[Quantitative study of the capillaries in a secreting salivary gland (electron-microscopic and morphometric...

Regularities in structural rearrangement of epithelium of blood capillaries in the rat parotid salivary gland have been studied under various functional conditions of the organ. The data obtained demonstrate that secretion is accompanied by dilatation of anuclear segments of capillary endothelium, decreasing thickness of endotheliocytes, rise of hematocrit number by adding the total area of the capillary fenestrated surface, the form factor of intraendothelial contacts and decreasing length of the contacting cytolemmas. Since extreme values of the metrical parameters studied have been revealed during the phase of the secrete excretion, a suggestion is made that increasing hydraulic permeability of the metabolic vessels with subsequent transport of the fluid to the terminal parts of the gland create the conditions promoting to reach the threshold level of pressure in acini that is necessary to overcome high resistance of nerrow intercalated sections for the secretion to reach the ducts.