Download tissues

Representative Sample Biology:
Tissues
TISSUES
1. Introduction
Organisms are either unicellular or multicellular. Accordingly the functions are performed either by
a single cell or by a group of cells. Cells, tissues, organs and organ systems split up the work in a way
that exhibits division of labor and contribute to the survival of the body as a whole. This work division
ensures proper specific defined function of the body.
In Unicellular organisms like bacteria, all the functions like digestion, respiration and reproduction
are performed by a single cell. In the complex body of multicellular animals, the same basic functions
are carried out by groups of cells in a well-organized manner. The body of a simple organism like Hydra
is composed of different types and the number of cells. The human body is composed of billions of cells
to perform various functions. In multicellular animals, a group of similar cells along with intercellular
substances perform a specific function. Such an organization is called as tissue.
Tissues vary according to their origin and function, and are different in plants and animals.
2. Types of Tissue in A Plant
Plant tissues can also be divided differently into two types on basis of their division ability:
1. Meristematic tissues
2. Permanent tissues.
2.1. Meristematic Tissue
Meristematic tissue consists of actively dividing cells, leading to increase in length and thickness of the
plant. The primary growth of a plant occurs only in certain, specific regions, such as in the tips of stems
or roots. It is in these regions that meristematic tissue is present. Meristematic tissues are classified on the
basis of their location. They are of the following types:
(a) Apical Meristem: Apical meristem is present on the stem apex, root apex, flower buds and leaf
buds. They are actively dividing cells that require proper nutrition and energy for the division
and
Tissues
44
hence are green in color to carry out photosynthesis. They are responsible for growth in length, i.e.
primary growth.
(b) Lateral Meristem: Lateral meristems are found along the side of the stem. It consists of cells
which mainly divide in one plane and cause the organ to increase in diameter and growth. Lateral
Meristem usually occurs beneath the bark of a tree in the form of Cork Cambium and in vascular
bundles of dicots in the form of vascular cambium. They are responsible for growth in girth or
width, i.e. secondary growth.
(c) Intercalary Meristem: Intercalary meristem is present at the base of a leaf or internodes. They
are present on the either sides of the node.
Fig: Position of meristem in a growing plant
PLANCESS CONCEPTS
The cells of meristematic tissues are similar in structure and have thin and elastic primary cell
wall made up of cellulose. Each cell contains a dense cytoplasm and a prominent nucleus.
Normally the meristematic cells are oval, polygonal or rectangular in shape. Meristematic
tissue cells have a large nucleus with small or no vacuoles; they have no intercellular spaces.
Vipul Singh
AIR 1, NSTSE 2009
www.plancessjee.com
45
Tissues
Mind Map:
2.2. Permanent Tissue
When the cells of a meristematic tissue divide to a certain extent, they become specialized for a particular
function. This process is called as the differentiation. After differentiation, the cells lose their capability
to divide and is differentiated to their capability to perform various functions of the organism. The tissue
becomes permanent tissue after differentiation. Permanent tissues are of two types, the simple permanent
tissue and the complex permanent tissue.
(a) Simple permanent tissue:
These tissues are called simple because they are composed of similar types of cells which have common
origin and function. Simple permanent tissues are of three types, viz. parenchyma, collenchyma and
sclerenchyma.
1) Parenchyma: The cells of parenchyma have thin cell
wall. They are loosely packed; with a lot of intercellular
spaces between them. Parenchyma consists of the
largest portion of a plant body. The main function of
parenchyma is to provide support and to store food.
In aquatic plants, large air cavities are present in
parenchyma. Some parenchyma contain chlorophyll
and perform photosynthesis, in this case it is called
a chlorenchyma. Parenchyma with large air cavities
provide buoyancy to the plant, then the parenchyma is known as aerenchyma.
