Sinusoidal capillaries (or sinusoids) have a discontinuous endothelium and basement membrane. The sinusoids have large, irregular shaped lumens (15 to 30 µm in diameter). The large gaps allow for the free exchange of large macromolecules and cells.
Sinusoidal capillaries are found in a number of organs including the liver, spleen, and bone marrow.
Sinusoids are also found in the adrenal gland. The adrenal cortex is composed of endocrine cells that produce steroid hormones. They are richly supplied by a network of sinusoids.