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LEARNING OUTCOME

1.1 CELL THEORY

**Describe the cells as the smallest independent unit of lifeand form the basis of living organisms.

1.2 PROKARYOTIC AND EUKARYOTIC CELLS

**Compare the structure of prokaryotic & eukaryotic cells1.3 PLANT AND ANIMAL CELLS

**Detailed structure ( plant and animal )

**Compare plant and animal cells

1.4 CELLS AS BASIC UNIT OF LIVING ORGANISMS

**Specialized cells.a) plant meristem,parenchyma,collenchyma,sclerenchyma

b) animal epithelium, nerves, muscle, connective tissue -(DESCRIPTION OF STRUCTURE FUNTION AND DISTRIBUTION)

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CELL THEORY.

THEORY; All living organisms are composed of one or more

cells.

Cells- basic units of structure and function in an

organism. cells have the same chemical composition.

Cells come only from reproduction of existingcells- mitosis

Genetic materials- pass to daughter cells during

cell division. P/S virus/chloroplast/mitochondria have their

own DNA

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1.2

Prokaryotic And Eukaryotic CellsTYPES OF CELLS

Prokaryotic (prokaryote)

Eukaryotic (eukaryote) Cells

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Prokaryotes

Pro = before; karyon = nucleus

Single celled organism

relatively small 0.5 to 10 um

lack membrane-bound organelles

earliest cell type

No nucleus/ no nuclear envelope

E.g.; bacteria/yanobacteria(blue green algae)

Surrounded by cell wall

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Eukaryotes

Eu = true; karyon = nucleus

10-100 micrometer

contain membrane-boundorganelles

Evolved from prokaryotes byendosymbiotic association of twoor more prokaryotes

Include Protists, Fungi, Animals,and Plants ( cell wall made ofcellulose)

E.g.; Protist/fungi/animal and

plant

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Features of Prokaryotic Cells

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Cytoplasm semi-fluid cell interior

no membrane-bound organelles

location for metabolic enzymes

location of ribosome for protein synthesis

Ribosome. The smaller (70 S) type.

Nucleoid region where naked DNA is found

Nucleoid (orNuclear Zone) The region of the cytoplasm that contains DNA. It is not

surrounded by a nuclear membrane.

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DNA. Always circular, and not associated with any proteins

to form chromatin naked DNA

Plasmid. Small circles of DNA, used to exchange DNA

between bacterial cells, and very useful for geneticengineering.

Cell membrane. made of phospholipids and proteins, like eukaryotic

membranes- separates the cell from the environment


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Mesosome. A tightly-folded region of the cell membrane containing all the

membrane-bound proteins required for respiration andphotosynthesis.

Can also be associated with the nucleoid.

Cell Wall. Made of murein (not cellulose), which is a glycoprotein (i.e. a

protein/carbohydrate complex, also called peptidoglycan).

There are two kinds of cell wall, which can be distinguished by aGram stain: Gram positive bacteria have a thick cell wall andstain purple, while Gram negative bacteria have a thin cell wallwith an outer lipid layer and stain pink.


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Cell Wall

rigid structure - maintain its shape (made of

peptidoglycan)

Capsule (orSlime Layer).

A thick polysaccharide layer outside of the cell wall,

like the glycocalyx of eukaryotes.

Used for sticking cells together, as a food reserve, as

protection against desiccation and chemicals, and as

protection against phagocytosis.


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Capsule outer sticky protective layer

this is in NO way the same as the cell wall of a plant cell

Flagellum. A rigid rotating helical-shaped tail used for

propulsion(movement)

The motor is embedded in the cell membrane and is driven by aH+ gradient across the membrane.

Clockwise rotation drives the cell forwards, while anticlockwiserotation causes a chaotic spin.

This is the only known example of a rotating motor in nature.


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Features of Eukaryote Cells

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Cytoplasm (or Cytosol).

