Lecture 12: Animal Tissues

(3) Connective Tissues(3) Connective Tissues• Connective tissue functionsConnective tissue functions:: - - They mainly to bind They mainly to bind تربطتربط and support and support تدعمتدعم other tissues.other tissues.

• Structure:Structure:– Connective tissues have a population of cells scattered Connective tissues have a population of cells scattered مبعثرةمبعثرة

through an extracellular matrixthrough an extracellular matrix الخلوي بين الخلوي الوسط بين .. الوسط

– The matrix generally consists of fibers The matrix generally consists of fibers أليافأليافthat may be that may be liquid, jellylike, or solid.liquid, jellylike, or solid.

– In most cases, the connective tissue cells secrete the matrix.In most cases, the connective tissue cells secrete the matrix.

– The matrix may be The matrix may be solidsolid (as in bone), (as in bone), softsoft (as in loose connective (as in loose connective

tissue), or tissue), or liquidliquid (as in blood). (as in blood).

Lecture 12: Lecture 12: Animal TissuesAnimal Tissues

There are three kinds of connective tissues fibers, which are all proteins:

a)- Collagenous fibers (a)- Collagenous fibers (whitewhite) ) األلياف الكولالجيناأللياف الكولالجين:: Are made of Are made of collagencollagen and non-elastic and non-elastic غير مرنةغير مرنة

b)- Elastic fibers (b)- Elastic fibers (YellowYellow) ) األلياف المرنةاأللياف المرنة:: Are long threads of Are long threads of elastinelastin, which provide a rubbery quality., which provide a rubbery quality.

c)- Reticular fibers c)- Reticular fibers األلياف الشبكيةاأللياف الشبكية:: Are very thin and branched, and composed of Are very thin and branched, and composed of collagencollagen. It joins . It joins

connective tissues to adjacent tissues.connective tissues to adjacent tissues.

Types of connective tissues fibersTypes of connective tissues fibers

The major types of connective tissues in The major types of connective tissues in vertebrates are:vertebrates are:

A)- Loose connective tissueA)- Loose connective tissueالفجوي , , B)- Adipose connective tissueB)- Adipose connective tissueالدهني , , C)- Fibrous connective tissueC)- Fibrous connective tissueالليفي , ,

D)- CartilageD)- Cartilageالغضروف , , E)- BoneE)- Boneالعظم , ,

F)- BloodF)- Bloodالدمالدم ..Each has a structure correlated with its specialized Each has a structure correlated with its specialized

function.function.

Types of connective tissuesTypes of connective tissues

ضامة ضامة أنسجة أنسجة أصيلةأصيلة

هيكلية هيكلية أنسجة أنسجة

وعائية وعائية أنسجة أنسجة

A.A. Loose connective tissueLoose connective tissue النسيج النسيج

:: الضام الفجويالضام الفجوي - - Binds epithelia to underlying tissues and Binds epithelia to underlying tissues and

functions a holding organs in place.functions a holding organs in place. - It has all three fiber types.- It has all three fiber types.1.1. FibroblastsFibroblasts ليفية ليفية خاليا :خاليا

secrete the protein ingredients of the extracellular fibers.

2.2. Macrophages Macrophages خاليا خاليا are amoeboid : بلعميةبلعميةcells that engulfing bacteria and the debris of dead cells by phagocytosis.

- It composes of two cell types:

AA

BB

B.B. Adipose tissueAdipose tissueالنسيج الدهنيالنسيج الدهني :: It is a specialized form of loose connective It is a specialized form of loose connective

tissues that store fat in tissues that store fat in adipose cellsadipose cells خاليا دهنيةخاليا دهنية distributed throughout the matrix.distributed throughout the matrix.

•Adipose tissue Adipose tissue stores stores fuelfuel as fat molecules. as fat molecules.

•Each adipose cell Each adipose cell contains a large fat contains a large fat droplet that swells droplet that swells when fat is stored and when fat is stored and shrinks when the body shrinks when the body uses fat as fuel.uses fat as fuel.

Functions:Functions:

CC

C.C. Fibrous connective tissueFibrous connective tissueالنسيج الضام الليفيالنسيج الضام الليفي :: - It is dense, due to its large number of It is dense, due to its large number of collagenous collagenous

fibers.fibers.- The fibers are organized into parallel bundles making - The fibers are organized into parallel bundles making

it strong.it strong.

This type of connective This type of connective tissue tissue attaching attaching muscles to bonesmuscles to bones, and , and joining bones to bonesjoining bones to bones at joints.at joints.

Functions:Functions:

DD

D.D. Cartilage Cartilage الغضروفالغضروف (Skeletal Tissue): It has an abundance of collagenous fibers embedded It has an abundance of collagenous fibers embedded

in a rubbery matrixin a rubbery matrix

ChondrocytesChondrocytes الخاليا الخاليا helps making helps making ::الغضروفيةالغضروفيةcartilage flexible cartilage flexible support material.support material.

We have cartilage We have cartilage in nose, ears, and in nose, ears, and vertebral disks.vertebral disks.

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E.E. BoneBoneالعظمالعظم (Skeletal Tissue):The skeleton supporting most vertebrates is made of The skeleton supporting most vertebrates is made of

bonebone, a mineralized connective tissue. This bone , a mineralized connective tissue. This bone ccontains osteoblastsالخاليا العظمية that deposit a matrix of collagen.

•Bone is harder than Bone is harder than cartilage.cartilage.

•Hard mammalian Hard mammalian bones consists of bones consists of repeating units called repeating units called osteonsosteons عظمية عظمية محافظ محافظ(Haversian system).(Haversian system).

•Each osteon has a Each osteon has a central canalcentral canal containing blood containing blood vessels and nerves vessels and nerves that service the that service the bone.bone.

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F.F. BloodBloodالدمالدم (Vascular Tissue): Functions differently from other connective tissues, Functions differently from other connective tissues,

but it does have an extensive extra-cellular matrix.but it does have an extensive extra-cellular matrix. The matrix is a liquid called plasma, consisting of water, salts, The matrix is a liquid called plasma, consisting of water, salts,

and a variety of dissolved proteins.and a variety of dissolved proteins.

Types of blood cells are: Types of blood cells are: 1.1. ErythrocytesErythrocytes (red blood (red blood

cells), cells),2.2. LeukocytesLeukocytes (white blood (white blood

cells) cells) 3.3. PlateletsPlatelets..

Functions of cells:Functions of cells:• Red cells carry oxygen.Red cells carry oxygen.• White cells function in White cells function in

defense against microbes.defense against microbes.• Platelets help in bloodPlatelets help in blood

clotting.clotting.

4.4. Nervous tissueNervous tissue:: Senses stimuli and transmits signals from Senses stimuli and transmits signals from

one part of the animal to another.one part of the animal to another. The functional unit of nervous tissue is the The functional unit of nervous tissue is the neuronneuron, or , or

nerve cell.nerve cell. It consists of a It consists of a cell bodycell body and two or more extensions, and two or more extensions,

called called dendritesdendrites and and axonsaxons..

•Dendrites Dendrites transmit nerve impulsestransmit nerve impulses from their tips toward the rest of the from their tips toward the rest of the neuron.neuron.

•Axons Axons transmit impulses toward transmit impulses toward another neuron or toward an another neuron or toward an effectoreffector, such as a muscle cell., such as a muscle cell.