07_TISSUES class 9

August 21, 2022 admin Off Uncategorized

Introduction

All living organisms are made of the cells. A unicellular organism (e.g., Amoeba, Paramecium, etc.) has a single cell in its body, i.e., a single cell performs all basic life activities. For example, in Amoeba, movement of a cell, intake of food and respiratory gases (O₂), intracellular digestion, metabolism, respiration, osmoregulation and excretion are all done by the same cell. However, in carry out only a few functions efficiently. These functions are taken up by different groups of cells. Thus, we can say that there is a division of labour in the multicellular organisms.
In human beings, muscle cells contract and relax to cause movement of a body part, nerve cells or neurons carry messages, blood flows to transport oxygen, food, hormones and waste materials (CO₂, urea) and so on.
In plants, cells of phloem conducts food from leaves to other parts of the plant. Thus, we see that cells, which specialize in a function, are grouped together and form a tissue;xylem, phloem, parenchyma are all examples of tissues.
The term tissue was coined by Bichat in 1792. Study of tissues is calledhistology.
A group of cells similar in structure that work together to perform a particular function forms a tissue.
All cells of a tissue have common origin. For example, human nervous tissue (present in brain, spinal cord and nerves) has nerve cells or neurons, which are basically same structurally and functionally. All neurons of nervous tissue originated from the same germinal layer called ectoderm (more aptly the neural ectoderm).

Importance of tissues.

Formation of tissues has brought about a division of labour in multicellular organisms.
Tissues become organized to from organs and organs into organ system.
Workload of individual cell has decreased due to origin of tissues.
As a result of improved organization and higher efficiency, multicellular organisms have higher survival.

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

Plants and animals are two different types of organisms. Plants are autotrophic organisms, so prepare their own food by photosynthesis. Moreover, plants are stationary or fixed organisms; they do not have to move from place to place in the search of their food. Since they do not consume or need much energy, so most of the plant tissues are supportive, which provide them with structural strength. Most of these tissues such as xylem, phloem, sclerenchyma and cork are dead tissues; they do not contain living protoplasm.
Animals on the other hand, are heterotrophic organisms. They have to move in search of food, mate and find shelter, so they need more energy as compared to plants. Mostof the tissues they contain, are living (i.e., they having living protoplasm).

Plant Tissues	Animal Tissues
· In plants, dead supportive tissues are more abundant as compared to living tissues.	· In multicellular animals living tissues are more common as compared to dead tissues.
· They require less maintenance energy.	· They require more maintenance energy.
· There is a differentiation of meristematic and permanent tissues.	· Such a differentiation is absent in them.
· Due to activity of meristematic tissue plants continue to grow throughout life.	· Animals do not show growth after reaching maturity. Reparative growth is present.
· Organization of plant tissues is simple	· Organization of animal tissues is complex with development of more specialized and localized organs and organ systems.
· Tissues organization is meant for stationary habit of plants	· Tissues organization is targeted towards high mobility of animals.

6.2 Plant tissues

Based on the capacity to divide, the plant tissues have been classified into two fundamental types, meristematic and permanent.

6.2.1 Meristematic Tissues

Meristematic Tissues: A meristem or meristematic tissue is a simple tissue composed of a group of similar and immature cells (meristematic cells)which can divide and form new cells.

Characteristics of Meristematic Cells

Ability to grow and divide
Small immature cells.
Isodiametric, rounded, oval or polygonal.
Absence of intercellular spaces.
Walls are thin, elastic and made of cellulose.
Nucleus conspicuous.
Cytoplasm dense.

l Vacuolesabsent or very small

Crystals absent
Endoplasmic reticulum small.
Proplastids are present instead of plastids.
Mitochondria have simple structure.
Rate of respiration is very high.

Function

Meristematic tissue acts as a parent tissue from which other tissues develop.
These tissues take part in growth by formation of new cells.

3 With the help of meristems, plants continue to produce new, leaves, branches of stem and flowers, fruits and root hairs.

The place of injury in plants is healed up by the formation of new cells by meristems.
The plant shoots lodged or bent by wind are made to grow upright by activity of intercalary meristem.

Meristematic tissues are growth tissues and are found in the growing regions of the plant. According to their position in the plant, meristems are apical, lateral and intercalary.

Apical meristems.

These are situated at the growing tip of stems and roots, e., at shoot apex and root apex.
Apical meristems are also found at apices of the leaves.
It brings about the elongation of the root and stem.
It results in an increase in the height of the plant, which is called primary growth.

Lateral meristems.

These are found beneath the bark (called cork cambium) and in vascular bundles of dicot roots and stems (called vascular cambium).
They occur in thin layers.
Cambium is the region which is responsible for growth in thickness.
It causes the organ (stem or root) to increase in diameter and girth. This is called secondary growth.
For example, cork cambium or phellogen produces a protective cork on the outside and secondary cortex tissue inside.

Intercalary meristems.

They arelocated at the base of leaves or internode, e.g., stems of grasses and other monocots.
Such tissues also occur below the nodes (e.g., mint). It produces an increase in the length of an organ such as leaves and internodes.

Section of root showing

Meristematic Tissue

Section of Shoot showing
Meristematic Tissue

Permanent Tissue

They are those tissues, in which cells have lost the capacity to divide and have attained a permanent shape, size and function due to morphological, biochemical and physiological differentiation. Depending upon their origin, permanent tissues are of two types, primary (derived from apical and intercalary meristem) and secondary (derived from a lateral meristem). On the basis of composition, permanent tissues can be simple, complex.

Simple Permanent Tissues

A simple permanent tissue is that tissue which is made up of similar permanent cells that carry out the same function or similar set of functions. Simple permanent tissues are of three types – parenchyma, collenchyma and sclerenchyma.

Parenchyma

Parenchyma is a simple permanent living tissue which is made up of thin-walled similar isodiametric cells. It is the most abundant and common tissue of plants. Typically the cells are isodiametric (all sides equal).

