Published by Hodder Education © 2010 Helen McGuinness The lymphatic system Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 1 Objectives By the end of this chapter you will be able to recall and understand the following knowledge: the functions of the lymphatic system the definition of lymph and how it is formed the connection between blood and lymph the circulatory pathway of lymph Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 2 Objectives the names and positions and drainage of the main lymphatic nodes of the head, neck and the body the immune response the interrelationships between the lymphatic and other body systems common pathologies of the lymphatic system. Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 3 Key words parotid nodes axillary nodes supratrochlear nodes thoracic nodes abdominal nodes pelvic nodes inguinal nodes popliteal nodes thoracic duct right lymphatic duct subclavian veins spleen tonsils thymus immunity specific immunity non-specific immunity antigen antibody humoral immunity cell-mediated immunity immunisation allergic reaction lymph oedema lacteals lymphatic capillaries tissue (interstitial) fluid lymphatic vessels lymphatic nodes deep cervical nodes superficial cervical nodes submandibular nodes occipital nodes mastoid nodes Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 4 Functions The lymphatic system is closely associated with the cardiovascular system. The lymphatic system assists the blood by draining the tissues of excess fluid and returning the fluid from the tissues back to heart. This helps to maintain blood volume, blood pressure and prevent oedema (waterlogging of the tissues). The lymphatic systems also plays an important role in the body’s immune system as the lymph nodes fight infection and generate antibodies. The lymphatic system also absorbs the products of fat digestion through the intestinal lymph vessels called the lacteals. Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 5 Definition of lymph Lymph is a clear, colourless, water fluid derived from tissue fluid and contained within lymph vessels. Lymph is similar in composition to blood except that it has a lower concentration of plasma proteins. Published by Hodder Education © 2010 Helen McGuinness

6 Structures of the lymphatic system Description Function Lymphatic capillaries Minute blind-end tubes, similar in structure to blood capillaries Drain away excess fluid and waste products from tissue spaces of body Lymphatic vessels Similar in structure to veins Have one-way valves and thin, collapsible walls Carry lymph towards heart Lymphatic nodes Oval or bean-shaped structures covered by a capsule of connective tissue Made up of lymphatic tissue Filter lymph of micro-organisms, cell debris or harmful substances Lymphatic ducts (thoracic and right lymphatic) Thoracic duct is largest lymphatic vessel and extends from second lumbar vertebra up through thorax to root of neck Right lymphatic duct is very short in length Lies in root of neck Collect lymph from whole body and return it to blood via subclavian veins Published by Hodder Education © 2010 Helen McGuinness

7 Circulatory pathway of lymph The circulatory pathway of lymph begins with lymphatic capillaries which lie in the tissue spaces between the cells. Tissue (interstitial) fluid drains into lymphatic capillaries and the excess fluid becomes lymph. Lymphatic capillaries merge to form larger vessels called lymphatic vessels which convey lymph in and out of structures called lymph nodes. Published by Hodder Education © 2010 Helen McGuinness

8 Circulatory pathway of lymph Lymph passes through at least one node where it is filtered of cell debris, micro-organisms and harmful substances. Once filtered, the lymph is collected into two main ducts – the thoracic duct (the largest duct), which collects lymph from the left side of the head and neck, left arm, lower limbs and abdomen, and the right lymphatic duct, which collects lymph from the right side of the head and neck and the right arm. The collected lymph is then drained into the venous system via the right and left subclavian veins. Published by Hodder Education © 2010 Helen McGuinness

9 Circulatory pathway of lymph 1. Plasma escapes blood capillary and bathes tissue cells 2. Excess fluid flows through a network of lymphatic capillaries 3. Tissue fluid enters lymph vessels where it becomes lymph 4. Larger lymphatic vessels lead to lymph nodes 5. Lymph passes through at least one lymphatic node where it is filtered 6. Filtered lymph is collected into lymphatic ducts 7. Collected lymph is drained into the venous system via the subclavian veins Published by Hodder Education © 2010 Helen McGuinness

