TISSUES

BYCYNTHIA DIAS

TSPS, EKM

PLANT TISSUES

• Since the function of cells are taken up by different group of cells, we can say that there is division of labour in multicellular organisms.

• A group of cells that are similar in structure and work together to achieve a particular function forms a tissue

• Plants and animals are made up of different types of tissues

• The term tissue was coined by the scientist Bichat in 1792, and the study of tissues is called Histology.

• He is known as the father of histology.

THE IMPORTANCE OF TISSUES• Formation of tissues has brought about a division of

labour in multicelluar organisms• Tissues become organised to form organs and

organs into organ systems• As a result of improved organisation and higher

efficiency multicellular organisms have higher survival

• Plants are autotrophic organisms, so prepare their own food by photosynthesis, they are stationary and do not move from place to place, hence they do not need much energy. Most of the tissues in plants are dead and provide structural strength.

• Animals on the other hand are heterotrophic organisms, they move in search of food and hence need more energy compared to plants, most of the tissues they have are living.

• Hence the plants and animals are made of different types of tissues.

• There are some tissues in plants which divide through out their life, they divide for the growth and reproduction of the plant

• Such ever dividing tissues are localised in certain regions of the plant body, thus based on the dividing capacity of the tissues they are classified into two

Plant tissues

Meristematic tissue

Apical Lateral Intercallary

Permanent tissue

Simple Parenchyma

Collenchyma

Sclerenchyma

Complex

Xylem

Phloem

MERISTEMATIC TISSUES• They divide continuously and help in increasing

the length and girth of the plant • They are similar in structure and have thin

cellulose cell walls• They are spherical or isodiametric in shape• They are compactly arranged and no intercellular

spaces between them• They have few vacuoles or no vacuoles at all• They are found in the growing regions of the

plant, according to their positions, meristems are apical, lateral and intercallary

APICAL MERISTEMS• They are situated at the growing tip of the stems

and roots, i.e., at shoot apex and root apexLATERAL MERISTEMS• They are found beneath the bark and in vascular

bundles of dicot roots and stems. Cambium is the region which is responsible for growth in thickness.

INTERCALLARY MERISTEMS• They are located at the base of the leaves or

internode , e.g., stems of grasses and other monocots

PERMANENT TISSUE • Cells derived from division of meristematic tissue

take up specific role and lose the ability to divide thus forming a type of permanent tissue.

• The developmental process by which cells derived from meristematic tissue, take up a permanent shape, size and function is called differentiation

• The permanent tissue is divided into two The simple permanent tissue and The complex permanent tissue

SIMPLE PERMANENT TISSUE• They are composed of cells which are structurally

and functionally similar1. PARENCHYMA• It forms the bulk of the plant body• They are living and possess the power of division• The cells are rounded or isodiametric in shape• The cell wall is thin and can be said to be having

living protoplasm.• Intercellular spaces are abundant • It is widely distributed in plant bodies such as

stems, roots, flowers and fruits

• If chlorophyll is present it is called chlorenchyma, it performs photosynthesis

• in aquatic plants large air cavities are present in the parenchyma to give buoyancy to the plant, such type of parenchyma is called aerenchyma

Collenchyma • are a type of parenchyma cells, which are living

but is charecterised by the depositon of extra cellulose at the corners of the cells .

• In collenchyma intercellular spaces are absent, at times chlorophyll is present in them

Functions • It is a mechanical tissue and hence provides

mechanical support and elasticity• Thus it provides flexibility to the organs where

they are found

Aerenchyma

SCLERENCHYMA• These are dead cells devoid of protoplasm • The cell walls are thickened of lignin , such cell

walls are lignified • The cells are closely packed with no intercellular

spaces• The cells of sclerenchyma are of two types Fibres andsclerids

Fibres • The fibres consist of very narrow, thick and lignified

cells• The fibres are usually pointed at both ends and are

clustered into strands

Sclereids • In contrast to fibres the sclereids are called the stone cells

or the grit cells, which are dead cells• The sclerenchyma occur in patches or in layers• They are found in the stems, roots, veins of leaves, hard

covering of seeds and nuts• Sclereids form the gritty part of most of the ripe fruits and

contributes to the hardness to the seed coat and nutshell • The husk of coconut is sclerenchymatous.Functions • It is mainly mechanical and protective in function• It gives strength, rigidity, flexibility and elasticity to the

plant body

PROTECTIVE TISSUE• The protective tissue include the epidermis and cork

(or phellem)EPIDERMIS• The epidermis is present in the outermost part of the

plant body such as leaves, flowers, stem and roots• The epidermis is one cell thick and is covered with

cuticle• Cuticle is a waterproof layer of a waxy substance

called cutin, which is secreted by the epidermal cells.• Cells of epidermis are elongated and flattened and

do not contain any intercellular spaces

• They are living cells and are similar to parenchyma cells

Function • Their main function is to protect the plant from

desiccation and infection• The cuticle heps to reduce water loss by evaporation

and helps in preventing the entry of pathogensCORK• As plants grow older the outer protective tissue

undergoes certain changes, a strip of secondary meristem called phellogen or cork cambium replaces it.