They may be oval, rounded or polygonal in outline. The cell wall is made up of cellulose. Cells may be closely packed or have small intercellular spaces for exchange of gases. Internally each cell encloses a large central vacuole and a peripheral cytoplasm containing nucleus. The adjacent parenchyma cells are connected with one another by plasmodesmata.

Functions

Storage of food.
Providing turgidity to softer parts.
Checking water loss in the form of epidermis.
Formation of water absorbing epiblema in root.
Photosynthesis in the form of chlorenchyma.
Secretion

Collenchyma

Collenchyma is a simple permanent tissue of nonlignified living cells which possess pectocellulose thickenings in specific areas of their walls. The cells appear conspicuous under the microscope due to their higher refractive index. The cells are often enlongated. They are circular, oval or angular in transverse section. Internally each cell possesses a large central vacuole and a peripheral cytoplasm. Wall possesses uneven longitudinal thickenings in specific area.

Collenchyma is found below the epidermis in the petiole, leaves and stems of herbaceous dicots.

Functions

It provides mechanical strength to young dicot stems, petioles and leaves.
While providing mechanical strength, collenchyma also provides flexibility to the organs and allows their bending, g..,Cucurbitastems.
It prevents tearing of leaves
Collenchyma allows growth and elongation of organs.
Being living, its cells store food.

Sclerenchyma

The cells of sclerenchyma are long, narrow, thick and lignified. These are closely packed without intercellular spaces. Their walls are usually pointed at both ends. The walls of their cells are often so thick that the cell cavity or lumen is nearly absent. Often oblique thin areas are found in their walls. These are calledpits. The middle lamella that is the wall between adjacent cells is conspicuous. Sclerenchyma cells are dead cells devoid of protoplasm. Sclerenchymatous cells are found abundantly in plants. The length of sclerenchyma cells varies from 1 mm to 550 mm in different plants. Their main function is to give mechanical support to plants. Sclerenchyma is of two types, sclerenchyma fibresand sclereids.

Differences between collenchyma and sclerenchyma

Collenchyma	Sclerenchyma
· It consists of living cells.	· It consists of dead cells.
· Its cells contain cytoplasm.	· Its cells are empty.
· Its cell walls are cellulosic.	· Its cell walls are lignified.
· The thickening of cell wall is not uniform.	· Cell wall thickening is uniform.
· Lumen of the cell is wide.	· Lumen of the cell is narrow.
· It provides mechanical support and elasticity to the plant body.	· It is chiefly mechanical tissue.

Protective Tissue

The protective tissues include epidermis and cork (or phellem).

Epidermis.The epidermis is usually present in the outermost lays of the plant body such as leaves, flowers, stem and roots. Epidermis is one cell thick and is covered withcuticle. Cuticle is a waterproof layer of a waxy substance called cutin, which is secreted, by epidermal cells. Cuticle possesses variable thickness in plants, for instance it is thicker in xerophytic (or desert) plants. Cells of epidermis are elongated and flattened and do not contain any intercellular space between them. Their inner contents are similar to parenchyma cells (they are living cells).

The main function of epidermis is to protect the plant from desiccation and infection. In fact, cuticle of| epidermis helps to reduce water loss by evaporation from the plant surface and helps in preventing the entry of pathogen (bacteria, fungi etc.).

The aerial surfaces of many plants bear cutinised hair over their epidermis. They are caller trichrome. They reduce the rate of transpiration. The seeds of cotton contain numerous long unicellular hairs, which form the husk of cotton. In roots, the younger parts are covered with uncutinised layer of epidermis called epiblema. Some of the epiblema cells give rise to tubular outgrowths called root hairs. These long unicellular root hairs increase the absorptive surface area of the root. They pass into the soil interspaces to absorb water and minerals.

Cork. As plants grow older, the outer protective tissue (i.e., epidermis) undergoes certain changes. A stripof secondary meristem, called phellogenor cork cambium replaces epidermis of stem. Cork cambium is a simple tissue having only one type of cells. The cells of cork cambium are rectangular and their protoplasts are vacuolated and contain tannins and chloroplasts. Cork cambium gives off new cells on its both sides, thus, forming cork (phellem) on the outer side and the secondary cortex or phellodermon the inner side. The layer of cells which is cut by cork cambium on the outer side ultimately becomes several layered thick cork (bark) of trees. Cells of cork are dead and compactly arranged without intercellular spaces. The walls of cork cells are heavily thickened with an organic substance (a fatty substance), called suberin deposits.The suberin makes these cells impermeable to water and gases. The cork cells do not contain protoplasm but arefilled with resin or tannins. In case of an onion bulb too, in the skin of onion the cell walls become thick and water proof due to addition of suberin.

Cork and bark are not the same structures. While cork includes outer products of cork cambium, the bark includes the outer products of cambium such as secondary phloem and also cork cambium and cork.

Cork is protective in function. Cork cells prevent desiccation (loss of water from plant body), infection and mechanical injury. Cork is light and does not catch fire easily. Due to these properties, cork is used as insulators, shock – absorbers, linoleum (used as flooring) and sports goods (in making of shuttle cocks, cricket balls, wooden paddles of table tennis, etc.) Commercial cork is obtainedfrom the stem surface of cork oak tree found in Southern Europe and North Africa.

STOMATA

Epidermis of a 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 concave sides of these guard cells face each other and have a space forming stomatal opening.The Guard cells are the only epidermal cells which contain chloroplast, the rest being colorless.

The stoma allows gaseous exchange to occur during photosynthesis and respiration. During transpiration too, water vapour also escapes through stomata.

During photosynthesis, carbon dioxide gas is taken in by the stomata from the atmosphere and oxygen gas is released (i.e. 02 is a byproduct of photosynthesis). However, during respiration of plants, oxygen is taken in and carbon dioxide is released via stomata. Photosynthesis takes place during daytime (in light), but respiration occurs both in the day and night time.