This is the solution within the cell membrane.

contains enzymes -glycolysis (part of respiration) and other

metabolic reactions together with sugars, salts, amino acids,

nucleotides and everything else needed for the cell to function. All living content excluding nucleus and plasma membrane


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Nucleus. largest organelle.

Surrounded by a nuclear envelope-double membranewith nuclear pores - large holes containing proteins

that control the exit of substances (RNA/ribosomes)from the nucleus.

The interior is called the nucleoplasm, which is full ofchromatin- a DNA/protein complex in a 1:2 ratiocontaining the genes.

During cell division the chromatin becomescondensed into discrete observable chromosomes.

The nucleolus is a dark region of chromatin, involvedin making ribosome.


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Mitochondrion (pl. Mitochondria). sausage-shaped organelle (8m long)-where aerobic

respiration takes place in all eukaryotic cells.

Mitochondria are surrounded by a double membrane:the outer membrane is simple and quite permeable,while the inner membrane is highly folded into cristae-large surface area.

The space enclosed by the inner membrane is called

the mitochondrial matrix, and contains small circularstrands of DNA.

The inner membrane is studded with stalked particles,which are the site of ATP synthesis.


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Chloroplast. Bigger/fatter than mitochondria, chloroplasts-site of

photosynthesis,-only found in photosyntheticorganisms (plants and algae).

enclosed by a double membrane, also have a thirdmembrane (thylakoid membrane)-folded into thylakoiddisks which then stacked into piles( grana)

The space between the inner membrane and thethylakoid is called the stroma.

The thylakoid membrane contains chlorophyll andother photosynthetic pigments arranged inphotosystems, together with stalked particles, and isthe site of photosynthesis and ATP synthesis.

Chloroplasts also contain starch grains, ribosomesand circular DNA.


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Ribosomes. These are the smallest and most numerous of the cell

organelles, and are the sites of protein synthesis.

They are composed of protein and RNA, and aremanufactured in the nucleolus of the nucleus.

Ribosomes are either found free in the cytoplasm-siteof proteins synthesis for the cell's own use, or theyare found attached to the rough endoplasmic

reticulum, where they make proteins for export fromthe cell.

They are often found in groups called polysomes.

All eukaryotic ribosomes are of the larger, "80S", type.


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Smooth Endoplasmic Reticulum (SER). Series of membrane channels involved in

synthesizing and transporting materials, mainly lipids,needed by the cell.

Rough Endoplasmic Reticulum (RER). Similar to the SER, but studded with numerous

ribosomes, which give it its rough appearance.

The ribosomes synthesis proteins, which areprocessed in the RER (e.g. by enzymaticallymodifying the polypeptide chain, or addingcarbohydrates), before being exported from the cellvia the Golgi Body.


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Golgi Body (or Golgi Apparatus).

Another series of flattened membrane vesicles,

formed from the endoplasmic reticulum.

F(x)transport proteins from the RER to the cellmembrane for export.

Parts of the RER containing proteins fuse with one

side of the Golgi body membranes, while at the other

side small vesicles bud off and move towards the cellmembrane, where they fuse, releasing their contents

by exocytosis.


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Vacuoles. These are membrane-bound sacs containing water or

dilute solutions of salts and other solutes.

Most cells can have small vacuoles that are formed

as required, but plant cells usually have one verylarge permanent vacuole that fills most of the cell, sothat the cytoplasm (and everything else) forms a thinlayer round the outside.

Plant cell vacuoles are filled with cell sap, and are

very important in keeping the cell rigid, or turgid. Some unicellular protoctists(protist) have feedingvacuoles for digesting food, or contractile vacuoles forexpelling water.


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Lysosomes.

These are small membrane-bound vesicles

formed from the RER containing a cocktail of

digestive enzymes.

They are used to break down unwanted

chemicals, toxins, organelles or even whole

cells, so that the materials may be recycled. They can also fuse with a feeding vacuole to

digest its contents.


