Sinusoidal capillaries, also known as sinusoids, are a special type of blood capillary characterized by a larger diameter and a more irregular shape compared to other capillaries. They are primarily found in the liver, spleen, bone marrow, and some endocrine glands. These capillaries have a discontinuous endothelium and basal lamina, allowing for the free exchange of larger molecules and cells between the blood and surrounding tissues.