The process of transpiration helps the xylem tissue in the conduction of water and dissolved mineral salts by mass flow mechanism.

Complex Permanent Tissues

VASCULAR TISSUE SYSTEM

Vascular plants have specialized tissue called vascular tissue. Vascular tissue carries water and nutrients throughout the plant and helps support the plant. There are two kinds of vascular tissue; both kinds of vascular tissue contain specialized conducting cells:

xylem

Moves water and minerals upward from roots to leaves.
When water and minerals are absorbed by the roots of a plant, these substances must be transported up to the plant’s stems and leaves. Xylem is the tissue that carries water and dissolved substances upward in the plant.
Xylem consists of tracheids vessels, xylem parenchyma and xylem fibres.
Tracheids are long, thick walled sclerenchyma, narrow cells of xylem with thin separations between them. Water moves from one tracheid to another through pits, which are thin, porous areas of the cell wall.
Vessel elements are short, sclerenchyma, wide cells of xylem with no end walls. Vessel elements do not have separations between them, they are arranged end to end liked barrels staked on top of each other. These vessels are wider than tracheids, and more water moves through them.
The function of xylem parenchyma is storage of food and side ways conduction of water.
Fibres are mainly supportive in function.
Angiosperms, or flowering plants, contain tracheids and vessel elements.
Gymnosperms, or cone bearing seed plants, contain only tracheids.

Xylem

PHLOEM

· Moves sugars or saps in both directions throughout the plant originating in the leaves.

· Sugars made in the leaves of a plant by photosynthesis must be transported throughout the plant.

· Phloem tissue conducts sugars upward and downward in a plant.

· The sugars move as sugary sap.

· Phleomconsitrs of sieve tubes, companion cells, phloem fibres and phloem paranechyma.

· Sieve tubes members are cells of phloem that conduct sap. Sieve tube members are stacked to form long sieve tubes. Compounds move from cell to cell through end walls called sieve plates.

· Companion cells are parenchyma cells of phloem that enable (assist) the sieve tube elements to function.

· Phleomparenchyma are living parenchyma cells found in between sieve tubes. Their function, is storage of food.

Phleomfibres are only non living components of phloem and their function is providing mechanical support.
Each sieve tube element has a companion cell. Companion cells control the movement of substances through the sieve tubes.

Differences between xylem and phloem

Xylem	Phloem
· It conducts water and minerals.	· It conducts organic solutes or food materials.
· Conduction is mostly unidirectional, i.e., from roots to apical parts of the plant.	· In it conduction may be bidirectional, i.e., from leaves to storage organs or growing parts or from storage organs to growing parts of plants.
· Conducting channels or tracheary elements.	· Conducting channels are sieve tubes.
· Components of xylem include tracheids, vessels, xylem parenchyma and xylem fibres.	· Components of phloem include sieve tubes, companion cells, phloem parenchyma and phloem fiibres.
· Three of the four elements of xylem are dead (i.e., tracheids, vessels and fibres). Only xylem parenchyma is living.	· Three of four elements are living (i.e., sieve tubes, companion cells and phloem parenchyma) only phloem fibres are dead.
· In addition to conduction, xylem provides mechanical strength to the plant.	· Phloem performs no mechanical function for the plants.

Differences between Meristematic Tissues and Permanent Tissues

Meristematic Tissues	Permanent Tissues
· Its component cells are small, spherical or polygonal and un-differentiated.	· Its component cells are large, differentiated with different shapes.
· Cytoplasm is dense. Vacuoles are nearby absent.	· Large central vacuole occurs in living permanent cells.
· Intercellular spaces are absent.	· Intercellular spaces are often present.
· Cell wall of its cells is thin and elastic.	· Cell wall of its cells is thin or thick.
· Nucleus of each cells of this tissue is large and prominent.	· Nucleus of each cell of this tissue is less conspicuous.
· Its cells grow and divide regularly.	· Its cells do not normally divide.
· It is a single tissue.	· It can be simple, complex or specialized.
· Its cells are metabolically active.	· Metabolic rate of cells of this tissue is slow.
· Cell organelles of is cells are simple.	· Cell organelles of its cells are well developed.
· Cells of this tissue do not contain crystals and other inclusions.	· Its cells may be living or dead.
· It provides growth to the plant.	· It provides protection, support, conduction photosynthesis, storage, etc.

Animal Tissues

Animal tissues are divided into four major classes on the basis of their functions:

Epithelial Tissue :It covers or lines the free surfaces of other tissues. It serves several functions such as protection, secretion, excretion and also forms receptors.

Connective Tissue :It supports and connects various tissues.

Muscular Tissue :It causes movement of the skeleton and other internal organs and contraction and relaxation.

Nervous Tissue:It transmits messages in the form of impulses, thus coordinating the activities of body.

Epithelial Tissue

One of the simplest animal tissues is epithelium. Epithelium is a lining tissue. It consists of a single layer of cells covering the surface of the animals and the organs, cavities and tubes within it. The epithelium lining the inside of heart, blood vessels and lymph vessels is referred to as endothelium.

Structure

Typically all individual cells of epithelium are firmly attached with each other. These cells rest on a non-cellular basement membrane.

Functions

It functions are varied and involves protection of underlying tissues, production of motion (ciliated epithelium), absorption of digested material, secretory and also sensory function (olfactory region of nose, taste buds of tongue, retina of eye are all example of sensory functions of epithelium).

(a) Simple squamous epithelium :In such a type of epithelium, the cells are flattened. This gives a sheet like appearance in surface view. It is found in places where the protective covering also needs to be readily permeable to molecules in solution for e.g., the lining of capillaries, alveoli in lungs.

It is also called as pavement epithelium or tessellated epithelium as cells arranged like tiles.

Examples: Lining of blood vessel’s wall (endothelium), mesothelium, Bowman’s capsule, loop of Henle, alveoli of lungs, terminal bronchiole, etc.

