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THE RESPIRATORYSTRUCTURE &BREATHING MECHANISMIN HUMAN ANDANIMALS

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INTRODUCTION

Movement of the gases betweenrespiratory surfaces & externalsurfaces is entirely by diffusionThe respiratory surfaces are adaptedfor maximum gases exchange byincreasing the total surface area.The larger the respiratory surface area,the higher the rate of gas diffusion.

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CHARACTERISTIC OF RESPIRATORYSURFACES OF GASES EXCHANGE

(a) Large total respiratory surface area- branched, folded & numerous inuantity- !mall in si"e

#b) Moist $espiratory !urface- To facilitate gases diffusion

#c) Thin wall of respiratory surfaces- one cell thic%

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UNICELLULAR MICROORGANISM( Amoeba Sp .)

ery small in si"eThe total surface area-volume is large'xygen diffuse into the cell & (arbonioxide diffuse out of the cell throughthe plasma membrane down theconcentration gradient

*o special respiratorystructure

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INSECTS

TRACHEAL SYSTEM

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TRACHEAL SYSTEM

(onsist of a networ% of air tubes calledas tracheae which open to the outsidethrough small pores called spiracles.

+ pairs of spiracles on the thorax andabdomenach spiracles is protected by valves

which control the opening & closing ofthe spiracles.

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TRACHEAL SYSTEM

Each tracheae is supported by chitin rings toprevents the air tube from collapsingThe tracheae branches into finer tubes called

tracheoles which are in direct contact withthe insects tissues & organsases exchange occurs between tracheoles

& cells by diffusionLarger insects such as grasshopper have airsacs to speed up the movement of gases to& from the insects body

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The Adaptat !" !# T$a%he! e'F!$ Ga'e' E %ha" e

*umerous & very fine tracheolesMoist tracheoles walls

Thin epithelial cells of tracheoles

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BREATHING MECHANISM OFINSECTS

INHALATION:

The abdominal muscle relax and thevalve of spiracles open.The pressure in trachea decrease/ir is forced into the body throughthe spiracles.

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BREATHING MECHANISM OFINSECTS

EXHALATION:

The abdominal muscle contract

The pressure in tracheae increase.The air is forced out of the bodythrough spiracles

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FISH(GILLS)

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RESPIRATORY STRUCTURES

!peciali"ed respiratory structurescalled gills0 pairs of gills which are covered byoperculumach gill is composed of filamentswhich are supported by gill arch

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The filaments have numerous thin-walled lamellae to maximise the surface area for gasesexchangeThe gill filaments have thin membrane & rich

supply of blood capillaries to facilitate efficientgases exchange

RESPIRATORY STRUCTURES

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Efficiency of gases exchange is enhancedby the countercurrent exchangemechanismWater flows over the gills in one direction& the blood flows in the opposite direction

1ater flows

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"reathing mechanism of fish is helped byventilation (combination of movement ofoperculum and the floor of the mouth#

$ish ventilate by swimming and byopening & closing the operculum to drawswater into the mouth & passes the gills

BREATHING MECHANISM

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2nhalation #3lows of water into the mouth)

Mouth open % the floor of mouth is loweredcaused the volume of buccal cavity increasesressure in the mouth cavity decreases &outside increases!'igher outside pressure causes the operculumclose & water enters the mouth

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xhalation #3lows of water through the gills)Mouth closes % the floor of mouth is raisedcaused the volume of buccal cavitydecreases4ressure in the mouth cavity increases &outside decreases!1ater flows through the lamellae & gaseousexchange occur between the blood capillaries& water!'perculum open due to higher inside pressure& water flows out

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BREATHING MECHANISM

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AMPHIBIAN

mphibian breathe through the s%in,mouth & lungs.)n the water% the frogs s*in functions as

the respiratory surfaces for gaseousexchange!/daptation of s%in5

+ thin s*in+ moist s*in+ ,upplied with many blood capillaries

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RESPIRATORY STRUCTUREOF AMPHIBIAN

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RESPIRATORY STRUCTURE

The lungs consist of a pair of thin-walled sacs connected to the mouth through an openingcalled glottis !The membranes lungs are thin, moist &

covered by networ* capillaries.The lungs of frogs are not as efficient as thelungs of human because they are not e uipped with a rib cage - diaphragm'owever% they have strong muscular walls ofbucco+pharyngeal floor!

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BREATHING MECHANISM

2*6/L/T2'*5"ucco+pharyngeal walls lowered% glottisclosed!ressure inside mouth decreases% air isforced into the mouth through nostrils!.ostril closes & bucco+pharyngeal walls

raises up& glottis open ir passes to the lungs & gaseousexchange occurs

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76/L/T2'*5Lungs muscle contract% air is expelledfrom the lungs,ome of air escapes through the nostrilsThe rest mixes with the air in the bucco+pharyngeal cavity

BREATHING MECHANISM

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HUMANS RESPIRATORYSYSTEM

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The trachea is supported by rings ofcartilage (/+shaped# to prevent the tube

from collapsingThe lower end of trachea divides into 0tubes called bronchi.The bronchi branches repeatedly intosmaller tubes called bronchioles !Each bronchioles ends in a cluster of airsacs called alveoli.

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)nner surface of alveoli is lined with a layerof moist epithelial cellsuter surface of alveoli is covered by anetwor* of blood capillaries

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BREATHING MECHANISM

)nvolves combinedaction of theintercostals muscleand diaphragm!0 sets of intercostalsmuscle1+ external

intercostals muscle+ internalintercostals muscle

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"reathing involves the alternate process ofinhalation & exhalation

2*6/L/T2'*5+ xternal intercostals muscle contract &)nternal intercostals muscles relax+$ib cage move upwards & outwards+ iaphragm contracts & flatten at the sametime+ olume of thoracic cavity increases

+ 'igher atmospheric pressure outside causesthe air to rush in through the nostrils!

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E2' L T) .1+ xternal intercostals muscle relax &)nternal intercostals muscles contract+$ib cage move downwards & inwards+ iaphragm relaxes & curves upward atthe same time+ olume of thoracic cavity decreases

+ 'igher pressure in alveoli inside causesthe air to rush out through the nostrils!

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