What explains the movement of solute and solvent into interstitial tissues in a dead body?

The movement of solute and solvent into interstitial tissues in a dead body is primarily explained by diffusion. Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In a dead body, metabolic processes that typically regulate circulation and solute transport cease, and as a result, solutes and solvents continue to move based on their concentration gradients.

In the absence of blood flow or active transport mechanisms provided by the circulatory system, diffusion becomes the primary method of movement for substances. For example, fluids can seep from blood vessels into surrounding tissues due to the concentration differences between the blood (which may have retained certain solutes) and the interstitial spaces. As concentration gradients equalize over time, diffusion effectively facilitates this movement until equilibrium is reached.

In contrast to diffusion, other mechanisms such as filtration involve the movement of fluids under pressure, which is not applicable in a dead body where active circulation has ceased. Vasoconstriction typically refers to the narrowing of blood vessels in response to certain stimuli and is not a relevant factor once the body is deceased, as it pertains to living physiological responses. Thus, diffusion accurately describes the passive, concentration-driven movement of solutes and solvents in this context.