What are the key functions of the lymphatic system?.

Choice A rationale:

Diffusion is the primary mechanism for capillary exchange. It allows small molecules, such as gases, lipids, and lipid-soluble molecules, to move directly through the membranes of the endothelial cells of the capillary wall.

Choice B rationale:

Filtration is a pressure-driven mechanism that moves volumes of fluid from an area of higher pressure in a capillary bed to an area of lower pressure in the tissues. However, it is not the primary mechanism for capillary exchange.

Choice C rationale:

Gravity does not play a direct role in capillary exchange.

Choice D rationale:

Colloid osmotic pressure is a type of pressure that interacts with hydrostatic pressure to drive fluid movement in capillaries. However, it is not the primary mechanism for capillary exchange.

The correct answer is Choice B.

Choice A rationale:

Venules are small vessels that collect blood from the capillaries and transport it to the veins. They are not primarily involved in the exchange of nutrients, wastes, and hormones.

Choice B rationale:

Capillaries are tiny vessels that branch out from arterioles to form networks around body cells. They are the primary sites for the exchange of gases, nutrients, and waste between blood and tissues.

Choice C rationale:

Arterioles are small branches of arteries that lead to capillaries. They primarily regulate blood pressure and blood flow, not the exchange of substances.

Choice D rationale:

Veins carry deoxygenated blood back to the heart. They are not the primary sites for substance exchange.