2) Collenchyma: Collenchymatous tissue acts as a supporting tissue
in the stems of young plants. It provides mechanical support,
elasticity, and tensile strength to the plant body. It helps in
manufacturing sugar and storing it as starch. It is present in
the margin of leaves and resists tearing effect of the wind. Cells
are elongated with thick primary walls thickened with cellulose
and no intercellular spaces. Cells that have chloroplasts perform
photosynthesis.
Tissues
46
3) Sclerenchyma: The cell wall is very thick with
lignin which is a water proof material. The cells
are dead and intercellular space is absent. The
nucleus is absent. It provides a structural rigidity
to the plant parts. Examples of sclerenchyma are
bark, coconut husk. They are fibers present in
a vascular tissue to transport water or sclereids
found in the cortex, pith, phloem for strength and
firmness. These cells are involved in a mechanical
support and protection for seeds.
PLANCESS CONCEPTS
The cells of sclerenchymatous cells can be classified as:
Fibers- Fibers are long, elongated sclerenchymatous cells with pointed ends. They help in
water transportation.
Sclerides- These are sclerenchymatous cells which are short and possess extremely thick,
lamellated, lignified walls with long singular piths.
The main function of Sclerenchymatous tissues is to give support to the plant.
Vipul Singh
AIR 1, NSTSE 2009
Mind Map:
b) Complex permanent tissue: The complex tissue consists of more than one type of cells which
work together as a unit. Complex tissues help in the transportation of organic material, water
and mineral up and down the plants. That is why it is also known as conducting and vascular
tissue. Complex permanent tissues are of two types, viz. xylem and phloem. Xylem and phloem
together make the vascular bundle in plants.
www.plancessjee.com
47
Tissues
i) Xylem: Xylem consists of:
• Tracheid
• Vessel Members
• Xylem fibers
• Xylem parenchyma.
Xylem is a chief, conducting tissue of the vascular plants. It conducts water and mineral ions. The cells
of xylem are dead; except the cells of xylem parenchyma. Tracheid and vessels are tubular structures and
thus they provide a channel for conduction of the water and minerals. Xylem fiber provides structural
support to the tissue. Xylem parenchyma stores the food.
Fig: Position of Xylem in plant
Tissues
48
Fig: Structure of tracheid, sieve-tube, sieve-plate, vessel membranes of Xylem.
ii) Phloem: Phloem consists of:
• Sieve tube
• Sieve cell
• Companion cell
• Phloem fibre
• Phloem parenchyma.
Sieve tubes are tubular cells with perforated walls. Sieve
tubes are the conducting elements of phloem. Phloem is
responsible for the translocation of food in the plants. The
transport of food in phloem is both upward and downward
movement.
www.plancessjee.com
49
Tissues
Mind Map:
PLANCESS CONCEPTS
Plant tissues are categorized broadly into three tissue systems: the epidermis, the ground
tissue, and the vascular tissue.
• Epidermis - Cells forming the outer surface of the leaves and of the young plant body.
• Vascular tissue - The primary components of a vascular tissue are the xylem and phloem.
These transport fluid and nutrients internally.
• Ground tissue - Ground tissue is less differentiated than other tissues. Ground tissue
manufactures nutrients by photosynthesis and stores reserve nutrients.
Vipul Singh
AIR 1, NSTSE 2009
Tissues
50
3. Types of tissue in animal
Animal tissues are of four types, viz. epithelial tissue, connective tissue, muscular tissue and nervous
tissue.
3.1. Epithelial Tissue
The epithelial tissue forms a covering or lining of most of the organs. The cells of epithelial tissue are
tightly packed and form a continuous sheet. There is a small amount of cementing materials between
the cells and there is no intercellular space. Due to the absence of blood vessel supply to the epithelium,
its permeability plays an important role in the exchange of materials among various organs. It also plays
an important role in osmoregulation. All epithelial tissues are separated by the underlying tissue by an
extracellular fibrous basement membrane.
