What occurs at flame cells in flatworms?

Flame cells in flatworms play a crucial role in the excretory system, functioning specifically to excrete waste products from the organism. These specialized cells are part of a network of tubules and have a unique structure that includes cilia, which create a flame-like appearance as they beat. This beating helps to propel bodily waste through the tubules and eventually expel it from the body.

Flatworms lack a true circulatory or respiratory system, so the roles of absorption of nutrients and respiration of oxygen are managed differently in these organisms—primarily through diffusion across their body surface. Additionally, while flatworms do have circulatory processes to distribute materials within their tissues, the regulation of blood flow is not a function associated with flame cells. Therefore, the primary and defining role of flame cells is the excretion of waste, affirming that the correct answer relates to this vital excretory function.