Hephridia, often referred to in the context of invertebrate zoology, are specialized excretory structures found in certain organisms, particularly in annelids (like earthworms) and some mollusks. They function to remove metabolic wastes and regulate the internal balance of water and salts. Each hephridium typically consists of a tubule that opens to the exterior, allowing for the elimination of waste products from the body. These structures play a crucial role in maintaining homeostasis within the organism.