THE LYMPHATIC SYSTEM Immunity Fluid balance Drainage of toxins and waste products

THE SYSTEM The anatomy consists of: vessels like veins, drainage ducts, capillaries, specific organs with definite capsules Eg spleen and nodes. There are also areas where lymphatic tissue and cells are found in groups such as the Peyers patches in the small intestines The cells of the system are our defence, leucocytes and lymphocytes of many different types.

The anatomy of this system includes Primary organs : Bone Marrow Thymus Secondary organs Spleen Lymph nodes MALT(mucosal associated lymphatic tissue ) The appendix The tonsils The adenoids Peyers patches Lymphatic vessels which are like veins with valves Capillaries which begin as blind ended vessels. Larger lymph vessels Ducts and Trunks Thoracic duct Right lymphatic duct Inguinal trunk Collecting points Cysterna chyli

The Thymus The thymus is entirely formed from lymphatic tissue, it is extremely active up until adolescence and then it is thought to atrophy It does however remain active. The thymus is the site of maturation for T Cells.

The spleen is entirely formed from Lymphatic tissue, it contains both red and white blood cells which are found in the red and white pulp which forms the organ. The spleen breaks down old red and white blood cells and stores blood like a resrvoire. It works with the liver in break down of red blood cells and in foetal blood production. THE SPLEEN

Lymphocytes Lymphocytes are created in the bone marrow from where they travel into the blood stream and to other organs and areas of the system. Some cells are differentiated and fully matured when they leave the bone these are known as B Cells and large lymphocytes. Others are not and will mature either in the blood stream or in specific areas in the system. They include monocytes and macrophage capable of phogocytosis, plus lymphocytes which mature in the thymus; when these cells mature they are called T cells and perform the most important job of orchestrating the immune response.

Blood travels around the body to and from the tissues delivering nutrients and removing waste. Whereas whole blood cannot leave the blood capillaries, the things it carries can and do. They can be carried in interstitial fluid, this fluid bathes the tissues delivering oxygen and food. It also collects carbon dioxide and other waste products. Following the completion of this work it is picked up by lymphatic capillaries, passing through their porous walls where the pressure is lower than in the blood capillaries.

Lymph passes through vessels, is filtered by the lymph nodes and eventually passes into the drainage ducts back to the venous system via the subclavian veins at the base of the neck close to the clavicles.

Lymph Nodes Known as the biological filters of the system ;Lymph from all small and medium vessels passes through them. They are placed strategically around the body at both deep and superficial levels. Each node is formed by lymphatic tissue,encapsulated by a white fibrous tissue outer coating. They vary in size, many are described as coffee bean size and shape. They have an outer cortex and an inner medulla which is divided up by trabeculae into germinal centres with drainage sinuses. The nodes contain many B cells, T cells and macrophage. Lymph enters the node through Afferent vessels and leaves through Efferent vessels.

Positions of Superficial nodes Axillary Inguinal Popliteal There are many deep nodes throughout the pelvic, abdominal and thoracic cavities. The lymph from lower nodes drains into the cysterna chyli at the level of the 1 st lumbar vertabrae, from there it travels up the thoracic duct and into the subclavian veins. Cysterna chyli Thoracic duct Drainage areas. Supratrochlear

Immunity Humeral immunity B cells which in the presence of antigen develop into : 1. Memory cells 2. Plasma cells which produce antibodies In response to antigen Cellular immunity T cells which in the presence of antigen develop into : 1.Memory cells 2.Helper cells 3.Cytolitic cells and 4.killers There are a number of ways of looking at this ; perhaps a simple way is to say that all immunity is acquired, some naturally and passively via our mother’s antibodies and some more actively,which we build through subsequent encounters with germs in our lives. Artificially acquired immunity we get through vaccination. Immunity falls into 2 groups ; Both B and T cells develop into specific types of defence cells in response to specific germs Cellular immune cells deal with viruses. Humeral immune cells deal primarily with bacteria.