Final answer:
Blood from the thyroid gland is drained into the internal jugular vein which leads to the subclavian vein, ensuring proper circulation from this metabolically crucial gland.
Step-by-step explanation:
The blood is drained from the thyroid gland into the internal jugular vein (IJV) which then leads to the subclavian vein. Specifically, veins from the thyroid gland merge with the network of veins in the neck, and the blood then flows into the internal jugular vein. This vein runs parallel to the common carotid artery and primarily drains blood from the brain before joining the subclavian vein. The role of the thyroid gland in regulating metabolism, along with the need for proper blood flow from it, highlights the importance of its vascular connections to the IJV and the systemic circulation.