Types Of Skeleton And Supporting Systems In Animals

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Table Of Contents

1. Meaning of skeleton
2. Types Of skeleton
3. Supporting System in animals, cuticles, bones, and cartilages
4. Revision Questions

Meaning Of Skeleton

Meaning: Skeleton is a 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 one place to place. The skeleton depending on the position of certain organism in the 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.

Types Of Skeleton

There are three main types of skeleton. Hydrostatic skeleton, exoskeleton and endoskeleton

Hydrostatic (fluid) skeleton

Hydrostatic skeleton is the types of skeleton possessed by soft-bodied animals. They have fluid pressure to provide support. Fluid is secreted to fill the spaces in the body. The fluid presses against the muscular body wall causing the muscles to contract, exacting pressure against the fluid. This helps to maintain the shape and form of the animal. Examples of organisms with this type of skeleton is the earthworm and anemones.

Exoskeleton

Exoskeleton is a types of skeleton which is found outside or external part of the body of some animals. Most vertebrates do possess cuticle which is composed of chitin. Chitin is a non-living substance commonly found covering the outer part of the body of some animals. Some external skeletal tissue encloses, support, give shape, protects and also enable the animals to move.

Examples of organisms with exoskeleton are invertebrate like euglena, paramecium, hydra, tapeworm, snails, insects, prawns, crabs, spiders, millipede and crayfish. Organisms with this type of skeleton can also grow by a process called moulting or ecdysis. In this process, an organism shed of its old skeleton, grow and later covered with a new one.

Endoskeleton

Endoskeleton is a types of skeleton which is found inside the body of animals. Endoskeleton exists in a bony or cartilaginous skeleton of fishes, toad, lizards, birds and mammals. Endoskeleton in vertebrates is made of cartilages and bones. Endoskeleton in mammals are the skull, vertebra column or backbones, ribs and the bones of the fore are hind limbs.

Bone of Axial and appendicular skeleton

The skeletal system of bones in mammals and that of the rabbits are grouped into two major parts. These are Axial and appendicular skeleton.

1. Axial skeleton: The axial skeleton is made up of the skull, vertebra column or backbone, ribs and sternum of breastbone.
2. Appendicular skeleton: The appendicular Skeleton is made up of the limb girdle (pectoral and pelvic girdles) and the limbs (fore limbs and hind limbs).

Functions Of Skeleton In Man

The functions of skeleton in man includes:

1. Support: The rigid framework of the skeleton gives support to the body. The vertebral column, pelvic girdle and pectoral girdle provides a framework by which the viscera can be supported. As a result, the organs are prevented from crushing each other and the shape of the body is maintained. The vertebral column or backbone forms a pillar-like structure to which the girdles and ribs are attached.

2. Protection: The skeleton protects important and delegate organs of the body. Is called forms a protective covering for the dedication of the brain. It also has the complicated structures of the inner ear and the eyeball. The vertebral column protects the spinal cord. The rib-cage protects all the important organs of the thorax such as the heart, lungs and blood vessels. Pelvic girdle protects abdominal organs especially the urinary bladder and the female reproductive organs.

3. Movement: The whole skeleton is made up of several pieces of bones which are jointed and brings about movement. The skeleton provides a base for the attachment of muscle which brings about movement of the body and limbs and it gives them the ability to bend and twist in any desired direction. The contraction and relaxation of the muscles attached to bones also bring about movement.

4. Respiration: The skeleton also aid in respiration. The thoracic bone of the ribs, caged together with the muscles attached to them, assists in respiration (i.e. inspiration and expiration).

5. Manufacture of blood cells: The white and red blood cells are manufactured in the marrow of long bones.

6. Muscle attachment: Skeleton provides places for the attachment of muscles. Muscles are attached to bones by means of tendons.

7. Shape: The skeleton also provides or give shape to the body. It enables organisms to be easily recognized by the shape given by the skeleton.

8. Storage of mineral salt: The skeleton also helps to store important mineral salt such as calcium and phosphorus, hence some bones are sources of food or minerals for some mineral animals, e.g. bone meal as livestock feed.

The skull: The mammalian skull is made up of several flat bones which are joined together by means of joint called sutures.

The three major part of the skull are:

• The cranium or brain box which holds or contains the brain.
• The facial skeleton which supports the nose, eyes and the muscles of the cheek.
• The jaws which are made up of the upper jaw (maxilla) and lower jaw (mandible) which contains the teeth.

Functions Of The Skull

• It protest the brain
• It gives shape to the head
• It protect vital organs in the head, e.g. eyes, nose and ears.
• It bears the teeth which aid grinding of food.

Forms and component of skeletal materials

There are three forms of skeletal materials found in animals. This skeletal materials are cuticle, bones and cartilages.

1. Cuticles: The cuticle is composed of a protein called chitin and a thin waterproof layer of wax. Chitin is a non-living substance, 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 skeleton material (i.e cuticle) are mainly the arthropods which are insect, crabs, scorpion and prawns.

2. Bones: Bone is a tissue and a major component of the vertebral skeleton. It consists of living bone cells (osteocytes), protein fibers (collagen) and minerals mainly calcium phosphate and calcium carbonate.

The mineral (non-living) component is made up of the mass of a bone. As a result, bone is a stronger and more rigid tissue than cartilage. 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, which are bony fishes, toads, lizards, snakes, birds and mammals.

3. Cartilages: Cartilage is a tissue found in the skeleton of a complex vertebrates. It consists of living cells (chondroblasts), carbohydrates and protein fibers. 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 cartilaginous fishes like sharks, rays and mammals generally.

Types Of Cartilages

In mammals, there are three types of cartilage:

1. Hyaline cartilage: This is found in the (i)trachea and bronchi which keep them open (ii) surfaces of movable joints (iii) the protruding part of the nose which supports it.
2. Fibro-cartilage: It is a tougher than hyaline cartilage and it is found in the discs between the small bones (vertebra) of the vertebra column.
3. Elastic cartilage: This is found in the external ear (pinnae) and epiglottis.

The vitamins and minerals element necessary for healthy bone development are:

1. Vitamin – D/Calciferol, Vitamin C (form the cement of Bone)
2. Mineral elements – calcium/phosphorus/magnesium.

Difference Between Bones And Cartilages

1. Bone is made up of living and non-living cells – cartilage is made up of mainly living cells.
2. It is not flexible, especially in adult ones – It is very flexible both in adult and young.
3. Bone is made up of hard substance – cartilages made up of soft substance.
4. Bone can never be replaced by cartilage – cartilage can be replaced by bone.
5. Bone is made up mainly of mineral salts – It is not made up mainly of mineral.
6. Bone is a stronger and more rigid tissue – cartilage is not so strong but it is a flexible tissue.

Revision Questions

1. What is a skeleton?
2. List and discuss the types of skeleton
3. (a) what is cartilage? (b) state three types of cartilage.
4. (a) What is skull? (b) state the functions of the skull.
5. Discuss briefly 5 functions of skeleton.