The Human Body in Health and Illness, 4th edition Barbara Herlihy Chapter 20: Lymphatic System

Lesson 20-1 Objectives List three functions of the lymphatic system. Describe the composition and flow of lymph. State the location of the following lymph nodes: cervical nodes, axillary nodes, and inguinal nodes. Describe the four lymphoid organs: lymph nodes, tonsils, thymus gland, and spleen. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Lymphatic System: Functions Returns interstitial fluid to the blood Absorbs fats and fat-soluble vitamins Helps the body defend itself against infection The lymphatic system consists of lymph, lymphatic vessels, lymphoid organs and tissue. The system is diffusely distributed. The slide’s figure illustrates the importance of lymphatic drainage. After mastectomy and removal of lymph nodes, drainage diminishes and edema forms (lymphedema). A malignant tumor can also block the flow of lymph, causing edema and discomfort. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymphatic Vessels and Veins Veins and lymphatic vessels drain interstitial fluid. Lymphatic vessels are parallel to the veins. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Blood interstitial fluid lymph Formation of Lymph Blood interstitial fluid lymph Water, dissolved solute, and some leaked protein leave the blood capillaries and enter the interstitial space; at this point it is called lymph. Much of the interstitial fluid and all leaked protein is drained into the lymphatic vessels. Lymph originates from the blood and returns to the blood. What would happen if the lymphatic vessels did not absorb the leaked protein from the interstitial space? The protein would act oncotically within the interstitial space, blocking the reabsorption of water and causing edema. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymph Nodes and Lymph Vessels Lymphatic vessels travel with veins, help with drainage Lymph travels through vessels to nodes Nodes: Sites of phagocytosis and immune response Phagocytosis occurs within the nodes, helping ward off infection. The nodes also participate in the immune response by producing T lymphocytes. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

What Makes Lymph Move? Milking action of skeletal muscles Exercise is good. Movement of chest during respiration Creates variations in pressure. Rhythmic contractions of lymphatic smooth muscle Vessel walls contract to push lymph along. Why is massage therapy often given to a woman with lymphedema secondary to mastectomy? The massage mimics the milking action of the skeletal muscles, helping force lymph out of the interstitial space. Why are neither blood pressures nor injections given in the affected arm of a patient with lymphedema? Taking a blood pressure in the affected arm would be uncomfortable. Poor circulation in the arm would also prevent an injected drug from leaving the area, leading to poor drug absorption and possible infection. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymphatic Drainage: Main Ducts Two drainage areas: Right lymphatic duct and thoracic duct Both ducts drain into subclavian veins. The thoracic duct drains much of the body, shown in gray in the figure. The right lymphatic duct, shown in flesh tone, drains lymph from the right side of the head, the right arm, and the thorax. Lymph is formed from blood and returns to blood. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymphoid Organs Lymph nodes Tonsils Thymus gland Spleen MALT (mucosal-associated lymphoid tissue) Lymphoid organs are diffusely distributed. They help defend the body from diseases such as infection and cancer. The lymphoid tissues in many other organs are referred to as MALT, mucosal-associated lymphoid tissue. The lymphoid organs support the immune role of the lymphocytes by filtering pathogens and cancer cells and by helping produce lymphocytes. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymph Node: Two Compartments Lymph nodules Lymphocytes and macrophages Immunity, phagocytosis Lymph sinuses Are lymph-filled spaces Bathe lymph nodules Lymph flows into the node via the afferent lymphatic vessel and is drained by the efferent lymphatic vessel. In this way, it moves from node to node and ultimately to one of the large lymphatic ducts. Sometimes lymph nodes become malignant, called a lymphoma (Hodgkins and non-Hodgkins). Initially, lymphoma is characterized by painless swelling of the involved lymph node. Why is the lymphatic system often the first site for metastasis? There are lymph nodes near almost every cell in the body, so lymph nodes easily pick up cells shed by a nearby tumor. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymphatic System: Diffuse Lymphatic vessels drain most of the body. Nodes are grouped. Cervical Axillary Inguinal The figure illustrates the diffuse nature of the lymphatic system. It also shows the three major groupings of lymph nodes. Tonsillitis can cause painful swelling of cervical lymph nodes. Cancer of the breast can cause swelling of the axillary lymph nodes. Similarly, tumors in the pelvic region can cause swelling in the inguinal nodes. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymphoid Organs: Tonsils Pharyngeal tonsils or adenoids Palatine tonsils often target of tonsillectomy Lingual tonsils Tonsils are partially encapsulated lymph nodes in the throat. Why is the location of tonsils there so strategic? Many pathogens enter the body through the mouth, so the location of the tonsils in the throat helps prevent infection. What is a possible complication of tonsillectomy? Hemorrhage is an infrequent but possibly lethal complication. In addition, the administration of general anesthesia is of concern. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymphoid Organ: Thymus Gland Assists development of immune system before puberty Secretes thymosins Produces T cells (lymphocytes) Thymosins play a role in the maturation and function of lymphocytes. Originally formed in the bone marrow, the T lymphocytes mature in the thymus, hence the name, “thymus-derived lymphocytes,” or T cells. Around puberty, the thymus gland involutes. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lymphoid Organ: Spleen Red pulp: Venous sinuses filled with blood and phagocytes White pulp: Contains lymphocytes Stores RBCs and platelets Removes old RBCs and platelets The spleen is the largest lymphoid organ. Located in the LUQ, it very vascular. It functions somewhat as a lymph node. An overactive spleen may prematurely remove platelets, causing thrombocytopenia and bleeding. A splenectomy may be done to treat this condition. After about 120 days, an RBC’s membrane become ragged, signaling its removal by the spleen. The use of a heart-lung machine may similarly damage RBCs; their premature removal by the spleen can result in anemia. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.