Anatomy of the Spleen

Study Notes

The spleen is covered by a capsule of dense connective tissue that sends trabeculae to divide it into incomplete splenic lobules.
The capsule and trabeculae contain smooth muscle fibers that contract to deliver blood from the spleen into circulation under certain conditions.

The parenchyma consists of white pulp (splenic nodule) and red pulp.
White pulp:
- Composed of periarterial lymphatic sheath formed of reticular connective tissue supporting the artery.
- Lymphatic nodules are scattered within the periarterial sheath, containing a concentration of "B" lymphocytes.
- Lymphatic nodules push the central arteries toward the periphery, becoming eccentric in position.
Red pulp:
- Consists of a network of branching and anastomosing sinuses separated by highly cellular partitions called cords of Billroth or splenic cords.
- Has a looser texture than white pulp and is supported by networks formed by reticular fibers and cells.

Acts as a blood reservoir, storing blood rich in RBCs due to the contraction of the splenic vein leading to the sweeping of plasma through the walls of venous sinuses.
A haemopoietic organ producing lymphocytes (mainly in white pulp) and monocytes (from haemocytoblasts in the red pulp).
Filters blood using free and fixed macrophages.

Types: pharyngeal tonsil, palatine tonsils, and lingual tonsils.
Incompletely encapsulated aggregates of lymphoid tissues guarding the inlet of the oropharynx.
React to airborne and ingested antigens by forming lymphocytes and creating an immune response.

Bilateral tonsils with a dense fibrous capsule isolating them from surrounding connective tissue.
Superficial aspect covered by stratified squamous, non-keratinized epithelium with 10-12 deep crypts that invaginate the tonsillar parenchyma.
Composed of numerous lymphoid nodules, many with germinal centers.