Class 9 Science Chapter 6 Notes Tissues
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Chapter 6 : Tissues
A tissue is a group of cells with a Similar structure, Organised to Carry out specific fonctions.
DIVISION OF LABOUR AND TISSUES
- In multicellular organisms, there is division of labor where different groups of cells take up different functions.
- The cells specialized to carry one particular function occur together and form a cluster of cells. Such a cluster of similar cells in the body forms a tissue ( L. texere = to weave ) .
- The tissue may be defined as a group of cells that have a common origin, shape and structure. They work together to achieve a common function.
IMPORTANCE OF TISSUES
- Formation of tissues has resulted in division of labor in multicellular organisms.
- Tissues become organized to form organs and organs further get organized into organ systems .
- Origin of tissues has reduced the work load of individual cells.
- Due to improved organization and higher efficiency of tissues , multicellular organisms have higher survival
Are Plants and Animals made of the same Type of Tissues
- There are noticeable differences between the plant and animal tissues. Some of the differences are :
- Most plant tissues are supportive and provide mechanical strength. They need less energy and maintenance, while animal tissues carry out different functions and need more energy.
- In plants , most of the tissues are dead , whereas in animal tissues are living .
- In plants , the growth is limited to certain regions but it is uniform in all the cells in animals .
- There is a clear demarcation in dividing and non-dividing tissues in plants but it is absent in animal tissues .
- Tissue organization is simple in plants but in animals, tissue organization is complex.
- Unlike animals, some tissues in plants divide throughout the life and are localized in certain regions.
- Meristematic Tissues Meristematic ( Gk . meristos = divided ) tissues are formed of young , compactly arranged undifferentiated living cells that keep dividing and add new cells throughout the life of a plant.
- The growth of plants occurs only in certain specific regions.
- This is because the dividing tissue , also known as meristematic tissue , is located only at these points
Types of Meristematic Tissues
Based on their location in the plant body following three types of meristems are found :
1. Apical Meristem : It is found at the growing tips of stem , roots and growing young leaves . It is also called primary meristem .
2. Intercalary Meristem : It is located at the base of leaves and twigs and at the base of internodes.
3. Lateral Meristem : It is found as cambium in the vascular bundles of dicot stem and root and as cork cambium beneath the bark.
II. Permanent tissues
- Permanent tissues are formed of cells that have lost their capacity to divide.
- Though derived from meristematic tissues , they have definite permanent shapes and are specialized to carry out different functions.
- Permanent tissues form the bulk of plant body .
( i ) SIMPLE PERMANENT TISSUE
Simple permanent tissues are made up of only one type of structurally and functionally similar cells.
- It consists of relatively inspecialized cells with thin cell walls .
- They are live cells.
- They are usually loosely packed, so that large spaces between cells ( intercellular spaces ) are found in this tissue .
- This tissue provides support to u plants and also stores food .
- In some situations, it contains chlorophyll and performs photosynthesis, and then it is called chlorenchyma.
- In aquatic plants , large air cavities are present in parenchyma to give buoyancy to the plants to help them float .
- Such a parenchyma type is called Yaerenchyma .
- The parenchyma of stems and roots also stores nutrients and water
- The flexibility in plants is due to another permanent tissue.
- It allows easy bending in various parts of a plant ( leaf , stem ) without breaking .
- It also provides mechanical support to plants.
- The cells of this tissue are living, elongated and irregularly tickened at the corners.
- There is very intercellular space.
- It is the tissue which makes a the plant hard and stiff .
- The husk of a coconut . It is made of ei sclerenchymatous tissue.
- The cells of this tissue are dead.
- They are long and narrow as the walls are thickened due to lignin (a tH chemical substance which acts as cement and a hardens them).
- These walls are so thick ir that there is no internal space inside the cell.
- This tissue is present in stems, ti around vascular bundles, in the veins of ir leaves and in the hard covering of seeds and nuts.
- It provides strength to the plant parts Activity
Protective tissues include epidermis and cork.
Epidermis ( Gk / epi = upon + derma = skin )
Epidermis is the simple permanent tissue, protective in function. It forms one – cell – thick covering over all the parts of plant .
Characteristics of Epidermis
Epidermis is formed of living cells, arranged in a single layer.