• It has only one type of cells

• The epidermis of the leaf is not continuous at some places due to the presence of small pores called stomata .

• Each stoma is bounded by a pair of specialised epidermal cells or two kidney shaped cells called guard cells

• The guard cells are the only epidermal cells which contain chloroplast

• The stomata helps in gaseous exchange to occur during photosynthesis and respiration.

• During transpiration too, water vapour escapes through stomata

COMPLEX PERMANENT TISSUE• The complex tissue consist of more than one type of

cells having a common origin, they have a common function

• They transports water, mineral salts(nutrients) and food materials to various parts of the plant body

• They are of two types 1. Xylem 2. Phloem• Xylem and the phloem are both the conducting

tissues and known as the vascular tissues , together they constitute the vascular bundles.

XYLEM• Xylem is a vascular and mechanical tissue, it is a

conducting tissue• It is composed of four different types of cells1. Tracheids 2. Vessels or tracheae3. Xylem parenchyma4. Xylem sclerenchyma or fibres• Except xylem parenchyma all the other xylem

elements are dead and are bounded by thick lignified walls

• Of the four the vessels are the most important

Vessels • They are shorter and wider than tracheids• They are tube like structures formed by a row of

cells placed end to end• the transverse walls between the vessels elements

are partially or completely dissolved to form continuous channels or water pipes.

Tracheids • They are elongated cells with tapering ends. • They also conduct water • Since they do not have open ends, water passes

from cell to cell via pits

• Xylem parenchyma stores food and helps in lateral conduction of water

Function • Conduction of water and mineral salts up from the

roots to all parts of the body• Since the cell walls are lignified they give mechanical

strength to the plantPHLOEM• Phloem is composed of the following four elements1. Sieve tubes 2. Companion cells 3. Phloem parenchyma 4. Phloem fibres

Functions • The phloem helps in the conduction of

photosynthetically prepared food from the leaves to the storage organs and later from there to the different parts of the storage organs

ANIMAL TISSUES

Animal tissues

Epithelial

squamous

cuboidal

Coloumnar or grandula

r

Ciliated

Muscular

Striated

Smooth

Cardiac

Connective

Areolar

Tendon

Ligament

Adipose

Skeletal

Cartilage

Bone

Fluid

Blood

Lymph

Nervous

• On the basis of the function they perform we can think of different types of animal tissues

• Animal tissues can be mainly divided into 41. Epithelial tissue2. Connective tissue3. Muscular tissue4. Nervous tissue

EPITHELIAL TISSUE • The protective tissue in the animal body is the

epithelial tissue • The cells of the tissue are tightly packed without

intercellular spaces forming a continuous sheet • It covers most of the organs and cavities within the

body• It forms a barrier to keep different body systems

separate • The epithelium is usually separated from the

underlying tissue by an non-cellular fibrous basement membrane, which is made of a protein called collagen

• Skin and lining of the mouth, blood vessels, alveoli and kidney tubules are made of epithelial tissue

Functions • The cells of the body surface form the outer layer

of skin • The lining of the mouth, and alimentary canal and

some of the internal organs are protected • They help in absorption of water and nutrients • They also help in the elimination of waste

products• Some epithelial tissues are secretory in function,

they secrete substances like sweat, saliva(mucus), enzymes etc.

The different types of epithelial tissue arei. Squamous epithelium ii. Cuboidal epithelium iii. Columnar epithelium iv. Glandular epithelium v. Ciliated epithelium SQUAMOUS EPITHELIUM • They are irregularly shaped thin, flat cells which fit together like

floor tiles and form a compact tissue • It forms the delicate lining of the cavities like mouth, oesophagus,

nose, alveoli etc and of blood vessels and covering of the tongue and skin

Functions• It protects the underlying parts of body from mechanical injury,

entry of germs, and drying. • It forms a selectively permeable surface through which filteration

occurs

STRATIFIED EPITHELIUM• This is found in the skin and covers the external

surface of the skin • It is a type of squamous epithelium, the cells of

the tissue are arranged in many layers, to prevent wear and tear

• Since they are arranged in many layers they are called stratified squamous epithelium

CUBOIDAL EPITHELIUM• It consist of cube like cells which are square in

section • It is found in the kidney tubules, thyroid vesicles

and glands ( salivary glands, sweat glands, etc)• It provides mechanical support

COLUMNAR EPITHELIUM• It consist of cells which are taller• The nuclei are towards the base• It forms the inner lining of the stomach, small

intestine, gall bladder and colon forming the mucous membrane

• It facilitates functions such as absorption and secretion

CILIATED EPITHELIUM• Certain cuboidal or columnar epithelium cells

have a free border which bear thread like or hair like cytoplasmic outgrowths called cilia

• These cilia can move and their movement pushes the mucus forward.

• Such cells form the ciliated epithelium• It forms the lining for the trachea(wind

pipe/respiratory tract), bronchi(lungs), kidney tubules etc.

