Tissues Class 9 – Chapter 6

Tissue

• The group of cells that combine together to perform a common function is called as tissues.
• Multicellular organisms show division of labor because a particular function is carried out by a cluster of cell that is also known as tissues at a definite place in the body.
• In tissues the cells are arranged and designed so as to give the highest possible efficiency of the function they perform.
• All cells of tissues have a common origin.
• Tissues can be of simple and complex types.

Also Check – What is the Utility of Tissues in Multicellular Organisms?

Plant tissues

Plant tissues can be divided into 2 fundamental types on the basis of its dividing capacity.

Meristematic tissue

• Meristematic tissue which are also known as growth tissue always keep dividing giving rise to new cells.
• Meristematic tissues consist of actively dividing cells present in the growing regions of plants.
• These tissues are responsible for the growth of the plant.
• Plants grow only in those regions where meristematic tissues are present.
• Cells forming meristematic tissues are very active.
• They have dense cytoplasm.
• They have thin cellulose walls.
• They have prominent nuclei.
• They lack vacuoles because vacuoles are full of cell SAP, which provides turgidity and rigidity to the cell. This causes hindrance to cell division.
• New cells produced by Meristem are initially like those of Meristem. Their characteristics changes once they grow and become differentiated as components of other tissues.

ALSO CHECK–Meristematic Tissue -Definition, features and functions

Meristematic tissue are Classified into Three types

1. Apical Meristem

It is present at the growing tips of stems and roots.

2. Intercalary Meristem

It is present at the base of the leaves or internodes of twigs.

3. Lateral Meristem

It is present on the lateral sides of stems and roots.

Also Check – 12 Important Difference between Meristematic and Permanent Tissues

Permanent tissues

• Permanent tissues are formed when meristematic tissue loses their ability to divide.
• The cells of permanent tissues have attained a permanent shape size and function by the process called differentiation.

ALSO CHECK–Protective Tissue in Plants-Define, Types, Functions

Permanent tissues are divided into two types

1. Simple permanent tissues
   
2. Complex permanent tissues
   

Simple permanent tissue

• Simple permanent tissues are made up of only one type of cells.
• The cells forming these tissues are similar in structure and functions.

Simple Permanent Tissues are further divided into three types

• Parenchyma
  
• Collenchyma
  
• Sclerenchyma
  

Also Check – Differentiate between Parenchyma , Collenchyma and Sclerenchyma on the basis of their cell wall.

Meristematic tissues tends to form different types of permanent tissues as a result of differentiation which are as follows

Parenchyma

• These are the living cells with thin walls.
• Parenchyma cells are uniformly thin.
• The cells are loosely packed with large intercellular spaces.

Functions of parenchyma

• It serves as a food storage tissue
• This tissues provide support to plants
• The parenchyma which contains chlorophyll are called chlorenchyma.
• The parenchyma cell contains large air cavities in aquatic plants which gives buoyancy to the plant. These parenchyma cells are called Aerenchyma.
• Parenchyma of stems and roots also stores nutrients and water.

Collenchyma

• Collenchyma are found in leaf stalks below the epidermis and leaf midribs.
• This cells are living, elongated and irregular thickened at the corners due to deposition of pectin.
• They have very little intercellular spaces. 

Functions of collenchyma

• It provides mechanical support and elasticity to plant.
• It provides  easy bending in various parts of the plant like tendrils and stems of climbers without breaking.

Sclerenchyma

• Their present in stem, around vascular bundles, in the vein of leaves and in the hard covering of seeds and nuts.
• The cells of this tissues are dead.
• The cells are long and narrow in appearance.
• Cell walls are hard due to lignin deposition.
• There is no internal space between the cells.

Functions of sclerenchyma

• It makes plants hard and stiff.
• It forms a protective covering around seeds and nuts.
• It gives rigidity flexibility and elasticity to the plant body.

Complex permanent tissue

• This type of tissues have more than one type of cells having a common origin.
• In this type of tissues cells have different appearances and they all co-ordinate to perform a common function.
• The Transportation system of plant is composed of complex permanent tissues.

There are two types of complex permanent tissues.

• Xylem
  
• Phloem
  

Also Check – Functions of the Xylem and Phloem

Xylem

• It helps in the transportation of water and Minerals from Roots to the other parts of the plant.
• Cells of xylem have thick walls and many of them are dead cells.

