Vetinerary Assistant Practice Exam

Which of the following glands secretes hormones directly into the bloodstream?

1. Salivary gland

2. Thyroid gland

3. Exocrine gland

4. Liver

The correct answer is: Thyroid gland

The thyroid gland is the correct answer because it is an endocrine gland, which means it secretes hormones directly into the bloodstream. This hormonal secretion plays a crucial role in regulating various metabolic processes within the body, including metabolism, growth, and development. The hormones produced by the thyroid, such as thyroxine (T4) and triiodothyronine (T3), are transported through the blood to target organs, where they exert their effects. In contrast, salivary glands are exocrine glands that release their secretions through ducts, such as saliva into the mouth, rather than directly into the blood. Exocrine glands, by definition, secrete substances through ducts and not into the bloodstream. While the liver does produce various substances, including hormones like insulin-like growth factors, it primarily functions in metabolism and detoxification, and does not classify as a gland that secretes hormones into the bloodstream in the way endocrine glands do. Therefore, the thyroid gland is uniquely positioned in its role of hormone secretion into the bloodstream, making it the definitive choice in this context.