How does acoelomates work without body cavities? 


An acoelomate is an animal that does not possess a body cavity. Unlike coelomates (eucoelomates), animals with a true body cavity, acoelomates lack a fluid-filled cavity between the body wall and digestive tract. Acoelomates have a triploblastic body plan, meaning that their tissues and organs develop from three primary embryonic cell (germ cell) layers.

These tissue layers are the endoderm (endo -derm) or innermost layer, mesoderm (meso-, -derm) or middle layer, and the ectoderm (ecto-, -derm) or outer layer. Different tissues and organs develop in these three layers. In humans, for example, the epithelial lining that covers internal organs and body cavities is derived from the endoderm. Muscle tissue and connective tissues such as bone,blood,blood vessels and lymphatic tissue are formed from mesoderm.

In addition to not having a body cavity, acoelomates have simple forms and lack highly developed organ systems. For example, acoelomates lack a cardiovascular system and rrspiratory and must rely on diffusion across their flat, thin bodies for gas exchange. Acoelomates commonly possess a simple digestive tract, nervous system, and excretory system.

They have sense organs for detecting light and food sources, as well as specialized cells and tubules for eliminating waste. Acoelomates commonly have a single orifice that serves as both an inlet for food and an exit point for undigested waste. They have a defined head region and display bilateral symmetry, ​which means they can be divided into two equal left and right halves.

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