STRUCTURAL ORGANISATION IN ANIMALS

In this post we will be briefly covering the following topics – 4  tissue types, namely Epithelial, Connective, Muscular, Neural Tissue and Organs and Organ Systems.

A group of similar cells of common origin along with intercellular substances performing a specific function is known as tissue.

Animal tissues are broadly classified into four types: (i) Epithelial, (ii) Connective, (iii) Muscular and (iv) Neural.

Tissue

Origin

Function

Epithelial

Ecto, meso, endodermal

Protection, absorption, secretion etc.

Connective

Mesodermal

To connect, support, transport etc

Muscular

Mesodermal

Locomotion and movement

Nervous

Ectodermal

Control and coordination

Epithelial Tissue

This tissue has a free surface, which faces either a body fluid or the outside environment and thus provides a covering or a lining for some part of the body.

The cells are compactly packed with little intercellular matrix.

There are two types of epithelial tissues namely simple epithelium and compound epithelium. Simple epithelium –

    

 

Connective Tissue

Connective tissues are most abundant and widely distributed in the body of complex animals.

They are named connective tissues because of their special function of linking and supporting other tissues/organs of the body.

In all connective tissues except blood, the cells secrete fibres of structural proteins called collagen or elastin which provide strength, elasticity and flexibility to the tissue.

These cells also secrete modified polysaccharides, which accumulate between cells and fibres and act as matrix (ground substance).

Connective tissues are classified into three types: (i) Loose connective tissue, (ii) Dense connective tissue and (iii) Specialised connective tissue.

 

Muscle Tissue

  • Each muscle is made of many long, cylindrical fibres arranged in parallel arrays. These fibres are composed of numerous fine fibrils, called myofibrils.

  • Muscle fibres contract (shorten) in response to stimulation, then relax (lengthen) and return to their uncontracted state in a coordinated fashion.

  • Their action moves the body to adjust to the changes in the environment and to maintain the positions of the various parts of the body.

  • In general, muscles play an active role in all the movements of the body.

  • Muscles are of three types, skeletal, smooth, and cardiac.

Neural Tissue

  • Neural tissue consists of neuron and neuroglial cells.

  • Neural tissue exerts the greatest control over the body’s responsiveness to changing conditions.

  • Neuron, an excitable cell is the unit of neural system.

  • The neuroglial cells which constitute the rest of the neural system protect and support neurons.

  • Neuroglia make up more than one half the volume of neural tissue in our body.

  • When a neuron is suitably stimulated, an electrical disturbance is generated which swiftly travels along its plasma membrane.

  • Arrival of the disturbance at the neuron’s endings, or output zone, triggers events that may cause stimulation or inhibition of adjacent neurons and other cells

 ORGAN AND ORGAN SYSTEM

  • Tissues organise to form organs which in turn associate to form organ systems in the multicellular organisms, this results in more efficient and coordinated system of cells.

  • Each organ is made of one or more type of tissues.

  • Complexity in organ and organ systems displays certain evolutionary trend.

 

Hope this article helped you! Goodluck!