"Tissues" Chapter:-6 Class 9

• Tissue term coined by:- Marie Francois Xavier Bichat in 1792
• Father of Histology:- Marie Francois Xavier Bichat
• Founder of Histology:- Marcello Malpighi
• Term Histology Coined by: Mayer (1819)
• Study of Tissues:- Histology

1) Tissues :-
Tissue is a group of cells having similar structure and function.
In plants and animals groups of cells called tissues carry out
specific functions.
Eg :- In human beings the cells of the muscular tissue contract and
relax and help in movements.
In plants the cells of the vascular tissue conduct water and food
from one part of the plant to the other.

Importance of Tissues
Formation of tissues has brought about a division of
labour in multicellular organisms.
Tissues become organised to form organs and organs into
organ systems.
Workload of individual cell has decreased due to origin of
tissues.
Due to improved organisation and higher efficiency,
multicellular organisms have higher survival.

Why do plants and animals are
made of different types of tissues?

3) Planttissues :-
Plant tissues are of two main types. They are Meristematic tissues and
Permanent tissues.
i) Meristematic tissues :- are of three types. They are Apical meristematic
tissues, Intercalliary meristematic tissues and Lateral meristematic tissues.
ii) Permanent tissues :- are of two types . They are Simple permanent tissues
and Complex permanent tissues. Simple permanent tissues are of three
types. They are Parenchyma, Collenchyma and Sclerenchyma. Complex
permanent tissues are of two types. They are Xylem and phloem.
Plant tissues
Meristematic tissues Permanent tissues
Apical Intercalliary Lateral
meristematic meristematic meristematic
tissues tissues tissues
Simple permanent Complex permanenttissues
tissues
Parenchyma Collenchyma Sclerenchyma
Xylem Phloem

a) Meristematictissue :-
Meristematic tissues are found in the growing regions of the plant like the tips
of root, stem and branches. They divide continuously and help in the growth
the plant. They are of three types.
of
i) Apical meristematic tissues :- are present in the tips of stems and roots.
They help in increase of the height of the plant, which is called primary
growth. Helps in elongation of roots and stems.
Lateral meristematic tissues :- are present in in the sides of stems andii)
roots. They help to increase the girth of the stems and roots, secondary
growth
Inter-calary meristematic tissues :- are present at the base of leaves andiii)
internodes and help in the growth of those parts.

Why there are no vacuoles in the intercalary meristem?
 Meristematic cells divide frequently and give rise to new cells
and hence they need dense cytoplasm and thin cell wall
 Vacuoles are responsible for storage of food in water. The
intercalary tissues do not store them.
 Moreover, vacuoles contain sap which provides rigidity to a cell.
This property of vacuoles may not allow the intercalary tissues
to divide and manufacture new cells. Hence vacuoles are not
present in them.

Functions of Meristematictissue :-
 It acts as a parent tissue from which other tissues develops.
 Take part in the growth by formation of new cells.
 With the help of meristems, plants continues to produce new leaves,
branches of stem, and root, flowers, fruits and root hairs.
 The place of injury is healed up by the formation of new cells by meristems.

b) Permanent tissues :-
Permanent tissues are formed from meristematic tissues. They do not divide
and have permanent shape and size. They differentiate into different types of
permanent tissues. Permanent tissues are of two main types. They are Simple
permanent tissues and Complex permanent tissues.
i) Simplepermanent tissues :- are made up of one type of cells. They
are of three types called Parenchyma, Collenchyma and Sclerenchyma.
Parenchyma :- consists of loosely packed thin walled cells having more
intercellular spaces. Some parenchyma cells in leaves contain chloroplast
and prepares food by photosynthesis. Some parenchyma cells have large air
cavities which help the plant to float on water called as Aerenchyma. Some
parenchyma cells of roots and stem store water and minerals.
Collenchyma :- consists of elongated cells having less intercellular spaces
and thicker at the corners. They give flexibility and allows easy bending of
different parts like stem, leaf etc. They also give mechanical support to the
plant.
Sclerenchyma :- consists of long, narrow, dead thick walled cells. The cell
walls contain lignin a chemical substance which act like cement and hardens
them. It gives strength and hardness to the plant parts.
Are of two types:- Fibres and Sclereids

