Today's Objectives List the functions of the lymphatic system Explain the difference between lymph, blood plasma and interstitial fluid. (intercellular fluid) Explain what filters the lymph in the body Describe how the Lymphocytes create immunity to a pathogen

Lymphatic System: Overview Consists of two semi-independent parts A meandering network of lymphatic vessels (moves Lymph) Lymphoid tissues and organs scattered throughout the body (Filters Lymph) Returns interstitial fluid and leaked plasma proteins back to the blood Lymph – interstitial fluid once it has entered lymphatic vessels

Different names for the SAME FLUID*** Blood plasma is the watery part of human blood. Interstitial fluid (intercellular fluid) is the fluid found surrounding all the cells of the body Lymph fluid is found in lymph vessels **** These 3 different fluids are the same fluid just with different names depending on where the fluid is located. (blood plasma = Lymph = Interstitial fluid) http://www.youtube.com/watch?v=ZdYxx4CHb-A&feature=related

The lymphatic system It transports a watery clear fluid called lymph = interstitial fluid .  This fluid distributes immune cells and other factors throughout the body. It also interacts with the blood circulatory system to drain fluid from cells and tissues. The lymphatic system contains immune cells called lymphocytes, which protect the body against antigens (viruses, bacteria, etc.) that invade the body. 

Main functions****** The lymphatic system is composed: lymph vessels lymph nodes organs The functions: to collect and return interstitial fluid, including plasma protein to the blood, and thus help maintain fluid balance to defend the body against disease by producing lymphocytes (B-cells, and T-cells) http://www.youtube.com/watch?v=xHvvijasVw8&feature=related

Lymph organs Lymph organs include the bone marrow, lymph nodes, spleen, and thymus. Precursor cells in the bone marrow produce lymphocytes. B-lymphocytes (B-cells) mature in the bone marrow. T-lymphocytes (T-cells) mature in the thymus gland.

Lymphocytes***** T cells B cells Both create memory cells for immunity Manage the immune response Helper and Suppressor T cells Attack and destroy foreign cells B cells Produce plasma cells, which secrete antibodies Antibodies immobilize antigens Both create memory cells for immunity

Lymphatic Vessels A one-way system in which lymph flows toward the heart Lymph vessels include: Microscopic, permeable, blind-ended capillaries Lymphatic collecting vessels

Lymphatic System Figure 20.1a

Lymph Capillaries

Lymph movement Lymph vessels are closely associated with the circulatory system vessels. Contraction of skeletal muscle causes movement of the lymph fluid through valves.

Lymphatic Vessels

Lymph Transport The lymphatic system lacks an organ that acts as a pump Vessels are low-pressure conduits Uses the same methods as veins to propel lymph Pulsations of nearby arteries Contractions of smooth muscle in the walls of the lymphatics

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Lymph Nodes Their two basic functions are: Filtration – macrophages destroy microorganisms and debris Immune system activation – monitor for antigens and mount an attack against them http://www.youtube.com/watch?v=qTXTDqvPnRk&feature=related

Structure of a Lymph Node Figure 20.4a, b

Spleen Largest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm Functions stores disease-fighting components of the immune system (lymphocytes) Immune surveillance and response Cleanses the blood – takes out old and defective red blood cells

Filtering Lymph nodes are filters of the lymph The spleen is a filter for old red blood cells  

Disorder of the Lymphatic System Lymphoma is a group of cancers that affect the cells that play a role in the immune system, and primarily represents cells involved in the lymphatic system of the body. They often originate in lymph nodes, presenting as an enlargement of the node (a tumor).