Capillaries are the smallest blood vessels, consisting of a single layer of endothelial cells and a basal lamina. There are three types of capillaries:
Continuous capillaries: These have uninterrupted endothelial lining and are found in most tissues, including muscles and the brain. Fenestrated capillaries: Characterized by pores in their endothelial lining, they are present in organs requiring rapid exchange of substances, such as the kidneys and intestines. Sinusoidal capillaries (sinusoids): These have larger openings and are found in the liver, spleen, and bone marrow, allowing the passage of large molecules and cells.
