Transcript Thymus and Spleen

Thymus and Spleen
The Spleen: What is it good for?
1. Filters blood
2. Iron Retrieval
3. RBC reserve
4. Immune Response*
5. Fetal Hematopoiesis
The ‘White’ Pulp
• Appears basophilic on H&E
and red on silver stain
• Site where immune response is
mounted; formation of germinal
centers
• Germinal centers with B cells
and B cell derivatives push the
‘central artery’ off to the side
White Pulp Vasculature
• The central artery is found
in the white pulp
• The central artery is
surrounded by the PALS,
which is T cells
• Penicilli branch from the
central artery into the red
pulp
White Pulp Vasculature
• The central artery is found
in the white pulp
• The central artery is
surrounded by the PALS,
which is T cells
• Penicilli branch from the
central artery into the red
pulp
White Pulp Vasculature
• The central artery is found
in the white pulp
• The central artery is
surrounded by the PALS,
which is T cells
• Penicilli branch from the
central artery into the red
pulp
Red Pulp Vasculature:
• Penicilli give rise to
ellipsoids
• Ellipsoids are capillaries
ensheathed by reticular
cells and macrophages;
their lumens are often
occluded in histo sections
• Blood is filtered by
macrophages through
fenestrations in the
sinusoids
Sinusoids
See how the basal lamina is interrupted; evident with
both stains
Sinusoids
Lining of endothelial cells: apposed to one another, but remain separated
Macrophages extend their processes into the lumen of the sinusoid (you can
see the remains of RBCs in macrophages)
The Red Pulp
• Appears Red on H&E
• Composed of sinusoids and
Cords of Billroth
• The cords are the parenchyma
of the red pulp; they are
composed of reticular tissue w/
macrophages, red blood cells,
and lymphocytes
Silver Stain
*Notice how reticular fibers are evident with silver stain and not H&E
*Notice the difference in appearance with the two different stains