Lignin:- It is complex polymer which acts as a cement and hardens cell
wall. It provides flexibility and great tensile strength. Its makes the cell
wall impermeable, so important substances are unable to pass through it.
S.I Sclerenchyma Fibres Sclereids
1 Are elongated, spindle shaped, thick
walled dead cells
Are thick walled dead cells.
2 Are elongated in bundles, nets and
cylinders
Occur singularly or in groups.
3 Do not form covering of any plant
organ
Form covering of nuts and
seeds.
4 Provide mechanical strength. Provide stiffness.

Parenchyma Collenchyma Sclerenchyma

Protective Tissue
• Protective Tissue include epidermis and cork
(Phellem)
1.Epidermis:- Outermost layer of the plant body such as leaves,
flowers, stem and roots. Made up of single layer of cell and
covered with cuticle (made up of water proof layer of waxy
substance called cutin). Cuticle of Xerophytic (desert) plants
are thicker.
Function:- Main function is to protect the plants from
desiccation and infection. Cuticle of epidermis helps to reduce
water loss by evaporation from the plant surface and also helps
in preventing the entry of pathogen (bacteria, fungi etc.)

Q. Why do plants in desert areas have a waxy coating
of cutin over them?
Ans:-The epidermis cells of plants that are found in deserts have a
waxy coating of cutin over them because it prevents water loss
from the plants surface since water is already scarce in such areas.

Stomata:- It is a small pores, found on the green stems,
under surface of plant leaves.
 Each stomata is bounded by a pair of specialized epidermal
cells or two kidney-shaped cells called guard cells.
 Guard cells are the only epidermal cells which contain
chloroplast, rest being colourless.
 Guard cells is responsible for the opening and closing of
stomata and helps to regulate the rate of transpiration.
Function:- Allows gaseous exchange to occur during
photosynthesis and Respiration. During transpiration too,
water vapour also escape through it

Transpiration
•The process of loss of water or removal of excess
water from the plants in the form of water
vapour through stomata.

Importance of Transpiration
• It creates a negative pressure gradient that helps to draw
water and minerals up through the plant from its roots.
• Helps to keep the plant cool on hot weather-a method of
evaporating cooling.
• It supports photosynthesis and encourages the exchange of
gases, helping in maintaining levels of CO2 and O2 in the
atmosphere.
• Plays a significant role in the water cycle and releases approx.
10% of water back into the environment.
• Creates water vapour that forms into fog and clouds.

2. Cork:- The dead protective tissue between the bark and
cambium in woody plants, with suberin (waxy substance)
deposits making it impervious to gasses and water.
As the roots and stem grow older with time, epidermis go some
certain changes and become cork cambium or Phellogen.
Cork cells are dead cells and they don not have any intracellular
spaces. It does not catch fire easily and is light therefore it used
as a insulator and in sports goods.
Function:- Protective in function. Prevents desiccation (loss of
water from plant body), infection and mechanical injury.

Q. Why do branches of old trees are different than the
stems of a new plant?
 As a plant grows older the meristematic cells start covering the
upper layer of the plants instead of the epidermis.
 These are the dead cells that have no special function in the
plants but to provide them rigidity. They make the branches of
the plants thick.
 This is often called the Bark or the thick cork of the tree.
 The bark of the trees contains a substance
called Suberin which makes it waterproof and does not allow
gaseous exchanges.

ii) Complex Permanent Tissue:- are made up of more than one type of
cells. There are two types of complex tissues. They are Xylem and Phloem.
They are called vascular or conducting tissues. Responsible for transport of
water, minerals salts (nutrients) and food materials to various parts of plant body.
Xylem :- consists of tracheids, vessels, xylem parechyma and xylem fibres.
The cells have thick walls and many of them are dead cells. The tracheids
and vessels help to transport water and minerals from roots
to all part of the plant. Xylem parenchyma stores food and fibres help in
support.
Phloem :- consists of sieve tubes, companion cells, phloem parenchyma and
phloem fibres. The sieve tubes and companion cells transports food from
leaves to all parts of the plant. Phloem parenchyma stores food and fibres
help in support. They can transport materials in both direction. Except for
phloem fibres, phloem cells are living cells.

