What is the primary method by which materials such as O₂,CO₂,and nutrients are exchanged between the blood and surrounding tissues?

Question

Quizplus · Accepted Answer

The primary method by which materials such as O₂, CO₂, and nutrients are exchanged between the blood and surrounding tissues is passive diffusion of substances across the capillary wall down their concentration gradients. This occurs as the blood flows through tiny capillaries which have thin walls that allow for the movement of small molecules such as oxygen and carbon dioxide by diffusion. Nutrients and other biomolecules such as glucose and amino acids also move across the capillary walls by diffusion. Active transport is not the primary method of exchange as it requires energy and is used for specific molecules that cannot passively diffuse across the capillary walls. Osmotic pressure drawing water and solutes out of the capillary and bringing these dissolved nutrients into contact with the tissue cells is involved in the movement of fluids but not specifically in the exchange of materials between the blood and tissues. Processes of ultrafiltration and reabsorption are involved in the formation of urine by the kidneys and are not directly involved in the exchange of materials between the blood and tissues.

What Is the Primary Method by Which Materials Such as O₂,CO₂,and