blood vessel sinusoid http://purl.obolibrary.org/obo/UBERON small blood vessel similar to a capillary but with a fenestrated endothelium. Sinusoids are found in the liver, lymphoid tissue, endocrine organs, and hematopoietic organs such as the bone marrow and the spleen. Sinusoids found within terminal villi of the placenta are not comparable to these; they possess a continuous endothelium and complete basal lamina[WP].