Exoskelton

EXOSKELETON- ARTHROPODS

Striking features

  • The hard outer covering of arthropod is made of chitin, it forms the Exoskeleton which covers the external surface of the body
  • It passes through the mouth and lines the anterior part of the alimentary tract which is called Stomodaeum
  • It also goes through the anus into posterior part of alimentary canal which is called Proctodaeum
  • Exoskeleton is usually in the form of chitinous plates called Sclerites
  • The dorsal sclerite is called Tergum
  • Ventral sclerite is called  Sternum
  • Lateral plate between tergum and sternum is called  Pleuron
  • The tergum, sternum and pleuron of each segment are united by more flexible portions of exoskeleton which are termed  sutures
  • As arthropods grow the exoskeleton will become too small for it, so it periodically casts off  the exoskeleton and a new exoskeleton is formed
  • Casting off, of the exoskeleton is called Ecdysis or moulting
  • The exoskeleton is lined by wax layer which serves as waterproofing to protect arthropods from desiccation
  • The wax layer is covered by a cement layer whose function is to protect the vital wax layer

Function of exoskeleton

Acts as,

  • Protection to the internal organs
  • The first line of defence against extrinsic injuries
  • Limiting membrane or skin
  • For attachment of muscles
  • Gives rigidity to the body
  • Waterproofs  the insect
Last modified: Friday, 23 September 2011, 4:07 AM