10 Lymph nodes of head and neck Name Position Areas where drained from Cervical nodes (deep) Deep within neck, located along the path of larger blood vessels (carotid artery and internal jugular vein) Drain lymph from larynx, oesophagus, posterior of scalp and neck, superficial part of chest and arm (superficial) Located at side of neck, over sternomastoid muscle Drain lymph from lower part of ear and cheek region Submandibular nodes Beneath mandible Drain chin, lips, nose, cheeks and tongue Occipital nodes At base of skull Drain back of scalp and upper part of neck Published by Hodder Education © 2010 Helen McGuinness

11 Lymph nodes of head and neck Name Position Areas where drained from Mastoid nodes (post auricular) Behind ear in region of mastoid process Drain skin of ear and temporal region of scalp Parotid nodes At angle of jaw Drain nose, eyelids and ear Published by Hodder Education © 2010 Helen McGuinness

12 Lymph nodes of head and neck Published by Hodder Education © 2010 Helen McGuinness

Areas from where drained 13 Lymph nodes of body Name Position Areas from where drained Cervical nodes (deep) Deep within the neck, located along the path of larger blood vessels Drain lymph from larynx, oesophagus, posterior of scalp and neck, superficial part of chest and arm (superficial) Located at side of neck over sternomastoid muscle Drain lymph from lower part of ear and cheek region Axillary nodes In underarm region Drain upper limbs, wall of thorax, breasts, upper wall of abdomen Supratrochlear/ cubital nodes In elbow region (medial side) Upper limbs which passes through the axillary nodes Thoracic nodes Within thoracic cavity and along trachea and bronchi Organs of thoracic cavity and from internal wall of thorax Published by Hodder Education © 2010 Helen McGuinness

Areas from where drained 14 Lymph nodes of body Name Position Areas from where drained Abdominal nodes Within abdominal cavity, along branches of abdominal aorta Organs within abdominal cavity Pelvic nodes Within pelvic cavity, along paths of iliac blood vessels Organs within pelvic cavity Inguinal In groin Lower limbs, external genitalia and lower abdominal wall Popliteal Behind knee Lower limbs through deep and superficial nodes Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 15 Lymph nodes of body Published by Hodder Education © 2010 Helen McGuinness

16 Other lymphatic organs Other lymphatic organs include the spleen, tonsils and thymus gland. Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 17 Types of immunity Immunity is the ability of the body to resist infection and disease by the activation of specific defence mechanisms. There are two types of immunity – specific and non-specific. Non-specific immunity is programmed genetically from birth and includes mechanical barriers (skin and mucous membrane), chemicals, inflammation, phagocytosis and fever. Specific immunity involves interaction between an antigen and an antibody. An antigen is any substance that the body regards as foreign or potentially dangerous, and against which it produces an antibody. Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 18 Types of immunity An antibody is a specific protein produced to destroy or suppress antigens. There are two types of immune response produced by different types of lymphocytes – humoral immunity involving B-lymphocytes which produce free antibodies that circulate in the bloodstream and cell-mediated immunity effected by helper T-cells, suppressor T- cells and natural killer (NK) cells that recognise and respond to certain antigens to protect the body against their effects. Immunisation is when the body is artificially stimulated into producing antibodies. Published by Hodder Education © 2010 Helen McGuinness

Published by Hodder Education © 2010 Helen McGuinness 19 Types of immunity An allergic reaction may occur when a foreign substance, or antigen, enters the body. An allergic reaction can only occur if the person has already been exposed to the antigen at least once before and has developed some antibody to it. Antibodies are located on the cells in the skin or mucous membranes of the respiratory and gastro- intestinal tracts. Typical antigens include pollen, dust, feathers, wool, fur, certain foods and drugs. Published by Hodder Education © 2010 Helen McGuinness