Epithelial tissues are of the following types:
a) Simple Epithelium: The simple epithelium is
composed of a single layer of cells. This type of
epithelial tissue forms the lining of blood vessels and
alveoli facilitating exchange of gases and fluids.
b) Cuboidal Epithelium: These cells are cube-shaped,
provide a mechanical support. Linings of kidney
tubules and ducts of salivary glands are composed
of cuboidal epithelium. Cells of epithelium may
play the role of secretion and then they are called
glandular epithelium. It helps in secretion, excretion
and absorption of materials from the food or blood.
c) Columnar Epithelium: These cells are columnshaped that facilitates secretion and absorption.
Example: the lining of the intestine is composed
of columnar epithelium. In some organs, columnar
epithelium has cilia present on the outer surface
which facilitate movements of certain substances.
www.plancessjee.com
51
Tissues
The ciliated epithelium in the respiratory
tract pushes the mucus forward produced in
the goblet cells.
d) Stratified Epithelium: Cells of the stratified
epithelium are in many layers. Basal layer is
in contact with the basement membrane
and newer cells occupy the upper layers.
Skin is an example of stratified epithelium.
Stratification of layers prevents wear and
tear. This is highly water proof and resistant
to mechanical injury.
Mind Map:
3.2. Connective Tissue
The cells of a connective tissue are loosely scattered in a matrix secreted by its cells. The matrix can be a
fluid, jelly like, dense or rigid. The nature of the matrix depends on the function, which a connective tissue
serves. It helps in binding bones and cartilages, packing, supporting structures of the body. Following are
the various connective tissues:
i) Connective tissue proper: matrix – jelly, less rigid.
ii) Skeletal Tissue: matrix is solid.
iii) Vascular tissue: matrix is fluid.
i) Connective tissue proper:
Loose Connective tissue proper: It has less fiber and more matrix.
Dense Connective tissue proper: It has more fiber and less matrix.
Tissues
52
Loose Connective tissue proper:
a) Areolar Connective Tissue: Areolar tissue is found between the skin and muscles, around the
blood vessels and nerves and in the bone marrow. Areolar tissue fills up the gap between the
tissues and provides support. It also helps in repairing the tissues, as packing material, produces
antibodies.
b) Adipose Tissue: Adipose tissue is composed of fat globules. This tissue is found below the skin
and beneath the organs. Adipose tissue provides an insulation and works as a cushion. Adipocytes
are large cells with soft jelly like matrix and less fibers.
Dense Connective tissue proper:
a) Tendon: It is a tough non fibrous dense tissue. It is white in colour with great strength and less
flexibility. It joins skeletal muscle to the bone for contraction.
b) Ligament: It is a dense yellow fibrous tissue with strength and elasticity that binds bones together
for bending.
ii) Skeletal Tissue:
a) Bone: The bone is mainly composed of osteoblasts. The bone makes the skeletal system. The
skeletal system is responsible for providing a structural framework to the body. It provides
protection to important organs and facilitates movements. It has a fluid in it that is called as the
bone marrow. The matrix is concentric rings made up of collagenous protein.
b) Cartilage: The cartilage is mainly composed of chondrioblasts. The cartilage is present at the
ends of the articulatory bones. Cartilage is also present in external ear, bronchii, etc. a nonporous tissue filled with a fluid called lacunae. The major function of the cartilage is support and
flexibility.
iii) Vascular tissue
a) Blood: The blood is composed of blood cells, platelets and plasma. The blood plays an important
role in the transportation of various substances in the body. It also helps in osmoregulation and
temperature control, transportation of oxygen and nutrients.
b) Lymph: It is a light yellow colored fluid made up of plasma and WBC. It helps in exchange of
materials between blood and tissue fluid.
(contd.)
www.plancessjee.com
53
Tissues
Exercise — 1
Fill in the Blanks
Q.1. meristem occur at the apices of the roots and stem.
Q.2 type of parenchyma is seen in Petiole of banana.
Q.3 When Xylem and Phloem are arranged on alternate radius then the Vascular Bundle of
type.