Squamous epithelium

(b) Columnar epithelium

l These cells are tall, pillar-like with subcentric nucleus which lie in the same line in all cells

l No intercellular space at apical surface but may be little at basal surface.

l Meant for absorption, storage, synthesis and secretion.

e.g. Lining (mucosa) of stomach and small intestine.

l In intestine gives typical brush border look due to microvilli at apical surface.

Columnar epithelium

Differences Squamous epithelium and columnar epithelium

Squamous epithelium	Columnar epithelium
· The component cells are thin and flat.	· The component cells are pillar-like.
· The nucleus lies in the centre of the cell which generally bulged out.	· The nucleus is located near the base of the cell.
· This tissue occurs in lung alveoli, blood capillaries, Bowman’s capsule, buccal cavity.	· It occurs within the layer of stomach and intestine, their glands and the covering of epiglottis.
· It functions as a selectively permeable barrier, in ultrafiltration and wear and tear.	· It takes part in absorption, secretion and protective covering.

(c) Cuboidal epithelium

Cells are cubical in shape. Normally this epithelium forms the lining of glands or their ducts. A classical example is the epithelial lining of the follicles of thyroid.

Cuboidal Epithelium

(d) Ciliated epithelium

A specialized form of lining tissue is ciliated epithelium. Usually columnar in shape, the free surfaces of each cell bears numerous cilia capable of beating rapidly and rhythmically. This helps in causing motions producing currents. In mammals ciliated epithelium lines tubes and cavities in which materials have to be moved. e.g., ciliated epithelium is found in the lining of respiratory tract for expelling dust particles; in oviduct ciliated epithelium causes movement of ova.

Ciliated epithelium

(e) Glandular epithelium

l Cells are secretory so they are spacious.

l The cells of this tissue are of any shape like cuboidal, columnar, oval, spherical or irregular.

l Cells together may take different shape or remain single to act as gland, hence classified as two main types :

Simple glandular epithelium(single cell individually acts as glande.g., Goblet cells).

(ii) Compound glandular epithelium (many cells together form a unit gland e.g., all common glands).

Exocrine and Endocrine Glands

l Both are formed by the invagination of epithelial lining into connective tissue part.

l Exocrinegland retains the connection with upper epithelial layer that forms duct; product is released outside i.e. at the site of action through its own duct.

l Endocrinegland later loses connection from parent (upper) epithelium and becomes ductless, product (hormones) is released inside i.e., into the blood, which carries it to the site of action.

(h) Pseudostratified epithelium

l This type of epithelium is basically of ciliated type.

l Cells belong to same layer, but due to excess and early growth of neighbouringcells.Some cells remain subdued and can not reach the surface hence appear to be in another layer. Examples: Patches in the lining of pharynx, nasal chamber, trachea, covering of epiglottis, some part of vasa deferentia and oviduct funnel, etc.

Compound Epithelial Tissue

(i) Stratified Epithelium

The cells of stratified epithelium are arranged in many layers. The deepest layer, resting on a basement membrane, consists of columnar cells. The intermediate cells are polyhedral or cubical and the superficial layers are made up of flattened cells.

(j) Stratified Squamous

This is found on surfaces which may be subjected to friction, mechanical injury or desiccation. The layering may vary from a few layers (e.g., corneal epithelium) to many layers (e.g., epidermis).

Non-keratinized epithelium is found on covering surfaces, which are not subjected to desiccation while the keratinized variety is present on exposed skin surfaces.Stratified squamous epithelium is of two types:

l Non-keratinized

e.g. Lining of mouth, pharynx, oesophagus and anus, urethra, vagina

l Keratinized

e.g. Epidermis covering the whole surface of the body.

Connective Tissue

l The connective tissues of the body connect and anchor parts. They are often referred to as supporting tissues because they give support to the body and its organs. All of the supporting tissues possess two characteristics in common :

l They are all developed from the embryonic mesenchyme, which is itself derived from the primitive mesoderm.

(i) Connective tissue proper,

(ii) Skeletal connective tissue

(iii) Fluid connective tissue

CONNECTIVE TISSUE PROPER

The connective tissue as such refers to connective tissue proper. Features of typical connective tissue are as follows:

(a) Areolar Tissue :

Aerolar tissue is the most typical kind and can be regarded as the general form.
It is a loose; irregular connective tissue which has a very widespread distribution.
Areolar tissue connects the skin to the underlying structures and fills any unoccupied spaces between organs.
It penetrates with the blood vessels and nerves into the various tissues and organs. In the fresh conditions it is soft and transparent and contains numerous potential cavities.
The presence of these spaces is responsible for the name (areolar – “little areas” or spaces). Pathologically, these spaces may become filled with fluid resulting in oedema (swelling).
Areolar tissue consists of a matrix that contains various kinds of cells and fibres namely collagen and elastic fibres.
Intercellular matrix :In a fresh spread preparation of areolar connective tissue, the matrix is optically homogenous and transparent. The intercellular matrix contains several protein polysaccharide complex.

(b) Adipose connective tissue

l Fat (food) storing tissue, mainly in subcutaneous layer.

l Made of adipocytes, interstitial cells give rise to adipocytes and some elastic fibres which provide strength.


Adipose Tissue

l Increase in the amount of this tissue is called obesity

l Fat is deposited in three forms: olein, stearin and palmitin, which is more influenced by female sex hormone (estrogen).

l As secondary sexual character, it gives curvy look to the female body.

l Acts as thermal insulator hence specially important for homoeotherms.

l As shock absorber, it forms the padding around internal organs. Examples: Mammary gland, Camel’s hump, Blubber of Whale, Dolphin, etc. These are the type of commonwhite fat.

l Protects the baby from temperature-shock after birth, and provides extra energy and heat.

White fibrous connective tissue

l White fibrous connective tissue is cord like structure, mainly made of collagenous fibres. e.g.Tendonwhich connects muscle to bone.

