Lymphatic System Bullet Notes PDF

Bullet Notes on LYMPHATICS Functions of the Lymphatic System: 1. Fluid Balance: Returns excess interstitial fluid to the bloodstream to maintain fluid balance. Prevents tissue swelling (edema). 2. Fat Absorption: Absorbs fats and fat-soluble substances from the digestiv...

Bullet Notes on LYMPHATICS Functions of the Lymphatic System: 1. Fluid Balance: Returns excess interstitial fluid to the bloodstream to maintain fluid balance. Prevents tissue swelling (edema). 2. Fat Absorption: Absorbs fats and fat-soluble substances from the digestive tract. Specialized lymphatic vessels called lacteals absorb lipids and transport them as chyle. 3. Defense/ Immune Response: Filters lymph and blood to detect and respond to foreign substances. Houses and activates lymphocytes, contributing to immune defense. Provides a site for immune cells to encounter antigens and initiate a response The lymphatic system includes: lymph, lymphatic vessels, lymph nodes, tonsils, spleen, and thymus The lymphatic system does not circulate fluid to and from tissues. It carries fluid in one direction, from tissues to circulatory system. Fluid moves from blood capillaries into tissue spaces. Most of the fluid returns to the blood, but some of the fluid moves from the tissue spaces into lymphatic capillaries to become lymph. Lymphatic capillaries are present in most tissues of the body except the CNS, bone marrow, and tissues lacking blood vessels, such as the epidermis and cartilage. Lymphatic capillaries join to form larger lymphatic vessels which resembe small veins. The lymphatic vessel converge and eventually empty into the blood at two locations (1) Lymphatic vessels from the right upper limb and the right half of the head, neck, chest form the RIGHT LYMPHATIC DUCT which empties into the right subclavian vein (2) Lymphatic vessels from the rest of the body, enter the THORACIC DUCT Summary: Fluid moves from capillaries into tissues and from tissues into lymphatic capillaries to form lymph. Valves, located along in lymphatic vesseks, also ensure one-way flow of lymph. Tonsils have 3 groups: The paired palatine tonsils- located on each side of the posterior opening of the oral cavity (removal is called tonsillectomy) The pharyngeal tonsils - located near the internal opening of the nasal cavity (removal is callee adenoidectomy) The lingual tonsil - is on the posterior surface of the tongue The tonsils form a protective ring of lymphatic tissue around the openings between the nasal and oral cavities and the pharynx. They protect against pathogens and other potential harmful material entering from the nose and mouth. Lymph nodes - rounded structures, vary from size of a small seed to that of a shelled almond. They are distributed along the various lymphatic vesseks, and most lymph passes through at least one lymph node before entering the blood. They can be classified as superficial and deep There are 3 superficial aggregations of lymph nodes on each side of the body: (1) inguinal nodes in the groin (2) the axillary nodes in the axilla (armpit) (3) the cervical nodes in the neck A dense connective tissue CAPSULE surrounds each lymph node Extensions of the capsule, called TRABECULAE, subdivide a lymph node into compartments containing lymphatic tissue and lymphatic sinuses. The lymphatic tissue consists of lymphocytes and other cells that can form dense aggregations of tissue called LYMPHATIC NODULES. Note that lymphatic nodules are NOT the same as lymph nodes. Lymphatic nodules are areas of tissue within lymph nodes and other organs as well. Lymph flows through lymph nodes, passing through the different areas Lymph enters the lymph node through the afferent vessels. Once inside the lymph node, lymph passes through the lymphatic tissue and sinuses and eventually exits through efferent vessels. As lymph moves througn the lymph nodes, two functions are performed. First function: To activate the immune system. Pathogens in the lymph can stimulate lymphocytes in the lymphatic tissue to divide. The lymphatic nodules containing the rapidly dividing lymphocytes are called GERMINAL CENTERS. The newly produced lymphocytes are relessee into the lymlh and eventually reach the blood, where they circulate and enter