Friday, June 28, 2013

Tissues - Biology, Class - IX


 1. What is a tissue?
Ans.:  A tissue is a group of cells of similar structure and origin performing a similar function.

2. Write about the basic components of the tissue.
Ans.: All types of tissues have two basic components:
(i) Cells: Having common origin and function.
(ii)  Intercellular substances: Are non-living, fibrous, jelly-like substances.

3. Classify tissues.
Ans.: Tissues are broadly classified as animal tissues and plant tissues. The animal tissues are
      divided into four major types on the basis of their functions. These are,
(i)  Epithelial tissues, which are protective in nature as they cover free surfaces of the organs, and
     also form glands.
(ii)  Connective tissues, which join and support other tissues.
(iii) Muscular tissues, which bring about movements of body parts and locomotion by their ability
       to contract.
(iv) Nervous tissues, which control and co-ordinate the activities of various body parts.
The plant tissues are broadly classified into two major types:
(i)  Meristematic tissues, which constitute living cells capable of division.
(ii)  Permanent tissues, which constitute group of cells incapable of cell division. These tissues are
      further divided into several types on the basis of their place of occurrence, nature and function.

4. Differentiate between plant tissues and animal tissues.
Ans.:

Plant tissues
Animal tissues
(i)  dead, supportive tissues are more abundant to provide mechanical strength.
(i)  living tissues are more common.
(ii)  there is differentiation of meristematic and permanent tissues
(ii) such a differentiation is absent.
(iii)  tissue organization patter is of stationary type.
(iii)  tissue organization pattern is towards active locomotion.
(iv)  plants need less maintenance energy.
(iv)  animals need more maintenance energy.
(v)  tissue organization is simple.
(v)  tissue organization is complex.

 5. Write about Epithelial tissue.
Ans.: The epithelial tissue is composed of one or more layers of cells and is the simplest among all
     types of tissues. It forms outer covering of the body and the lining of the internal organs, and hence, also called covering tissue or epithelium.
Functions of epithelial tissue:
(i)  Protection: Epithelia protect the underlying cells from mechanical and chemical injuries and
     bacterial or viral infection.
(ii)  Acts as Barriers: It acts as selective barriers.
(iii)  Absorption: Helps in absorption of water and nutrients.
(iv)  Elimination: Helps in elimination of waste products.
(v)  Secretion: Some epithelial tissues secrete secretion, such as sweat, saliva, mucus, enzymes, etc.
(vi) Respiration: Epithelia of alveoli of lungs exchange oxygen and carbon dioxide between blood
       and inhaled air.
(vii) Exoskeleton: It produces exoskeleton structures, such as scales, feathers, hair, nails, claws,
       horns and hoofs.
(viii) Regeneration: This tissue facilitates rapid healing of wounds by its regeneration power.

6. Write the structure of epithelial tissue.
Ans.: The cells of epithelial tissue are closely packed with no intercellular space.  The cells of
     epithelia rest upon basement membrane, formed of mucopolysaccharides and collagen fibrils. It
     is always associated with connective tissue.

7. Classify the epithelial tissue.
Ans.: On the basis of the shape of cells and their function, the epithelial tissue is further classified
     into various types.

Characteristic property
Squamous epithelium
Cuboidal epithelium
Columnar epithelium
Ciliated epithelium
Shape of cells
It consists of thin, flat, disc-like polygonal or irregular-shaped cells with round and flat nucleus.
It consists of cube-like cells of almost equal height and width.
It consists of tall, cylindrical, pillar-like cells. Basal part of the cell bears oval nucleus.
It consists of tall cells with cytoplasmic hair-like cilia at free ends.
Appearance of cells
Adjacent cells fit together like tiles on a pavement or floor.
Cells appear square-like in vertical section but their free surface seems to be hexagonal
The free ends of the cell consists of finger-like projections called microvilli.
Cells may be cuboidal or columnar and are, therefore, also called ciliated cuboidal epithelium or ciliated columnar epithelium.
Place of occurrence
Forms the lining of nose, pericardial cavity, blood vessels, lung alveoli, bronchioles, Bowman’s capsule, etc.
Present in kidney tubules, salivary glands, ciliary body, choroid layer of eye, sweat glands, etc.
Present in the inner surface of stomach, intestine, gall bladder, gastric glands, salivary glands, etc.
Present in the lining of trachea, fallopian tube, bronchi, nasal passage, kidney tubules, etc.
Functions
(i) protects the underlying parts of the body from mechanical injury.
(ii) prevents the entry of germs inside our body.
(iii) prevents desiccation of organs.
(iv) facilitates diffusion of gases
(i) provides mechanical support to the organs.
(ii) secretion of gastric juices.
(iii) absorption and excretion.
(i) helps in absorption of nutrients.
(ii) secretion gastric juices.
(iii) provides mechanical support to the organs.
(i) causes movement of small solid particles or mucus in a specific direction through the ducts.
(ii) causes movement of ovum and zygote towards the uterus.
(iii) helps in removing unwanted particles from trachea.