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Cytoskeleton. This is a network of protein fibres extending throughout all

eukaryotic cells, used for support, transport and motility.

The cytoskeleton is attached to the cell membrane and gives the

cell its shape, as well as holding all the organelles in position. There are three types of protein fibres (microfilaments,

intermediate filaments and microtubules), and each has acorresponding motor protein that can move along the fibrecarrying a cargo such as organelles, chromosomes or othercytoskeleton fibres.

These motor proteins are responsible for such actions as:chromosome movement in mitosis, cytoplasm cleavage in celldivision, cytoplasmic streaming in plant cells, cilia and flagellamovements, cell crawling and even muscle contraction inanimals.


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Centriole.

This is a pair of short microtubules involved in

cell division.

Before each division the centriole replicates

itself and the two centrioles move to opposite

ends of the cell, where they initiate the spindle

that organises and separates thechromosomes.


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Undulipodium (Cilium and Flagellum). This is a long flexible tail present in some cells and

used for motility.

It is an extension of the cytoplasm, surrounded by thecell membrane, and is full of microtubules and motorproteins so is capable of complex swimmingmovements.

There are two kinds: flagella (no relation of the

bacterial flagellum) are longer than the cell, and thereare usually only one or two of them, while cilia areidentical in structure, but are much smaller and thereare usually very many of them.


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Microvillus (MICROVILLI) These are small finger-like extensions of the cell membrane

found in certain cells such as in the epithelial cells of theintestine and kidney, where they increase the surface area forabsorption of materials.

They are just visible under the light microscope as a brushborder.

Cell Membrane (or Plasma Membrane).

This is a thin, flexible layer round the outside of all cells made ofphospholipids and proteins.

It separates the contents of the cell from the outsideenvironment, and controls the entry and exit of materials.

The membrane is examined in detail later.


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Cell Wall. This is a thick layer outside the cell membrane used to give a

cell strength and rigidity.

Cell walls consist of a network of fibers, which give strength but

are freely permeable to solutes (unlike membranes). A wickerwork basket is a good analogy.

made mainly of cellulose, also contain hemicelluloses, pectin,lignin and other polysaccharides.

-built up in three layers > primary cell wall, the secondary cell walland the middle lamella.

There are often channels through plant cell walls calledplasmodesmata, which link the cytoplasms of adjacent cells.

Fungal cell walls are made of chitin (poly-glucosamine).

Animal cells do not have a cell wall, though they do have a layerof carbohydrate outside the cell membrane called the cell coat,

or glycocalyx.


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Microscopic structures of plant

and animal cells

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COMPARISON- PROKARYOTIC&

EUKARYOTIC CELLSCHARATERISTICS PROKARYOTES EUKARYOTES

1. SIZE Small cells ,diameter-0.5-5 micrometer Large cells, up to 40

micrometer

2.DNA Circular & free in cytoplasm-naked DNA DNA is associated with histone

protein to form chromosome

3.NUCLEUS Not enclosed by membrane-naked Bounded by membrane(nucleus envelope)

4.ORGANELLES No membrane bound organelles/ no

centriols and microtubules

Has membrane bound

organelles;

mitochondria,chloroplast,centri

ols.etc.

5.RIBOSOMES Small ( 70 s) large (80 s)

6.CELL WALL Present- made up from peptidolican Only plant(cellulose), fungi

and chitin

7.FLAGELLA Present- movement Absent

8.CELL DIVISION Simple fission Mitosis

9.REPRODUCTION No sexual systems Meiosis and fertilization

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PLANT CELL

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Tissue and Organs in plant:

Dermal Tissue System (epidermis)-forms theouter layer of a plant.

Ground Tissue System

(parenchyma/collenchyma/sclerenchyma)-

(makes up the bulk of roots and stems Vascular Tissue ( xylem& phloem)-transports

water and food throughout the plant.

The FOUR Plant Organs are ROOTS,

STEMS, LEAVESAND FLOWERS.

