9th Class Science The Fundamental Unit of Life Tissues

         Tissues

 

A group of cell performing similar function is called tissue. Both plants and animals contains tissues which are different in nature. In this part we will discuss about both plant and animal tissue.

 

             Plant Tissue

Plant tissue is divided into two types Meristematic tissue and Permanent tissue. First we will discuss about meristematic tissue.

 

             Meristematic Tissue

The meristematic tissues are the continuously dividing tissues, which are found in the growing region of the plant. It helps in growth and development of the plant. According to their position in the plant, it is of three types, such as, apical meristem, intercalary meristem, and lateral meristem. The apical meristem is found in the root tips or the shoot tips of the plant. It helps in longitudinal growth of the plant.

 

The lateral meristem is found in the bark and in vascular bundles of the dicot roots and stems of the plant, whereas the intercalary meristem is found at the base of the leaves or i.nternodes. The main function of the meristematic tissue is to form new cells and helps in the growth of the plant. The apical meristem helps in longitudinal growth, lateral meristem helps in diametrically growth and intercalary meristem increases the length of the organ of the plant.

 

             Permanent Tissue

These tissues develop from meristematic tissue. Actually these are the meristematic tissue which have lost the power of division. It is further subdivided into two groups as simple permanent tissue and complex permanent tissue.

The simple permanent tissues are composed of similar cells. It is of three types:

Parenchyma, Collenchyma, and Sclerenchyma.

 

Parenchyma Tissue: These cells are living and still possess the power of division. They are founded in different shapes such as round, oval, elongated etc. It has thin cell wall and small nucleus. It is founded in stem, roots, leaves and fruits of the plant. It helps in filling the space between the other tissues and provides turgidity and rigidity to the plants. It also stores and assimilates food for the plants.

 

 

Collenchyma: It is similar to that of parenchyma, except for deposition of extra cellulose at the corner of the cells. The intracellular space are generally absent and contain few chloroplast. They are located below epidermis and didribs of dicot leaves. The main function of the collenchymas tissue is to provide mechanical strength and elasticity to the plants. It also provides flexibility to the stems, which helps in bending of stems.

 

 

• Sclerenchyma: These are basically dead cells and its walls are made up of thick deposition of lignin. It is made up of two types of cells such as fibers and sclereids. Fibers consist of long narrow, thick and lignified cells and sclereids are irregular shaped dead cells founded in cortex, pith etc of the plants. They are also found in stems, roots, hard coverings of seeds and nuts and stems. For example, husk of coconuts is made up of sclerenchyma. The main function of sclerenchyma is to provide mechanical strength and helps to withstand various strains to the plants.

 

 

            Complex Permanent Tissue

Complex permanent tissues are the tissues made up of more than one type of cell, having common origin. The complex permanent tissues are of two types, such as, xylem and phloem tissue.

 

Xylem: It is a conducting tissue which consists of tracheids, vessels, xylem parenchyma and xylem sclerenchyma. All the xylem elements, except for xylem parenchyma, are dead cells and bound by thick lignified wall. Vessels are long tube like structures, formed by a row of cell placed end to end. Tracheids are elongated cell, which conduct water from one cells to another via pits. Xylem parenchyma stores foods and helps in lateral conduction of water. The main function of xylem is to carry water and mineral salts from roots to the shoots of the plants. It also gives mechanical support to the plants.

 

 

Phloem: It is made up of Sieve tubes. Companion cells. Phloem Parenchyma and Phloem Fibers. Except for phloem fibers all are living cells. Sieve tubes are long cylindrical tube like structures composed of elongated thin walled cells. The walls of sieve tubes are perforated. The other cell is companion cells that is associated with the sieve tube containing dense and active cytoplasm. The main function of phloem is to transport potosynthetically prepared food from leaves to the storage organs and to other parts of the plant body.

   

 

 

 

 

        Which tissue helps in longitudinal growth of the plant?

(a) Lateral Meristem

(b) Intercalary meristem

(c) Apical Meristem

(d) Simple Meristem

(e) None of these

 

Answer: (c)

 

 

          Which plant tissue helps in storage of food?

(a) Parenchyma

(b) Collenchyma

(c) Sclerenchyma

(d) Xylem

(e) None of these

 

Answer: (a)

 

 

        The parenchyma which contains large air cavities that give buoyancy to the plants is:

(a) Chlorenchyma

(b) Aerenchyma

(c) Parenchymatous

(d) Collenchyma

(e) None of these

 

Answer: (b)

 

 

           The complex polymer which acts as a cement and harden the cell of the plant tissue is:

(a) Fibers

(b) Sclereids

(c) Lignin

(d) Lumen

(e) None of these

 

Answer: (c)

 

 

        The waterproof layer of a waxy substance which are present on the outermost layer of plant body is called:

(a) Cutin

(b) Phellogen

(c) Cambium

(d) Phelloderm

(e) None of these

 

Answer: (a)

 

 

              Animal Tissue

On the basis of the function performed by the tissues in the animal body they are classified as Epithelial Tissue, Muscular Tissue, Connective Tissue, and Nervous tissue. Now we will discuss about the various tissues in details.

