Histology of the Thymus and Peripheral Lymphoid Organs Flashcards
Name three encapsulated lymphoid organs.
- Lymph Nodes
- Thymus
- Spleen
What structures are considered primary lymphoid organs?
Bone marrow
Thymus
How does lymph enter and exit a lymph node?
Lymph enters in the afferent lymphatic vessels into the subcapsular space
Then they exit through the efferent lymphatic vessels
The lymph node is made up of three regions, what are they?
Cortex
Paracortex
Medulla
What separates the cortex?
Trabeculae
What is contained in the cortex?
Germinal centers full of active cell proliferation and apoptosis
Mostly B cells
Some macrophages
What is the paracortex mostly comprised of?
T cells and some B cells
What is contained in the medulla?
B cess, a few T cells and plasma cells
Where do the blood vessels enter and exit?
At the hilum
Why is the high endothelial venule important?
It is the site for recognition and diapedesis of lymphocytes from the blood into the lymphatic space of the node.
Contain selectins
What occurs in the thymus?
Proliferation, differentiation and selection of thymocytes
When does the thymus involution occur?
Around puberty
What composes the cortex of the thymus?
More densely packed set of developing thymocytes having dark nuclei. It also stains darker
Where can you find more mature thymocytes in the thymus?
In the less densely packed medulla.
What kind of cells are found just beneath the capsule?
Blast cells that divide and give rise to other immature thymocytes