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Specialized cell : Plant

Meristem

Meristems- cells that undergo repeated division.These are the cells from which all other cells in the plant originate.

No undergoes differentiation.2 types of meristem : 1) apical>shoot and root

2) lateral>cambia-vascular cambium-cork cambium

three types : primary, secondary, and pericycle.The primary meristems give rise to primary tissues in the plant,

which elongate the plant by either shoots or roots.Secondary meristems form the basis of secondary tissues thatenlarge the diameter of the stem or root.

the pericycle is a specialized meristem-found only in the rootsystem-gives rise to branch roots.

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Meristem, parenchyma, collenchyma,

sclerenchyma, xylem, and phloem tissues

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Parenchyma Unspecialized and are found in all organs of plant.

Can divide and give rise to more specialized cells.

Living at maturity

Isodiametrical/ polyhedral(many sided)-capable 4 cell division

Thin 1st cell wall and without 2nd cell walls

Loosely packed

Involved in food storage.

Involved in apoplast pathway 4 mvment of water and minerals.

Divide to 4 type: 1) epidermis

2) mesophyll

3) endodermis

4

) pericycleCollenchyma- thicker primary walls.

- Polygonal shape

- f(x) : mechanical support Form bundles underneath epidermis.

Flexible support to immature regions of the plant.


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Sclerenchyma Sclerenchyma cells have thick secondary walls impregnated with lignin.

Most are non living.

More rigid than collenchyma cells Most cells death at functional maturity

Can be divided into 2 types:

a) fibres- elongated

b) scelereids( stone cells ) - spherical - can be found in the

cortex, pith and phloem* Function supporting element of the plant

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Xylem

Xylem transports water and minerals fromthe roots to the leaves.

Tracheids

elongated, with tapered ends and have lignifiedwalls

Matured cells death with empty lumen Pits in end walls.

Vascular rays

Fibers

Vessel Elements Larger, with perforated plates in their end walls.

Long ,narrow tube formed


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Xylem

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Phloem

Phloem transports sucrose and other organic

compounds from the leaves to the roots.

Sieve-tube members are conducting cells.

Contain cytoplasm but no nuclei.

Channels in end walls.

Plasmodesmata extend from one cell to another through

sieve plate.

Companion cells- contain nucleus, vacuoles, ribosomes and

mitochondria


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Phloem

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PARENCHYMA CELLS

Characteristic :

>Living and unspecialized

>isodiametrical,sometimes elongated

>Composition :cellulose, pectins and hemicellulose, coveringof cutin

>Large central vacuole with cytoplasm pushed to side of wall

>Thin cell wall

>Loosely packed, large intercellular air space

Function :

> Provided support in herbaceous plant

> Gaseous exchange

> Food storage> Replacement of injured and damage cells

Distribution :

>Cortex ,pith , medullary rays ,packing tissue in xylem andphloem

SPECIALIZED PARENCHYMA

1) Epidermis : single layer covering plant body, elongatedand flattened, protection against desiccation and infection

2) Mesophyll : between upper and lower epidermis ofleaves

3) Pericyle : between central vascular tissue andendodermis in roots,isodiametrical,retain meristematicactivity giving rise to lateral root and 2nd growth

4) Endodermis :singled celled betwn outer cortex and

inner pericycle tissue; impregnated suberin formingCasparian strip which prevent passage of water via apoplastpathway

COLLENCHYMA CELLS

Characteristic :> Living , unevenly thickened (extra cellulose at corners of hecells)

> Polygonal and elongated with tapering ends

> Composition: cellulose , pectins and hemicelluloses

> small intercellular air spaces@ non exist

Function:

> support And mechanical strength

Distribution : Outer region of cortex: below epidermis

SUMMARY OF SPECIALISED PLANT CELLS: FUNCTION & DISTRIBUTION

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SCLERENCHYMA CELLS

Characteristic :

