Copy of Respiratory System

8/12/2019 Copy of Respiratory System

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Respiration - process of obtaining oxygenfrom the external environment & eliminatingCO2.

Two Types of Respiration

1. External respiration - oxygen andcarbon dioxide exchanged between theexternal environment & the body cells.

- takes place in fetal membranes, at

the surface of the skin, in gills and in lungs.2. Internal Respiration essential gases

are then exchanged with the tissues in therespective capillary beds.


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Efficiency of external respiration is increased

by providing a large surface of contact

between the water or air and the blood, andby maintaining the contact of each blood cell

with the medium for an adequate time.

Ventilation pumping of water in gills and of

air in lungs.Common Respiratory Organs

1. Gills

2. Cutaneous Respiration

3. Larval Gills

4. Swim Bladder and Lungs


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Basic structure of internal gills is similar for all

fishes:

Each gill bar consists of a part of a visceral skeleton,

blood vessels derived from the corresponding aortic

arch, cranial or cervical nerves intrinsic branchialmuscles and the related epithilium

Bars may or may not be extended by gill septa

Most bars carry one or more rows of gill rakers

Each gill bar bears two rows of gill filaments calledprimary filaments that is strengthen by fine skeletal

gill rays

a bar with filaments forms a partition between

adjacent gill chambers


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Exchange of oxygen and carbon dioxide between blood and

water.

Excretion and osmoregulation (Bony Fishes)

Gills of freshwater bony fishes admit water and absorb

salts while gills of marine bony fishes pass water and

excrete salts.

Types of Internal Gills

Pouched gills (Agnathans)

- gill filaments are arranged over the surface of discrete,

pouch like gill chambers

Septal gills (Elasmobranchs)

- Gill chambers tend to be longer to communicate more

widely with the pharynx internally and externally

through the vertical gill slits instead of pores.


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Opercular gills (Osteichthyes)

- septa are usually shorter that their

filaments or even absent so that the gill barsremain to anchor the gill filaments.

- gills of teleost are the most efficientrespiratory organ.

Types of Gill Bars Holobranch if it bears anterior and

posterior rows of filaments

Hemibranch if it bears on the surface only

Pseudobranch - if the filaments on theposterior surface of the mandibular arch aremodified to serve a non respiratoryfunction.


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Present in protochordates , important in food

getting, connection with a ciliated groove, the

endostyle.

Serve as respiration and in food getting

(amphioxus).Number of gills slits is greater in lower forms and

lesser in higher forms:

- Amphioxus (140+) - Modern fishes (5)

- Hagfishes (7 to 14 pairs) - Teleosts (4)

- Lampreys ( 6 pairs) - Amphibians (3)

- Sharks ( 5 slits)


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Development of internal gills is related to the

pharynx.Pharynx portion of the foregut that lies between

the developing oral cavity and the esophagus lined byendoderm.

In agnatha, the first pharyngeal pouch becomes a

typical gill chamber. In other fishes, the first pharyngeal pouch is lost or

is reduced in size and in function.

In Tetrapods, the first pouch becomes the cavity ofthe middle ear, most posterior pouches form gill

chambers.

Some larval amphibians lose their pouch- likecharacter after contributing glandular andlymphatic tissues from their epithelial linings.


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Ostracoderms took water into the pharynxthrough the mouth, passed it through the gillpouches and expelled it from the headthrough the branchial pores.

Cyclostomes also expel water through

branchial pores but water enters and leavesthe gill pouches from the external branchialpores

Elasmobranchs draw water into the pharynx

through the mouth and spiracles. Some active teleosts swim continuously and

water constantly enters through the gills bythe swimming process.


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Internal organs that are filled with air andfunction primarily in respiration.

Gas Bladders Internal organs that are filledwith gas but are not respiratory in function.

more than 20 genera of Bony fishes are habitual

air breathers In anurans and caecilians, the lungs develop

from the paired lateral evaginations of the guttube.

The lungs of amniotes develop from a single,ventral evaginations of paired areas of endodermlocated posterior to the pharyngeal pouches.

Lungs evolved during the Devonian period


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Anura have large but short lungs, the wallshave several partitions to provide a totalrespiratory surface of 1cm/g body weight butvarying inversely with the effectiveness of

cutaneous respiration Apoda usually retain only the right lung,

labyrinthodonts had the most advanced lungsof the class resembling those of reptiles

Urodela have simpe, long and slender sacswith smooth walls; most species have losttheir lungs entirely, skin or gills servingrespiratory function instead.


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Lungs of Reptiles

- Partitions can be sparse or dense, shallow or deep,

evenly or unevenly distributed.

- trachea and bronchi are larger and supported bycartilaginous rings

- each bronchus enters the lungs near the middle or

anterior end but not at the apex

- larynx is consists of cricoid and arytenoids cartilages that

are joined by the hyoid apparatus. Lungs of Mammals (More efficient)

- lobes may be absent but usually there are at least two

lobes on the left and three lobes on the right.

-smooth muscles and mucous glands are present in the

walls

- the trachea divides into right and left primary bronchi

that divides into smaller bronchi which further divide into

numerous membranous bronchioles.

- these nonciliated brochioles open into alveolar ductsystem which are clusters of 10 to 30 alveoli, where actual


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May be located high in the body cavity to

enable the fish to remain upright withoutexpending muscular effort.

Gas bladders may be long or short, straightor curved, simple or partitioned into two or

three lobes. Physostomous If the gas bladder functions

as a lung. Joined by the pneumatic duct.

Physoclistous if the gas bladder is not

respiratory in function. No pneumatic duct physoclist bladder => hydrostasis

=> sound production

=> pressure reception


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Air breathing Actinopterygian fishes uses two

cycle sequence;

- the pharynx expands drawing expired gas

from the lungs into the buccal cavity- pharynx contracts forcing this gas to exit

through the open mouth of gill chambers

- fresh air enters the buccal cavity through

the mouth- with mouth closed, the pharyx force the

air into the lungs.


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Anurans are pulse pump breathers

Ventilation by aspiration is more efficient

- inspiration is by negative pressure created inthe thoracic or abdominal cavities.

- expiration is either passive or results from

constriction of these cavities.

- one cycle system with simpler but efficient

Labyrinthodonths => first aspiration breathers

- breathing was interrupted by locomotion just

like in lizards.Crocodilians have diaphragmatic muscle which

pulls the liver toward the pelvis sucking the

lungs that causes inhalation.


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Turtles inhale when muscles crossing the limb

apertures of the shell enlarge the internal

cavity.

Inhalation and exhalation of snakes is forced

by the action of muscles inserted on the ribs

and ventral skin.

Respiration of Birds involves differentmuscles;

- sternum is actively rocked downward and

forward for inspiration and is raised for

expiration. Lungs of mammals are inflated by the

negative pressure resulting from the

contraction of the dome shaped diaphragm

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