EM 310 Spleen

Spleen

Scanning electron micrograph (SEM) of red pulp of the spleen. A labyrinth of splenic cords (cords of Billroth) separated by sinusoidal capillaries.

Splenic Cords (cords of Billroth) - cellular aggregations of red/white blood cells and reticular cells/fibers
- (yellow) - form the framework of the cords
  - Reticular Cells - stellate-shaped cells that wrap around bundles of reticular fibers
  - Reticular Fibers - type III collagen that forms cross links
- (green) - mostly neutrophils and lymphocytes
- (purple) - surface covered with many small projections (pseudopodia)
- (red) - unique capillaries that simply terminate and blood flows into the surrounding red pulp
  - Sheath of macrophages surround the vessel
(tan) - specialized blood vessels of an unusual structure
- Endothelium - spindle-like cells separated by small gaps
  - Long cells oriented lengthwise to the direction of blood flow
  - Allows easy passage of cells into and out of the capillary
- Nuclei bulge into the lumen
- Larger than other types of capillaries
(blue) - attached to sinus walls and within the splenic cords

Courtesy of Tsuneo Fujita, Department of Anatomy, Niigata University, School of Medicine, Niigata, Japan