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LymphaticSystem Lymphatic System The Lymphatic System By Scott Ford, M.Ed. •Composed of: •Lymph •Lymphatic vessels •Lymphatic tissue •Lymphatic organs http://mrfordsclass.net | YouTube: mrfordsclass | Facebook: mrfordsclasslearning | Twitter: mrfordsclass Basic Functions What is Lymph • Brings materials back to the blood system • Carries fluid from tissue spaces back to the blood • Blood capillaries absorb around 85% of fluid that is filtered out of them • The lymphatic system catches the rest • Carries away proteins and large particulate matter from tissue spaces • Immunity • Because the lymphatic system brings back large molecules and fluids from the body there are check points through the lymphatic system designed to identify and destroy bad stuff • Lipid Absorption • Lacteals found in the small intestine absorbed dietary lipids that cannot be absorbed by the blood capillaries • Typically a clear, colorless fluid • Similar to blood plasma Composition of Lymph Edema • As lymph first flows from tissues it is almost the same as interstitial fluid • When the system fails proteins and fluid accumulate in the interstitium • Protein concentration is around 2g/dL, in some tissue like it can be as high as 6g/dL • A major route for the absorption of nutrients from the gastrointestinal tract • Some others things that can be found: • Hormones • Bacteria • Viruses, Cellular debris, macrophages www.mrfordsclass.net • As blood moves through the circulatory systems fluids and small molecules pass from the plasma into the surrounding tissues • Much of this fluid is reabsorbed by the blood vessels, lymph is a collection of the fluid that does not make it back • 85% is reabsorbed • Also found within lymph are larger molecules that can not pass into the blood capillaries, like large proteins, fats and other substance • Proteins need the lymphatic system to get back into the circulatory system • Accumulation of proteins in the interstitial space increase colloid osmotic pressure of the interstitial fluid, allows more fluid filtration into interstitium 1 LymphaticSystem The Path Lymphatic Capillaries • Lymphatic systems primary job is to bring fluids back into the circulatory system • Because it brings fluids back from the interstitial spaces, it makes sense to start there • Microscopic tubes that are found within the interstitial spaces • Not found in: CNS, cartilage, cornea, bone and bone marrow Lymphatic capillaries Lymphatic vessels Lymph node Lymphatic vessel Lymphatic Vessels • Like veins but thinner • Three layers: • Tunica Intima • Tunica Media • Tunica Adventitia • Semilunar valves prevent lymph from flowing backwards Lymphatic trunk Collecting duct Subclavian vein • Walls are like blood capillaries • Single layer endothelium • Special lymphatic capillaries in the small intestine absorb digested fats TunicaIntima • Innerendotheliallining TunicaMedia • Middlelayerofsmoothmuscleandelasticfibers TunicaAdventitia • Outerlayerofconnectivetissue Lymphatic Nodes Lymphatic trunk • Vary in size and shape • Typically bean shaped • Lymphatic vessels drain into trunks • Filter lymph for microorganism, infected cells and other materials that do not belong www.mrfordsclass.net • Trunks are named for the regions they serve • Lumbar trunk • Intestinal • Intercostal • Bronchomediastinal trunks • Subclavian • Jugular 2 LymphaticSystem Collecting duct Collecting duct • Lymphatic trunks drain into one of two collecting ducts • Thoracic Duct • Right Lymphatic Duct • Lymph from left side of head, left arm, parts of chest enter thoracic duct • Most of lymph from lower part of body flows up thoracic duct and empties into venous system at junction of left interior jugular vein and subclavian vein • Lymph from right side of neck, head, right arm, parts of thoracic enter right lymph duct, enters the venous system at junction of right subclavian vein and internal jugular veins Thoracic Duct Right Lymphatic Duct • Largest and longer of the two • Starts in the abdomen • Passes up through the diaphragm next to aorta • Comes up anterior to vertebral column • Empties into left subclavian • Drains from following trunks: • Intestinal • Lumbar • Intercostal trunks • Left subclavian • Left jugular • Left bronchomediastinal trunks • Starts at the right thorax at the merger of the right jugular, right subclavian and right bronchomediastinal trunk • Receives the drainage from: • Right arm • Right side of thorax • Right side of head • Empties into the right subclavian vein Lymph Movement Lymph Movement • Flow of lymph is similar to movement of venous blood • Valves preventing lymph from flowing backwards • Total rate of lymph flow is around 120 mL/hr • 2-3L/day • Rate of lymph flow is determined by • Interstitial fluid hydrostatic pressure • Lymph flow is very low in normal situations • If the pressure rises lymph flow can increase • If pressure increases too much the flow remains constant • Lymphatic pump • Squeezing of the vessels that move lymph along the vessels • External factors like exercise the lymphatic pump may dramatically increase movement of lymph • Like venous blood, the movement of lymph is a very low pressure system • Under even less pressure then venous blood • Basically lymph moves when the lymph vessels are squished www.mrfordsclass.net 3 LymphaticSystem The Lymph Nodes Garbage Pick Up • Located along the lymphatic pathways • The most numerous of the lymphatic organs (covered later) • Bacterial and other small materials can easily pass into the lymph • Contain large numbers of lymphocytes and macrophages • Primary Jobs • Filter possible bad stuff before it returns to the bloodstream • Monitor body fluids • Site of T and B cell activation • Lymph passes through series of check points, nodes, on its way to the blood • In these nodes the bacteria and other junk is filters out, or phagocytized by macrophages Anatomy of Lymph Nodes Anatomy of Lymph Nodes • Vary in size and shape • Typically bean shaped • Materials entering the node attach to the convex surface • Leaving node at hilum • An indented area • Nodes are encapsulated by connective tissue Location of Nodes Lymphatic Organs • There are around 450-600 lymph nodes found throughout the body • Depends on source • There is lymphatic tissue, which is basically a collection of lymphocytes in connective tissue • The major collection of lymph nodes are: • Cervical region • Axillary region • Supratrochlear region • Inguinal region • Pelvic cavity • Abdominal cavity • Thoracic cavity • Primary Lymphatic Organs (produce mature lymphocytes) • Red bone marrow • Thymus www.mrfordsclass.net • The capsule extends into the node and compartmentalized the node into the structural units known as lymph nodules • Lymphatic organs are more defined • Secondary Lymphatic Organs (mature lymphocytes migrate to) • Lymph nodes • Tonsils • Spleen 4 LymphaticSystem Red Bone Marrow Thymus • Two types of bone marrow: • Yellow • Adipose tissue, not worries about it for the lymphatic system • Red • Discussed in the endocrine system • Red Bone Marrow produces blood (hemopoiesis) • Supplies lymphocytes to the immune system • A soft structure enclosed in a capsule • Located in the mediastinum posterior to the sternum • Active in children • After puberty starts to shrink and fill with fat • As a child it plays a part in production of T lymphocytes Tonsils Spleen • Patches of lymphatic tissue found at the entrance to the pharynx • Protect the body against pathogens that can enter through the mouth or nose • Largest of the lymphatic organs • Found in the upper left portion of abdominal cavity • Posterior and lateral to stomach • Three sets of tonsils • Pharyngeal tonsil (adenoids) • Palatine tonsils • The biggest of the three • Most common site of infection • The tonsils remove din a tonsillectomy • Lingual tonsils www.mrfordsclass.net • Allows for cells of the immune system to proliferate • Monitors blood for foreign or damaged cells • Removes old blood cells • White Pulp • Deals with immune response • Red pulp • Mechanical filtration of red blood cells 5