Difference between Xylem & Phloem

4) Animal tissues :-
Animal tissues are of four main types . They are :- Epithelial tissue, Muscular
tissue, Connective tissue and Nervous tissue.
i) Epithelial tissues :- are of different types. They are :- Squamous, Columnar,
Cuboidal, Glandular etc.
ii) Muscular tissues :- are of three types. They are :- Striated, Unstriated and
Cardiac.
iii) Connective tissues :- are of different types. They are :- Blood, Bone,
Ligaments, Tendons, Cartilage, Areolar, Adipose etc.
iv) Nervous tissue :- consists of nerve cells called neurons.
Animal tissues
Epithelial tissue Muscular tissue Connective tissue Nervous tissue
Squamous
Columnar
Cuboidal
Glandular
Striated
Un-striated
Cardiac
Blood
Bone
Ligaments
Tendons
Cartilage
Areolar
Adipose

• Protective Tissue of animal body as epidermis of plants.
• The cells are tightly packed, form continuous sheets, very little
or no intracellular spaces and covers most of the organs and
cavities within the body.
• Forms the barrier to keep different body system separate.
• Forms the outer covering like skin, outer covering of organs,
inner lining of blood vessels, lungs, oesophagus, kidney
tubules, etc.
• Lies on the delicate non-cellular basement membrane which
contain special form of matrix protein called collagen.
• Secrete variety of substances such as Sweat, saliva, enzyme etc.
Epithelial Tissue (Epithelium)

Types of Epithelium Tissue
1.Squamous Epithelium:- These are
thin, flat cells that are closely packed.
The squamous epithelial cells line the
cavities of the mouth, esophagus,
alveoli, and blood vessels.
Function:- This tissue gives protection
against mechanical injury and also
blocks the entry of germs. Also forms a
selectively permeable surface through
which filtration occurs.
If the squamous epithelium is arranged
in many layers, it is a compound
squamous tissue called the stratified
squamous epithelium. We find these
kinds of tissues in the skin and also the
lining of the esophagus.

2.Cuboidal Epithelium:- These cells
are cuboidal in shape. They are
found in the salivary glands, kidney
tubules, sweat glands, etc.
If the cuboidal epithelium is
arranged in many layers it forms
the stratified cuboidal epithelium.
It is found on the inner side of the
pancreatic ducts and salivary
glands.
Function:- Their main function
includes absorption, secretion,
and excretion. Also provide
mechanical support.

3.Columnar Epithelium:- The columnar epithelium has cells that are pillar-
like and column-like. The nuclei are towards the base and sometimes the
free ends of cells have a brush border containing microvilli . We can find
them in the lining of the stomach, intestine, colon, forming mucous
membrane. Also forms the lining of gall bladder and oviducts and facilitates
movement across the cells.
Function:- Their main function includes absorption (eg. Stomach, intestine)
and secretion (eg. Mucus by goblet cells or mucous membrane)

4.Glandular Epithelium:- These are modified columnar epithelial
tissues which secrete chemicals. They are large cells that present
in the tear glands, sweat glands etc.
Function:- Their main function is secretion.
Goblet cells are unicellular intraepithelial mucin-secreting glands scattered within simple
epithelia, such as cuboidal, columnar, and pseudostratified epithelia. Their role is to protect
the surface of epithelium, lubricate it, and catch harmful particles.

