25.7
Estrutura detalhada e funções dos gânglios linfáticos
Os linfonodos são estruturas em forma de feijão que se agrupam ao longo dos vasos linfáticos nas regiões inguinal, axilar e cervical. Cada linfonodo é…
Os gânglios linfáticos são pequenas estruturas em forma de feijão que se agrupam ao longo dos vasos linfáticos. Eles estão localizados principalmente nas regiões inguinal, axilar e cervical.
Esses nós têm uma cobertura externa chamada cápsula, que estende as trabéculas para dentro, dividindo o nó em compartimentos.
Histologicamente, cada linfonodo pode ser dividido em córtex superficial e medula profunda.
O córtex compreende células dendríticas, macrófagos e folículos densamente compactados de linfócitos B. Após a apresentação do antígeno pelas células dendríticas, os linfócitos B amadurecem em células plasmáticas produtoras de anticorpos e células B de memória.
O córtex interno consiste principalmente de linfócitos T migrados do córtex. Ele também contém células dendríticas, que podem ativar os linfócitos T.
A linfa entra nos gânglios linfáticos por meio de linfáticos aferentes e flui através de seios da face cheios de fibras reticulares, linfócitos e macrófagos.
A linfa é filtrada dentro desses seios. Os macrófagos eliminam substâncias estranhas por meio da fagocitose, enquanto os linfócitos destroem patógenos por meio de respostas imunes.
A linfa filtrada deixa o linfonodo por meio de linfáticos eferentes e emerge da outra extremidade do nódulo no hilo.
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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.