spleen white pulp morphology trait spleen marginal sinus morphology trait Any measurable or observable characteristic related to the shape, structure, color, or pattern of the border region surrounding the spleen B cell follicles and the periarteriolar lymphoid sheath (PALS) that separates it from the marginal zone that mediates lymphocyte entry into the white pulp from the blood. Note that there is no consensus in the literature about which compartments constitute the white pulp or the ramifications of the microvasculature. In addition, notable differences exist between humans and rodents. In this ontology, the marginal sinus (which may not exist in human) has been included as part of the white pulp. Trait.ontology VT:0002363 splenic marginal sinus morphology trait