> Polygonal and elongated with tapering

ends, tightly packed with no intercellular airspaces

> Deposits of lignin on 1st cell wall resulting

in death matured cells ; incapable of

elongation at maturity

Function :

> support and mechanical strength

:provided great tensile and compressionalstrength as a result of deposits of lignin at

cellulose cell wall

2 types of sclerenchyma cells :

fibre and sclereids

Sclerenchyma fibre : elongated,

polygonal with tapering ends, death

at maturity, no protoplasm ,narrow

empty lumen, pit present, tapering

ends overlapping and interlocked

with one another thus provided

mechanical strength

Scelereids(stone cells): shorter

than fibres , dead cells with thickerlignified cell wall, simple pit present ,

found in stems,leaves, fruits and

provide strength and support plant

structures and organs

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Epithelial cell/ epithelium

One of the simplest tissues.

However, it can be built up into tissues of

varying complexity.

Lining tissues : in it simplest form, it consists of asingle layer of cells covering the surface of the

body and the organs within it.

Specialized cell : Animal

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Epithelial cell

Also lines various spaces and tubes ( in

which situation it is usually referred to asendothelium).

Typically the individual cells : firmly

attached to each other.


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Epithelial cell

rest on a basement membrane.

have a free surface

The main function of epithelial tissues is

protection.


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Epithelial cell

Other functions:

To increase the surface area for the

reabsorption of materials/which absorption

can take place.

Exchange materials by diffusion.

As a gland ; secrete mucus or enzyme.


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Types of Epithelial Tissues

Simple

Epithelial

Tissues

Stratified

Epithelial

Tissues

Pseudostratified

Epithelial

Tissues

Epithelial

Tissues

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Simple Epithelial Tissues

1. Simple squamous epithelial tissues.

2. Simple cuboidal epithelial tissues.3. Simple columnar epithelial tissues.

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Simple squamous epithelial tissues

Cells are flattened.

Disc- shape nucleus

The sheet of cell is delicate, thin and leaky.

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Functions:

exchange of material/protect underlying tissues

lubricates the movement between adjacent

surface./facilitated diffusion of gaseous across alveoli

Distribution:

the linings of blood vessels.

alveoli

mouth cavity Bowmann capsule

Simple squamous epithelial tissues

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Simple cuboidal epithelial tissues

Cells are cubical in shape.

View from free

surface are polygonal.

Specialized for

secretion.

Make up the epitheliaof kidney tubules and many glands thyroid andsalivary glands.

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Simple columnar epithelial tissues

Cells are elongated at right angle to the basement membrane.

Relatively large cytoplasmic volume.

Often located where

secretion or activeabsorption is an

important function.

Distribution: linings of small intestine( stomach)

oviduct/ ventricles of brain

nasal cavity.

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Stratified Epithelial Tissues

Several layer of cells.

With only the lower ones

columnar and metabolicallyactive.

Division of lower cells

causes older one topushed upward forwardsurface, becomingflattened as they move.

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Functions only for protection.

Main location skin; mouth and vaginal lining.

Stratified Epithelial Tissues

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Pseudostratified Epithelial Tissues

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Nerve cell

Neurons Cell body contains nucleus.

Dendrites receive signals from sensory receptors.

Axon conducts nerve impulses.

Any long axon is also called a nerve fiber. Covered by myelin sheath.

Types of Neurons:

1) Motor Neurons take nerve impulses from the CNS to muscles

or glands.

2) Sensory Neurons take impulses from sensory receptors toCNS.

3) Interneuron convey nerve impulses between various parts of

the CNS.


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Neurons

The pathway of communication between the brainand the body.

Electrical impulses pass along the neurons from

stimuli receivers to the effectors .

Neurons differ considerably in structure but allneurons have three things in common;

Cell body

Fine cytoplasmic fibre dendron or dendrite

Axon.

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The cytoplasm of neurons cell body is

densely packed with mitochondria,

ribosomes, golgi body and rough

endoplasmic reticulum.

Neurons can be classified by their function.

