Which organ has receptor molecules that recognize specific hormones?

The target organ is the correct answer because it contains specific receptor molecules designed to interact with certain hormones. When a hormone is released into the bloodstream by an endocrine gland, it travels to its target organ, where it binds to these receptors. This binding initiates a particular response in the target organ, which can lead to various physiological effects depending on the hormone and the tissue involved.

For example, insulin is a hormone secreted by the pancreas, and its target organ is the liver, muscles, and fat tissues, where it binds to insulin receptors to regulate glucose uptake. The specificity of this interaction is crucial for the proper functioning of the endocrine system and maintaining homeostasis.

The other options do not have the specific role in recognizing hormones. An endocrine gland is responsible for producing and releasing hormones but does not primarily function as the target site. Excretory organs, such as the kidneys, deal with waste removal and do not have receptors specific to hormones in the same regulatory context. Muscle tissues are responsive to hormones but do not have a unique set of receptor molecules allowing them to be categorized as target organs specifically for hormonal action.