In aerial parts, epidermis is covered with a waterproof and noncellular waxy covering called cuticle.
Cells form a continuous layer , but in leaves epidermis has small openings called stomata ( sing . stoma ).
Each stoma is guarded by a pair of bean – shaped guard cells which govern opening and closing of stomatal aperture .
Functions of Epidermis
1. Epidermis protects the underlying tissues from mechanical injury, chemicals and infection.
2. Cuticle of epidermis protects against water loss and desiccation. It checks the rate of transpiration and evaporation and prevents wilting.
3. Stomata in the epidermis of leaves help in gaseous exchange during respiration and photosynthesis.
Cork ( Phellem )
( Gk phellos = cork )
In old dicot stems and roots , the cells of protective tissue at the periphery change into cork cells .
Characteristics of Cork
Cork cells are dead and closely packed without any intercellular spaces.
Their thick cell walls are deposited with waterproof , waxy substance called suberin .
Suberin makes cork cells impervious to water and air .
Functions of Cork
1. Protection : It protects the plant from infection, mechanical injury and desiccation.
2. Lenticels : These are found on the outer surface of cork help in the aeration of inner tissues.
3. Commercial Use : The commercially used bottle cork is derived from the cork plant called Quercus suber. Cork is used in the manufacture of stoppers , sports goods , for thermal insulation and as shock absorber .
Complex permanent tissue
- Complex tissues are made of more than one type of cells.
- All these cells coordinate to perform a common function.
- Xylem and phloem are examples of such complex tissues.
- They are both conducting tissues and constitute a vascular bundle.
- Xylem consists of tracheids , vessels , xylem parenchyma and xylem fibres.
- The cells have thick walls, and many of them are dead cells.
- Tracheids and vessels are tubular structures,
- This allows them to transport water and minerals vertically.
- The parenchyma stores food and helps in the sideways conduction of water.
- Fibres are mainly supportive in function.
- Phloem is made up of four types of elements:
- sieve tubes, companion cells, phloem fibers and the phloem parenchyma .
- Sieve tubes are tubular cells with perforated walls .
- Phloem is unlike xylem in that materials can move in both directions in it .
- Phloem transports food from leaves to other parts of the plant.
- Except for phloem fibers , phloem cells are living cells.
Based on their functions , animal tissues are classified into following four types :
1. Epithelial tissue or epithelium – Protective tissue or Covering tissue
2. Connective tissue – Packing tissue
3. Muscular tissue – Contractile tissue
4. Nervous tissue – Coordinating tissue
Epithelial Tissue – The Protective Tissue
( Gk , epi = upon + thelio = to grow )
- Epithelial tissue is protective animal tissue.
- It forms continuous sheet ( the epithelium ) on both external and internal surfaces of the body and body organs .
- it is also called covering tissue.
Location of Epithelial Tissues
- 1 Epithelium occurs as a protective covering all over the body. It also covers all the body organs. It forms the outermost layer of skin.
- Epithelium forms lining of body cavities and cavities of all the hollow organs .
- It lines the buccal cavity, pharynx, oesophagus, stomach, nose, air tubes, lungs and all blood vessels. The epithelial tissue that forms the outer covering is called epithelium and the one that lines the cavities is called endothelium .
Characteristics of Epithelial Tissue
- Epithelial cells are closely placed . They do not have intercellular spaces.
- The cells are tightly held together by cell junctions and cementing substance .
- Anything entering or leave the body must cross at least one layer of epithelium.
- Epithelium cells may be flat cuboidal or columnar
- Epithelium does not have blood supply
Functions of epithelial tissue
- protection: Surface epithelial cells protect the underlying cells from mechanical and chemical injuries and bacterial or viral infections
- Absorption: Intestinal epithelium helps in the absorption of water and nutrients .
- Secretion: Some epithelial tissues produce secretions like sweat, saliva, mucus, enzymes, tears, etc.
- Excretion: Lining of kidney tubules helps in elimination of waste products.
- Respiration : Epithelium of alveoli of lungs helps in the exchange of oxygen and carbon dioxide between
- Regeneration : This tissue facilitates rapid healing of wounds by its regeneration power
- Epithelia play an important role in regulating the exchange of materials between the body and the external environment and also between different parts of the body.
- Acts as Barriers : It acts as selective barriers .