On the basic, there are three types of

neuron;

Neurons

T f N

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Types of Neurons

Sensory

neuron

Motorneuron

Intermediary/

Relay neuron

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A Nerve Cell (Neuron)

Cell BodyDendrites

Axon of another

neuron Axon

MyelinSheath

Dendrites of another

neuron

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Neuroglia

Supporting cells in the central nervous

system.

There are several types of glial cell in the

brain and spinal cord.

As a group, they do far more than simply

glue neurons together.

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Muscle cell

In the invertebrate body there are three

types of muscle cell;

a) Skeletal muscle.

b) Smooth muscle.

c) Cardiac muscle.


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Skeletal muscle

Attached to the bones by tendons.

Responsible for voluntary movement.

Also called striated muscle.

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Smooth muscle

Found in the walls of internal organs digestive tract, urinarybladder etc.

Spindel shaped.

Responsible in involuntary activities.

Contract more

slowly than

skeletal muscle.

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Cardiac muscle

Form the contraction wall of the heart. Striated like skeletal muscle but have branched.

The ends of the cells are joined by intercalated

disc.

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Connective tissues

The major types of connective tissues invertebrates are:

a) Bone

b) Cartilage

c) Blood

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Bone Tissue

The skeleton supporting

the body of most

vertebrates.

Bone is a mineralized

connective tissues.

Bone-forming cells

called osteoblasts;deposit a matrix of

collagen.

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The combination of hard mineral and flexible collagen makes boneharder than cartilage.

Hard mamalian bone consists repeating units called Harvesiansystems.

Each system has concentrate layers of the mineralized matrix, depositedaround a central canal containing blood vessels and nerves that servicethe bone.

Once osteoblast become trapped in their own secretion , calledosteocytes.

The osteocytes are located in lacunae, space surrounded by the hardmatrix and connected to each other by long thin extensions.

Bone Tissue

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Cartilage Tissue

Has an abundance of collagenous fibers embedded ina rubbery matrix called chondroitin sulphate.

Chondroitin sulphate and collagen are secreted by

chondrocytes

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Cells confined to scattered spacescalled lacunae in the matrix.

The composite of collagenous fibersand chondroitin sulphate make cartilagea strong yet somewhat flexible supportmaterial.

Main locations ; nose, ears, the ringsthat reinforce the windpipe,caps on the

ends of some bones.

Cartilage Tissue

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Blood

Although blood functions differently from other

connective tissues, it does meet the criterion of having

an extracellular matrix called plasma.

The plasma consists of water, salts and a variety of

dissolved proteins

Suspended in plasma are two classes of blood cells,erythrocytes (red blood cells), leukocytes (white blood

cells) and cell fragments called platelets.

E th t

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Erythrocytes

o the most numerous blood cells (5 to 6 million per cubicmillimeter)

o the structure of the red blood cell is another excellent ofstructure fitting function.

o a human erythrocytes is

a biconcave disk, thinner

in the center than

at its edges.

o mammalian erythrocytes

lack nuclei an unusual

characteristic for living cells

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.

the major function of erythrocytes is to carryoxygen.

the small size of erythrocytes also suits their

function the smaller the cells, the greeter thetotal area of plasma membrane in a given volumeof blood.

the biconcave shape also adds to its surface area.

erythrocytes production occurs in the red marrowof bone

Erythrocytes

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Leukocytes

5 major types:

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their collective function is to fight infections in various

ways

monocytes and neutrophils are phagocytes which engulfand digest bacteria and debris from our own dead cells.

lymphocytes become specialized as B cells and T cells

which produce the immune response against foreignsubstances

Leukocytes

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the third cellular element of blood, platelets are fragments of cellsabout 2 3 m in diameter.

they have no nuclei.

originate as pinched off cytoplasmic fragments of large cells in

the bone marrow.

the function of platelets is in the important process of blood

clotting.

Platelets

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47455770 Biology Sem1 Chap1