8. What is the utility of tissues in multi cellular organisms?
Ans.: With the increasing degree of multi cellularity in living beings, it became difficult for each cell
    to efficiently perform all the physiological functions of the body. Hence, nature assigned
    specialized function to different group of cells called tissues. Thus, the utility of tissues in multi
    cellular organisms is to perform specific functions of the body.

9. Write about connective tissue and its functions.
Ans.: Connective tissue is concerned with connecting and binding different tissues or organs of the
     body. As such, it connects one bone with another and a bone with muscle. Connective tissue also
     provides the structural framework and mechanical support to different tissues.
Structure: Three components are present in all the connective tissues. These are intercellular
     medium, connective tissue cells and fibres.
Functions of connective tissue:
(i)  Binding: Connective tissue binds other tissues together in the organs.
(ii) Support: Bones and cartilages are hard endoskeleton of body which give support to muscles.
(iii) Storage: Fats remain stored inside adipose tissues.
(iv) Attachment: Connective tissues binds the different tissues together.
(v) Transport: Blood and lymph which are fluid connective tissues help in the transport of various
      materials in the body.
(vi) Padding and Packing: Areolar connective tissue acts as padding and packing material in
      different organs.
(vii) Defence: Plasma cells, lymphocytes and macrophages found in the matrix of connective tissue
      strengthen the immune system of the body.
(viii) Repairing: Collagen fibres of connective tissue help in repairing of injured tissues of wounds.

10. Classify the connective tissues.
Ans.: The connective tissue can be divided in to the following main types:
(i). Areolar tissue: It is the most abundant of all types of connective tissues. Areolar tissue contains
    practically all components that can be found in connective tissue. It has large amount of matrix.
    This tissue is present under the skin, in between and around muscles, bone marrow, nerves and
    blood vessels. It fills the space between different tissues and organs, hence called packing tissue.
Functions of areolar tissue :
(a) the primary function is to bind tissues. It binds skin with muscles, blood vessels and nerves to body parts.
(b) it helps in healing of wounds and repair of tissues after injury.
(c) it provides rapid diffusion of oxygen and nutrients from blood vessels.
(d)  it provides strength, elasticity and support to body parts.
(e)  it helps in fighting foreign antigen and toxin.
(g)  it fills spaces between tissues and organs.
(ii)  Dense connective tissue: It is a fibrous connective tissue, which is characterized by
     systematically and densely packed fibres and cells.
(iii)  Adipose tissue: It consists of large number of oval and rounded adipose cells filled with fat
     globules.
Adipose tissues are present below the skin, between the internal organs, around blood vessels and
     kidneys and in yellow bone marrow.
Function of adipose tissue:
(a)  adipose tissue acts as food reservoir by storing fat.
(b)  it forms shock-absorbing cushion around kidneys and eyeballs.
(c)  it acts as an insulator and regulates body temperature.
Note: Adipose tissue forms hump of camel and blubber of whale.
(iv) Skeletal tissue: Skeletal connective tissue forms the endoskeleton of the body of vertebrates. It
    includes cartilage and bone.

11. Write about fluid connective tissue.
Ans.: It is a special type of connective tissue which maintains link among different parts of the body.
          It receives materials from certain parts of the body and transports them to the other parts. 
          Fluid connective tissue constitutes the transport system of animals. It consists of two basic
          components – blood and lymph.