5.Ciliated Epithelium:- When the
columnar epithelial tissues have a
free border which bear thread like
cytoplasmic outgrowths called cilia,
then they are ciliated epithelium.
Found in the sperm ducts, lines the
trachea (wind pipe), bronchi
(lungs), kidney tubules and oviducts
(Fallopian tubes).
Function:- The rhythmic movement
of the cilia helps in the movement
of solid particles (eg. Mucus) in one
direction through ducts.

b) Muscular tissue :-
Muscular tissue helps in the movements of the body. It consists
of elongated cells called muscle fibres. It contains a protein called
contractile protein which contracts and relaxes and helps in
movements. Muscles which can move under our will are called
voluntary muscles. Muscles which do not move under our will are
called involuntary muscles.
i) Striated muscles :- are voluntary muscles having light and dark
striations. The cells are long, cylindrical and are multinucleated.
They are also called skeletal muscles because they are attached to
bones. They help in voluntary movements of the body.
ii) Unstriated muscles (Smooth muscles) :- are involuntary muscles
having no striations. The cells are long and spindle shaped and are
uninucleated. They are present in alimentary canal, blood vessels,
bronchi of lungs, iris of eye etc. They help in involuntary
movements.
Cardiac muscles :- are involuntary muscles having faint striations.iii)
The cells are long, cylindrical, branched and uni-nucleated. They
are present in the heart and helps in the contraction and relaxation
of the heart.

c) Connective tissue :-
 Most abundant tissue in the body.
 These tissues cells are widely separated from each other than in
epithelial tissues and intracellular spaces (matrix) are present in larger
amount.
 Matrix is fibrous in nature and binds other tissues. In fact, the nature of
matrix decide the function of connective tissue.
 Connective tissue connects and joins the different parts of the body
together.
 Made up of cells like fibroblast cells, fat cells, macrophages,
leukocytes, and mast cells.
 Functions:-
 Provide mechanical support
 Transport of material from one part of the body to another.
 Store energy.
 Protection
 Insulation by Adipose tissue

Aerolar tissue Adipose tissue
Bone tissue Cartilage tissue

Fibres of connective Tissue
•The three types of connective tissue fibres are:-
Tissue Purpose Location
Collagenous fibers
(White Type 1)
Bind bones and other tissues to
each other, Tensile strength.
tendon, ligament, skin,
cornea, cartilage, bone,
blood vessels, gut, and
intervertebral disc.
Elastic fibers (Yellow)
Elasticity i.e. Allow organs like
arteries and lungs to recoil
means return to its original
length
extracellular matrix
Reticular fibers
Form a scaffolding for other
cells i.e. provide support by
forming network of thin fibers
liver, bone marrow, and
lymphatic organs

Cells of Connective Tissue
• Fibroblasts:- They are large cells with irregular processes, manufacture
collagen and elastic fibres and a matrix of extracellular material.
Function:- Active in tissue repair.
• Adipose cells:- Store fats (lipids) in their vacuoles. Also known as
adipocytes.
• Macrophages:- These are large irregular shaped cells with granules in
the cytoplasm. Important part of the body defence mechanism because
they are actively phagocytic, engulfing and digesting cell debris, bacteria
and other foreign bodies. Monocytes develop in bone marrow, circulate in
the bloodstream, and migrate into connective tissue, where they
differentiate into macrophages.
• Mast Cells:- They secrete substances such as heparin (anticoagulant),
histamine (vasodilator) and serotonin (vaso-constrictor). They promote
inflammation of the infected cell.
• Immunocytes:- These include cells such as lymphocytes and plasma
cells both producing antibodies for the immune response.

Cells and components Connective Tissue

Types of Connective Tissue
Areolar/Loose Dense
Regular
Tendons Ligaments
Adipose Skeletal
Cartilage Bone
Fluid
Blood Lymph

1. Loose/Areolar:- has a sparse, irregular network of White collagen and
yellow elastic fibers suspended within a relatively large amount of ground
substance. Some of which can engulf bacteria and prevent infection (eg.
Macrophages). Most simplest and widely distributed connective tissue.
Found around muscles, blood vessels and nerves.
Function:-
 Acts as a supporting and packing tissue between organs lying in the
body cavity. Matrix of this tissue is important in diffusion of oxygen and
nutrients from small blood vessels.
 Helps in repair of tissues after an injury.
 Helps in combating foreign toxins.
 Fixes skin to underlying muscles.

