Download biology

TISSUES
CLASS- IX
A group of cells that is similar in structure work together to achieve a particular function
This cluster of cells, called a tissue,, is arranged and designed so as to give the highest possible efficiency of
function.
Blood, phloem and muscle are all examples of tissues.
The study of tissue is histology.
In unicellular organism (Amoeba) single cell performs all basic functions, whereas in multi-cellular
multi
organisms (Plants and Animals) shows division of labor as Plant tissue & Animal tissues.
Utility of tissues in multicellular organisms
1.Division of labour 2. Higher organization 3. Higher survival
Plant Tissue
Plant tissues are two types: Meristems & Permanent tissues.
Meristems: The Meristems are the tissues having the power of cell division. It is found on those regions of
the plant which grows.
Types of Meristems;
1. The Apical meristems – It is present at the growing tip of the stem and roots and increases the length.
2. The lateral meristems - present at the lateral side of stem and root (cambium) and increases the girth.
3. The intercalary meristems - present at internodes or base of the leaves and increase the length between
the nodes.
Since cells of meristematic tissue are highly active so they have dense cytoplasm. Vacuole is
i absent in these
cells.
Because ,vacuole is a hinderance in cell division.
Permanent Tissue:
Once the cells of meristematic tissue divide to a certain extent, they become specialized for a particular
function. This process is called differentiation
differentiation.
Once differentiation is accomplished, the cells lose their capability tto
o divide and the tissue becomes
permanent tissue.
Permanent tissues are of two types, simple permanent tissue and complex permanent tissue
Simple permanent tissue is composed of similar types of cells. Simple permanent tissues are of three types,
parenchyma, collenchyma and sclerenchyma
Parenchyma: Tissues provide the support to plants. The cells of parenchyma have thin cell wall. They are
loosely packed and has large intracellular space. Parenchyma makes the largest portion of a plant body.
- Parenchyma with chlorophyll which performs photosynthesis is called as chlorenchyma.
-In aquatic plants, large air cavities are present in parenchyma. This provides buoyancy to
the
plant, and then the parenchyma is known as aerenchyma. Main function of Parenchyma stores food and
water.
Collenchyma: Tissue provides mechanical support, thickened at the corners, have very little intercellular
space. It allows easy bending of various parts of a plants without breaking . Collenchymas provides some
degree of structural rigidity with flexibility.
Location- Below epidermis in the leaf Stalk. Due to this, the leaf talk can easily bend but does not break
Sclerenchyma: The cell wall in sclerenchyma is highly thickened all around. The cells are dead and
intercellular space is absent. Sclerenchyma provides structural rigidity to plant parts.
Bark is composed of sclerenchyma.
Another example of sclerenchyma can be seen in the coconut husk.
Tissue makes the plant hard and stiff, thickened due to lignin .
Location- present in stem,vascular bundle,veins of leaves,hard covering of seeds and nuts.
Various types of simple tissues: (a) Parenchyma (i) transverse section, (ii) longitudinal section;
(b) Collenchyma (i) transverse section, (ii) longitudinal section;
(c) Sclerenchyma (i) transverse section,(ii) longitudinal section.
Note- Middle lamella is connecting adjacent cell wall.
Epidermis :
• The outermost layer of cells, called epidermis. The epidermis is usually made of a single layer of
cells.
• The entire surface of a plant has this outer covering of epidermis. It protects all the parts of the plant.
• Most epidermal cells are relatively flat. Often their outer and side walls are thicker than the inner
wall.
Leaf part,
• Epidermal cells on the aerial parts of the plant often secrete a waxy, water-resistant layer on their
outer surface.
o This aids in protection against loss of water, mechanical injury and invasion by parasitic
fungi.
o Since it has a protective role to play, cells of epidermal tissue form a continuous layer
without intercellular spaces.
• In some plants living in very dry habitats, the epidermis may be thicker since protection against
water loss is critical.
• In some plants like desert plants, epidermis has a thick waxy coating of cutin (chemical substance
with waterproof quality) on its outer surface.
Stomata
• small pores here and there in the epidermis of the leaf. These pores are called stomata. Stomata are
enclosed by two kidney-shaped cells called guard cells. They are necessary for exchanging gases
with the atmosphere.
• Transpiration (loss of water in the form of water vapour) also takes place through stomata
Root Part,
• Epidermal cells of the roots, whose function is water absorption, commonly bear long hair-like parts
that greatly increase the total absorptive surface area.
Older epidermal cell,
• As plants grow older, the outer protective tissue undergoes certain changes. A strip of
• secondary meristem replaces the epidermis of the stem. Cells on the outside are cut off from this
layer. This forms the several-layer thick cork or the bark of the tree. Cells of
• cork are dead and compactly arranged without intercellular spaces . They also have a chemical called
suberin in their walls that makes them impervious to gases and water.
a) Guard cell and Epidermal Cell Lateral View. b) Guard cell and Epidermal Cell Surface View.
