- histology
- supporting fibroelastic tissue
- capsule
- coarse trabeculae
- fine reticulum
- white pulp
- lymphatic nodules
- around an arteriole called malphigian corpuscle
- red pulp
- collection of cells in interstices of reticulum
- all types of lymphocytes
- all 3 types of blood cells rbc,wbc,platelets
- fixed and free macrophages
- vascular system
- traverses the organ
- Composed of red pulp (occupies 75% of splenic volume) and white pulp separated by marginal zone
- Red pulp:
- Filters old / damaged red blood cells
- Traversed by thin walled venous sinusoids lined by littoral cells, a type of endothelial cell which also stains with histiocytic markers and has a discontinuous wall, allowing passing of red blood cells between sinus and cords
- Sinuses are separated by splenic cords (cords of Billroth) containing a labyrinth of splenic macrophages, which filter red blood cells and ingest old (normal lifespan is 120 days), damaged (seen in hereditary spherocytosis, sickle cell anemia) or antibody coated red blood cells
- White pulp:
- Forms sheaths of lymphoid cells around arteries (periarteriolar lymphatic sheath), composed of T cells and lymphoid follicles (B cells) with surrounding mantle zone (proliferating B cells) and outer marginal zone (memory B cells)
- Traps antigens for processing
- In young infants, immature marginal zone may contribute to increased susceptibility to bacterial infections or sudden infant death syndrome (Hum Pathol 2004;35:113)
- Blood flow:
- Arteries terminate in fine penicilliary arterioles surrounded by lymphocytes, then enter red pulp sinusoids, then to splenic veins
Discussion