Xylem consists of many types of elements which are as follows

Tracheids

• These are dead cells.
• They are long.
• They have tubular structure with tapering ends.
• They transport water and minerals vertically.

Vessels

• They are dead cells, with lignified walls.
• These are long tube-like structures.
• They are formed by a row of cells placed end to end.
• They also help in transportation of water.

Also Check – What are the Differences between the Transport of Materials in Xylem and Phloem

Xylem parenchyma

• They are the only living cells of xylem.
• Xylem parenchyma has thin cell walls.
• They store food.
• The help in sideways conduction of water.

Xylem Fibers

• They are dead cells.
• They are elongated cells with tapering ends.
• They have thick cell walls.
• This fibers are associated with xylem.
• They are supportive in function.

Phloem

• Food is prepared in the leaves by the process of photosynthesis.
• It transports food from leaves to other parts of the plants.
• Materials can move in both directions in it.
• All phloem cells are living except phloem fibers.

Phloem tissues are made up of five types of elements.

• Sieve tubes
  
• Sieve cells
  
• Companion cells
  
• Phloem fibres
  
• Phloem parenchyma
  

Sieve tubes

• These are living cells.
• They are tubular cells with perforated walls.
• They have a thin layer of cytoplasm.

Sieve cells

• These are long conducting cells.
• They do not form sieve tubes.
• The major difference between sieve cells and sieve tube is the lack of sieve plates in sieve cells.

Companion cells

• These are small elongated cells having thin walls which are not perforated and have active cytoplasm.
• Companion cell helps sieve tubes in the translocation of food.

Phloem fibers

• These are thick-walled sclerenchyma cells.
• It provides mechanical strength to the tissue.

Phloem parenchyma

• These are thin walled cells.
• It helps in storage and slow lateral conduction of food.

ALSO CHECK–List the Characteristics of Cork . How is it Formed? Mention its Role or functions.

Animal tissues

On the basis of functions animal tissues are divided into four basic types

• Epithelial tissue
  
• Connective tissue
  
• Muscular tissue
  
• Nervous tissue
  

Epithelial tissue

Characteristics features of epithelial tissue

• It covers most organs and cavities of the body.
• It forms a barrier to keep different body systems separate from each other.
• In this tissue cells are tightly packed and form a continuous sheet.
• There is no intercellular space between them.
• There is a very small amount of cement in the material between them.
• Epithelial tissue is separated from underlying tissue by an extracellular fibrous basement membrane containing collagen.

Functions of epithelial tissue

• It is the protective tissue in the animal body.
• It protects the underlying cells from dying, injury, infection and also from harmful effects of chemicals.
• It plays an important role in regulation of the exchange of material between the body and external environment and between different body parts.
• It helps in elimination of waste products from the body.
• It helps in absorption of water and nutrients and in  diffusion of gasses.

Epithelial tissue is further Classified on the basis shape of the cell arrangement.

• Squamous epithelium
  
• Cuboidal epithelium
  
• Columnar epithelium
  
• Glandular epithelium
  

Squamous epithelium

It constitutes the skin which protects the body.

It is further divided into two types

• Simple squamous Epithelium
  
• Stratified squamous Epithelium
  

Simple squamous epithelium

Characteristic features of simple squamous epithelium

• It is single layered and closely fitted epithelium.
• Cells are very thin and flat and appear as tiles.
• It forms delicate lining of blood vessels.
• It also forms the lining of lung alveoli.
• It also covers the esophagus and the lining of the mouth.

Function of Simple Squamous Epithelium

• Facilitate diffusion of gases and small molecules.
• Simple Squamous Epithelium are common where absorption or transport of materials is important.
• They play an important role in diffusion, osmosis and filtration. This makes them important in the kidney, in the alveoli of lungs and in the walls of capillaries.

Stratified squamous epithelium

Characteristic features of stratified squamous epithelium

• It is found on the side of the skin.
• Resistance to mechanical injury.
• It is waterproof.
• These tissue cells are arranged in many layers to prevent their wear and tear.