Types of Epithelial Tissue
- Simple Squamous Epithelium
- Simple Squamous Epithelium (Squamous epithelium is made up of thin, flat, disc-like, polygonal cells)
- Simple squamous epithelial cells are extremely thin and flat and form a delicate lining.
- The oesophagus and the lining of the mouth are also covered with squamous epithelium.
- The skin , which protects the body , is also made of squamous epithelium .
- Skin epithelial cells are arranged in many layers to prevent wear and tear .
- Epithelial are arranged in a pattern of layers , the epithelium is called stratified squamous epithelium.
- Simple Squamous Epithelium : Made up of single layer of flat cells.
Location : Simple squamous epithelium forms the lining of nose , pericardial cavity , blood vessels , lung alveoli , bronchioles , coelomic cavity , Bowman’s capsule , etc.
- Cuboidal Epithelium
- Cuboidal epithelium is composed of cube – like cells of almost equal height and width. Skin epithelial cells are anged in may layers to Prevent wear and tear .
- Cuboidal epithelium (with cube shape cells) forms the lining of kidney tubules and ducts of salivary gland.
- Cubodial epithelium provides mechanical support.
- Cuboidal epithelial can secrate substance at the epithelial substance.
Location : Cuboidal epithelium is present in Kidney tubules , Salivary glands , Ciliary body and Choroid layer of eye , Sweat glands , Pancreatic duct , Thyroid follicles , etc. It is also present in the germinal epithelium of Testes and ovaries.
Functions of Cuboidal Epithelium
- Mechanical support: It provides mechanical support to the organs where it is present.
- secretion : Cuboidal epithelium of digestive tract secretes digestive enzymes and of endocrine glands secretes hormones.
- Columnar Epithelium Columnar epithelium consists of tall , cylindrical , pillar – like cells .
- The columnar (meaning pillar like) epothelium facilitates movement across the epithelial barrier
- In the respiratory tract the columnar epithelial tissuealso has cilia which are hair like projection on the outer surfaces of epithelial cells.
- These cilia can move and their movement pushes the mucuc forward to clear it.
Location : Columnar epithelium lines Pharynx , Stomach , Intestine , Larynx and Oviduct . It is also found in Sweat glands and Sebaceous glands.
Functions of columnar epithelium
columnar epithelium functions in secretion and absorption. It provides mechanical support to the organs .
- Cells may be cubical or columnar.
- On its free surface are present protoplasmic outgrowths called cilia .
- It helps in the movement of ova in the fallopian tube.
Blood is a type of connective tissue.
- Connective tissue binds or connects various tissues and organs in the body and provides them rigidity, support and protection.
- It is also called packing tissue .
- It is the most abundant tissue in animal body .
Characteristics of Connective Tissue
- Connective tissue is formed of large intercellular matrix, connective tissue cells and fibers.
- It has fewer number of cells scattered in the matrix .
- Matrix is the nonliving , jelly – like ground substance.
- Large number of white and yellow fibers are present in the matrix.
- Matrix and fibers are secreted by cells of connective tissue.
Types of Connective Tissue
The connective tissue can be divided into the following main types :
Connective Tissue proper
- Areolar Tissue
- Adipose Tissue
- White fibrous Tissue – Tendon
- Yellow Fibrous Tissue – Ligament Tissue
Connective Tissue Proper
- Areolar Tissue it is the basic and most widely distributed connective tissue, in which fibers are loosely arranged in a meshwork.
- Its matrix is jelly – like and contains four types of cells and three types of fibers
- It fills the space inside the organs.
- Areolar tissue supports internal organs and help in repair of tissues.
- It fills the space inside the organs, supports internal organs and helps in repair of tissues.
Location : Areolar tissue is found below the skin , in the kidneys and testes and surrounds the muscle bundles , blood vessels , etc.
- Adipose Tissue
( L. adeps = fat )
- It is a fat storing connective tissue .
- Its cells become large and oval due to the storage of fat globules.
Location : Adipose tissue is present below the skin ( subcutaneous fat ) between the internal organs around blood vessels and kidneys , below the eyeballs and in yellow bone marrow .
Functions of Adipose Tissue
- Storage: It stores fat in the form of fat globules.
- Insulation : Acts as heat insulator. Subcutaneous adipose tissue in polar animals protects them against severe winter .