Protective tissue-Older epidermeral cell
Functions: Epidermis
(i) The main function of epidermis is to protect the plant from desiccation and infection.
(ii) Cuticle of epidermis cuts the rate of transpiration and evaporation of water and prevents wilting.
(iii) Stomata in epidermis allow gaseous exchange to occur during photosynthesis respiration.
(iv) Stomata also help in transpiration
Functions: cork cell
(i) Cork is protective in function. Cork cells prevent desiccation, infection and mechanical injury.
(ii)Cork is used in the making of a variety of sport goods such as cricket balls, table tennis, shuttle cocks,
wooden paddles etc
Complex permanent tissues: The complex tissues are made of more than one type of cells. All these cells
coordinate to perform a common function.
They are subdivided as;
Xylem: It consists of tracheids, vessels, xylem parenchyma and xylem fibers. The cells have thick walls,
Function - aids in conduction of water and minerals.
Xylem is composed of trachieds, vessels, xylem parenchyma and xylem fibres. The cells of xylem are dead;
except the cells of xylem parenchyma. Trachieds and vessels are tubular structures and thus they provide a
channel for conduction of water and minerals. Xylem fibre provides structural support to the tissue. Xylem
parenchyma stores food.
Phloem: It consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibers.
Phloem is composed of sieve tubes, companion cells, phloem fibre and phloem parenchyma. Sieve tubes are
tubular cells with perforated walls. Sieve tubes are the conducting elements of phloem. Phloem is
responsible for translocation of food in plants. The transport of food in phloem is a two way movement.
Function - Phloem transports food material to other parts of the plants.
Animal Tissue
Animal tissues: Sub divided as epithelial tissue, connective tissue, muscular tissue and nervous tissue.
Epithelial tissue: It is a protective covering forming a continuous sheet. Simple epithelium is the one which
is extremely thin in one layer, whereas stratified epithelium are arranged in pattern of layers.
No intercellular spaces.
Anything entering or leaving the body must cross at least one layer of epithelium. As a result, the
permeability of the cells of various epithelia plays an important role in regulating the exchange of
materials between the body and the external environment and also between different parts of the
body.
Regardless of the type, all epithelium is usually separated from the underlying tissue by an
extracellular fibrous basement membrane.
Structure
Location
Function
• transportation
• lining of blood vessels
Squamous epithelium
of
substances
occurs through a selectively
Simple
and alveoli
permeable surface.
,Flat,Thin,Forming
•
oesophagus
and
• Secretion of lubricative substance
Delicate lining
the lining of the mouth
• epithelial cells are arranged
in many layers to prevent wear and tear in
stratified squamous
•
Skin
skin
epithelium.
• inner lining of the
• absorption and secretion
Columnar epithelium
intestine
facilitates
(meaning ‘pillar-like’)
movement across the epithelial barrier.
epithelium
• has cilia, which are hair-like
projections on the outer surfaces of epithelial
cells.
cilia can move, and their
Ciliated columnar
movement pushes the mucus forward to clear
epithelium.
• Respiratory tract,
it.
Cuboidal epithelium
with cube-shaped
Cells
Glandular epithelium.
•
lining of kidney
tubules
•
ducts of salivary
glands,
• provides mechanical support
• Epithelial cells often
acquire additional specialisation as gland
cells, which can secrete substances at the
epithelial surface.
Sometimes a portion of the
epithelial tissue folds inward, and a
multicellular gland is formed.
Eg- Sweat and oil gland
CONNECTIVE TISSUE
The cells of a connective tissue are loosely scattered in a matrix.
The matrix can be a fluid, jelly like, dense or rigid. The nature of matrix depends on the function a
connective tissue serves.
Following are the various connective tissues:
Blood has a fluid (liquid) matrix called plasma, in which red blood cells (RBCs), white blood cells
(WBCs) and platelets are suspended.
The plasma contains proteins, salts and hormones.
Blood flows and transports gases, digested food, hormones and waste materials to different parts of
the body.
Types of blood cells
Bone is another example of a connective tissue.
Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.
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.
Cartilage: The cartilage is a connective tissue with solid matrix composed of proteins and sugars.
cartilage smoothens surfaces at joints .It is commonly seen in nose, ear, trachea, and larynx.
Hyaline cartilage
Note- Hyaline transparent matrix. Chondrocyte is cartilage cells.
Two bones can be connected to each other by another type of connective tissue called the ligament.
This tissue is very elastic. It has considerable strength. Ligaments contain very little matrix.