Functions of Stratified Squamous Epithelium

• Stratified Squamous Epithelium tissues protect underlying structures from mechanical or chemical abrasion and stress.
• Stratified Squamous Epithelium also protects the body from desiccation and water loss.

Cuboidal epithelium

Characteristics features of cuboidal epithelium

• It is made up of cube shaped cells.
• Each cell has a round nucleus.
• It forms the lining of the ducts of salivary glands.
• It forms the lining of kidney tubules.
• It forms the Germinal epithelium of gonads.

Functions of cuboidal epithelium

• It gives mechanical support to the glands.
• It helps in absorption.
• It helps in excretion.
• It helps in secretion of material.

Columnar epithelium

Characteristic features of columnar epithelium

• These tissues are made up of tall, pillar life cells with elongated nuclei.
• It is generally found in the inner lining of the intestine where absorption and secretion occurs.

Functions of columnar epithelium

• It helps in absorption and secretion of material.
• It facilitates movement across the epithelial barriers.

Ciliated columnar epithelium

Characteristic features of ciliated columnar epithelium

• The epithelial cells of this tissue possess cilia and that’s why It is called as ciliated columnar epithelium.
• The cilia have the ability to move.
• It is found in the respiratory tract and also lines oviduct, sperm ducts, kidney tubules etc.

Functions of ciliated columnar epithelium

• The movement of cilia pushes substances like mucus forward.
• Ciliated columnar epithelium transport particles in a specific direction through wave-like movements.

Glandular epithelium

Characteristic features of glandular epithelium

• Cells of glandular epithelium secrete substance at the epithelial surface.
• Sometimes a portion of epithelial tissue folds inwards. This results in the formation of multicellular glands which are called glandular epithelium.

Functions of glandular epithelium

• Glandular Epithelium helps in secretion of fluids into ducts or fluids of the body.
• Glandular epithelium secretes enzymes, hormones, milk, mucus, sweat, wax and saliva.

Connective Tissue

Characteristic features of connective tissue.

• Connective tissues are specialized to connect various body organs with each other.
• The cells of connective tissue are loosely packed, living and embedded in an intercellular matrix that may either be jelly-like, fluid, dense or rigid in nature.
• The Matrix which is present in connective tissue differs in concordance with the function of the particular connective tissue.
• Connective tissue connects two or more bones to each other. They also connect muscles to bones, bind different tissues together and also gives support to various parts of the body.

Functions of Connective tissues

• Connective tissue binds different tissue together.
• It gives support to various parts of the body.
• It also helps in transportation of important elements to all parts of the body.
• It also helps in regulating the temperature of the body.
• It also helps in repair of tissue.
• Some connective tissues also act as an insulator.

Types of Connective Tissue

Blood

Blood is a connective tissue that has fluid matrix that links to different parts of the body.

Functions of blood connective tissue

• It helps to maintain the continuity of body.
• It transports nutrients, gases, hormones and vitamins to various tissues of the body.
• It carries excretory products from tissues to excretory organs.
• It regulate body temperature.
• It provides oxygen to all parts of the body.
• It also helps to remove carbon dioxide from the body cells.

Blood contains many components suspended in it which are as follows

• Plasma
  
• RBC( red blood corpuscles)
  
• WBC ( white blood corpuscles)
  
• Platelets etc.
  

The properties shown by different blood cells in the body are as follows

RBCs

• It helps to transport respiratory gases ,Oxygen and Carbon dioxide.
• It contains hemoglobin which helps in the transportation of the gases.
• The average lifespan of RBC is about 120 days.

WBCS

• There are also called as leukocytes, their main function is to fight diseases by producing antibodies.
• There are many types of white blood cells which performs different functions.

Monocytes– These are the types of white blood cells which helps to breakdown bacteria.

Lymphocytes– These are the types of white blood cells which create antibodies to fight against diseases.

Neutrophil– These are the types of white blood cells which acts like first line of Defense.

Basophils- These are the types of white blood cells which helps to control body’s immune response.

Eosinophils– These are the types of white blood cells which kills parasites and cancer cells and help with allergic responses.

Also Check – 9 Important Functions of Blood Plasma

Bones

• Bones is the strongest non flexible connective tissue.
• It is porous.
• It is highly vascular.
• It is mineralized ,hard and rigid.
• Its matrix is made up of proteins and acid rich in salts of calcium and phosphorus.

