They contain a single layer of endothelial cells,
 and glomeruli of the kidney are balls of them.
In Henoch-Schonlein pupura, these structures in the skin are attacked by antibodies, and these structures
 become excessively permeable in Clarkson's disease. Pericytes are responsible for regulating these
 structures within the brain. One type of these lack pinocytotic vesicles and are only found in the liver,
 known as the sinusoidal type, which is a specific version of the fenestrated type. An equation describing
 these entities contains the reflection and filtration coefficients and shows the balance between hydrostatic
 and oncotic pressure; that equation is named for Starling. They contain a single layer of endothelial cells,
 and glomeruli of the kidney are balls of them. In the lungs, O2 from the alveoli move into these structures,
 beds of which exchange nutrients and waste with body tissues. For 10 points, name this class of blood
 vessels, the body's smallest.
In Henoch-Schonlein pupura, these structures in the skin are attacked by antibodies, and these structures
 become excessively permeable in Clarkson's disease.
{capillaries} [or blood vessels before "{Clarkson’s disease}" is read; prompt after]