12. Differentiate between tendons and ligaments.
Ans.:

Characters
Tendons
Ligaments
(i)  Structure
Made up of white collagen fibrous tissue
Made up of yellow fibrous tissues
(ii)  Nature
Tough and non-elastic
Strong and elastic
(iii)  Arrangement of fibroblasts
Present in rows between fibres
Scattered in matrix in between the bundles of white fibres
(iv)  Function
Join muscle to bone
Join bone to bone

13. Differentiate between bone and cartilage.
Ans.:

Bone
Cartilage
(i)  they are hard and inflexible endoskeleton
(i)  they are soft and flexible endoskeleton
(ii)  porous in nature
(ii)  non-porous in nature
(iii)  blood vessels are present
(iii)  blood vessels are absent
(iv)  matrix arranged in lamellae
(iv)  matrix not arranged in lamellae.
(v)  matrix contains protein and mineral salts
(v)  matrix made up mainly of protein
(vi)  long bones contain bone marrow in hollow, narrow cavity
(vi)  bone marrow absent. Cartilage is always solid.

 14. Differentiate between RBC and WBC.
Ans.:

RBC
WBC
(i)  red in colour
(i)  colourless
(ii)  smaller in size
(ii)  larger in size
(iii)  they occur in large numbers – 4 to 6 million/cubic mm
(iii)  they are fewer in numbers – 6000 to 9000/cubic mm
(iv)  they are circular and biconcave in shape
(iv)  they are round or amoeboid in shape
(v)  they are devoid of endoplasmic reticulum, mitochondria, ribosomes and centrioles
(v)  they retain endoplasmic reticulum, mitochondria, ribosomes and centrioles
(vi)  they are without nucleus
(vi)  they are nucleated cells
(vii)  they occur only inside blood vessels
(vii)  they occur inside blood vessels as well as lymph vessels.

 15. Differentiate between blood and lymph.
Ans.:

Blood
Lymph
(i)  red in colour due to the presence of haemoglobin.
(i)  colourless as haemoglobin is absent.
(ii)  flows inside arteries, veins and blood capillaries.
(ii)  flows inside lymph channels, lymph vessels and lymph capillaries.
(iii)  consists of plasma, RBC, WBC and platelets.
(iii)  consists of plasma and WBC.
(iv)  plasma bears higher percentage of proteins, calcium and phosphorus.
(iv)  plasma bears few proteins and lesser amount of calcium and phosphorus.
(v)  glucose concentration less.
(v)  glucose concentration is more.
(vi)  amount of carbon dioxide and metabolic wastes is less than that in lymph
(vi)  amount of carbon dioxide and metabolic wastes is more than that in blood.

 16. Write about blood and its functions.
Ans.: Blood is a mobile connective tissue. It measures about 5-5.5 litres in an adult human being. Blood is a mobile connective tissue. It measures about 5 to 5.5 litres in an adult human being.  Blood has two main components, plasma – which is a fluid, and corpuscles – which are blood cells.
Functions of blood:
(i)  blood plasma helps in the transport of nutrients, hormones, waste materials and vitamins to every part of the body.
(ii)  RBC help in the transport of respiratory gases like oxygen and carbon dioxide from lungs to tissues and back.
(iii)  WBC help to fight diseases by engulfing and destroying foreign bodies by producing antibodies and antitoxin.
(iv) blood platelets help in the clotting of blood at the site of injury.
(v) blood helps in thermoregulation, water balance and maintenance of pH of body.

 17. Write about blood cells.
Ans.: There are three types of blood cells – red blood cells, white blood cells and platelets.
(i)  Red blood cell or erythrocytes: They are most abundant of the three types of blood cells. Their most important character is the presence of an iron protein, haemoglobin. They are manufactured in bone marrow their lifespan in human being is about 120 days.
(ii) White blood cells or leucocytes: These are rounded or amoeboid, nucleated, colourless cells. WBC are formed in red bone marrow, spleen, thymus and lymph nodes. The lifespan of different types of WBC ranges from eight hours to four days.
(iii) Blood platelets: Blood platelets are minute, rounded, colourless, biconvex and non-nucleated bodies. They are not cells but pieces of certain giant cells or the bone marrow. They help in clotting of blood at the site of the wound. They are present inside the heart, arteries, veins and blood capillaries.