- Body Contours: Provides shape, to the body.
White Fibrous Connective Tissue – Tendon
( Gk . tenon or L. tendo = to stretch )
- It is dense fibrous connective tissue.
- Tendons connect muscles to bone and another type of connective tissue.
- It occurs in the form of sheets or tendons.
- These Tendon fibers provide great strength but limited flexibility .
Sheets of this tissue form covering of bones and cartilages .
It also occurs in the duramater of brain and spinal cord.
It forms tendon at the end of skeletal muscles and attaches muscles to the bones.
Yellow Fibrous Connective Tissue – Ligament
Ligament ( L Ligare = to bind or ligamentum = band )
- Two bones can be connected to each other by another type of connective tissue called the ligament.
- This tissue is very elastic: Bundles of this tissue form ligaments
- It has considerable strength.
- Ligaments contain very little matrix .
- Sheets of this tissue form a covering of Blood vessels, Arteries and Bronchioles.
- It contains considerable Strength
- Bundles of yellow fibrous connective tissue form ligaments. These attach bones to each other at the joints .
- Because of elasticity, ligaments allow bending and rotational movements of bone over a joint.
Sprain is caused due to overstretching of ligaments.
Skeletal Tissue – The Supporting Tissue
The skeletal tissue comprises of cartilages and bones and forms the supporting framework of the body
(L. catilago = gristle)
- It is relatively soft and elastic skeletal tissue
- It is harder than connective tissue proper.
- Its matrix is dense and elastic due to the presence of a special protein the chondrin.
- The solid matrix is composed of proteins and sugars.
Location of Cartilage : Cartilage is present in the epiglottis, larynx, tracheal rings, nasal septum pinna at the Cends of bones and in between the ribs and sternum.
Functions of Cartilage
- Cartilage supports various body parts . In cartilaginous fishes ( sharks ) , cartilage forms the whole skeleton and supports the whole body and fins .
- At the end of the long bones cartilage prevents wear and tear
- Bone is another example of a connective tissue.
- It forms the framework that supports the body.
- It also anchors the muscles and supports the main organs of the body. It is a strong and nonflexible tissue.
- Bone is much harder, rigid and nonflexible skeletal tissue.
- It forms the skeleton of vertebrates.
- The matrix of bone is very hard because of collagenous protein ossein and presence of salts such as phosphates and carbonates of Calcium.
Location of Bones : Bones form the endoskeleton of vertebrates.
Functions of Bone
- Cells of bone marrow give rise to blood corpuscles.
- Bones form the supporting framework and protect internal organs.
- Long bones help in locomotion.
- These provide surface for the attachment of muscles.
- Bones are reservoir of Calcium and Phosphorus.
Blood (Vascular or Fluid Tissue – The Transporting Tissue)
- Blood are fluid connective tissues.
- These transport nutrients , oxygen , vitamins and hormones to the cells and remove nitrogenous wastes , CO , and other products from the cells.
- Blood is bright red – colored fluid connective tissue . It forms 8 – 10 % of body weight.
- Blood is formed of plasma and blood cells or blood corpuscles.
Functions of Blood
1. Blood transports oxygen, nutrients, hormones, etc. to every part of the body.
2. It collects wastes from every part of the body.
3. It helps in thermoregulation, water balance and maintenance of pH of body.
4. RBCs help in the transport of respiratory gases ( oxygen and carbon dioxide ) from lungs to tissues and back .
5. WBCs help to fight diseases by engulfing and destroying foreign bodies by producing antibodies and antitoxins.
6. Blood platelets help in the clotting of blood at the site of injury.
- Plasma is the fluid matrix of blood.
- It forms about 55% of the blood by volume .
- Dissolved in the plasma are found proteins, inorganic salts, nutrients, hormones, antibodies (gamma globulins), nitrogenous wastes and gases.
- Blood plasma transports and distributes nutrients , O , and hormones to various cells of the body and removes nitrogenous wastes and CO2 .
- plasma help in blood clotting antibodies provide immunity against microbial infections.
Red Blood Corpuscles ( RBCs ) or Erythrocytes
- The shape and size of RBCs vary in different types of vertebrates.
- The presence of haemoglobin gives blood its red color.