other lymphatic tissues. The lynphocytes are part of the ADAPTIVE IMMUNITY that destroys pathogenz. Second function of the lymph nodes: To remove pathogens from the lymph througn the action of macrophages. Cancer cells can spread from a tumor site to pther areas of the body through the lymphatic system. At first, however, as the cancer cells pass through the lymphatic system, they are trapped in the lymph nodes, which filter the lymph. During radical cancer surgery, malignant (cancerous) lymph nodes are removed, and their vesseks are cut and tied off to prevent cancer from spreading. Spleen— roughly the size of a clenched fist, located in the left , superior corner of the abdominal cavity. The spleen is located in the left, superior cornet of the abdominal cavity The spleen has an outer CAPSULE of dense connective tissye and a small amount of smooth muscle. TRABECULAE from the capsule divide the spleen into small, interconnected compartments containing two specialized types of lymphatic tissue: (1) white pulp - lymphatic tissue surrounding the arteries within the spleen (2) red pulp - is associated with the veins. It consists of a fibrous network, filled with macrophages and rbcs, and enlarged capillaries that connect to the veins The spleen filters BLOOD instead of lymph. Cells within the spleen detect and respond to foreign substances in the blood and destroy old and damaged RBCs. Lymphocytes in the white pulp can be stimulated in the same manner as in lymph nodes. Before blood leaves the spleen through veins, it passes through the red pulp. Macrophages in the red pulp remove foreign substances and worn-out RBCs through phagocytosis. The spleen also functions as a reservoir, holding a small volume of blood. The spleen is often ruptured in traumatic abdominal injuries. Thymus - is a bilobed organ roughly triangular in shape. It is located in the superior mediastinum, the partition dividing the thoracic cavity into left and right parts. Each lobe of the thymus is surrounded by a thin connective tissue CAPSULE. TRABECULAE fro, the capsule divide each lobe into LOBULES. Near the capsule and trabeculae, lymphocytes are numerous and form dark-staining areas called the CORTEX. A lighter-staining, central portion for the lobules, called the MEDULLA, has fewer lymphocytes. The thymus is the site of maturation of T-lymphocyte cells. Large numbers of T cells are produced in the thymus, but most degenerate. The T cells that survive the maturation process are capable of reacting to pathogens. The mature T cells migrate to the medulla, enter the blood, and travel to other lymphatic tissues, ahere they help protect against pathogens. @@ Comparison of the filtration functions of the lymph nodes and spleen: Lymph Nodes: Filtration of Lymph: Lymph nodes filter lymph, the fluid that circulates through the lymphatic system. Primary Function: Detect and trap pathogens, foreign particles, and cancer cells in lymph, preventing them from entering the bloodstream. Immune Response: Contains B-cells, T-cells, and macrophages that help identify, neutralize, and initiate an immune response to the trapped pathogens. Spleen: Filtration of Blood: The spleen filters blood rather than lymph. Primary Function: Removes old or damaged red blood cells (RBCs) and recycles iron. It also traps pathogens and foreign particles in the bloodstream. Immune Response: Contains white pulp rich in lymphocytes and macrophages that detect and destroy blood-borne pathogens. Key Differences: Lymph Nodes filter lymph (tissue fluid) and respond to localized infections.  Spleen filters blood, removes old RBCs, and responds to systemic blood-borne infections. In summary: Lymph nodes handle local immune surveillance via lymph, while the spleen manages blood filtration and systemic immune functions. @@@@ 1. Lymphatic System Overview Functions: Fluid balance, fat absorption, immune response. Components: Lymph, lymphatic vessels, lymph nodes, tonsils, spleen, thymus. 