Final answer:
The hormone interacting with the excretory and endocrine systems to control water in the bloodstream is antidiuretic hormone (ADH). ADH and aldosterone work together to maintain water balance by regulating kidney function and water reabsorption.
Step-by-step explanation:
One hormone interacts with the excretory system and the endocrine system to control the amount of water in the bloodstream. This hormone is known as antidiuretic hormone (ADH), also called vasopressin. ADH is synthesized in the hypothalamus and released from the pituitary gland. Its primary function is to regulate water balance by increasing water reabsorption in the kidneys, which reduces the volume of urine produced and concentrates the urine, thus conserving water. Another hormone, aldosterone, produced by the adrenal cortex, also plays a critical role in controlling water balance by enhancing sodium reabsorption, which is often accompanied by water reabsorption via osmosis, thereby contributing to homeostasis in the organism. Together, these hormones and the systems they interact with maintain the proper balance of fluids in the body.