What system is composed of glands that secrete hormones, carried by the bloodstream to target cells? A. Endocrine B. Lymphatic C. Nervous D. Cardiovascular

The system that is composed of glands that secrete hormones, which are then carried by the bloodstream to target cells, is the Endocrine system.

Explanation:

1. Endocrine System: The endocrine system is responsible for producing and secreting hormones that regulate many bodily functions including metabolism, growth, reproduction, and mood. Hormones are chemical messengers that travel through the bloodstream to organs and tissues, signaling them to take necessary actions.

2. Lymphatic System: This system is primarily involved in immune responses and the transport of lymph, a fluid containing infection-fighting white blood cells.

3. Nervous System: The nervous system transmits signals that control bodily functions but does not use hormones for communication in the same way the endocrine system does.

4. Cardiovascular System: While it circulates blood and nutrients, it does not specifically refer to hormone secretion or regulation.

Final Answer:

A. Endocrine