Tissue: Animals and Plant Tissues, Types and Functions

Tissue is a group of cells that are similar in structure and function.

• The word tissue is derived from an old French verb, 'tissu', which means “to weave”. 
• Cells are the smallest units that can carry out life functions and make up all living things.
• A group of similar cells working together for a specific function is called a tissue.
• So, muscles, bones, skin, and even blood are all different types of tissues.
• Tissues, found in both plants and animals, are formed by groups of similar cells working together.

Key Terms: Tissue, Cells, Animal tissues, Plant tissues, Histology, Multicellular organism, Epidermis, Muscles, Unicellular organisms, Types of tissues

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What are Tissues?

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“Tissues are groups of cells, classified according to the size, shape, and functions of these cells.”

The study of tissue is known as histology, and the study of disease-related tissue is known as histopathology.

• Tissue is a level of organization in the body of a multicellular organism.
• They are formed from groups of cells with similar structures and functions.
• There is no tissue found in the bodies of unicellular organisms.
• They are found in animals and plants.

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Types of Animal Tissues 

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There are mainly four types of tissues found in animals. These are

• Connective Tissue
• Muscle Tissue
• Nervous Tissue
• Epithelial Tissue

Multicellular organisms organize tissues into functional units called organs. These four types of tissue have different purposes and can vary in origin depending on the organism.

Connective Tissues

Connective tissues are groups of cells separated by a non-living material called the extracellular matrix.

• This matrix provides shape and support to organs and other structures.
• Examples of connective tissues include blood, bone, tendon, adipose tissue (fat), ligaments, and areolar tissue.

There are three types of connective tissues

• Fluid Connective Tissue
• Fibrous Conctive Tissue
• Skeletal Connective Tissue

Muscle Tissue

Muscular tissues, found in animals, are contractile tissues responsible for movement. They allow the body to move as a whole and also enable internal organs to function.

There are three types of muscle tissue:

• Skeletal Muscle: These tissues are typically attached to bones
• Cardiac Muscle: These tissues are found in the heart.
• Visceral or Smooth Muscle: These tissues are found in the inner walls of organs.

Nervous Tissue

Nervous tissue forms the major components of the central nervous system (CNS), including the brain and spinal cord. In the peripheral nervous system (PNS), it forms cranial nerves and spinal nerves.

Epithelial Tissue

Epithelial tissues are formed by cells that cover external body surfaces and line internal organs. This includes the skin, the reproductive tract, the airways, and the inner lining of the digestive tract.

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Functions of Animal Tissues

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Different types of tissues have different functions in the body. The following are the functions of animal tissues

Functions of Connective Tissue

Connective tissue performs a variety of essential functions in the body.

• It holds organs in place and gives the body its shape.
• It acts as a protective layer for various organs.
• It helps fight against germs and infections through phagocytosis (engulfing foreign particles).
• It plays a crucial role in transporting water, nutrients, minerals, hormones, gases, wastes, and other substances throughout the body.

Functions of Muscle Tissue

Muscle tissues are responsible for various movements in the body, including walking, running, lifting, chewing, picking and dropping objects, etc. Some additional functions are

• Maintaining posture
• Constricting organs and blood vessels
• Enabling both voluntary and involuntary movements
• Pumping blood and regulating blood flow in arteries
• Controlling respiration by regulating air movement

Functions of Nervous Tissue

Nervous tissue forms the communication network of the nervous system, enabling functions like:

• Responding to stimuli
• Stimulating and transmitting information
• Playing a major role in emotions, memory, and reasoning
• Maintaining stability and environmental awareness
• Controlling and coordinating metabolic activities

Functions of Epithelial Tissue

Epithelial tissue performs a wide variety of functions in the body, including:

• Sensory reception, excretion, filtration, and other metabolic activities
• Providing mechanical strength and resistance
• It protects internal organs against pathogens, toxins, physical trauma, and radiation.
• It helps the movement of materials through filtration, diffusion, and secretion.

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Types of Plant Tissues

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Other than animal tissues, plants also have tissues to perform different functions. Like animal cells, plant cells gather to make up plant tissues.

The plant tissues are classified based on two important criteria:

• Based on the different parts of plants
• Based on the different types of cells

Based on parts of the plants, plant tissues are classified as

• Epidermis: This is the outermost layer of cells covering leaves, stems, flowers, and other plant parts. 
• Vascular Tissue: This complex tissue system is responsible for transporting fluids and nutrients throughout the plant.
• Ground Tissue: This is the most abundant type of plant tissue and fills the space between the epidermis and vascular tissues.

Based on the different types of cells plant tissues are classified as

• Meristematic tissues
• Permanent tissues

Meristematic Tissues

Meristematic tissues are groups of young, immature cells that continuously divide.

• This cell division allows plants to grow in length and width.
• These tissues can be further classified based on their position, function, plane of division, origin, and development.

The three main types of meristematic tissues, depending on their position on the plant body, are:

• Apical Meristem
• Lateral Meristem
• Intercalary Meristem

Permanent Tissues

These are the groups of dead or living cells that are produced by meristematic tissues.

• These tissues lose their ability to divide frequently and are located at certain specific places in the plant.
• Permanent tissues have a permanent task to perform in the plant.

There are three types of permanent tissues:

• Simple Permanent Tissues
• Complex Permanent Tissues
• Special or Secretory Tissues

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Functions of Plant Tissues

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Different types of plant tissues have different functions in the plant. The following are the functions of plant tissues

Functions of Meristematic Tissue

The functions of meristematic tissues are

• These tissues are responsible for the growth of new organs.
• Responsible for both primary and secondary growth of the plant.
• Involved in the movement of water and nutrition within the plants.
• It gives rise to the epidermis layer, cortex, endodermis, ground tissue, and vascular tissue.
• It is the outermost tissue, and functions by protecting from mechanical injury.

Functions of Permanent Tissues

The functions of permanent tissues are

• In aquatic plants, these tissues help them float on water.
• These tissues provide hardness to fruits, nuts, and other structures.
• They contain chloroplasts, essential organelles for carrying out photosynthesis in plant cells.
• They are also involved in secretion, transportation of materials throughout the plant, and providing mechanical support.

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Things to Remember

• A group of cells having similar structures and functions is known as Tissue. 
• Tissue is a level of organization in the body of a multicellular organism. 
• It helps in the formation of a multicellular organism as a whole.
• Tissues are found in both animals and plants.
• Types of tissues in an animal body are: Epithelial, Connective, Muscular, and Nervous.
• Types of tissues in plants are Meristematic and Permanent.