Animal Body Cavities

Body Cavities

• Coelomates
• Most triploblastic animals have fluid-filled body cavity
• Coelom: True body cavity
• derived from mesoderm
• Pseudocoelomates
• Triploblastic animals that lack mesoderm lining
• Have a hollow cavity, but it is not fully lined with mesoderm
• Aceolomates
• Triploblastic animals that lack a body cavity

Function of Coelom

• Coelom cushions internal organs from physical damage
• Allows organs to shift Examples: Gut digesting, heart beating etc.
• Some fluid filled cavities used as a hydrostatic skeleton
• Fluid is incompressible
• allows muscle to flex using the fluid as an anchor (instead of bones)
• Some animals lost / gained coelom cavities throughout evolutionary history