Yellow elastic connective tissue

l Yellow elastic connective tissue is cord like and made of mainly elastic fibres.e.g.Ligamentwhich connects bone to bone.

SKELETAL CONNECTIVE TISSUE

l The skeletal connective tissue forms framework of the body and provides surface for the attachment of muscle.

l It is mainly of two types: cartilage and bone

Cartilage

l Skeleton in vertebrates initially formed as cartilage hence is primitive to bone.

l The mesenchyme differentiates into chondrioblasts which give rise to chondriocytes; the fibrous covering is perichondrium.

l Chondriocytes exist as singlet, doublet and cell nests within the lacunae

l The cartilaginous tissues are classified as follows:

l Hyaline cartilageis transparent, smooth like glass; with less or no fibres. Typical and major type cartilage in the body.e.g. cartilages of larynx, tracheal rings, hyoid apparatus of frog, etc.

l Fibrous cartilageiswith abundant collagenous fibres hence, appears opaque; strongest cartilage present between two bones. e.g. Intervertebral disc and pubic symphysis of mammals, Ischium, pubis and cartilage of frog.

l Elastic cartilageconsists mainly of elastic fibres, hence forms thin and elastic parts like. e.g. Pinna, nose tips, epiglottis in mammals, eustachian tube, etc.

Hyaline cartilage

l Calcareous cartilagehas extra deposition of CaCO₃hard like bone. e.g. Supra scapula in pectoral girdle of frog.

Bone

Structure of Bone

l The outer most fibrous layer of bone is periosteum,osteoblasts give rise to osteocytes or bone cells. These cells are arranged in concentric layers around the central cavity, which contains cavity, through this cavity also pass nerves and blood vessels.

l Fibres of Sharpey are the radial fibres traversing inside from outer layer the strength of the bone. Its number increases with age.

l Birds bone is pneumatic, sustain air cavities to reduce the weight of bone as flight adaptation.

Table: Comparision between cartilage and bones

Characters	Cartilage	Bone
1. Content of matrix	Mainly (90%) organic substance	Mainly inorganic substance (65-70%) and rest organic substance (30-35%)
2. Main organic substance	Chondroitansulphate	Collagen substance
3. Special protein	Chondrin	Ossein
4. Inorganic substance	Mainly CaCO₃	Mainly Ca(PO₄)₂
5. Cavity	Absent	Central cavity called as bone marrow
6. Position of basic components	Chondriocytes are scattered in matrix	Osteocytes are arranged in concentric layers
7. Layers of matrix	Absent	Layers form lamellae
8. Lacunae	Without canaliculi	With canaliculi
9. Coverings	Only perichondrium	Both periosteum and endosteum
10. Blood supply & Nerve supply	Absent	Both types of supplies takes place through a special cavity and canals
11. Mode of nutrition	Received by simple diffusion	Received directly through blood supply

Mammalian bone

l Consists of many longitudinal Haversian canals parallel to central cavity and transverse Volkmann’s canals connecting them. Through these pass blood vessels and nerve.

l Osteocytes get arranged around Haversian canals instead of central cavity.

l All these together form Haversian system or osteon, a structural unit of mammalian bone, each consists of osteocyte lamella.

Mammalian Bone

III. FLUID CONNECTIVE TISSUE OR BLOOD VASCULAR TISSUE

l In most animals blood collects excretory and other wastes from the body and flows within closed vessels except few invertebrates.

l Transport entire materials like nutritive substance, respiratory gases, hormones, etc. throughout the body

l Constitutes internal environment of the body and defense system.

l In human body the amount is 5 to 6 litre, i.e. about 8% of total body weight
(90 ml/kg).

l pH is slightly alkaline, strictly maintained; 7.2 for venous and 7.4 in arterial blood.

l Color-Venous blood bluish; Arterial blood bright red.

l Increasing bluishness due to accumulation of venous blood in any part is called as cyanosis.

l Blood is described by separating its two components: (i) Intercellular substance or matrix, called plasma(54-60%), (ii) Cellular componentorformed element includes RBC, WBC and Platelets (40-46%).

Lymph

Lymph is a colourless fluid that is filtered out of the blood capillaries. Since it is a part of blood, its composition is similar to that of blood except that red blood corpuscles and some blood proteins are absent in it. In the lymph, white blood cells are found in abundance.

Functions :

Lymph transports the 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.
Being loaded with WBCs such as lymphocytes, the lymph protects the body against infection. It forms the defence or immune system of the body.

Plasma

l A viscous fluid medium in which blood cells remain suspended hence also called as ground substanceof blood.

l Pale yellow but transparent fluid, constituting 4.5 to 5% of total body weight.

l Plasma consists of mainly water (90 – 92%), Proteins (6 – 7%), minerals (0.9 – 1%), and glucose (0.1%) in almost fixed ratio.

l Other substances whose ratio vary from place to place and time to time include hormones, enzymes, lipids, amino acids, antitoxins, vitamins, urea, uric acid, creatinine, and gases like NH3, CO2, O2, and N2.

l Inorganic salts (minerals) are mainly as bicarbonates and chlorides of sodium, other salts like – phosphates, carbonates, sulphates and iodides of Ca, Mg, K and Fe are present in traces.

Cellular components

Erythrocytes (RBC)

l Erythropoiesis is the process by which RBC’s are produced.

l As completely differentiated cell it doesn’t divide and has no centrosome

l These are also called as terminated cellfor the loss of its structural functional organisation and short life span.

l Simply as sac of haemoglobin this cell is present in only vertebrate blood and have evolved for the transport of gases.

l Mammalian RBC is without the nucleus, mitochondria, ribosomes, ER and Golgi bodies.

l Viability and source of energy depend upon its membrane and glycolysis.

l Very elastic and flexible, undergoes deformation to pass through narrow capillaries.

l Contains antigen of blood group and an enzyme, carbonic anhydrase, which helps in CO₂ transport.

l Number of RBC primarily depends upon physical activity of the organism.