2. Lymph and Lymphatic Vessels Lymph: Fluid derived from interstitial fluid; contains lymphocytes. Lymphatic Capillaries: Blind-ended vessels that collect fluid; located throughout most of the body. Lymphatic Vessels: Have valves to ensure one-way flow; merge to form larger ducts. Major Ducts: Thoracic Duct: Drains most of the body. Right Lymphatic Duct: Drains the right upper limb, right thorax, and right head/neck. 3. Lymphatic Organs and Tissues Primary Lymphatic Organs: Red Bone Marrow: Site of B-cell maturation. Thymus: Site of T-cell maturation; shrinks with age (involution). Secondary Lymphatic Organs: Lymph Nodes: Filter lymph; contain lymphocytes and macrophages. Located in clusters, e.g., cervical, axillary, inguinal regions. Spleen: White Pulp: Immune function, contains lymphocytes. Red Pulp: Removes old red blood cells and platelets. Tonsils: Protect against inhaled/ingested pathogens; types include palatine, pharyngeal, and lingual. 4. Lymph Flow Driven by skeletal muscle contraction, thoracic pressure changes, and valves. Lymph moves from capillaries to vessels, through nodes, and eventually into the bloodstream via ducts. 5. Immune System Function Innate Immunity: Non-specific defense; includes barriers (skin, mucous membranes), phagocytic cells (macrophages, neutrophils), natural killer cells, and inflammation. Adaptive Immunity: Specific defense; involves T-cells and B-cells. Humoral Immunity: B-cells produce antibodies.  Cell-mediated Immunity: T-cells destroy infected or abnormal cells. 6. Immune Cells Lymphocytes: B-cells (produce antibodies), T-cells (cytotoxic, helper, regulatory). Antigen-presenting Cells: Macrophages, dendritic cells. 7. Antibody-Mediated Immunity (Humoral) B-cells activated by antigen binding and T-helper cell signals. Plasma Cells: Produce antibodies. Memory B-cells: Provide faster response upon re-exposure to antigen. 8. Cell-Mediated Immunity Cytotoxic T-cells: Directly kill infected cells. Helper T-cells: Enhance immune response. Memory T-cells: Provide long-term immunity. 9. Immune Response Activation Primary Response: First exposure to antigen; slower, produces memory cells. Secondary Response: Faster, more effective due to memory cells. 10. Clinical Considerations Edema: Excess fluid accumulation due to lymphatic obstruction. Tonsillitis: Inflammation of the tonsils. Lymphedema: Localized swelling due to impaired lymphatic drainage. HIV/AIDS: Virus attacks T-helper cells, weakening adaptive immunity. @@@ 1. Innate Immunity (Non-Specific Immunity) General Features: First line of defense; non-specific; immediate response. Physical Barriers: Skin, mucous membranes. Chemical Barriers: Stomach acid, lysozyme in tears. Cells Involved: Phagocytes: Macrophages and neutrophils (engulf and digest pathogens). Natural Killer (NK) Cells: Kill virus-infected or tumor cells. Processes: Inflammation: Localized tissue response to injury, attracts immune cells. Fever: Elevated body temperature to inhibit pathogen growth. Complement System: Proteins that help destroy pathogens. 2. Adaptive Immunity (Specific Immunity) General Features: Specific response to pathogens; slower to initiate but has memory. Key Cells: B-cells: Involved in antibody-mediated immunity. T-cells: Involved in cell-mediated immunity. Characteristics: Specificity: Targets specific antigens.  Memory: Faster and stronger response upon re-exposure to an antigen. 3. Antibody-Mediated Immunity (Humoral Immunity) B-cells: Produced in bone marrow and differentiate into plasma cells and memory B-cells. Plasma Cells: Produce antibodies that neutralize or mark pathogens for destruction. Antibodies: Bind to specific antigens to neutralize pathogens or make them targets for other immune cells. Memory B-cells: Provide long-term immunity and a quicker response upon re-exposure to the same antigen. 4. Cell-Mediated Immunity T-cells: Produced in bone marrow, mature in the thymus. Types of T-cells: Cytotoxic T-cells (CD8+): Directly kill infected or cancerous cells. Helper T-cells (CD4+): Activate other immune cells (B-cells and cytotoxic T-cells). Regulatory T-cells: Suppress immune response to prevent overactivity. Targets: Effective against intracellular pathogens (e.g., viruses, some bacteria) and abnormal cells (e.g., cancer). 