Monday, March 7, 2011

Types of skeletal systems in animals

The term skeleton refers to the framework of the animal body around which the whole body is built. Skeleton is the collective name for all the hard and rigid structures in the body forming the framework of the body. The skeletal systems are of three basic types that are;
  • Hydrostatic skeleton
  • Exoskeleton
  • Endoskeleton
Each one of these is now described in detail;
  • Hydrostatic skeleton:
Some of the soft bodied invertebrates like the sea anemones and annelids etc are deprived of hard skeleton. In such animals the coelom filled with a fluid acts as a kind of skeleton and this skeletal system is called the hydrostatic skeleton. It provides support and helps in locomotion. The body of sea anemone is surrounded by muscle fibers and tentacles surround its mouth. The body and the tentacles are extended with the seawater present in the cavity of sea anemone. The pressure of muscle fibers on the liquid in the body cavity helps in maintaining the position of sea anemone in water. Hydrostatic skeleton in the earth worm enables it to move on the earth.
  • Exoskeleton:
The exoskeleton is that type of skeleton which lies outside the soft parts of the body, providing a covering to them. It is in the form of hard and rigid plates composed of dead substance secreted by cells. Familiar examples of this type of skeleton are those found in the insects, the horny scales, feathers and hairs. In many cases the exoskeleton is very rigid and heavy. It restricts the movements of the animal to the extent that the animal is passive and slow or even sessile.
One group of animals however has attained a very successful solution of the difficulty posed by the rigidity and weight of the exoskeleton. These animals are arthropods. They are completely encased in a very light substance known as chitin. Furthermore, the exoskeleton instead of being formed of just one piece or even two pieces, is divided into several distinct sections. Thus the arthropods have ease of motion with a protective outer covering. This is a factor in their biological success. It presents one great disadvantage, which is that if the animal is to grow at all it must remove its exoskeleton. Arthropods do this by molting or ecdysis.
  • Endoskeleton:
Endoskeleton develops within the skin or in the deeper tissues. The vertebrate skeleton is basically an endoskeleton made up of two types of tissues: bone and cartilage. During early embryonic development the endoskeleton is composed of notochord and cartilage. The notochord in most vertebrates is replaced by vertebral column and the cartilage is replaced by bone in most adults. The endoskeleton gives shape and support to the body and provides a mean of locomotion. For detailed study of human skeleton, visit the link: Human skeletal system

1 comment:

  1. thanks for the very informative post. Such information is what i need for my assignment in basic anatomy. :-)