L8 Lymphatic System PDF

Lymphatic system Dr. Marim Fayz Lecture of anatomy & embryology Definition The lymphatic system is part of the vascular system and an important part of the immune system, that consists of a network of vessels, tissues and organs that help the body to get rid of...

Lymphatic system Dr. Marim Fayz Lecture of anatomy & embryology Definition The lymphatic system is part of the vascular system and an important part of the immune system, that consists of a network of vessels, tissues and organs that help the body to get rid of toxins, waste and other unwanted materials. It also helps maintain fluid balance in the body. Structure of Lymphatic System Lymphatic organs Network of lymphatic vessels Lymph Lymphatic Organs Primary lymphatic organs Produce lymphocytes from stem cells and are sites of B and T cells maturation. Bone marrow Thymus fetal liver Secondary lymphatic organs They are the sites of further differentiation of lymphocytes. Lymph nodes Spleen Tonsils MALT  Bone Marrow It fills the cavities of the bones. From the bone marrow, B cells immediately join the circulatory system. On the other hand, T cells travel from the bone marrow to the thymus, where they develop further. Mature B and T lymphocytes exit the primary lymphatic organs and transported via the bloodstream to secondary lymphoid organs in search of pathogens where they become active by contact with foreign materials.  Thymus It is an soft, bilobed organ. Site of thymus  Lymph Nodes They are an organized collection of lymphatic tissue. They are distributed all over the body along the lymphatic vessels. They contain numerous lymphocytes, which filter the flow of lymph passing through them. Each of them has afferent and efferent lymphatic vessels. Size of lymph node  Function of Lymph Nodes Act as filter for lymph fluid, to remove debris and pathogens from the lymph. Play an important role in the immune response to infection by the lymphocytes, first encounter the pathogens (antigens)….. activates lymphocytes …. form antibodies. Activated lymphocytes carried in the lymph, and eventually enter the bloodstream, which distributes them throughout the body.  Spleen Is a large encapsulated mass of vascular and lymphoid tissue Site: Structure & Function of spleen: It filters the blood. It contains great numbers of both B and T lymphocytes that kill the foreign microorganisms and stop infections from spreading. The spleen has only efferent vessels.  Pharyngeal The Tonsils Palatine Each tonsil is a mass of lymphoid tissue. Lingual tonsils.  The tonsils do not possess afferent lymphatics. Its efferent lymphatics drain to regional lymph node. The tonsils help to trap pathogens, such as bacteria or viruses, that enter through mouth or nose. They contain immune cells that produce antibodies that kill these pathogens before they can spread to the rest of the body.  The circulating lymph Lymph is a clear and colorless fluid; Lymph is the term used to describe interstitial fluid once it has entered the lymphatic capillaries. As blood circulates through the body, blood plasma leaks into tissues through the thin walls of the capillaries. The portion of blood plasma that escapes is called interstitial or extracellulr fluid once the body's cells have delivered its nutrients and removed debris, most of this fluid returns to the venous circulation through tiny blood vessels called venules and continues as venous blood. The remainder becomes  Lymphatic capillaries o They form wide-meshed plexuses in the extracellular matrices of most tissues. They begin as dilated, blind-ended tubes with larger diameters than those of blood capillaries. They are located interlaced among the arterioles and venules of the circulatory system, where interstitial fluid enters the lymphatic system to become lymph fluid. Tissues that densely packed with lymphatic capillaries: lungs Genitourinary GIT dermis of the skin. Tissues that haven’t lymphatic capillaries: CNS bone marrow teeth epidermis of the skin cornea of the eye.  Lymphatic circulation The lymphatic capillaries converge and join to form smaller lymphatic vessels, which in turn join to form larger lymphatic vessels, which are similar to veins. Called afferent lymphatic vessels. Lymphatic vessels deliver lymph to lymph nodes Then, efferent lymphatic vessels leave the lymph nodes. These intern collected to form larger lymphatic vessels known as lymphatic trunks. Lymphatic trunks drain into lymphatic duct. Through which the lymph is returned to the systemic venous circulation via either the right Lymphatic ducts o The upper right quadrant of the body (right sides of the head& neck, right side of the chest, and right upper limb) drains via the right lymphatic duct. o The remaining portions of the body drain into the larger thoracic duct.  The thoracic duct It is vein – like vessel, which conveys most of the lymph fluid to the venous blood stream. It is about 38-45cm long in adults. It extends from the level of thoraco-lumbar disc to the base of the neck. It begins from the upper end of cisterna chyli.