy of Lymphatic Organs and Tissues
- Lymphoid organs are comprised of multiple tissue types and are divided into two categories: primary and secondary lymphoid organs depending on how they support immune function. They include bone marrow, the thymus, lymph nodes, and the spleen. Lymphoid tissues are collections of lymphocytes and other immune cells in strategic locations within other organ systems that are sometimes called nodules. They include the tonsils and mucosa-associated lymphoid tissue (MALT).