Topic: Meaning Of Skeleton And Its Components
- Meaning Of Skeleton
- Forms And Components Of Skeleton And Examples
Meaning Of Skeleton
Skeleton is the bony framework of the body which provides support, shape and protection to the soft tissues and organs in animals. Without skeleton, animals may not be able to move or carry out other life processes.
The skeleton of animals enable them to move from place to place. The skeleton depending on the position of certain organism in evolutionary trend helps to determine the advancement and development of organisms, e.g. Man is able to stand erect than other organisms due to its sophisticated skeletal build-up.
Forms And Components Of Skeleton
There are three forms of skeleton or skeletal materials found in animals. These skeletal materials are cuticles, bones and cartilages.
1. Cuticles: The cuticle is composed of a protein called chitin and a thin water proof layer of wax. Chitin is a non-living substances, hence animals with this type of skeletal material can only grow by moulting or ecdysis. In this process, an organism sheds off its old skeleton and put on a new one. In other words, for an organism to grow, it has to put off the old skin. Cuticle is an exoskeleton which is located externally on the body. Examples of organisms with this type of skeletal material (i.e. Cuticle) are mainly the arthropods, e.g. Insects, crabs, scorpion, prawns etc.
2. Bones: Bone is a tissue and a major component of the vertibral skeleton. It consists of living bone cells (osteocytes), protein fibres (collagen) and minerals, mainly calcium phosphate and calcium carbonate.
The mineral (non-living) components is made up of 2/3 of the mass of a bone. As a result, bone is stronger and more rigid than cartilages. A bone usually consists of a hard outer layer (shaft) and a spongy or hollow cavity filled with bone marrow. Examples of organisms which have bones are mainly vertebrates, e.g. Bony fishes, toads, lizards, snakes, birds, mammals etc.
3. Cartilages: Cartilage is a tissue found in the skeleton of complex vertebrates. It consists of living cells (chondroblasts), carbohydrates and protein fibres. It is a tough and flexible tissue that has great tensile strength. It acts as a shock absorber, cushioning the effect of bones moving against bones during movement. Examples of organisms which possess cartilages are cartilagenous fishes like sharks, rays and mammals generally.
Types of Cartilages
In mammals, there are three types of cartilages:
1. Hyaline cartilage: This is found in (i) trachea and bronchi whick keep them open (ii) surfaces of movable joints (iii) the protruding part of the nose which supports it.
2. Fibro-cartilage: It is tougher than hyaline cartilage and it is found in the discs between the small bones (vertebra) of the vertebral column.
3. Elastic cartilage: This is found in the external ear (pinnae) and epiglottis.