Chapter 20.3, Problem 14BYGO

Summary Introduction

Introduction:

Due to the presence of small vessels, it is hard to measure the pressure in the capillaries. These factors make it difficult to understand the mechanism of the capillary exchange; theories of capillary exchange remain disputed. The stereomicroscope observation on the fingernail bed and eponychium has been the basis of study. The blood pressure of capillaries at the arterial end is about 32 mm Hg, and 15 mm Hg is found in the venous end. Due to their small narrow vessels, the blood pressure drops rapidly. The three routes in which the chemicals pass through capillary walls are the endothelial cell cytoplasm, intercellular clefts between the endothelial cells, and filtration pores of the fenestrated capillaries. The chemicals move through the capillary wall by diffusion, filtration, transcytosis, and reabsorption.