SUPPORT AND MOVEMENT IN ANIMALS

Skeleton – is a firm and rigid framework for support in animals.

Functions of the Skeleton

• Supports the weight of the animal’s body.
• Gives the body its shape.
• Provides surface for attachment of body muscles that facilitate movement.

Types of Skeleton

There are three types of Skeletons in animals:

(a) Hydrostatic skeleton

(b) Exoskeleton

(c) Endoskeleton

Exoskeleton

It is found in arthropods.

It is made of a polysaccharide called chitin that makes it waterproof.

Chitin is secreted by epidermal cells and hardens on secretion.

Chitin is not evenly deposited but is thin at joints to allow for efficient movement.

Functions of Exoskeleton

• Supports animal body weight.
• Protects inner delicate tissues against mechanical damage, desiccation and pathogenic invasion.
• Provides a surface for muscle attachment (essential for movement).

Disadvantage of Exoskeleton

• It limits growth. To permit growth, the exoskeleton is periodically shed, a process called moulting (ecdysis)

The Endoskeleton

Found in vertebrates.

In vertebrates, the muscles are external to the hard framework.

It is made up of living tissues i.e. cartilage or bone.

These tissues grow steadily within the animal body and therefore do no necessitate moulting to allow for growth.

Functions of the Endoskeleton

• Support the animal body weight and gives the body its shape.
• Protects delicate internal organs from mechanical injury e.g. heart, lungs, brain.
• Provides surface for attachment of muscles that bring about movement.
• Bones produce blood cells.
• Bones act as reservoir of Calcium and phosphate ions in the body.