Leucocyte (WBC)

l Leucocytes are regarded as policeman of the body, constitutes defence system.

l Active and nucleated cells of dividing nature; can change shape; mobile and phagocytotic.

l Cross through blood capillaries wall or diapedesis since their most functions are outside blood.

l Number (Total Count) is 5000 to 9000/ mm³, depicts body’s state of infection, it is in higher range in sick person.

l Leucocytes are classified into following two broad types:

(a) Agranulocytes : No granules in cytoplasm and nucleus large and of definite shape. These are: (1) Monocyte, (2) Lymphocyte

l Monocytes :These are largest WBC macrophages (phagocytotic) in tissue fluid, to move up unwanted material. Number (differential count) is approximately 4 to 11% i.e., about 200 to 700/mm3. Nucleus large, kidney or bean-shaped, may also be horse-shoe shaped.

l Lymphocyte :These are both small and large sized. Nucleus enormously large, spherical and occupies most area of cell. Cytoplasm is peripheral, rim-like. Its main role is in maintaining the immunesystem; forming antibodies (B-cells & T-cells).

l Neutrophils or heterophils: They take color with neutral stains (dyes). These are the main WBC type; with maximum number and variety of functions. The number is 60–65% of the total WBC i.e., 4000 to 5000/mm³, large sized and phagocytotic in nature. Neutrophils secrete chemicals like pyrogens, toxins (killer substance), antitoxins, inflammatory and anti-inflammatory substance, lysozymes etc. Nucleus is bi-lobed and the number of lobe increase with age.

l Eosinophil or acidophil: They take color with acidic dye, hence cytoplasm is alkaline. The number increases i.e., eosinophilia (in helminthic and the respiratory tract infections). The nucleus is bi-lobed, also phagocytic, but less motile than neutrophils, granules lysosomal with high peroxidase content.

l Basophils: They take color with basic dye, thus cytoplasm is acidic. Nucleus is twisted, S-shaped. Cytoplasm contains heparin, histamine and serotonin like mast cell.

Formed Elements of Blood with their number or percentage

Formed Element	Number or Percentage
· Erythrocytes (Red blood corpuscles)	· 4-6 million/mm³
· Leucocytes (White Blood Cells)	· 6000-9000/mm³
· A. Agranulocytes (i) Lymphocytes (ii) Monocytes B. Granulocytes (i) Neutrophils (ii) Eosinophils (iii) Basophils	30-35% 3-7% 55-60% 2-5% 0-1%
· Platelets	· 200,000-400,000/mm³

Differences between RBC (Erythrocytes) and WBC (Leucocytes)

Red Blood Corpuscles (RBCs)	White Blood Cells (WBCs)
· They are red in colour.	· They are colourless.
· Size of each RBC is about 7.2 micrometer.	· Size of WBCs varies between 10 to 20 micrometer.
· Their number is 4 to 6 million/mm³.	· Their number is 6000-900/mm³
· They are biconcave rounded in shape.	· The shape of WBCs is rounded to amoeboid.
· Nucleus is absent. (that is why they are called corpuscles).	· Nucleus is present.
· The cells contain haemoglobin.	· The cells do not contain haemoglobin.
· Most of the cell organelles are absent in these cells.	· Cell organelles are present in these cells.
· They are of only one type.	· They are of five types.
· Life span of each RBC is 120 days.	· Life span of each WBC is generally shorter (few hours to four days).
· They transport oxygen and to some extent carbon dioxide.	· They function in defence and immunity.

Blood platelets

l These are only found in mammalian blood and protoplasmic fragments are without nucleus, these are formed from megakaryocytes in bone marrow.

l They contains blood clotting factors, decrease in number, thrombocytopenia, hampers blood clotting.

l In other vertebrates (frog) and invertebrates, instead of platelets, these are nucleated cells called as thrombocytes or spindle cells.

Formed elements of blood

Muscular Tissue

l Most specialized tissue, only function is to generate movement or force.

l Converts chemical energy into mechanical energy like automobile machine.

l Machinery for movement is the set of actin and myosin proteins (both filamentous) as main component of the cytoplasm.

l The cell (completely differentiated) doesn’t divide, has no golgi bodies and centrosome and other parts called as: cytoplasm is called as sacroplasm,plasmalemma as sarcolemma, endoplasmic reticulum is sarcoplasmic reticulum (reduced as vesicles)

l Mitochondria (Sarcosomes) are the main organelle, largest in size and number. In vertebrate there are three types of muscles; (1). Skeletal muscle, (2). Cardiac muscle and (3). Smooth muscles

Skeletal muscle

l Associated with skeleton, generates external movement in the body.

l Cells are coenocytic long and cylindrical called as muscle fibrewhich isformed by the fusion of many myoblasts.

l Only parallel fibres are present in a muscle.

Striated Muscles

Structure of skeletal muscles

l Striations (alternate dark and light bands) are formed due to particular arrangement pattern of actin and myosin filaments – as revealed in electron microscopic structure of a myofibril.

l Lengthwise each myofibril consists of many sarcomeres, which is plate like zigzag structure through which thin filaments pass is the functional unit of muscle and constitute the area between two Z-lines.

l Dark band (Anisotropic band or A-band) consists of both actin (thin) and myosin (thick) filaments.

l Light band (Isotropic band or I-band) consists of only actin filaments.

Cardiac muscle

l The most versatile muscle is exclusively found in heart.

l Being striated it is structurally similar to skeletalmuscle except the presence of cross fibres, besides parallel fibres

l Intercalated discs which represent the joints of two myoblasts.

l Contraction pattern is rhythmicand alsofast controlled by autonomic nervous system (ANS).

l Untiring muscle (no fatigue), works ceaselessly throughout the life.

l Generates impulse like nerve (i.e. myogenic heart of vertebrates).

