Lymphatic System What is the lymphatic system? Lymphatic system: a network of vessels and nodes intermingled among capillaries of the cardiovascular system. It is associated with immunity and the lymph nodes consist of tissue where lymphocytes mature. Function: ● Transport fats from the digestive system to the bloodstream ● Transports lymph ● Return other large molecules such as proteins to blood ● Provide surveillance and defense against disease ● Hemopoiesis (production of lymphocytes) Lymph is a clear, watery fluid that is lost by capillaries. It enters the lymphatic system by diffusion, and it’s the most similar to interstitial fluid. Lymphatic Tissue Lymphatic Tissue The three types of lymphatic tissue are: ● diffuse lymphatic tissue ○ otherwise known as MALT, GALT, SALT, etc. ○ found in connective tissue of most organs ○ no capsule found ● lymphatic nodules ○ no capsule found ○ oval-shaped masses found singly or in clusters ● lymphatic organs ○ capsule present ○ filter tissue fluid Lymphatic Tissue cont. ● ● ● Primary lymphatic organs: where lymphocytes are formed and mature ○ 2 primary lymphatic organs: bone marrow and the thymus gland (lymphocytes are formed in the bone marrow and mature elsewhere) Secondary lymphoid tissue: arranged series of filters monitoring the contents of the extracellular fluids, also the site of lymphocyte activation ○ Lymph nodes, tonsils, spleen, Peyer’s patches, mucosa associated lymphoid tissue (MALT) Tertiary lymphoid tissue: arises in peripheral tissue of adults in response to chronic inflammation (allograft rejection, cancer, etc.) ○ The tissue resembles lymph nodes in their cellular content and organization, high endothelial venules, and lymphatic vessels Lymphatic Structure Lymph Vessels Structure: inner lining of simple squamous epithelial cells, next layer consists of smooth muscle (allows for peristalsis), the outermost layer is the adventitia that consists of fibrous tissue Lymphangion: the functional unit of a lymph vessel, the segment between 2 valves. Has the ability to contract and it can act as a contractile chamber or a resistance vessel. Lymph Nodes ● Lymph Nodes: small bean-shaped structures that are usually less than 2.5 cm in length. Filter lymph before it is returned to the blood ○ Structure: usually surrounded by connective tissue capsule that is divided into compartments called lymph nodules (masses of macrophages and lymphocytes separated by lymph sinuses) ○ The lymph enters through vessels on the convex side and exit at the hilum ○ 3 superficial regions where lymph nodes tend to cluster: ■ Cervical lymph nodes are in the neck, draining the neck and head. ■ Axillary lymph nodes are located in the armpit and upper chest, draining the arm and upper thorax. The upper thorax includes drainage from the skin over the breast and deeper portions of the breast. ■ Inguinal lymph nodes are in the groin and drain the legs and genitals. ● Fourth region: Submental/submaxillary lymph nodes are found in the floor of the mouth and drain lymph from the nose, lips, and teeth. Lymphatic Ducts Lymphatic Ducts ● The two major lymphatic ducts are the right lymphatic duct and the thoracic duct. ○ The right lymphatic duct drains the upper right quadrant of the body into the right subclavian vein and jugular vein. ○ The thoracic duct drains the remaining 75 percent of the body: everything below the diaphragm, the left arm, and the left side of the head, neck, and thorax. Spleen Spleen ● ● ● ● ● ● ● ● ● Largest lymphatic organ Located in the upper left abdominal cavity, beneath the diaphragm, and posterior to the stomach The capsule surrounds the spleen and divides the organ into lobules It has two types of tissue: white pulp and red pulp ○ White pulp: lymphatic tissue consisting mainly of lymphocytes around arteries ○ Red pulp: consists of venous sinuses filled with blood and cords of lymphatic cells (lymphocytes and macrophages) Blood enters spleen through the splenic artery and moves through sinuses where it is filtered and leaves through the splenic vein Lymphocytes in the spleen detect antigens in the blood The spleen also removes old and damaged erythrocytes from the blood It also produces monocytes, lymphocytes, and fetal erythrocytes The sinuses of the spleen can act as a reservoir for blood (can store 350 mL of blood and pump to cardiovascular system) Spleen Primary follicle: the sites of antigen presentation to B cells, and subsequent proliferation and differentiation Marginal zone: area between red and white pulp PALS: populated largely by T cells and surround central arteries within the spleen; the PALS T-cells are presented with blood borne antigens via myeloid dendritic cells. Germinal center: where mature B cells proliferate, differentiate, and