Tendons connect muscles to bones and are another type of connective tissue. Tendons are fibrous
tissue with great strength but limited flexibility.
Areolar Connective Tissue: It is found between the skin and muscles, around the blood vessels.
It supports internal organs.
It fills the space inside the organ and aids in repair of tissues.
Areolar Tissue
Note- Mast cell-produce histamine and reduce inflammation. Plasma cell- produces Antibodies.
Fibroblast- produce protrin fibre.Macrophages- Destory microbes and foreign particle.
Adipose Connective Tissue: Fat storing adipose tissue is found below the skin and between internal
organs.
The cells of this tissue are filled with fat globules.
Storage of fats also lets it act as an insulator.
MUSCULAR TISSUE
Muscular tissue consists of elongated cells, also called muscle fibres.
Muscle cells are specialized cells which have the capability to contract and expand.
Due to contraction and expansion, muscles facilitate various kinds of movements in the body.
Muscular tissues are of three types:
Striated Muscles: Under the microscope, these muscles fiber show alternate light and dark bands or
striations when stained. As a result, they are also called striated muscles.
Striated muscles are found in those organs where voluntary movement is possible, e.g. hands, legs, back,
neck, etc
The cells of this tissue are long, cylindrical, un branched and multinucleate (having many nuclei).
Smooth Muscles: The movement of food in the alimentary canal or the contraction and relaxation of blood
vessels are involuntary movements.
They are also found in the iris of the eye, in ureters and in the bronchi of the lungs.
The cells of smooth muscles are spindle shaped and each has one nucleus. uninucleate (having a
single nucleus). They are also called unstriated muscles
Cardiac Muscles: The muscles of the heart show rhythmic contraction and relaxation throughout life. These
involuntary muscles are called cardiac muscles.
Heart muscle cells are cylindrical, branched and uninucleat
Types of Muscle fiber - Striated muscle, (b) smooth muscle, (c) cardiac muscle
Nervous Tissue:
The tissue responds to stimuli. The brain, spinal cord and nerves are composed of nervous tissue or
neurons.
A neuron consists of Cell Body, cytoplasm, Nucleus, Dendrite, Axon, nerve ending. The neuron
impulse allows us to move our muscles when we want to respond to stimuli.
Neuron has a single long part, called the axon, and many short, branched parts called dendrites.
An individual nerve cell may be up to a metre long.
Many nerve fibres bound together by connective tissue make up a nerve.
Neuron-unit of nervous tissue
Question Bank
5. Function of guard cell and epidermal tissue
1. Definition of tissue and examples.
6. What are the functions of cuticle and stomata?
2. Difference between animal and plant tissue.
7. What is the differentiation?
3. What is Macrophages in aerolar tissue?
8. Function of xylem and cork or phloem tissue
4. Describe the term meristematic tissue.
9. Examples of permanent and simple tissue
10. Define the following terms and mention the
places where they are found.
• Epithelial tissue
• Squamous epithelium
• Cuboidal epithelium • Columnar epithelium in
the intestine • Glandular epithelium
11. What type of tissue is blood
12. What is the function of adipose connective
tissue
13. What is the difference between bone and
cartilage
14. Example of multinucleated tissues
15. Difference between striated and non-striated
fibre
29. Which structure protects the plant body
against the invasion of parasites?
30. Where is intercalary meristem found?
31. Based on ability to divide, how many types of
plant tissues are foun
32. What is lignin?
33. How are simple tissues different from
complex tissues in plant?
34. Which type of permanent tissue help
the aquatic plants to float?
35. Which are the tubular structures present in
xylem?
16. Structure of neuron with its all parts labelled
17. What is histology?
18. Basis of classification of animal tissue?
19. Name the Parenchyma with chlorophyll
which performs photosynthesis?
20. Distinguish between ligament and tendon?
36. Name one structure in your body, which bears
ciliated epithelium.
37. What is the utility of tissues in multi
cellular organisms?
38. Classification of animal tissue and their
function
21. Write short notes on Cardiac muscles?
22. What is the role of epidermis in plants?
23. How does the cork acts as a protective tissue?
24. Which tissue protects the entire body?
25. Which tissue make up the hisk of the coconut
26. Name the tissue which is present at the
growing tips of stem and roots.
39. Classification of plant
tissue and their
function
40. Sketch Adipose tissue and label its part.
41. Sketch Areolar tissue and label its part.
42. Sketch types of blood cells.
43. Sketch the longitudinal view of parenchyma
tissue.
27. What do you mean by parenchyma?
28. Name the tissue which allows easy bending in
various parts of a plant.
44. Sketch the transverse view of parenchyma
tissue.
45. Which type of epithelial tissue is present in
kidney tube?