Smooth Muscle

l Unstriped; hence structurally different from striated and cardiac muscles.

l Muscle cell spindle-shaped (not cylindrical), uninucleated each formed of single myoblast.

l Actin filaments remain attached, to dense bodies in the cytoplasm.

l There is no myofibril, no sarcomere and no Z-line.

l Actin and Myosin filaments are not arranged in any pattern hence no striations.

l Involuntary muscle, under ANS control is found in visceral organs (visceral muscle). Contraction in such muscles is termed as peristalsis, is rhythmic, slow and prolonged.

Smooth Muscle

Nervous Tissue

l This is coordinating or controlling tissue for entire body’s structural or functional organization.

l Exhibits highest degree of irritability and conductivity.

l It is ectodermal in origin and completely differentiated tissue cells do not divide at all (except some glial cells).

l Receiving, integrating, transforming and transmitting the coded information of stimuli to evoke response in the body are its specialized functions. This tissue consists of following two types of cells:

(i) Neurons – the actual nerve cell,

(ii) Neuroglia – the supporting cells,

Neurons

l These are structural and functional units of nervous tissue and highly excitable as well as specialized for generation and conduction of impulse.

l The longest (upto 1.5 m. or more), the most sophisticated and the most complicated in structure and function.

l Number is higher in large sized animals 100 billion in human body.

l Neurons consist of three parts; dendron, cyton and axon. Cyton is the cell body, while dendron and axon are the branches of the cell.

l Nissl’s granules remain only in the cyton part and they are the sites for protein synthesis.

l Neurons possess network of microtubules throughout the cell and constitute a transporting system.

l Centrosome is absent so neurons are unable to regenerate.

Dendron

l These are also called as afferent branches and are the receiving branch impulse enters the nerve cells through it. At terminal end each dendron gives rise to fine branches called dendrites.

Structure of a Neuron

l Certain axon of neurons also gives out branches at right angle and they are called as collateral fibres.

l The cytoplasm of axon is axoplasm with abundant neuro-fibril and mitochondria. The plasma membrane of axon is called as axolemma. Axons are main components of peripheral nervous system (PNS).

l In myelinated nerve it is covered with myelinated sheath made of Schwann cells. Cut gap at certain intervals in this sheath is called as node of Ranvier.

Cyton (perikaryon or soma or cell body)

l This part of neuron constitutes the grey matter of CNS, outside CNS in clusters form ganglion.

l Abundant cytoplasm with almost all organelles and Nissl’s granulesas colored body made of RNA, Nissl’s granules are also called as trigoid bodies which are secretory in nature. Ribososomes and Golgi bodies are also present in the cytonic region.

Synapse

l It is the joint of two neurons – between the axon of one neuron and the dendron of another neuron.

l Axon is termed as pre synaptic terminalwhile, dendron as post synaptic terminal.

l Synapse are classified into following two types and their classification is based on following distinguishing features:

Neurotransmitters

l There are more than 30 types of substances discovered so far which are directly or indirectly involve in the conduction of nerve transmission and they are collectively called as neurotransmitters.

l Acetylcholine, this is excitatory for nerve and general muscle, while, inhibitory for cardiac muscle.

l Sympathin, Histamine, Noradrenaline (adrenalin) are excitatory for all muscles and nerves.

l Serotonin, dopamine and GABA (amino-butyric acid) are inhibitory for all.

Types of neurons

l The neurons are classified on the basis of number of dendrons and functionality.

l On the basis of number of dendrons, neurons are classified into following types:

l Unipolar neurons: Without dendron, only one branch present is axon.

e.g. Embryonic brain cells.

l Bipolar neurons: Only one dendron and one axon hence with two branches.

e.g. Neurons present in the retina of eyes.

Multipolar neurons: More than one dendron, hence, has many branches.

e.g. All commonneurons.

l On the basis of functional characteristics, neurons are of following three types:

l Sensory neuron: Carries impulse from sensory organ to brain, also called as afferent neuron.

Motor neuron: Carries impulse from brain to effector organ (i.e. muscles) hence, also called efferent neuron.

l Interneuron: Acts as adaptor between sensory and motor neurons in the CNS.

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EXERCISE

Very short answer type questions

What is a tissue?
How many types of tissues are in organisms?
Name the region in which parenchyma tissue is present?
What do you mean by meristematic tissue?
What is the difference between meristematic and permanent tissue?
Give one example of animal tissue as connective?
How the neuron acts as animal tissue?
What is the utility of tissues in multicellular organisms?
What are tracheid and where they found?
What are the functions of cuboidal epithelium?
Name the difference in the function of collenchyma and sclerenchyma.
Define meristems.
Name two types of sieve elements found in phloem.
What are the two types of fibres of the connective tissue?
Name the tissue that lines the urinary bladder. State any one advantage of this tissue being present there.

Short Answer type questions

How many types of elements together make up the xylem tissue? Name them.
How are simple tissues different from complex tissues in plants?
Differentiate between parenchyma, collenchyma and sclerenchyma on the basis of their cell wall?
What are the functions of stomata?
How many types of elements together make up the phloem tissue? Name them.
Give the differences between bone and cartilage.
Give the function of lymph and blood?
Name all different types of tissues present in animal?
Why as blood called connective tissue?
What is the function and location of stratified squamous epithelium?

Long answer type questions

Diagrammatically show the difference between the three types of muscle fibers.
Draw a well labelled diagram of a unit of nervous tissues with their functions?
Identify the type of connective tissue in the following. Skin, bone, blood, lining of cavities.
Show the type of animal tissues using flow chart.
Draw the different types of epithelial tissues with their functions?
Describe the structure of adipose tissue and with their functions?
What is the specific function of the cardiac muscle?
State the difference between simple tissues of plants.
Name different types of meristematic tissue and draw diagram to show their location.
Give the flow chart of plant tissues.
Write a note on plant tissues.
How a plant tissue is different from animal tissue?
Name the region in which parenchyma tissue is present?
Name the main components of xylem. Which of these is most suitable for carrying water?
Sketch the elements of (a) Xylem and (b) Phloem.
Write the function of blood plasma?
Describe various types of epithelial tissues with the help of labeled diagrams.
Name the tissues which perform the following functions.

