7.2The respiratory structures and

breathing mechanisms in humans and animals

Prepared byAzneezal Ar-Rashid

6 October 2009

Curious to know about..

• Protozoa

• Insects

• Fish

• Amphibian

• Human?

Respiratory structure of organisms

Organism Respiratory structure

Human Lungs

Protozoa Plasma membrane

Fish Gills

Insect Tracheal system

Amphibian Lungs

Skin

Mouth

Protozoa, eg : Amoeba sp., Paramecium sp.

• Unicellular– Does not need any special respiratory structure

• Plasma membrane– Serves as its respiratory surface

• Very small in size– Has a relatively LTSA (large total surface area)

• Body surface is always moist– It lives in the pond and lake, to allow gases to dissolve easily

• Simple diffusion– Takes place quickly, across the thin plasma membrane

Amoeba BreathingDid you know?

Because amoeba is so small,

the surface area of its cell membrane is very large compared with the

small volume of its cytoplasm.

The demands of the respiratory processes

in the cytoplasm can

therefore be met by simple diffusion of

carbon dioxide between the cytoplasm and the surrounding water. Oxygen diffuses in

and carbon dioxide diffuses out.

carbon dioxide

oxygenmaximum distance for diffusion is about 0.1mm

Paramecium sp.

How about insects?Insect Internal Structures

Insects eg : bee, grasshopper

• Special respiratory structure• Tracheal system

– Network of air tubes called trachea• Trachea

– Wall of each trachea is lined with ring of chitins, to prevent it from collapsing

– Open to the outside through 10 pairs of tiny holes called spiracles• Spiracles

– Present along the sides of the thorax and abdomen • Valves

– Each spiracle has valves, which open or close to allow the air moving in or out of the body

• Tracheoles– Each trachea branches into many smaller tubes called tracheoles– Numerous tracheoles provide big surface area– Go deep into the muscle tissues

Insects

• The breathing system in insects consists of a series of tubes called tracheae.

• The tracheae connect to the atmosphere by openings called spiracles. Air diffuses through the spiracles and tracheae to all parts of the body supplying the organs directly with air.

Insects

• The tracheae branch repeatedly until they end as very fine, thin-walled tubules through which oxygen and carbon dioxide can diffuse freely into and out of the tissues

Breathing mechanisms of insects

• Rhythmic – Rhythmic contractions & expansion of the

abdominal muscles cause the air to move into and out of the trachea, through the spiracles

• During inhalation– Abdominal muscles relax– Valves of the spiracles are open– Air pressure decreases

• During exhalation– Abdominal muscles contract– Air pressure increases, in the trachea– Forces the air out, through spiracles

trachea

spiracles

Diagram of insect tracheal system

Cockroach

spiracles

Tracheal supply to muscle tissue

tracheaspiracle

muscle

tracheolefluid

rings of chitin

Caterpillar

spiracles

Fisheg : tilapia (tropical fish)

Fish gills Gill filament

Gill bar

There are usually 4 gills on each side

Fish Gill Filaments

The thousands of fine branches on each filament expose a large surface area to the water. Blood circulates in the filament branches and is separated from the water by a thin

epithelium so that oxygen and carbon dioxide diffuse through easily

Respiratory Flow in Fish

mouth gills

Breathing current

• Water is taken in through the mouth, passes over the gills and is expelled via the operculum.

• Movements of the mouth floor and operculum create the current and the ‘valves’ (skin flaps) maintain a one-way flow

How aboutamphibians?

Frog

The frog has a

moist skin

Toad

nostrilWater surface

Buccal cavity

Frog

• Breathe through :– Skin– Mouth– Lungs

• Amphibia are vertebrates, represented in the UK by frogs and toads.

• Amphibia can survive both on land and in water. • In water they obtain oxygen by absorbing it

through their skin. • On land they can breathe through their skin but

they also use their lungs. • Although, in the UK, amphibia can spend a great

deal of time on land, they have to return to water to reproduce

Breathing mechanisms

• The frog draws air in through its nostrils and pumps it into the lungs by movements

of its mouth floor.

Body temperature. Amphibia are often described as ‘cold-blooded’ but, in fact, their temperature varies with that of their surroundings.

The adaptations of the skin for gaseous exchange in water and on land

• Thin– Their skin is thin– Very permeable

• Moist– It is kept moist with secretions from its mucus

glands

• Blood capillaries– Rich supply of blood capillaries

The adaptations of the mouth for gaseous exchange in water and on land

• Large buccal cavity

• Blood capillaries

• Muscular floors – Act as a pump to suck in air and to pump out

the air alternately

• Two lungs• Elastic, connected to the mouth by an opening

called glottis• Folded

– The inner wall of the lungs are folded, to increase the surface area for gaseous exchange

• Moist– Wall of the lungs are moist, to enable fast diffusion

• Blood capillaries

The adaptations of the lungs for gaseous exchange in water and on land

Breathing mechanisms of the frog

• Inhalation

• Exhalation

Inhalation

• Mouth and glottis are close, nostrils are open, buccal cavity lowers

• Low pressure in the buccal cavity occurs, causes the air from the outside to flow in through the nostrils

• The nostrils close, the glottis open and the buccal cavity rises

• The increased air pressure forces air from the cavity into the lungs through glottis

• Lungs become inflated, when air is pushed in from the buccal cavity

Exhalation

• Lung muscles contract

• Air is pushed out through nostrils

• Abdominal muscles and the elasticity of the lungs help to exhale the air

• This method is called positive pressure

Did you know?

• The lungs of frogs are less efficient as compared to the human

• They do not have ribcage

• No diaphragm, to help in the contraction of the lungs

• Only by pumping action– Of the muscula floor of buccal cavity to inhale

and exhale through the nostrils

Credit & million of thanks to

http://www.biology-resources.com/

Thanks to Dr D G Mackean

Whizz Thru Biology – Oxford Fajar (2009)