 

           Epithelial Tissue

The tissue which are found on the outermost layer of the animal body called epithelial tissue. The cells of this tissue are tightly packed and hence it form a continuous sheet. It is also found in the inner lining of buccal cavity, blood vessel, alveoli, and kidney tubules. It is made up of matrix protein called collagen. It helps in absorption of water and nutrients in the inner lining of stomach. It also helps in elimination of waste products from the body of the animals. Depending upon the shape and function of the cells, it is of five types:

 

The different types of epithelial tissue are:

Squamous Tissue: It is made up of thin, flat, and irregular shaped cells. It is found in the inner lining of mouth cavities, oesophagus, nose, blood vessels and covering of tongue. It protects the underlaying part of the body from the injuries and germs.

 

     

Cuboidal Epithelium: It consists of cube like cells and hence it is called cuboidal epithelium. It is found in kidney tubules, salivary gland, sweat glands, testes and ovaries. It helps in absorption, excretion and secretion. It also provides mechanical support to the cells.

 

 

Columnar Epithelium: It consists of cells which are taller and pillar like. The nucleus is towards the base of the tissue. It is found in the linings of stomach, small intestine, and colon forming the mucous membrane. It’s also forms the inner lining of gall bladder and oviducts. It main function is to facilitate the movements and absorption of materials and their secretion.

 

 

Glandular Epithelium: The epithelium tissue which is modified to form glands and secrets chemicals for the function of tissues is called glandular epithelium.   

 

 

Ciliated Epithelium: The epithelium tissue which has hair like outgrowth on its surface is called ciliated epithelium. It is found in sperm ducts and wind pipe, bronchi, kidney tubules and oviducts. It helps in the movement of solid particles from one part of the cell to the another.

 

 

 

          Muscular Tissue

The muscular tissue are made up of muscle cells. They are elongated and larger in size. On the basis of their location, there are three types of muscular tissue. They are voluntary muscles, involuntary muscles, and cardiac muscles. The muscular tissue is responsible for the movement of the body and contains special proteins called contractile proteins which helps in movements.

 

Voluntary Muscles: The entire muscle fiber that show alternate dark and light bands and attached to bones are called skeletal muscles. Since these muscles works according to our will, they are called voluntary muscles. They are long, elongated, and unbranched. Also they are multinucleated and nuclei are in pheripheral position. They are found in muscles of limbs, body wall, face, neck, tongue, pharynx, diaphragm and upper part of oesophagus. They are powerful and helps in movement of body and its parts.

 

Involuntary Muscles: These muscles are smooth and founded in bundles. It is enclosed with a plasma membrane, uninucleated and are delicate, contractile threads called myofibrils that run longitudinally through the cell. Since they do not possess any bands, they are called smooth muscles. They are found in the walls of tubular organ except for heart. They are also found in the wall of alimentary canal and in the ducts of glands and blood vessels. The organ like stomach, iris, ureter, intestine etc possess these types of muscles. These muscles do not work according to our will and hence are called involuntary muscles. They help in movements of food in alimentary canal, also help in rhythmic movement of stomach and intestine.

 

Cardiac Muscles: These muscles show the characteristic of both voluntary and involuntary muscles. They are basically composed of branched of branched joined network of fibres. Each fibres is longitudinal myofibrils and centrally located nucleus and is uninucleated. There is a large amount of intracellular space which is filled with loose connective tissue which contains blood capillaries. They have alternate light and dark bands and also show densely stained cross bands. They are found in heart. Their main function are to carry out contraction and relaxation of hearts which helps it in pumping of blood into the body throughout the life.

 

               

 

           Connective Tissue

The connective tissue is a specialized tissue which helps in connecting the bones to muscles and binds tissues to give support to the different parts of the body. The cells of the connective tissues are separated from each other and are very less in number. It mainly consists of gel like homogenous substance called matrix. It is the nature of matrix which decides the function of the connective tissue. There are different types of connective tissue such as areolar tissue, dense regular connective tissue, adipose tissue, skeletal tissue, and fluid tissue. Now we will discuss about all these tissue in details separately.

Areolar Tissue: It is a loose connective tissue consisting of matrix. The matrix of these tissue contains two kinds of fibers, white collagen fibres and yellow elastic fibres. The matrix also contains fibroblast, which can engulf bacteria and protect us from infection. It is found around muscles, blood vessels and nerves. It helps in diffusion of oxygen and nutrients from small blood vessels. It helps in repair of tissues of injured parts of the body and fixes skins to underlying muscles. It also helps in fighting foreign toxins, which enters in our body.

