The structure that mediates arteriovenous shunts in the digits to regulate temperature is known as the:

The structure that mediates arteriovenous shunts in the digits to regulate temperature is known as the:

• A. Arteriovenous capillary plexus
• B. Sweat gland
• C. Glomus body
• D. Subcutaneous fat

Answer: (C)

Temperature regulation in the digits relies on a specialized arteriovenous shunt called the glomus body. This structure sits in the dermis of fingertips and toes and acts as a bypass channel between arteries and veins. It consists of a core cluster of glomus (modified smooth muscle) cells surrounding an arteriovenous channel, with innervation by the sympathetic nervous system to modulate its activity. The glomus body can open or close the shunt to control how much blood flows through the capillary bed versus bypassing it. When the body needs to conserve heat, the shunt preferentially allows blood to pass through the AV pathway, bypassing the capillaries and reducing heat loss to the skin. In warmer conditions, the shunt constricts and more blood is directed through the true capillary network, increasing heat exchange with the surrounding tissue and facilitating heat dissipation. This mechanism is particularly important in the digits, which have a high surface-area-to-volume ratio and are prone to rapid heat exchange. Sweat glands handle evaporative cooling, not arteriovenous shunting. Subcutaneous fat provides insulation rather than mediating direct AV blood flow. An arteriovenous capillary plexus describes a network of capillaries, not a distinct shunt structure with the regulatory apparatus of the glomus body.

Temperature regulation in the digits relies on a specialized arteriovenous shunt called the glomus body. This structure sits in the dermis of fingertips and toes and acts as a bypass channel between arteries and veins. It consists of a core cluster of glomus (modified smooth muscle) cells surrounding an arteriovenous channel, with innervation by the sympathetic nervous system to modulate its activity.

The glomus body can open or close the shunt to control how much blood flows through the capillary bed versus bypassing it. When the body needs to conserve heat, the shunt preferentially allows blood to pass through the AV pathway, bypassing the capillaries and reducing heat loss to the skin. In warmer conditions, the shunt constricts and more blood is directed through the true capillary network, increasing heat exchange with the surrounding tissue and facilitating heat dissipation. This mechanism is particularly important in the digits, which have a high surface-area-to-volume ratio and are prone to rapid heat exchange.

Sweat glands handle evaporative cooling, not arteriovenous shunting. Subcutaneous fat provides insulation rather than mediating direct AV blood flow. An arteriovenous capillary plexus describes a network of capillaries, not a distinct shunt structure with the regulatory apparatus of the glomus body.