Kehaõõn

Kehaõõn refers to a body cavity, a fluid-filled or air-filled space within the body of an animal. These cavities serve important functions in housing and protecting organs, facilitating movement, and enabling circulation of nutrients and waste products.

The presence and structure of body cavities vary significantly across different animal groups. In simpler organisms like flatworms, there is no true coelom; instead, their internal space is filled with mesenchyme. Organisms with a pseudocoelom, such as nematodes, have a fluid-filled cavity that is not completely lined by mesoderm. This pseudocoelom allows for more efficient internal transport than in acoelomates.

More complex animals, known as coelomates, possess a true coelom, which is a fluid-filled cavity entirely enclosed within the mesoderm. This true coelom is a defining characteristic of many animal phyla, including annelids, mollusks, arthropods, echinoderms, and chordates. The coelom plays a crucial role in hydrostatic skeleton function, allowing for movement through muscle contractions against the fluid. It also compartmentalizes organs, preventing them from pressing against each other, and provides space for organ development and growth. Furthermore, the coelomic fluid can act as a circulatory medium and facilitate waste removal. The development of a coelom is considered a significant evolutionary advancement, contributing to the complexity and diversity of animal body plans.