The document describes respiration in several organisms. It discusses: 1) Respiration in earthworms, which occurs through their moist skin via cutaneous respiration. Oxygen diffuses into their bloodstream and carbon dioxide diffuses out. 2) Respiration in spiders, which uses book lungs - pairs of sac-like structures containing many thin plates that increase surface area for gas exchange. 3) Respiration in bony fish like rohu, which uses gills - feathery structures in the gill slits that are highly vascular and divided into lamellae to efficiently uptake oxygen from water pumped over them by the operculum.

1. 2.1
2.1 Comparative Study of
Respiratory Organs (Structure & Function)
Dr. Prabhakar R. Pawar
Associate Professor in Zoology,
Mahatma Phule A. S. C. College, Panvel,
Dist. - Raigad, Navi Mumbai – 410 206
prpawar1962@gmail.com

2. Respiration
 Respiration is a biochemical process in which cells of an
organism obtain energy by combining oxygen & glucose,
resulting to release of carbon dioxide, water & ATP.
 Respiration is a metabolic process common in all living
beings.
 Respiration includes:
 Breathing.
 Transport of gases.
 Oxidation of food to liberate carbon dioxide & energy.
 Respiration is a biochemical process in which cells of an
organism obtain energy by combining oxygen & glucose,
resulting to release of carbon dioxide, water & ATP.
 Respiration is a metabolic process common in all living
beings.
 Respiration includes:
 Breathing.
 Transport of gases.
 Oxidation of food to liberate carbon dioxide & energy.

3. Processes of Respiration
 Respiration has two essential processes:
 External respiration/Breathing: A mechanical process of
exchange of respiratory gases (oxygen & carbon dioxide)
between the organism & surroundings.
 Internal respiration/Cellular or Tissue respiration: A
chemical process in which food is oxidized within the cells
to liberate free energy, carbon dioxide & water.
 Internal respiration takes place in the cytoplasm &
mitochondria of eukaryotic cells.
 Respiration has two essential processes:
 External respiration/Breathing: A mechanical process of
exchange of respiratory gases (oxygen & carbon dioxide)
between the organism & surroundings.
 Internal respiration/Cellular or Tissue respiration: A
chemical process in which food is oxidized within the cells
to liberate free energy, carbon dioxide & water.
 Internal respiration takes place in the cytoplasm &
mitochondria of eukaryotic cells.

4. Types of Respiration
• Respiration is of 2 types:
• Direct respiration:
 Exchange of gases between the environment & body
cells without the aid of respiratory organ or blood.
 Exchange of gases occur by diffusion across the body
surface.
 Examples: Amoeba, Hydra, Flat worms etc.
• Indirect respiration
 Involves special respiratory surfaces or organs like skin,
buccopharyngeal lining, gills & lungs and blood for
circulation of respiratory gases in the body.
 The body surfaces were impermeable for exchange of
gases, specialized structures were developed for gaseous
exchange.
• Respiration is of 2 types:
• Direct respiration:
 Exchange of gases between the environment & body
cells without the aid of respiratory organ or blood.
 Exchange of gases occur by diffusion across the body
surface.
 Examples: Amoeba, Hydra, Flat worms etc.
• Indirect respiration
 Involves special respiratory surfaces or organs like skin,
buccopharyngeal lining, gills & lungs and blood for
circulation of respiratory gases in the body.
 The body surfaces were impermeable for exchange of
gases, specialized structures were developed for gaseous
exchange.

5. Characteristics of Respiratory surfaces
 For efficient gaseous exchange, respiratory surface must
possess the following characteristics:
• Thin.
• Permeable to gases like oxygen & carbon dioxide.
• Moist.
• Highly vascular.
• Have large surface area.
• Must be in direct contact with the air or water.
 For efficient gaseous exchange, respiratory surface must
possess the following characteristics:
• Thin.
• Permeable to gases like oxygen & carbon dioxide.
• Moist.
• Highly vascular.
• Have large surface area.
• Must be in direct contact with the air or water.

