Located in LUQ of abdomen, anterior to left kidney, protected by 9th-11th ribs.
Sinusoids are long, vascular channels in red pulp (red arrows in A) with fenestrated “barrel hoop” basement membrane.
T cells are found in the periarteriolar lymphatic sheath (PALS) within the white pulp (white arrows in A).
B cells are found in follicles within the white pulp.
The marginal zone, in between the red pulp and white pulp, contains macrophages and specialized B cells, and is where antigen-presenting cells (APCs) capture blood-borne antigens for recognition by lymphocytes.
Splenic macrophages remove encapsulated bacteria.
Splenic congestion occurs during a splenic sequestration crisis (marked hemoglobin decrease, rapidly enlarging spleen), which develops due to vaso-occlusion within the cords of Billroth and splenic pooling of erythrocytes.
Repeated infarction leads to functional asplenia & autosplenectomy (splenic atrophy)
Splenic dysfunction (eg, postsplenectomy state in sickle cell disease): ¯ IgM → ¯ complement activation → ¯ C3b opsonization → susceptibility to encapsulated organisms.