GLANDULAR EPITHELIUM• The columnar epithelium is often modified to

form glands which secrete chemicals• Sometimes the tissue gets folded inwards and

hence the glands are formed

MUSCULAR TISSUE• The muscular tissue are made of muscle cells and these

cells are elongated and large sized , so they are also called the muscle fibres

• The movement of the body or limbs are brought about by the contraction and relaxation of the contractile protein present in the muscle cells.

• Most of the muscular tissue is attached to the bones and hence are called the skeletal muscles

• The movement of the muscles can be controlled as well as uncontrolled

• The type of muscles in which the movement is under our control are called the voluntary muscles

• And the type of muscles where the movement cannot be controlled are called the involuntary muscles

• The muscular tissue can be divided into 31. Striated muscles 2. Smooth muscles 3. Cardiac musclesSTRIATED MUSCLES• The muscles are also known as skeletal muscles or voluntary

muscles• The type of muscles show light and dark bands or striations

when stained, hence they are also known as striated muscles• The cells of this tissue are long, cylindrical, unbranched and

multinucleate.• They are attached to the bones and help in body movements• Each muscle cell is enclosed in a distinct plasma membrane

called the sarcolemma

SMOOTH MUSCLES • These are also known as the unstriated or the

involuntary muscles • They occur as bundles which are spindle shaped

and have a single nucleus• The movement of these muscles cannot be

controlled • The tissue are often seen in the walls of the

alimentary canal, visceral organs except the heart

CARDIAC MUSCLES• They show the charecteristics of both the striated

and smooth muscles • The cells of this muscles are branched cylindrical

and uninucleate, the intercellular spaces are filled with the connective tissue

• They have dark and light bands on them • The muscles around the heart show rhythmic

contraction and relaxation throughout the life , and hence these involuntary muscles are also known as the cardiac muscles

CONNECTIVE TISSUE• The connective tissue is specialized to connect and

anchor various body organs• It connects the bones to each other, bind the

tissues and give support to various parts of the body by creating a packing around the organs,

• Thus the main function of the tissue are binding, supporting and packing

• The cells of the tissue are living and are separated from each other

• A homogenous gel like intercellular substance called the medium or matrix forms the bulk of the connective tissue

• The space between the cells are filled with a non living matrix which may be solid as in bone and cartilage and fluid as in blood

• Thus blood is a type of connective tissue • Blood has a fluid matrix called the plasma, in

which the RBC, WBC and platelets are suspended • The plasma contains proteins, salts and hormones• The bone is another example of a connective

tissue• It is a strong and nonflexible tissue, embedded in

a hard matrix composed of calcium and phosphorus compounds

• Two bones are connected to each other by another type of connective tissue called ligament

• Tissue is very elastic and has strength and contains very little matrix

• The muscles are connected to the bones by another type of connective tissue called tendons

• Tendons are fibrous with great strength and limited flexibility

• Cartilage is another type of connective tissue, which has widely spaced cells

• The cartilage is seen at the surface of the joints, nose, ear, trachea and larynx

AREOLAR OR THE LOOSE CONNECTIVE TISSUE• The tissue is found between the skin and the muscles, around the

blood vessels and the nerves and in the bone marrow.• It fills the space inside the organs • It supports the internal organs and helps in repair of tissues after

an injury• Its matrix consist of two kinds of fibres The white collagen fibres The yellow elastic fibres or elastin• Also scattered in the matrix are several kinds of irregular cells like

the Fibroblast Adipose cellsMacrophagesMast cells immunocytes

Functions • It act as a supporting and packing tissue between organs• It fixes the skin to the underlying musclesADIPOSE TISSUE• Its an aggregation of fat cells or adipocytes• Each fat cell is rounded and contains a large droplet of fat

that almost fills itDENSE REGULAR CONNECTIVE TISSUETendonsLigamentsSKELETAL TISSUECartilage Bone

BONE• The bone cells are present in the fluid filled

spaces called lacunae• All lacunae of the bone communicate with each

other by a network of fine canals called canaliculiCARTILAGE• The matrix of the cartilage is composed of

proteins and is known as the hyaline matrix • The matrix is maintained by the chondrocytes

BLOOD RBC WBC PlateletsRBC• Its large in number and have iron containing red respiratory pigment, the

haemoglobin• The RBC is also known as the erythrocytes• they transport oxygen WBC• Heamoglobin is absent in them• The function of these cells is defence and immunity• They are of five types Neutrophils Basophils Eosinophils Lymphocytes Monocyte

NERVOUS TISSUE • It is a tissue which is specialized to transmit messages

within the body• Brain, spinal cord and nerves are all composed of

nervous tissue• The cells of this tissue are called nerve cells or

neurons• The neurons have the ability to receive stimuli within

or outside the body and to conduct impulses (signals) to different parts of the body

• The impulse travels from one neuron to another• Many nerve fibres bound together make up a nerve• The neurons have the three main parts

The cyton or the cell body The dendrons and the dendritesThe axon