Continuous Capillaries 17991 Are named because the cytoplasm of the endothelial cells is continuous when viewed in cross-section through a microscope. Cytoplasm appears as an uninterrupted ring, except for the endothelial junction. Differ from continuous capillaries in that their endothelial cells have numerous pores or fenestrations where the cytoplasm is very thin or absent. Found in kidneys, villi of the small intestine, choroid plexi of the ventricles of the brain, and endocrine glands. Sinusoids or Discontinuous Capillaries 17994 Are wider than capillaries and more torturous Contain spaces between endothelial cells instead of having the usual endothelial lining.
Basal lamina is incomplete or missing.
In addition, sinusoids contain specialized lining cells that are adapted to the function of the tissue. Other regions containing sinusoids include the spleen, parathyroid glands, adrenal cortex, and bone marrow. Veins which carry blood back to the heart, follow pathways roughly parallel to those of the arteries. Walls of veins are similar to those of arteries, in that they are composed of three distinct layers. Middle layer is poorly developed.