THE STRUCTURE and PERMEABILITY OF BLOOD CAPILLARIES
Published Jul 1, 1944 · J. Danielli, A. Stock
Biological Reviews
37
Citations
1
Influential Citations
Abstract
(1) Outside the single layer of endothelial cells composing the basic unit of the vertebrate blood capillary is a perithelium of connective tissue fibres, associated with which are connective tissue cells, contractile (Rouget) cells, etc. (2) Constriction of the lumen of a capillary may occur (a) by the intrusion of a few endothelial cells into the lumen, (6) by a more general activity of a length of endothelium, or (c) by the action of extra capillary cells, in which case folding of the capillary may ensue. (3) The rate of nitration through the capillary walls is controlled by (a) mechanical factors, (6) plasma and hormone factors, (c) local tonus and nervous control, (d) dietary factors. (4) The conclusion that there is a gradient of permeability to certain dyes is due to a misunderstanding of the experimental observations: the distribution of dye in such cases is precisely that predictable by Starling's ultrafiltration hypothesis for the case of a capillary slightly permeable to colloid. (5) Poiseuille's equation applies fairly accurately to the flow in blood capillaries, and the rate of development of oedema in perfused preparations obeys an equation based on Starling's hypothesis and on Poiseuille's equation. (6) Most substances reach the tissue cells as a result of filtration through the pores in the intracellular cement. Only a few substances, such as oxygen, pass with readiness through the endothelial cells themselves. (7) The capillary network may undergo changes which, with a given systemic blood flow, permit of independent variation (a) in the rate of blood flow through a tissue, (b) in the rate of filtration through the walls of the capillaries.