mutate their antibody genes (through somatic hypermutation aimed at achieving higher affinity), and switch the class of their antibodies Thymus Thymus ● ● ● ● ● The thymus is a soft organ with two lobes that is located anterior to the ascending aorta and posterior to the sternum. Larger in infants and decreases in size as people age The thymus processes the maturation of special lymphocytes called T-lymphocytes or T-cells. After the lymphocytes have matured, they enter the blood and go to other lymphatic organs where they help provide defense against disease. The thymus also produces a hormone, thymosin, which stimulates the maturation of lymphocytes in other lymphatic organs. Thymus Hassall’s corpuscle: one of the small bodies of the medulla of the thymus having granular cells at the center surrounded by concentric layers of modified epithelial cells — called also thymic corpuscle. The function is unclear. Accessory Lymphatic Organs Tonsils ● ● ● The tonsils are clusters of lymph nodes embedded at the base of the pharynx or throat. Tonsils contain deep pits called crypts which hold food debris, bacteria, and white blood cells. The three main sets of tonsils are: the pharyngeal tonsils, or adenoids; the palatine tonsils; and the lingual tonsils. ○ The adenoids can be found on the wall of the nasopharynx. ○ The palatine tonsils are located at the edge of the oral cavity, or on the palate of the mouth. The palatine tonsils are the largest and most susceptible to infection (tonsilitis). ○ Lingual tonsils are present on each side of the root of the tongue. Peyer's Patches Peyer's Patches are small masses of lymphatic tissue found in the ileum of the small intestine. They analyze and respond to pathogens in the intestine. Appendix The appendix has a minor role in immunity because it stores good bacteria. Blockage can lead to appendicitis, which can be fatal if the appendix ruptures. Accessory Lymphatic Organs Peyer’s Patches Lymphatic vs Cardiovascular System Differences: The lymphatic system is one-way and the lymph vessels do not form a complete circuit between the lymph organs. Lymph is also not pumped like blood; it is moved by contractions of skeletal muscle and other body movements. Similarities: Both lymphatic and blood vessels have the same 3 tunicas and valves to prevent backflow. Lymphatic and Immune System The organs of the lymphatic system contains lymphocytes and other white blood cells which destroy bacteria, dead tissue, and foreign matter. Some parts of the lymphatic system are also sites for lymphocyte creation and maturation. The lymphatic system also filters lymph and removes foreign bodies. After these substances have been filtered, the lymph returns to the veins. Absorption of Fats The second function of the lymphatic system is the absorption of fats and fat-soluble vitamins from the digestive system and the subsequent transport of these substances to the venous circulation. Absorption of fats: ● ● ● Hydrolysis of fats by lipase generates fatty acids and monoglycerides (single fatty acid joined to glycerol), this is then absorbed by epithelial cells and recombined into triglycerides There triglycerides are then coated with phospholipids, cholesterol, and proteins to form globules called chylomicrons which are water soluble Chylomicrons are first transported from an epithelial cell into the intestine via a lacteal ○ Lacteals are part of the vertebrate lymphatic system Absorption of Fats Disorders Will be covered in detail: Lymphadenopathy, lymphedema, Hodgkin’s Lymphoma, non-Hodgkin lymphoma Hodgkin’s Lymphoma Hodgkin lymphoma is a cancer of lymph tissue involving immune cells. The cancer is characterized by a type of lymphoid cell called the Reed-Sternberg cell. The Reed-Sternberg cell is in most cases a B cell and clonal. They are very large cells with abundant cytoplasm and two or more oval lobulated nuclei containing large nucleoli (red in the image below). The cause of Hodgkin’s lymphoma is unknown. Symptoms: The first sign is often a swollen lymph node that appears w/o cause and may spread to other lymph nodes. ● Fever and chills that come and go ● Itching all over the body that cannot be explained ● Loss of appetite ● Drenching night sweats ● Weight loss that cannot be explained ● Coughing, chest pains, or breathing problems Risk factors: ● Excessive sweating ● More common among people ● Pain or feeling of fullness below the ribs due to swollen spleen or liver 15-35 and 50-70 years old ● Pain in lymph nodes after drinking alcohol ● Past infection of Epstein-Barr virus ● Skin blushing or flushing ● People with HIV Hodgkin’s Lymphoma Treatment: Treatment depends on the following: ● The type of Hodgkin lymphoma ● The stage ● Your age and other medical issues ● Other factors, including weight loss, night sweats, and fever You may receive chemotherapy, radiation therapy, or both. High-dose chemotherapy may be given when Hodgkin lymphoma returns after treatment or does not respond to the first treatment. This is followed by a stem cell transplant that uses your own stem cells. Non-Hodgkin Lymphoma Non-Hodgkin's Lymphoma Non-Hodgkin's Lymphoma is a more common form of Hodgkin's Disease, with more widespread malignancy and a higher death rate. The main difference between Hodgkin’s and Non-Hodgkin’s is the presence of Reed-Sternberg cells. Symptoms: ● Swelling in the lymph nodes in the neck, underarm, groin, or stomach. ● Fever for no known reason. ● Recurring night sweats. ● Feeling very tired. ● Weight loss for no known reason. ● Skin rash or itchy skin. ● Pain in the chest, abdomen, or bones for no known reason. When fever, night sweats, and weight loss occur together, this group of symptoms is called B symptoms. Risk factors: ● Being older, male, or white. Having one of the following medical conditions: ● An inherited immune disorder ● An autoimmune disease ● HIV/AIDS. ● Human T-lymphotropic virus type I or Epstein-Barr virus infection. ● Helicobacter pylori infection. Taking immunosuppressant drugs after an organ transplant. Non-Hodgkin Lymphoma Treatment: Treatment depends on: ● The specific type of NHL ● The stage when you are first diagnosed ● Your age and overall health ● Symptoms, including weight loss, fever, and night sweats You may receive chemotherapy, radiation therapy, or both. Blood transfusions or platelet transfusions may be required if blood counts are low. Lymphedema Lymphedema: is the buildup of fluid in soft body tissues when the lymph system is damaged or blocked. Cause: Symptoms: Risk factors: When part of the lymph system is damaged or blocked, fluid cannot drain from nearby body tissues. Possible signs of lymphedema include swelling of the arms or legs. Cancer and its treatment are risk factors for lymphedema. ● There are two types of lymphedema. ● ● Primary lymphedema is caused by the abnormal development of the lymph system. Secondary lymphedema is caused by damage to the lymph system. The lymph system may be damaged or blocked by infection, injury, cancer, removal of lymph nodes ● ● ● Swelling of an arm or leg, which may include fingers and toes. (Stage II, Stage III is major swelling) A full or heavy feeling in an arm or leg (Stage I) A tight feeling in the skin. Trouble moving a joint in the arm or leg. ● ● ● ● Removal and/or radiation of lymph nodes in the underarm, groin, pelvis, or neck. Being overweight or obese. Slow healing of the skin after surgery. A tumor that affects or blocks lymph ducts, nodes, or vessels. Scar tissue in the lymph ducts under the collarbones, caused by surgery or radiation therapy. Lymphedema Prevention: Primary lymphedema cannot be prevented Secondary lymphedema: Avoid heavy lifting (including carrying heavy purses) with an affected arm. ● Drink plenty of fluids; dehydration can worsen lymphedema. ● Avoid environmental irritants in the affected area, such as insect bites or stings and sunburn. ● Practice good skin care and hygiene. ● Don't wear tight clothing or jewelry on the affected limb. Even the use of blood pressure cuffs on an affected arm should be avoided. Treatment: Damage to the lymph system cannot be repaired. Treatment of lymphedema may include the following: ● Pressure garments: put pressure on limbs to move prevent fluid from building up ● Exercise: helps the lymph vessels move lymph out of affected limbs ● Bandages: prevent area from refilling with fluid after it has moved out ● Skin care: prevent infection and keep skin from cracking ● Compression device: pumps connected to sleeve that wraps around the limb and applies pressure on and off Lymphadenopathy Lymphadenopathy: swollen lymph nodes Common areas: groin, armpit, neck, (there is a chain of lymph nodes on either side of the front of the neck, both sides of the neck, and down each side of the back of the neck), under the jaw and chin, behind the ears, on the back of the head Cause: ● Infections ● Autoimmune diseases ● Cancers Symptoms: When your lymph nodes first swell, you might notice: ● Tenderness and pain in the lymph nodes ● Swelling that may be the size of a pea or kidney bean, or even larger in the lymph nodes Other signs and symptoms you might have include: ● General swelling of lymph nodes throughout your body ● Hard, fixed, rapidly growing nodes, indicating a possible tumor Lymphadenopathy Treatment depends on the cause of swollen lymph nodes If bacterial infection, then treat with antibiotics Lifestyle and home remedies ● ● ● Apply a warm compress Take an over-the-counter pain reliever. Get adequate rest.