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Gedetailleerde structuur en functies van lymfeklieren
Lymfeklieren zijn boonvormige structuren die zich groeperen langs de lymfevaten in de lies-, oksel- en cervicale regio's. Elke knoop is verdeeld in co…
Lymph nodes are small, bean-shaped structures that cluster along the lymphatic vessels. They are majorly located in the inguinal, axillary, and cervical regions.
These nodes have an outer covering called the capsule, which extends trabeculae inward, dividing the node into compartments.
Histologically, each lymph node can be divided into superficial cortex and deep medulla.
The cortex comprises dendritic cells, macrophages, and densely packed follicles of B lymphocytes. Upon antigen presentation by dendritic cells, the B-lymphocytes mature into antibody-producing plasma cells and memory B cells.
The inner cortex mainly consists of T-lymphocytes migrated from the cortex. It also contains dendritic cells, which can activate the T-lymphocytes.
Lymph enters the lymph nodes via afferent lymphatics and flows through sinuses filled with reticular fibers, lymphocytes, and macrophages.
Lymph gets filtered within these sinuses. Macrophages eliminate foreign substances through phagocytosis, while lymphocytes destroy pathogens using immune responses.
The filtered lymph leaves the lymph node via efferent lymphatics and emerges from the other end of the node at the hilum.
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Q1: What are the main structural regions within a lymph node?
Lymph nodes contain two primary histological regions: the superficial cortex and the deep medulla. The cortex houses dendritic cells, macrophages, and densely packed B lymphocyte follicles. The inner cortex consists mainly of T lymphocytes and dendritic cells. The medulla contains activated B and T lymphocytes that distribute throughout the body after immune activation.
Q2: How do B lymphocytes mature within lymph nodes?
When dendritic cells present antigens to B lymphocytes in the cortex, the B cells mature into antibody-producing plasma cells and memory B cells. These activated cells then enter the medulla, where they are distributed throughout the body. This process enables the adaptive immune response to foreign substances.
Q3: What is the path lymph takes through a lymph node?
Lymph enters via multiple afferent lymphatic vessels at the node's convex surface and flows into the subcapsular sinus beneath the capsule. It then travels through trabecular sinuses parallel to the trabeculae and into medullary sinuses. Finally, lymph exits through one or two broader efferent lymphatic vessels at the hilum.
Q4: How do lymph nodes filter pathogens and foreign substances?
Sinuses within lymph nodes contain reticular fibers, lymphocytes, and macrophages that trap foreign substances. Macrophages eliminate pathogens through phagocytosis, while lymphocytes destroy them using immune responses. The slow lymph flow through multiple sinuses allows extended filtration time before lymph returns to the blood.
Q5: Why does lymph flow slowly through lymph nodes?
Multiple afferent vessels bring lymph into each node, but only one or two efferent vessels carry it out. This structural arrangement creates a bottleneck that slows lymph transit through the node. The reduced flow rate allows more time for immune cells and macrophages to filter and eliminate pathogens before lymph returns to circulation.
Q6: Where are lymph nodes located in the body?
Lymph nodes are small, bean-shaped structures that cluster along lymphatic vessels in three major regions: the inguinal nodes in the groin, axillary nodes in the armpits, and cervical nodes in the neck. These strategic locations allow lymph nodes to monitor and filter lymph from different body areas.
Q7: What role do dendritic cells play in lymph node function?
Dendritic cells in the cortex present antigens to B lymphocytes, triggering their maturation into plasma cells and memory B cells. In the inner cortex, dendritic cells activate T lymphocytes. These antigen-presenting functions enable lymph nodes to coordinate adaptive immune responses against pathogens.