- The lifespan of RBCs in man is about 120 days, after which they are destroyed in liven
- The worn out RBCs are always replaced by new ones. They are manufactured in bone marrow.
- The number of RBC in human males is 5-5.5 million per cubic milliliter of blood , while in females it is 4.5-5 million per cubic milliliter , whereas in infants it is 6-7 million per cubic milliliter .
White Blood Corpuscles (WBCs) or Leucocytes
- WBCs are formed in red bone marrow, spleen, thymus and lymph nodes.
- The lifespan of different types of WBCs ranges from eight hours to four days.
- The number of WBCs in human blood is 6,000 to 9,000 per cubic milliliter.
- They are not cells but pieces of certain giant cells of the bone marrow.
- They help in clotting of blood) at the site of wound by releasing a chemical thromboplastin.
- The number of blood platelets in human adult is 2-4 lakhs per cubic milliliter of blood.
- Muscular tissue consists of elongated cells, also called muscle fibres.
- Muscular tissue nrarly 40% of total body weight.
- It occurs in the form of bundles or sheaths.
- It also forms flesh of the body
- Muscles contain special proteins called contractile proteins.
Types of Muscular Tissue
The muscular tissue consists of three types of muscles:
- Striated or striped or skeletal or voluntary muscles
- Nonstraited or unstriped or visceral or involuntary or smooth muscels
- Cardiac muscles
Striated or Striped Muscles
- The muscle fibers of striated muscle have alternate bands of dark and light colour.
- they are called striated muscles.
- they are also called Skeletal muscles because their muscle bundles are attached to the bones and are responsible for their movement
- Striated muscles are also called voluntary muscles because their contraction is under the control of our will
- Striated muscles form nearly 50 per cent of the entire body weight
- Flesh in the body is made up of striated muscles.
Location: Striated muscles are present in the limbs , Face neck and diaphragm.
Functions of Striated Muscles
1. Striated muscles are associated with voluntary movements of body and body parts. These movements depend on the will of an organism.
2. They are responsible for locomotion.
3. Tongue movements are brought about by striated muscles. These help in ingestion of food.
4. Breathing movements and Blinking of eyes are also due to striated muscles.
- Smooth muscles are also called Nonstraited muscles or unstriped muscles because their myofibrils do not have dark and light bands.
- They are also called involuntary muscles because their contraction is not under the control of our will.
- The movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements.
- We cannot really start them or stop them simply by wanting to do so ! Smooth muscles or involuntary muscles control such movements.
- They are also found in the iris of the eye, in ureters and in the bronchi of the lungs.
- The cells are long with pointed ends ( spindle – shaped ) and uninucleate ( having a single nucleus ) .
- They are also called unstriated muscles.
- These involuntary muscles are called cardiac muscles.
- Heart muscle cells are cylindrical, branched and uninucleate.
Cardiac Muscles Location: cardiac muscles are found in the wall of heart only.
Functions: The pulsating movements of heart chambers are caused by the contraction of cardiac muscles. They pump blood from heart into the blood vessels (Arteries).
- The Coordinating Tissue Nervous tissue is highly specialized tissue for receiving stimuli and the transmission or conduction of these stimuli as electrochemical nerve impulses.
- It controls and integrates the activities of various parts of the body.
- All cells possess the ability to respond to stimuli.
- cells of the nervous tissue are highly specialized for being stimulated and then transmitting the stimulus very rapidly from one place to another within the body.
- The brain, spinal cord and nerves are all composed of the nervous tissue.
- The cells of nervous tissue are called nerve cells or neurons.
- A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair – like parts arise.
- Each neuron has a single long part, called the axon.
- Many Neuron have short branche parts called dendrites.
- An individual nerve cell may be up to a meter long.
Characteristics of Nervous Tissue
The nervous tissue is formed of neurons or nerve cells and nerve fibres
Functions of neurons or nerve cells and nerve fibres
- Many nerve fibers bound together by connective tissue make up a nerve.
- The combination of nerve and muscle tissue is fundamental to most animals.
- This combination enables animals to move rapidly in response to stimuli.
- Nerves in our body are like cables made up of many nerve fibres.
- Nerve fibers conduct messages from one part of the body to the other. They receive stimuli from the environment and send messages to the brain and spinal cord.
- Impulses from brain and spinal cord are carried to various body organs.
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