Protonefriidijärjestelmä

Protonefriidijärjestelmä refers to a type of primitive excretory organ found in some invertebrates. These organs are characterized by a tubule lined with cilia. The cilia beat in a way that creates a current, drawing waste products from the body fluids into the tubule. The tubule then filters these waste products and expels them from the body through a pore. Protonephridia are essentially a system of blind-ended tubules. They are not connected directly to the circulatory system in the way that more complex kidneys are. Instead, they collect coelomic fluid or interstitial fluid. The filtering process within the protonephridial tubule is thought to involve selective reabsorption of useful substances back into the body. Protonephridia are common in simpler multicellular animals such as flatworms, rotifers, and some annelids. They play a crucial role in osmoregulation, helping to maintain the correct balance of water and salts within the organism. The presence and complexity of protonephridial systems can vary significantly between different invertebrate groups. They represent an early evolutionary solution to the problem of waste removal and maintaining internal homeostasis.