[Biology Class Notes] on Classification of Tissues Pdf

All living organisms are made up of tiny building blocks called cells, which are the smallest units of life. These cells combine to form tissues, which further unite to form organs and organ systems. So, what is tissue in science?

All biotic organisms in the world are classified into two major categories: unicellular and multicellular organisms.

In higher multicellular organisms such as dogs and human beings, cells cluster together to form groups that perform a particular function. Each group performs a specific function and is known as a tissue.

To put it simply, a tissue is a group of cells that play a similar role. These are present in both plants and animals and represent levels of organization in living organisms. 

The study of tissues is called histology, and for plants, the subject is called plant anatomy.

Read on to know more about tissue and its types.

Classification of Tissues

Tissues form an intermediate organizational structure between cells and organ systems. Different groups of tissues with diverse functions group together to form an organ. In animals, therefore, a group of muscle cells combines together to form muscle tissue.

The classification of tissues in animals falls under four major categories. These are:

Before you learn more about what is the function of tissue, here’s a quiz for you to try:

Pop Quiz 1:

1. The study of tissues is known as ________.

1. Plant anatomy.

2. Morphology.

3. Histology.

4. Natural history.

Connective Tissues

In connective tissue, a group of cells separated by a non-living extracellular matrix combine to form a tissue. Connective tissues help provide mechanical strength, shape and rigidity to the organs and keep them in place. Examples of connective tissues include tendons, ligaments, bones, blood, adipose and areolar tissues. Further, there are three types of connective tissues. These are:

Connective tissues have several different functions in the human body, namely:

1. They provide insulation and protection against cold to the body.

2. They help bind the organs together and provide mechanical support to them.

3. Connective tissues help transport gases, water, hormones, nutrients and waste materials within the body.

Muscle Tissue

Muscle tissues help us to perform different actions and engage in activities like walking, running and locomotion. There are three types of muscle tissue:

Firstly, muscle tissues help us to maintain our posture. Secondly, they also aid in our involuntary and voluntary movements. For example, cardiac muscles help pump blood and regulate its flow in arteries and capillaries. 

Muscle tissues can also be classified on the basis of the conscious control a person has over those muscles. On this basis, there are two types of muscles in existence which are – Voluntary muscles and Involuntary muscles. Voluntary muscles move according to the will of the person and involuntary muscles move freely irrespective of the will of the person.

Nervous Tissue

Nervous tissues are present in the central nervous system that comprises the brain and spinal cord. In the peripheral nervous system, nervous tissues make up the cranial and spinal nerves.

Nervous tissues perform several vital functions, such as:

• These tissues also play a key role in the management of various emotions, memory, and the reasoning skills of an organism.

Epithelial Tissue

Epithelial tissues consist of cells that form the external covering of the body. These cover the organ surfaces such as the skin, the airways, the inner walls of our digestive tract as well as the reproductive tract. 

Epithelial tissues provide support and mechanical strength to the cells and tissues. They also help in the transportation of materials through diffusion, secretion, and filtration.

Moreover, epithelial tissues such as the ones beneath our skin help us in sensory reception and protect us against pathogens and physical trauma. They also secrete hormones, mucus, and enzymes from various endocrine organs.

Now that you have gone through the classification of tissues, it’s time to revise a few concepts with the following exercise.

Classification of the tissue present in the plants

Plants also have various types of tissues and can be classified into two categories. The first is based on the parts of plants whose tissue is present in the plant and the second is on the basis of types of cells.

By the first category, the plant tissues can be classified into three major groups, these three groups are:

a) Epidermis Tissues: These tissues are present on the outer surfaces of the leaves.

b) Vascular Tissues: They help in the transportation of the various fluids and nutrients. They are generally present at the middle of the stem and trunk and are spread all over the plant’s body.

c) Ground Tissues: Ground tissues are the ones that assist in the process of photosynthesis.

With the help of the second category, the plant tissue can be divided into two sub-categories.

a) Meristematic Tissues: These cells keep on producing new copies of themselves.

b) Permanent Tissues: These tissues have lost their ability to divide and recreate themselves.

Pop Quiz 2

1. What are the types of tissues?

1. Connective Tissues.

2. Nervous Tissue.

3. Epithelial Tissue.

4. Muscle Tissue.

5. All of the above.

Here is a classification of tissues chart to help you understand better.

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