Tissue and Supporting System

Biology SSS 1 Second Term

WEEK 1

Tissue and Supporting System

Performance Objectives

Student should be able to:

1. Define supporting system
2. Differentiate between the types of skeleton
3. Gives functions of supporting system

Content

Living organisms including plants and animals need tissues to enable them to carry out life processes. For example, without the various bones and tissues, vertebrates may not be able to stand, respire, move and carry out other life processes. The skeleton is the hard, bony framework of the body which confers protection, support and shape to organs and soft tissues of the body.

Types of Skeleton

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

Hydrostatic (Fluid) Skeleton

Hydrostatic skeleton is the type 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, exerting 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.

Exo (ecto) skeleton

Exoskeleton is the type of skeleton which is found outside or external part of the body of some animals. Most invertebrates 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. Such external skeletal tissue encloses, supports, gives shape, protects and also enable the animals to move. Organisms with this type of skeleton cal only grow by a process called moulting or ecdysis. This is the process whereby an organism sheds off its old skeleton, grows and later is covered with a new one.

Examples of organisms with exoskeleton include invertebrates like paramecium, euglena, tapeworms, insects, snails, spiders, crabs, millipedes etc.

Endoskeleton

Endoskeleton is the type of skeleton which is found inside the body of animals. Endoskeleton exists in bony or cartilaginous skeleton of fishes, toad, birds, lizards and mammals. Endoskeleton in vertebrates is made of cartilages and bones. Endoskeletons in mammals include the skull, vertebral column or back-bones, ribs and the bones of the fore and hind limbs.

Skeletal materials in Animals

There are three forms of skeleton or skeletal materials found in animals. These skeletal materials are Cuticle (chitin), cartilage and bone.

1. Cuticle or Chitin: Chitin is a non-living protein substance with a thin waterproof layer of wax. Animals with this type of skeletal material grow by moulting or ecdysis.
2. Cartilage: Cartilage consists of living cells (chondroblast), carbohydrates and protein fibres. It has a great tensile strength and provides a cushioning effect on bones moving against each other. There are three types of cartilage: Hyaline cartilage (found in trachea and bronchi, protruding part of the nose and surface of moveable joints), fibro-cartilage (found discs between bones of the vertebral column) and elastic cartilage (found in the external ear). Examples of organisms which possess cartilages are cartilaginous fishes like sharks rays and mammals.
3. Bone: Bone consists of osteocytes (bone cells), protein fibres (collagen) and minerals (mainly calcium phosphate and calcium carbonate). The bone has a hard outer layer (shaft) and a spongy hollow cavity filled with bone marrow. It is found mainly invertebrates.

Functions of supporting tissues in Plants and Animals

A. Protection

In animals, the skeleton protects important and delicate organs of the body. The skull forms a protective covering for the delicate tissue of the brain. It also houses 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.

In plants, some supporting tissues are known to protect the delicate parts of the plant body e.g. cambium and phloem tissues.

B. Support

In animals, 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.

C. Locomotion

In animals, 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 muscles 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.

D. Strength

In plants, the major supporting tissues namely sclerenchyma and collenchymas are two distinct forms of strengthening cells found in plants. They provide the necessary support required by plants.

E. Rigidity

The supporting tissues like collenchymas, sclerenchyma and wood fibres provide the necessary materials to make the plant strong against any external forces.

F. Resistance

The supporting tissues also provide the necessary materials which make the plants resilient and flexible thereby preventing the plants from being broken by the bending and twisting movements caused by strong winds.