5. Acquired Immunity Active Immunity: Natural Active Immunity: Exposure to a pathogen leads to disease and immune memory (e.g., chickenpox). Artificial Active Immunity: Vaccination stimulates immune response without causing disease. Passive Immunity: Natural Passive Immunity: Transfer of antibodies from mother to baby (placenta or breast milk). Artificial Passive Immunity: Injection of antibodies (e.g., anti-venom). @@@ 1. Lymph: What it is: A clear, colorless fluid derived from interstitial fluid. Function: Maintains fluid balance: Collects excess tissue fluid and returns it to the bloodstream, preventing edema. Immune surveillance: Contains lymphocytes, which help detect and fight infections. Transports nutrients: Carries absorbed fats (chyle) from the small intestine (via lacteals) to the blood. Significance: Without lymph, excess tissue fluid would accumulate, causing swelling and interfering with nutrient and waste exchange. 2. Lymphatic Vessels:  What they are: A network of vessels that transport lymph throughout the body, beginning with lymphatic capillaries and merging into larger lymphatic vessels and trunks. Function: Transport lymph: Collect lymph from tissues and move it towards the thoracic duct or right lymphatic duct, which return it to the bloodstream via the subclavian veins. One-way flow: Contain valves to ensure that lymph flows in one direction, preventing backflow. Significance: They act as the “plumbing” system of the immune system, ensuring excess fluid, waste products, and immune cells are efficiently transported to lymph nodes and eventually back into the bloodstream. 3. Lymph Nodes: What they are: Small, bean-shaped structures located along lymphatic vessels that act as filters for lymph. Function: Filter lymph: Remove pathogens, debris, and abnormal cells from lymph before it re-enters the bloodstream. Immune activation: House B-cells, T-cells, and macrophages. These cells identify and respond to infections, foreign particles, and abnormal cells. Immune response coordination: Serve as hubs where immune responses are coordinated and where pathogens are destroyed. Significance: Critical for immune defense; without lymph nodes, pathogens and harmful particles would not be properly filtered and neutralized before reaching the bloodstream. Summary of Differences: Lymph: The fluid containing immune cells, proteins, and waste products. Lymphatic Vessels: Transport system for lymph, moving it from tissues to the bloodstream. Lymph Nodes: Immune “checkpoints” that filter lymph and initiate immune responses. Together, these structures ensure fluid balance, transport fats, and provide immune defense against infections and disease. @@@ Lymph originates from interstitial fluid (also known as tissue fluid), which is the fluid that surrounds cells in tissues. Here’s how it forms 1. Blood Capillaries: As blood flows through capillaries, some plasma (containing water, nutrients, and small proteins) leaks out into the surrounding tissues to deliver nutrients and remove wastes. 2. Interstitial Fluid Formation: This leaked plasma forms the interstitial fluid that bathes the cells. It contains water, dissolved substances, and immune cells. 3. Lymphatic Capillaries: Excess interstitial fluid is collected by lymphatic capillaries, tiny, permeable vessels found throughout the body. Once inside these capillaries, the fluid is called lymph. Lymph then flows through the lymphatic system, ultimately returning to the bloodstream via the subclavian veins. This process helps maintain fluid balance in tissues and facilitates immune surveillance. Lymph contains the following key components: 1. Water: The majority of lymph is water, similar to plasma. 2. Proteins: Small amounts of plasma proteins that have leaked out of the capillaries. 3. Lymphocytes: Mainly B-cells and T-cells, which are crucial for immune surveillance and responses. 4. Dissolved Substances: Nutrients (e.g., glucose, lipids absorbed from the digestive tract). Electrolytes (such as sodium, chloride, and potassium). 5. Waste Products: Metabolic wastes from cells (e.g., urea, CO₂). 6. Pathogens: Bacteria, viruses, and other microbes that are transported to lymph nodes for immune processing. 7. Cellular Debris: Fragments from damaged cells or tissues. 8. Fats (Chyle): Lacteals in the small intestine absorb fats and fat-soluble vitamins, forming chyle, a milky white fluid. Lymph essentially acts as an intermediary fluid between blood and tissues, transporting immune cells and helping maintain fluid balance in the body.