Lymphatic Vessels+ducts
Capillary vessels and ducts that return lymph from the tissue to the blood. Carry lymph from the tissues to the lymphatic organs and then deliver it to the blood plasma
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| Term | Definition |
|---|---|
| Lymphatic Vessels+ducts | Capillary vessels and ducts that return lymph from the tissue to the blood. Carry lymph from the tissues to the lymphatic organs and then deliver it to the blood plasma |
| Lymph nodes | Pathogens & other harmful substances that are filtered from the lymph by specialized cells. The lymph leaves the node and continues the venous circulation. |
| Tonsils & Adenoids | lymphoid structures that protect entry to the respiratory system. |
| Lacteals | Absorb fats that cannot go into the blood. |
| interstitial fluid | Plasma from arterial blood that flows out of the arterioles into the capillaries and then flows into the spaces between the cells + tissues. Delivers nutrients, oxygen, and hormones to the cell. When it leaves the cell, it brings with it waste products + protein molecules that were created in the cells. About 90% of fluid returns to the bloodstream. Higher pressure |
| Lymph | 10-15% of returning interstitial fluid. Clear, watery fluid containing electrolytes and proteins. Collects the protein molecules within cells as it leaves and removes dead cells, debri, and pathogens from intercellular spaces. Lower protein concentration. Contains water, viruses, bacteria, dead cells, proteins, lipids, leukocytes, hormones, and cancer cells. |
| Lymphatic Circulation system | Flows in only one direction going upward. Lymph is filtered by lymph nodes located among lymphatic vessels. |
| Lymphatic Capillaries | Separate briefly to allow the lymph to enter the capillary. Microscopic that absorb interstitial fluid. Lower pressure. Not connected to other vessels. The blunt end absorbs interstitial fluid. |
| Lymph flow | Flows from the lymphatic capillaries to lymphatic vessels which are deeper within the tissues and have valves to prevent back-flow. |
| Right lymphatic duct | Collects lymph form the right side of the head, neck, and upper right quadrant and right arm. It empties into the right subclavian vein= proximal part of he main vein of the arm. |
| Thoracic Duct | Largest vessel in the body, collects lymph from the side of the body/ rest of the body and empties into the left subclavian vein. |
| 3 Major groups of lymph nodes | Cervical- located along the sides of the neck Axillary- underneath the arms Inguinal- groin area/ lower part of the abdomen |
| Lymphocytes | Formed in bone marrow. Undergo maturation and differentiation in lymphoid tissues. Differentiation= modified to perform a specific function. |
| Nature Killer Cells | kills cancer cells and cells infected by viruses, destroy cells transplanted from donor, same function of t-cells. |
| B-Cells | Produce antibodies. Fight viruses + bacteria that are in the blood. B cells transforms into plasma cells. |
| Plasma Cells | Developed from B cells, secrete large volume of antibodies coded to destroy specific antigens. |
| T-Cells | Originate from the thymus, cells-mediated immunity. Directly attack foreign and infected cells. |
| Cytokines | Group of proteins like interferons released by the T-cells, act as intracellular signals to begin immune response. |
| Interferons | Produces in response of antigens, viruses, and tumor cells. Activate immune response to increase defenses. |
| Thymus | Secretes hormones that stimulates the maturation of lymphocytes into T-Cells. |
| Spleen | Filters microorganisms and other foreign material from the blood. Forms lymphocytes + monocytes. |
| Hemolytic | Destroys worn-out RBC and releases their hemoglobin for reuse. Stores extra RBC and maintains balance between cells + plasma. |
| Lymphatic organs | Tonsils, thymus, spleen, lymph nodes, and red bone marrow. |
| Function 1 of Lymphatic system | Recover the interstitial fluid that did not reabsorb into the blood stream. Without it= tissues would be swollen= lymphedema. |
| Function 2 of Lymphatic system | Participates in immunity by picking up+ taking away foreign cells, cellular debri, and chemicals. |
| Function 3 of Lymphatic system | Absorption of dietary lipids in small intestine lumen. Absorbed by blood capillaries and lacteals- absorb lipids to be delivered to bloodstream. |
| Neutrophils | defend against harmful bacteria in the body |
| antigen-presenting cells (APCs) | elp the immune system recognize foreign invaders.When bacteria or viruses enter the body, some immune cells process these foreign materials and present their antigens to T lymphocytes, allowing T cells to detect and respond to the threat. |
| Type 1 of APCs | Macrophages – Derived from monocytes; they engulf and digest bacteria, debris, and dead cells. Big eaters and cleaners that also act as messengers. |
| Type 2 of APCs | Dendritic cells – Found in the skin, lymphatic organs, and mucous membranes; they capture foreign matter through receptor-mediated endocytosis and then migrate to lymph nodes to activate T cells. Scouts — they find invaders, grab samples, and run to the immune “headquarters” to warn T cells. |
| Type 3 of APCs | Reticular cells – Stationary cells located in the stoma of lymphatic organs; they process foreign material that arrives within those organs. Stationary guards who help identify invaders once they’re inside the immune base. |
| Tissue that do not have lymphatic capillaries | Bones, bone marrow, cornea, and cartilage. |
| Endothelial cells of lymphatic capillaries | Cells that overlap loosely, creating gaps for fluid, solutes, bacteria, and lymphocytes to enter |
| Anchoring Filaments | Protein strands that attach lymphatic capillaries to surrounding tissues and keep their gaps open. |
