<Li> Those with numerous transport vesicles, which are found primarily in skeletal muscles, fingers, gonads, and skin . </Li> <Li> Those with few vesicles, which are primarily found in the central nervous system . These capillaries are a constituent of the blood--brain barrier . </Li> <P> Fenestrated capillaries (derived from fenestra, Latin for "window") have pores in the endothelial cells (60--80 nm in diameter) that are spanned by a diaphragm of radially oriented fibrils and allow small molecules and limited amounts of protein to diffuse . In the renal glomerulus there are cells with no diaphragms, called podocyte foot processes or pedicels, which have slit pores with a function analogous to the diaphragm of the capillaries . Both of these types of blood vessels have continuous basal laminae and are primarily located in the endocrine glands, intestines, pancreas, and the glomeruli of the kidney . </P> <P> Sinusoidal capillaries (also known as a discontinuous capillary) are a special type of open - pore capillary, that have larger openings (30--40 μm in diameter) in the endothelium . These types of blood vessels allow red and white blood cells (7.5 μm--25 μm diameter) and various serum proteins to pass, aided by a discontinuous basal lamina . These capillaries lack pinocytotic vesicles, and therefore utilize gaps present in cell junctions to permit transfer between endothelial cells, and hence across the membrane . Sinusoid blood vessels are primarily located in the bone marrow, lymph nodes, and adrenal glands . Some sinusoids are distinctive in that they do not have the tight junctions between cells . They are called discontinuous sinusoidal capillaries, and are present in the liver and spleen, where greater movement of cells and materials is necessary . A capillary wall is only 1 cell thick and is simple squamous epithelium . </P>

Where are fenestrated capillaries most likely to be found