GENERAL HISTOLOGY

Detailed explanation-1: -There are three mechanisms that facilitate capillary exchange: diffusion, transcytosis and bulk flow. Capillary dynamics are controlled by the four Starling forces. Oncotic pressure is a form of osmotic pressure exerted by proteins either in the blood plasma or interstitial fluid.

Detailed explanation-2: -For substances carried by blood, the kinetic processes leading to intracellular reaction in the heart are (1) delivery by flow, (2) transport across the capillary wall either between or across endothelial cells, (3) diffusion in the interstitium, and (4) transsarcolemmal transport, passive or carrier mediated.

Detailed explanation-3: -Filtration is where substances are transferred from the capillary to the interstitial space. In contrast, the movement of substances from interstitial tissue to the blood in the capillaries is via a process called reabsorption. Net filtration pressure (NFP) determines whether a substance is filtered or reabsorbed.

Detailed explanation-4: -Small molecules can cross into and out of capillaries via simple or facilitated diffusion. Some large molecules can cross in vesicles or through clefts, fenestrations, or gaps between cells in capillary walls. However, the bulk flow of capillary and tissue fluid occurs via filtration and reabsorption.