The correct answer is Arteriovenous anastomosis.

- The skin plays a crucial role in thermoregulation, helping to maintain the body's core temperature.
- One of the key mechanisms involved in this process is the regulation of blood flow through specific vascular connections.

- An arteriovenous anastomosis (AVA) is a direct connection between an artery and a vein, bypassing the capillary bed.
- These AVAs are abundant in areas such as the skin of the fingers, toes, ears, and nose—regions particularly important in temperature regulation.
- By opening or closing these shunts, the body can either allow warm blood to flow close to the skin surface for heat dissipation or reduce blood flow to conserve heat.

- When the body needs to cool down, AVAs open, allowing increased blood flow to the skin’s surface, facilitating heat loss through radiation and convection.
- When conserving heat, AVAs constrict, redirecting blood away from the surface, minimizing heat loss.

Other types of anastomoses, such as arterioarterial, venovenous, or capillary plexus anastomoses, primarily contribute to collateral circulation but do not play a central role in regulating skin temperature.

Key points:
- Arteriovenous anastomoses bypass capillaries to directly connect arteries and veins.
- AVAs regulate skin blood flow and thus control heat loss or conservation.
- They are especially significant in thermoregulatory regions of the body.
- Other anastomoses help in collateral circulation but are not directly involved in thermoregulation.

Reference: Gray's Anatomy, 41st Edition, Chapter 8: Blood Vessels, p. 230-235