18. Write about lymph and its functions.
Ans.: Like blood, it is also a fluid connective tissue. Lymph is actually filtered blood which is similar to blood in composition except that it is devoid of RBC, platelets and some blood protein.  Lymph is a part of lymphatic system of the body. It occurs inside the lymph vessels.
Functions of lymph:
(i)  helps in the transport of nutrients. Nutrients that filter out from blood capillaries into lymph are transported back by lymph into blood through heart.
(ii)  helps in the transportation of fat absorbed from intestine to the venous blood.
(iii)  keeps the tissues and organs of the body moist.
(iv)  lymphatic organs produce lymphocytes which in turn produce antibodies to strengthen the immune system of the body.

19. Write about muscular tissue and its functions.
Ans.: Muscular tissue constitutes all the muscles of the body of an animal. It is responsible for the movement of organs and locomotion of body in response to stimuli.
Structure: The structural unit of muscle tissue is the muscle cells, which because of its elongated shape is also muscle fibre.  Each fibre consists of many fine fibrils called myofibrils.
Functions of muscular tissue:
(i)  it supports the bones and other organs of the body.
(ii)  muscles cause peristalsis of gut, heart beat, production of sound, etc.
(iii)  muscles cause movements of body parts and locomotion of the animals.
(iv)  facial expression also depends on muscles.
(v)  contraction of muscles causes delivery of a baby.

20.Classify muscular tissue.
Ans.: On the basis of structure, location and function, the muscular tissue is classified into three types: unstriated, striated and cardiac muscles.

21. Write about unstriated muscles and its functions.
Ans.: Unstriated muscles are involuntary in nature as they are not controlled by the will of an individual. Each of the cells bears a central nucleus lying in protoplasm.  These muscle fibres do not have a definite surrounding membrane. It is found in the wall of alimentary canal, urinary bladder, blood vessels, lungs etc.
Functions of unstriated muscles:
These muscles cause slow and prolonged contraction which is involuntary, i.e., not under the control of individual’s will. These muscles help in peristalsis of alimentary canal, urinary tract, blood vessels, etc., and contraction of other visceral organs.

22. Write about striated muscles and its functions.
Ans.: These are also called skeletal muscles as they remain attached to bones or voluntary muscles, because these muscles are under the control of our will. Each cell contains sarcoplasm and a limiting membrane. Striped muscles are found in limbs, body wall, tongue, pharynx, face, neck, etc.
Functions of striated muscles :
Striped muscles produce rapid and powerful contractions which help in the movement of limbs and consequently cause locomotion. They are also helpful in the movement of other body parts which are in voluntary control of the individual.

23. Write about cardiac muscles and its functions.
Ans.: Cardiac muscles are the muscles of heart. They are unique in the sense that they are supplied with nerves from both central and autonomous  nervous systems, but they are involuntary.
Cardiac muscles are found in the wall of heart.
Functions of cardiac muscles:
Cardiac muscles are the toughest muscles of the body which work tirelessly till the organism survives. They contract rapidly and rhythmically without any external stimulation, to pump the blood into blood vessels.

24. Write about nervous tissues and its functions.
Ans.: Nervous tissue is a specialized type of tissue responsible for the reception of stimuli and transmission of impulse to different parts of the body. Nervous tissues are found in brain and spinal cord.
Functions of nervous tissues:
 Nervous tissue is responsible for the reception and transmission of information between different parts of the body.

25. Write about Neurons and its functions.
Ans.: Neurons are structural units of the nervous tissue. These cells are specialized for the conduction of impulses over great distances at great speed. The parts of neurons are cyton, dendrons, dendrites and axon.
Functions of neurons:
(i)  carry impulses from the site of stimuli towards the central nervous system.
(ii)  carry impulses from central nervous system to skeletal muscles.
(iii)  these neurons are confined to central nervous system only. They connect sensory neurons to motor neurons.

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