Lymph Node VM Flashcards
What are lymph nodes surrounded by?
A capsule of connective tissue
What part of a lymph node does the efferent lymphatic vessel exit from?
The hilus
The stroma of a LN is made up of what?
Fibroblasts and reticular fibers
What are the trabeculae of a LN?
Extensions of the connective tissue capsule that penetrate into the interior parenchyma of the LN.
What is the subcapsular sinus?
The area of the LN into which lymph flows from the afferent lymphatic vessel.
How do you differentiate primary and secondary lymphoid follicles on histology?
Primary follicles: uniform staining, consist mostly of naive B cells.
Secondary follicles: lightly staining germinal center surrounded by a darker staining mantle zone
What does the presence of secondary lymphoid follicles in a LN indicate?
Activation, clonal expansion, and somatic hypermutation of B cells
What is the mantle zone and what does it consist of?
The darker staining outer rim of a secondary lymphoid follicle, comprised of the non-reactive B cells that were pushed aside by the activated B cells that comprise the germinal center.
Where are B cell germinal centers found in the LN?
The cortex (periphery)
Where do B cells do once activated in a germinal center?
Migrate the the LN medulla and secrete antibodies into the efferent lymphatics.
N.B. The B cells apparently form “medullary cords” as they travel in this way - not sure if that’s important at all.
T cells are found in what area of the LN? What other cells are found here?
The paracortical zone. Macrophages and APCs such as Langerhans and dendritic cells are also found here.
How does the paracortical zone appear on histology?
Uniformly staining
What type of venules populate the paracortical zone and what is their purpose?
High endothelial venules, which express lymphocyte-homing receptors that aid the migration of lymphocytes from the blood into the node.
What processes actually cause a lymph node to swell?
B and T cell expansion, sinus expansion, and histiocytosis. within the sinuses.