(i) Haemopoeisis (ii)Coagulation

(iii) Transmission of message (iv) Locomotion

(v) Formation of antibodies.

Name the following.
(a) Tissue that forms the inner lining of our mouth.
(b) Tissue that connects muscle to bone in humans.
(c) Tissue that transports food in plants.
(d) Tissue that stores fat in our body.
(e) Connective tissue with a fluid matrix.
(f) Tissue present in the brain.
List the charateristics of cork.How is it formed ? Mention its role.
What are the funtions of the stomata?
What is the role of epidermis in plants ?

Multiple choice questions

The tissue present in the lining of kidney tubules and ducts of salivary glands.

(a) Squamous epithelial tissue (b) glandular epithelium

Eosinophil is the example of

(a) Erythrocytes (b) Leucocytes

Of the following components of phloem is non-living

(a) Sieve tubes (b) companion cells

Which of the following tissues are composed of mainly dead cells?

(a) phloem (b) epidermis

(c)xylem (d) endodermis

Father of histology is

(a) Malpighi (b) Bichat

The term tissue was given by

(a) Robert Hooke (b) Mayer

Epithelial tissue always has an exposed outer face and an inner surface anchored to connective tissue by a thin, non-cellular structure called the

(a) nonstratified layer (b) stratified layer

Which type of tissue forms the inner lining of a blood vessel?

(a) epithelial (b) connective

Which type of tissue forms glands?

(a) connective (b) epithelial

The covering tissue of external and internal surfaces of animals is :

(a) connective (b) muscular

Trapped dust particles are pushed out of respiratory tract by

(a) ciliated epithelium (b) stratified epithelium

Nasal and genital tracts are lined by

(a) simple columnar (b) stratified columnar epithelium

Tissue found in area of regular wear and tear is

(a) simple squamous epithelium

(b) stratified squamous epithelium

(d) stratified cuboidal epithelium

Cardiac muscle fibres are

(a) branched (b) striated

Cylindrical muscle fibres which show alternate light and dark bands are

(a) smooth muscle (b) cardiac muscle fibres

Most abundant animal tissue is

(a) epithelium (b) muscular

(c)connective (d) blood

Matrix of connective tissue is produced by

(a) plasma cells (b) mast cell

Tendons and ligaments are

(a) dense connective tissue (b) loose connective tissue

Ligament connects a bone with

(a) skin (b) muscle

Matrix of cartilage in made of

(a) collagen (b) chondrin

Plasma content of blood is

(a)35% (b) 55%

Largest blood cells are

(a) monocytes (b) neutrophils

Short branched process coming out of a soma of neuron are

(a) dendrites (b) axons

Fluid part of blood after removal of corpuscles is

(a) plasma (b) lymph

Tendon is a structure which connects

(a) a bone with another bone (b) a muscle with a bone

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WORKSHEET – 1

Define the term ‘tissue’.

_______________________________________________________________________________

What is the importance of tissue in organisms?

_______________________________________________________________________________

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

_______________________________________________________________________________

Differentiate between a plant tissue and animal tissue.

_______________________________________________________________________________

Draw a table to define the plant tissue.

WORKSHEET – 2

What do you mean by a meristematic tissue?

_______________________________________________________________________________

What are the characteristics of the meristematic tissue?

_______________________________________________________________________________

What are the three type of meristematic tissue? Explain.

_______________________________________________________________________________

Draw a structure by showing a three type of meristematic tissue.

What do you mean by permanent tissue?

_______________________________________________________________________________

WORKSHEET – 3

What are the types of simple permanent tissues?

_______________________________________________________________________________

Draw a structure of parenchyma, collenchyma and sclerenchyma tissue.

Define the structure and functions of the simple permanent tissues?

_______________________________________________________________________________

What are the types of complex permanent tissues?

_______________________________________________________________________________

What are the components of xylem and phloem?

_______________________________________________________________________________

WORKSHEET – 4

Define the structure and functions of vascular tissues?

_______________________________________________________________________________

Draw a structure of xylem and phloem to showing different components in them.

Differentiate between xylem and phloem vascular tissue.

_______________________________________________________________________________

Differentiate between meristematic tissues and permanent tissues.

_______________________________________________________________________________

What are the differences between collenchyma, parenchyma and sclerenchyma tissues?

_______________________________________________________________________________

WORKSHEET – 5

Make an outline table of animal tissue.

_______________________________________________________________________________

How many types of epithelial tissue?

_______________________________________________________________________________

What are types of epithelial tissue?

_______________________________________________________________________________

Make a diagram to showing the different types of epithelial tissues.

Define the structure and function of different types of epithelial tissues?

What do you mean by exocrine and endocrine glands?

_______________________________________________________________________________

WORKSHEET – 6

Write a note on compound epithelial tissue.

_______________________________________________________________________________

What do you mean by connective tissue? Classify them.

_______________________________________________________________________________

Define the areolar tissue, adipose tissue, fluid tissue and skeletal tissues with their functions.

_______________________________________________________________________________

Differentiate between a cartilage and bone structure.

_______________________________________________________________________________

Make a table of a body fluid tissue and give a specific function of each of them.

WORKSHEET – 7

Differentiate between Red blood corpuscles and White blood cells.

_______________________________________________________________________________

What do you mean by muscular tissues?

_______________________________________________________________________________

Explain the structure and functions of muscular tissues.

_______________________________________________________________________________

Draw a structure of various muscular tissues?

Draw a structural and functional unit of nervous tissue and explain its functions.

notes

______________________________________________________________________________

notes

______________________________________________________________________________

notes

______________________________________________________________________________

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