2. Dense Regular:- composed of type I collagen fibers oriented in the
same direction. It provides tensile strength in one direction.
Characterized by ordered and densely packed collection of fibers. It
is the principal components of tendons and ligaments. Are of two
types:-
a.Tendons:- Are cord-like, strong, inelastic, structures that join
skeleton muscles to bone. It is a white fibrous tissue which has
great strength but limited flexibility.
b.Ligaments:- Are highly elastic and has great strength but contain
very little matrix. Connect bone to bone and are made up of
yellow and white fibers. It strengthen the joint and permit
normal movement but prevent over-flexing or over-extension.
Sprain is caused by excessive pulling (stretching) of ligaments.

3. Adipose:- They are basically an aggregation of
fat cells or adipocytes. Each fat cell is rounded or
oval and contain a large droplet of fat that almost
fills it. They are abundant below the skin,
between internal organs (eg. Kidney), in yellow
bone marrow. Adipose cells store surplus energy
in the form of fat and contribute to the thermal
insulation of the body.
Function:-
Serves as fat reservoir.
Provides shape to the limb and the body.
Keep visceral organs in position. It forms shock-
absorbing cushions around kidneys and eye
balls.
Acts as an insulator. Being a poor conductor of
heat, it reduces heat loss from body, i.e. it
regulates body temperature.

4. Skeletal:- This tissue includes Cartilage and Bone which form
the endoskeleton of a vertebrate body.

I. Cartilage
• It is a specialized connective tissue which is compact and less
vascular.
• Its extensive matrix is composed of proteins and is slightly
hardened by calcium salts.
• Its matrix is produced and maintained by the chondrocytes.
• It is a flexible connective tissue connecting joints between
bones, rib cage, ear, nose, rings of trachea etc. It acts like shock
absorbent.

II. Bone
• It is very strong and non-flexible tissue.
• It is porous, highly vascular, mineralised, hard and rigid.
• Made up of proteins (eg. Osteonectin, osteocalcin, proteoglycan and
collagen).
• Its matrix is rich in salts of calcium and magnesium such as
phosphates and carbonates of calcium and magnesium.
• These minerals are responsible for the hardness of the bone.
• Cell of bone is known as Osteoblasts or osteocytes.
• Functions:-
 Forms endoskeleton of human being and other vertebrates.
 Provide shape and support to body.
 Protects vital body organs such as brain, lungs etc.
 Serves as a storage site of calcium and phosphate.
 Anchors the muscles.

5. Fluid Connective Tissue:- They have a large number of different types
cells suspended in a fluid found substance (matrix). It links the different
parts of the body and maintains the continuity in the body.
Includes (a)Blood and (b) Lymph.

(a) Blood
• Cells of this tissue moves in a fluid or a liquid medium called
Plasma (55%) which contain inorganic salts and organic
compounds.
• The blood plasma does not contain proteins fibres but
contains cells called blood cells or blood corpuscles.
• Blood occur in blood vessels (Arteries, Veins, Capillaries)
• These blood corpuscles are:-
i. RBC:- Red Blood Cells or Erythrocytes:- RBC’s are large in
number and have iron containing red respiratory pigment
called haemoglobin. RBC’s of mammals are circular,
biconcave, disk-like and enucleated. It plays a vital role in the
transport of oxygen.