| Hydrostatic Pressure in Lymph Flow | When tissue pressure is high, it pushes flaps open to let fluid in; when pressure is higher inside the vessel, flaps close to stop backflow. |
| Larger Lymphatic Vessels | Vessels similar to veins with three tunics and one-way valves that prevent lymph from flowing backward. |
| Lymph Flow Mechanisms | Driven by skeletal muscle contractions, respiratory movements, smooth muscle in vessel walls, and artery pulses. |
| Lymphatic Trunks | Eleven major vessels that drain lymph from specific body regions into collecting ducts. |
| Major Lymphatic Trunks | Intestinal, lumbar, intercostal, bronchomediastinal, subclavian, and jugular trunks. |
| Cisterna Chyli | A sac formed by the merging of the intestinal and lumbar trunks that gives rise to the thoracic duct. A “collection basket” that gathers lymph (especially fatty lymph from digestion — called chyle) from the lower body and abdomen before sending it up through the thoracic duct. |
| Thoracic Duct | Drains From:Left jugular, left subclavian, left bronchomediastinal, intestinal, both lumbar trunks Empties into:Left subclavian vein |
| Right Lymphatic Duct | Drains From: Right jugular, right subclavian, right bronchomediastinal trunks Empties into: Right subclavian vein |
| MALT (Mucosa-Associated Lymphatic Tissue) | Lymphatic tissue found in mucous membranes of the respiratory, urinary, digestive, and reproductive tracts to protect against external pathogens. |
| Diffuse Lymphatic Tissue | Loosely organized lymphocytes found in connective tissue of mucosa; offers general protection in exposed body regions. |
| Lymphatic Nodules (Follicles) | Densely packed clusters of lymphocytes and macrophages found in lymph nodes, tonsils, appendix, and small intestine. |
| Peyer’s Patches (Aggregated Lymphoid Nodules) | Groups of lymphatic nodules located in the ileum of the small intestine that defend against digestive pathogens. |
| Primary Lymphatic Organs | Sites where lymphocytes become immunocompetent (able to recognize self vs. non-self). Includes the red bone marrow and thymus. |
| Secondary Lymphatic Organs | Sites where immunocompetent lymphocytes reside and respond to pathogens. Includes lymph nodes, spleen, and tonsils. |
| Red Bone Marrow | Found in spongy bone; performs hematopoiesis (formation of blood cells). Produces B and T lymphocytes. |
| B Lymphocyte (B Cell) Maturation | B cells fully mature in red bone marrow; only about 10% pass the selection process and are released into circulation. |
| T Lymphocyte (T Cell) Development | Immature T cells leave bone marrow and travel to the thymus for maturation and selection. |
| Cortex of Thymus | Dense outer region where immature T cells undergo selection; protected by the blood-thymus barrier. |
| Medulla of Thymus | Inner region where mature T cells multiply and complete their development; only about 2% pass the immunocompetence test. |
| Blood-Thymus Barrier | A barrier formed by epithelial cells and pericytes that prevents immature T cells in the cortex from being exposed to foreign antigens. |
| Thymic Hormones | Include thymosin, thymopoietin, thymulin, interleukins, and interferon; these regulate and stimulate T-cell development and function. |
| Thymic Selection | Process where ineffective or self-reactive T cells are destroyed; about 98% fail, while 2% mature and enter circulation. |
| Afferent Lymphatic Vessels | Bring (carry in) unfiltered lymph into the lymph node. “Afferent = arriving.” |
| Efferent Lymphatic Vessel | Carries filtered lymph out of the node through the hilum. “Efferent = exiting.” |
| Cortex (of Lymph Node) | Outer region containing lymphatic nodules, where immune responses begin. |
| Cortical Sinus | Narrow space between the capsule and cortex where lymph first enters inside the node. |
| Trabeculae | Extensions of the capsule that form partitions inside the lymph node, dividing it into sections. |
| Lymphatic Nodules (in Lymph Node Cortex) | Mantle zone: outer ring with T lymphocytes, macrophages, and dendritic cells. Germinal center: inner core with B lymphocytes and macrophages |
| Medullary Sinus | Inner space of the lymph node where lymph flows before leaving via the efferent vessel. |
| Medullary Cords | Strands of connective tissue in the medulla that support B cells, T cells, and macrophages. |
| Lymph Flow Pathway Through a Lymph Node | Afferent vessels → Cortical sinus → Lymphatic nodules → Medullary sinus → Efferent vessel |
| Immune Function of Lymph Nodes | Leukocytes monitor lymph for pathogens; macrophages destroy invaders. When lymphocytes multiply in response to infection, the node becomes swollen. |
| White Pulp (of Spleen) | Surrounds a central artery; contains T lymphocytes, B lymphocytes, and macrophages that check blood for pathogens. |
| Red Pulp (of Spleen) | Made of reticular tissue with erythrocytes, platelets, macrophages, and B lymphocytes; removes worn-out red blood cells and stores platelets. |
| Spleen – Function | Filters blood (not lymph); removes pathogens, debris, and old RBCs while recycling iron and storing platelets. |
| Blood Flow Through the Spleen | Splenic artery → Central artery (white pulp) → Splenic sinusoids (red pulp) → Splenic venules → Splenic vein |
| Tonsillar Crypts | Deep crevices in tonsils’ epithelial lining that trap pathogens and debris for immune processing by lymphatic nodules. |
| Lymphatic Nodules (Lymphatic Follicles) | Clusters of T lymphocytes, B lymphocytes, and macrophages within connective tissue not completely surrounded by a capsule; found scattered throughout body organs. |
| Structure of Lymphatic Nodules | Composed of lymphocytes and macrophages arranged in dense clusters within connective tissue, without a capsule. |
| Difference Between Lymph Node and Lymphatic Nodule | Lymph nodes are encapsulated and filter lymph; lymphatic nodules are unencapsulated clusters found within mucous membranes. |