 

 

Dense Regular Connective Tissue: It is a fibrous tissue, which is the main components of tendons and ligaments. Tendons are chord like strong, inelastic that join skeletal muscles to the bones. It is also a white fibre tissue which has great strength and limited flexibility. It consists of parallel bundles of collagen fibres containing fibroblasts.

 

The other one is ligament which connects bones to bones and is highly elastic in nature. It contains many collagen fibres and a very small amount of matrix. Fibroblast is compressed in between regular rows of fibres. It makes the joints strong and helps in the movement of bones and prevents over flexing.

 

Adipose Tissue: It is basically a collection of fat cell called adipocytes. Each adipocytes is round in shape and are arranged in lobules, separated by partitions of collagen and elastin fibres. These tissues are found below the skin and between the internal Organs and in yellow bone marrow. It helps in storing fats and provides shape to the limbs and body. It also forms shock absorbing cushions for some of the delicate organ like kidney, eye balls etc and also reduces the heat loss from the body and regulates body temperature.

 

Skeletal Tissue: It includes cartilage and bones that forms the endoskeleton of vertebrate of body. It is a specialized tissue which is compact and less vascular. The matrix of cartilage have a delicate network of collagen fibres and living cells. It is found in ear pinna, nose tip, epiglottis, ends of bones and ribs and rings of trachea. It provides support and flexibility to the body parts.

 

The other skeletal tissue is bone, which is non flexible, strong tissue. It is highly vascular and rigid. It is made up of protein and minerals that is responsible for the hardness of the bone. It forms the endoskeleton of the body and provides suppourt and shape to the body. It protects the delicate organ like brain, lungs, heart, liver etc.

 

• Fluid Connective Tissue: Blood and lymph is the fluid connective tissue. It consists of liquid matrix called blood plasma, which contains blood cells such as RBC, WBC, and platelets. RBC and WBC are living, while blood plasma and platelets are non living. The organic substance which are present in blood plasma are soluble protein such as albumin, globulins, fibrinogen, glucose, aminoacids, lipids, vitamins, enzymes, hormones and waste material such as urea and uric acid. RBC contains red pigments called haemoglobin. It contains erythrocytes which helps in transporting oxygen from one part of the body to another. The components WBC is of two types phagocytes and immunocytes. The phagocytes engulf bacteria and other foregin material and helps in body defence. The phagocytes includes neutrophils, basophils, and eosinophils. The immunocytes produces antibodies and maintain the immune system of the body. This includes lymphocytes which have spherical nucleus and little cytoplasm, with no granules. In the later stage it get changed into plasma cells. The blood platelets are the minute particles whose main function is to coagulate the bloods, at the site of injuries. The function of the blood is to transport nutrient, hormones, vitamins to the cells and also to remove the waste material from the blood. It also helps in protecting body from diseases. Platelets helps in clotting of blood at the site of injuries.

Lymph are the colourless fluid that contains WBC and other substance.

It transport nutrients and removes carbon dioxide and other nitrogenous waste from the body. It also form the immune system of the body.

 

• Nervous Tissue : It is a specialized tissue that transmit message from one part of our body to the other part.

Brain, spinal cord and nerve cell are all composed of nervous tissue. It consists of small cell called neurons. The message travels in the form of electrical impulse from one neuron to another. Each neuron is divided into three parts as cyton, dendron, and axon. The cyton contains nucleus and cytoplasm. The dendron arises from cyton and further branched into dendrites. The axons are the single long cylindrical cells which form branches with a swollen structure called knob. The dendrites receives impulses and the axon takes the impulse away from the cell body.

     

 

 

 

 

           The special form of matrix protein present in the epithelial tissue is called:

(a) Keratin

(b) Cytosine

(c) Collagen

(d) Cutin

(e) None of these

 

Answer: (c)

 

 

        Which tissue is present in the inner lining of mouth and oesophagus?

(a) Squamous

(b) Cuboidal

(c) Columnar

(d) Glandular

(e) None of these

 

Answer: (a)

 

 

         The tissue having alternate light and dark band and is multinucleated is called:

(a) Cardiac

(b) Voluntary

(c) Involuntary

(d) Muscular

(e) None of these

 

Answer: (b)

 

 

         Which tissue is present in ear pinna?

(a) Connective Tissue

(b) Muscular Tissue

(c) Cartilage Tissue

(d) Adipose Tissue

(e) None of these

 

Answer: (c)

 

 

       The functional unit of nerve cell is:

(a) Neuron

(b) Axon

(c) Dendron

(d) Cyton

(e) None of these

 

Answer: (a)

 

 

• Cell is the basic functional unit of all life forms.
• Plant cell consists of cell wall which is not present in animal cell.
• A group of cell performing similar function is called tissue.
• Plant tissue is divided into two parts as simple and permanent tissue.
• Nervous tissues consists of nerve cell.
• It is the nervous tissue which controls the functioning of the bodies.