Blood
ii. WBC:- White Blood Cells or Leucocytes:- These cells are involved in
protecting the body against both infectious diseases and foreign invaders.
Are of two main kinds:- 1. Phagocytes: They are capable of phagocytosis
and they carry out the function of body defence by engulfing bacteria and
foreign substances. Phagocytes are further of two types:- (a)
Granulocytes:- They have irregular shaped nuclei and cytoplasmic
granules with specific staining properties. They include neutrophils,
basophils and eosinophils. (b) Agranulocytes:- they have no cytoplasmic
granules and include the monocytes having large nucleus. They ultimately
migrate to body tissue and transform into macrophages and histiocytes.
2. Immunocytes:- They produce antibodies and are involved in the
immune response. They include lymphocytes and some of them transform
later into plasma cells.
iii. Platelets or Thrombocytes:- They are large piece of cells in the bone
marrow called megakaryocytes. They help to form blood clots or stop
bleeding and to help wounds heal.

Functions of Blood
• Transports nutrients, hormones and vitamins to the tissues and
transports excretory products from tissues to the liver and
kidney.
• The RBCs carry oxygen to the tissues for the oxidation of food
stuffs.
• The WBCs fight with disease either by engulfing and destroying
foreign bodies or by producing antitoxins and antibodies that
neutralise the harmful effects of germs.
• Platelets disintegrate at the site of injury and help in the
clotting of blood.

(b) Lymph
• It is a colourless fluid that is filtered out of the blood
capillaries. Its composition is similar to blood except RBCs and
some blood proteins are absent in it. In this WBCs are found in
abundance.
• Functions:-
 Transports nutrients (oxygen, glucose) that may have been
filtered out of the blood capillaries back into the heart to be
recirculated in the body.
 It brings CO2 and nitrogenous wastes from tissue fluid to
blood.
 As it is loaded with WBCs such as lymphocytes, the lymph
protects the body against infection i.e. it forms the defence or
immune system of the body.

Nervous Tissue
• This tissue is specialized to transmit messages within our body.
• Many nerve fibres bound together by connective tissue which makes
up a nerve.
• It transmit messages from brain to various parts of the body and vice
versa.
• Brain, Spinal Cord and nerves are all composed of nervous tissue.
• This tissue contains highly specialized cell called nerve cells or neurons.
• Neurons have the ability to receive stimuli from within or outside the
body and to conduct (send) impulse (signal) to different parts of the
body.
• Impulse travels from one neuron to another.
• Nerve impulses allow us to move our muscles when we want.
• The functional combination of nerve and muscles tissue is fundamental
to most animals which enables them to move rapidly in response to
stimuli.

Nerve cell (Neuron) :-
Neuron is the structural and functional unit of the nervous system. It
has a cell body called cyton containing a nucleus and cytoplasm. It has
several branched structures called dendrites. It has a long nerve fibre
called axon which is covered by a protective covering called Myelin
sheath. The junction between two neurons is called synapse.
Messages pass through the nerve cell in the form of chemical and
electrical signals called nerve impulse. The dendrites receive the
information and starts a chemical reaction which produce electrical
impulse which passes through the axon.

Neuron (Cont.)
• Purkinje cells are a special type of neuron found in the cerebellum. These
cells have highly developed dendritic trees which allow them to receive
thousands of signals.
• Myelin sheath is made by specialized cells called glia. In the brain, the glia
that make the sheath are called oligodendrocytes, and in the peripheral
nervous system, they are known as Schwann cells.
• Nodes of Ranvier are the spaces between the myelin coating on the
neuron's axon. Much like the plastic coating on a wire needs to be clear to
connect to an appliance and supply power, there must be breaks in the
myelin to conduct electricity in neurons.
 Electricity travels quickly through the axon wrapped in myelin. At the
nodes of Ranvier, electricity can be conducted within the cell's
environment, and the electrical signal will be propagated down the axon.
 At the nodes of Ranvier the cell membrane, or boundary of the cell is
exposed. This part of the membrane has proteins, called channel
proteins, which allow ions to enter and exit the cell. They're like doors for
the cell, letting specific people in and out.

"Tissues" Chapter:-6 Class 9

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"Tissues" Chapter:-6 Class 9