Q.4 Radial Vascular Bundle is seen in
Q.5 Meristem producing the secondary xylem and phloem is called
.
Q.6 Hard lignified thick walled, long and pointed cells in a plant are
.
Q.7 Collenchymatous hypodermis is found in
.
Q.8 Transpiration and exchange of gases are the functions of
Q.9 Parenchyma: Simple::Phloem:
Q.10 Striated muscle is also called
.
.
.
True/False
Q.11 Most of the plant tissues are supportive type.
True False
Q.12 Tissue ensures division of labor.
True False
Q.13 Sedentary existence contributes to the organ system design in animals.
True False
Q.14 Organ system is more complex in animals than in plants.
True False
Q.15 Cartilage heals slower than the skin because cartilage is a deeper tissue.
True False
Q.16 The inside lining of the intestine has a large surface area because of the presence of cilia.
True False
Q.17 Adipose is a type of connective tissue because that is where fat is stored.
True False
(contd.)
Tissues
54
Exercise — 2
Multiple Choice Question:
Q.1 Histamine secreting cells are found in:
a) Connective tissue b) lung
c) muscular tissue d) nervous tissue
Q.2 The layer of skin that actively divides is:
a) Stratum compactum
b) Stratum corneum
c) Stratum lucidum
d) Stratum malphigi/stratum germinativum
Q.3 Characteristics of simple epithelium is that they:
a) Are arranged indiscriminately
b) Continue to divide and help in organ function
c) Make a definite layer
d) None of the above
Q.4 Collagen is
a) Lipidb) Fibrous protein
c) Globular proteind) Carbohydrate
Q.5 Areolar connective tissue joins
a) Haemoglobinb) Hirudin
c) Myoglobind) Histamine
Q.6 Hair present on the skin are:
a) Epidermal in origin and are made of dead cells
b) Epidermal in origin and are made of living cells
c) dermal in origin and are made of living cells
d) dermal in origin and are made of dead cells
Q.7 The basement membrane is made up of:
a) no cell product of epithelium
b) epidermal cell only
c) endodermal cell
d) both a and c
(contd.)
www.plancessjee.com
Tissues
55
SOLUTIONS
EXERCISE 1
Fill in the Blanks:
1. apical meristem
2. Aerenchyma
3. radial
5. vascular cambium
6. Sclerenchyma
7. Dicot stems
9. Complex
10. Skeletal muscles
4. Roots
8. Stomata
True/False:
11. True
12. True
13. False
14. True
17. False
18. True
19. True
20. False
15. False
16. False
Match the Following:
21. 1 → e ; 2 → d ; 3 → a ; 4 → c ; 5 → b
22. 1 → c ; 2 → e ; 3 → d ; 4 → b ; 5 → a
Very Short Answer Questions:
23. Ligaments24. Tendons
25. Cardiac muscle
26. Neuron
27. Bone marrow
28. Blood, lymph
29. Protein, salts, hormones
30. Study of blood.
31. Study of tissues.
32. Protection and mechanical support.
33. Apical meristem
34. Schlerenchymatous tissue
Short Answer Questions:
35. The plant supporting tissues are the collenchyma and the sclerenchyma. The collenchyma is
made up of living and elongated cells that accumulate cellulose and pectin in some regions of the
cell wall making them unequally thick and thus providing flexibility.
(contd.)
Tissues
56
SOLUTIONS
EXERCISE 2
Multiple Choice Question:
1. A
2. D
3. C
4. B
5. D
6. A
7. A
8. A
9. D
10. B
11. B
12. C
13. A
14. B
15. B
16. C
17. D
18. A
19. A
20. C
21. D
22. C
23. B
24. D
29. A
30. A
Assertion & reasoning:
25. A
26. C
27. A
28. C
31. B
32. C
33. A
34. B
36. B
37. E 38. C
Picture based:
35. C
(contd.)
www.plancessjee.com