Functions of bone

• It forms the framework of the body.
• It supports all the body parts.
• It anchors the muscles and support the main organs.

Ligaments

• It is the type of connective tissue which connects bone to other bone.
• It is very elastic .
• It has considerable strength.
• It contains very little matrix.
• Their overstretching leads to sprain.

Functions of ligaments

• Ligament strengthen joints and permit normal movement.

Tendons

• This connective tissues are strong and inelastic structures.
• The joint skeletal muscles to bones.
• They are composed of white fibrous tissues.
• They have limited flexibility but great strength.

Cartilage

• It is a type of connective tissue having widely spaced cells.
• It contains solid Matrix called Chondrin.
• Chondrin is composed of proteins and sugar.
• It is present in nose ear trachea and larynx.

Functions of cartilage

• It provides smoothness to the bone surfaces at the joints.

Areolar tissue

• This connective tissue is found between the organ lying in the body cavity.
• It is located between skin and muscles.
• It is also located around blood vessels and nerves and in the bone marrow.
• It is a loose and cellular tissue.

Functions of areolar tissue

• It is supporting and packaging tissue.
• It fills the space inside the organs.
• It supports internal organs.
• It helps in the repair of tissues.

Adipose tissue

• Adipose tissue is a type of tissue which is located below the skin in between the internal organs.

Functions of adipose tissue

• It serves as a fat reservoir.
• It keeps visceral organs in position.
• It acts as an insulator due to storage of fats.

Muscular tissue

• Muscular tissues are made up of muscle fibres.
• It consists of Elongated cells.
• Muscular tissues are responsible for the movement of our body.
• Muscular tissues helps in the movement by contraction and relaxation.
• Contractile protein which is present in muscular tissue helps in contraction and relaxation of muscles.

Functions of muscular tissue

• Muscular tissue is responsible for the movement of our body.
• It also helps to maintain the posture of the body.
• Contraction and relaxation of heart.
• It is also important in involuntary function of our body .

Types of muscular tissue

• Striated muscles
  
• Smooth muscles
  
• Cardiac muscles
  
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Striated muscles

• Striated Muscles are found in our Limbs which move or stop as per our will.
• Striated muscles are also called as voluntary muscles.
• We can use this muscles by our conscious will.
• Striated muscles are attached to bones and that is why it is also called as skeletal muscles.
• The cells of striated muscles a long, cylindrical, unbranched and multinucleate.
• Striated muscles under the microscope shows alternate light and dark bands or striations.

Functions of striated muscles

• Main function of striated muscles is body movement.
• It also helps the process of respiration, locomotion and posture.

Smooth muscles

They are also called as involuntary muscles as we cannot move them as per our will.

These muscles are found in IRIS of eye, in ureters and in bronchi of lungs.

The cells constituting smooth muscle tissue a long , with pointed ends( spindle shaped) and uninucleate( single nucleus).

This metal do not show any dark or light band. And hence they are also called as unstriated muscles.

Functions of smooth muscles( involuntary muscles)

• The movement of food in the alimentary canal.
• The contraction and relaxation of blood vessels.
• Function of iris of eye.
• Please important role in ureters.
• Plays important role in bronchi of lungs.

Cardiac muscles

• This involuntary muscles are present only in our heart.
• Important role of cardiac muscles is to perform rhythmic contraction and relaxation throughout the life.
• The cells are cardiac muscles are cylindrical, uninucleate and branched.
• Cardiac muscles have stripes of light and dark band.

Nervous tissues

• The cells of this Nervous tissues are called as neurons.
• The cells of nerve tissue receives stimulus and transmit it from one part of the tissue to the other.
• Neurons are highly specialized for receiving stimulus.
• They transmits the stimulus very rapidly from one place to another with in the body itself.
• Brain spinal cord and nerves are composed of nervous tissues.
• Neurons of nerve tissues maybe up to meter long.

Also Check – What does a Neuron Look Like?

Neurons are composed of three major parts

Cell body– it consists of cytoplasm, nucleus and cell membrane.

Axon– it is a single long conducting fiber extending from neuron. Transmits Impulse away from the cell body.

Dendrites– these are short branched fiber of neuron which receives nerve impulses.