Human A&P Chapter 20 – Lymphatic System

The Lymphatic System What is the lymphatic system? What is the lymphatic system? It’s composed of: It’s composed of: Lymphatic vessels and Lymphatic vessels and Lymphoid organs Lymphoid organs

The Lymphatic System Functions: Functions: Return tissue fluid to the blood stream Return tissue fluid to the blood stream Why is this necessary? Why is this necessary? Example (~30L out of capillaries, 27L in) Example (~30L out of capillaries, 27L in) That extra 3L moves through the lymphatic system to the blood stream That extra 3L moves through the lymphatic system to the blood stream Fat transportation - lacteals Fat transportation - lacteals Immunity – defense against pathogens and other foreign material Immunity – defense against pathogens and other foreign material

Lymphatic Vessels Lymph capillaries – very permeable to interstitial fluid Lymph capillaries – very permeable to interstitial fluid Overlapping simple squamous epithelium Overlapping simple squamous epithelium Once interstitial fluid has entered a lymph capillary, it is called lymph Once interstitial fluid has entered a lymph capillary, it is called lymph Figure 20.1 and others Figure 20.1 and others

Lymphatic Vessels Lymph vessels – have one-way valves like the veins Lymph vessels – have one-way valves like the veins Lymph movement is similar to venous blood movement Lymph movement is similar to venous blood movement Figure Figure

Lymphatic Vessels The lymph vessels eventually converge to form: The lymph vessels eventually converge to form: the right lymphatic duct – drains the right arm and the right side of the head and thorax the right lymphatic duct – drains the right arm and the right side of the head and thorax the thoracic duct – drains the rest of the body the thoracic duct – drains the rest of the body These then dump lymph into the right and left subclavian veins These then dump lymph into the right and left subclavian veins Figure 20.2 Figure 20.2

Lymphatic Vessels Lymphangitis – red lines on the skin Lymphangitis – red lines on the skin As the lymph travels back to the blood stream it passes through many lymph nodes As the lymph travels back to the blood stream it passes through many lymph nodes Figure 20.2 Figure 20.2

Lymph Nodes Function as filtering stations for the lymph Function as filtering stations for the lymph Macrophages are in the lymph nodes Macrophages are in the lymph nodes What do they do? What do they do? B-cells and T-cells are also in the lymph nodes B-cells and T-cells are also in the lymph nodes What do they do? What do they do? Figure 20.4 Figure 20.4

Lymph Nodes (cont.) As B-cells and T-cells are activated by pathogens As B-cells and T-cells are activated by pathogens the lymph node becomes swollen the lymph node becomes swollen Sometimes the lymph nodes can get overwhelmed – buboes Sometimes the lymph nodes can get overwhelmed – buboes CD animation CD animation

Other Lymphoid Tissues Other lymphoid tissue/organs: Other lymphoid tissue/organs: Spleen - the filtering site for the blood Spleen - the filtering site for the blood splenectomy splenectomy MALT - contains macrophages, B-cells, and T-cells MALT - contains macrophages, B-cells, and T-cells No lymph filtering No lymph filtering Peyer’s patches, also around appendix and respiratory passageways Peyer’s patches, also around appendix and respiratory passageways Tonsils are accumulations of lymphoid tissue Tonsils are accumulations of lymphoid tissue Function? Function? swollen tonsils are a sign of a throat infection swollen tonsils are a sign of a throat infection Figure 20.5 Figure 20.5