6. 2.1.1 Respiration in Earthworm
2.1.1 Respiration in Earthworm
 Entire body surface performs
respiration.
 Cutaneous respiration - Skin
acts as respiratory surface.
 Skin - Highly vascular, always
kept moist by secretions of
integument glands, & coelomic
fluid.
 Exchange of gases through the
moist skin which is permeable to
respiratory gases.
 Entire body surface performs
respiration.
 Cutaneous respiration - Skin
acts as respiratory surface.
 Skin - Highly vascular, always
kept moist by secretions of
integument glands, & coelomic
fluid.
 Exchange of gases through the
moist skin which is permeable to
respiratory gases.

7. 2.1.1 Respiration in Earthworm
2.1.1 Respiration in Earthworm
 Blood contains haemoglobin
pigment dissolved in plasma.
 Atmospheric oxygen is taken up by
haemoglobin & is converted to
oxyhaemoglobin.
 Oxyhaemoglobin is circulated to
tissues where oxygen tension is
low.
 Oxyhaemoglobin breaks up to
release oxygen & haemoglobin in
reduced state.
 Oxygen is used for oxidation of
food.
 Carbon dioxide released mixes in
the blood & is diffused out of the
body through moist skin.
 Blood contains haemoglobin
pigment dissolved in plasma.
 Atmospheric oxygen is taken up by
haemoglobin & is converted to
oxyhaemoglobin.
 Oxyhaemoglobin is circulated to
tissues where oxygen tension is
low.
 Oxyhaemoglobin breaks up to
release oxygen & haemoglobin in
reduced state.
 Oxygen is used for oxidation of
food.
 Carbon dioxide released mixes in
the blood & is diffused out of the
body through moist skin.

8. 2.1.2 Book lungs in Spider
2.1.2 Book lungs in Spider
 Respiratory organs of spider are of 2
types: trachea & book lungs.
 Some spiders have trachea, some
have book lungs & others have both,
trachea & book lungs.
 Book lungs:
 2 hairless patches on ventral side
of spider’s abdomen.
 Situated ventro-laterally & opens
on ventral surface.
 Each book lung consists of
compressed sac-like cavity called,
pulmonary sac.
 Pulmonary sac is lined by a cuticle.
 Sac is divided into pulmonary
chamber & atrial chamber.
 Respiratory organs of spider are of 2
types: trachea & book lungs.
 Some spiders have trachea, some
have book lungs & others have both,
trachea & book lungs.
 Book lungs:
 2 hairless patches on ventral side
of spider’s abdomen.
 Situated ventro-laterally & opens
on ventral surface.
 Each book lung consists of
compressed sac-like cavity called,
pulmonary sac.
 Pulmonary sac is lined by a cuticle.
 Sac is divided into pulmonary
chamber & atrial chamber.

9. 2.1.2 Book lungs in Spider
2.1.2 Book lungs in Spider
 Pulmonary chamber:
 Distal part of book lung.
 Oval chamber with about 150
vertical leaf-like lamellae/plates.
 Plates are filled with haemolymph
& are arranged parallel to each
other.
 Presence of air space between the
plates, which allows circulation of
air around the plates.
 Plates resemble like leaves of a
book, so respiratory organs of
spider are called as ‘book lungs’.
 Book lungs open into chambers
called, ‘atria’.
 Pulmonary chamber:
 Distal part of book lung.
 Oval chamber with about 150
vertical leaf-like lamellae/plates.
 Plates are filled with haemolymph
& are arranged parallel to each
other.
 Presence of air space between the
plates, which allows circulation of
air around the plates.
 Plates resemble like leaves of a
book, so respiratory organs of
spider are called as ‘book lungs’.
 Book lungs open into chambers
called, ‘atria’.

10. 2.1.2 Book lungs in Spider
2.1.2 Book lungs in Spider
 Atrial chamber:
 Small, dorsoventrally compressed
air chamber.
 Forms proximal part of book lung.
 Opens outside through one or
several slits called ‘spiracles’.
 Roof is perforated by minute
openings called, ‘ostia’.
 Ostia communicate with the inter-
lamellar spaces of the pulmonary
chamber.
 Inspiration & expiration of the air
in the book lungs is controlled by
action of dorso-ventral & atrial
muscles.
 Atrial chamber:
 Small, dorsoventrally compressed
air chamber.
 Forms proximal part of book lung.
 Opens outside through one or
several slits called ‘spiracles’.
 Roof is perforated by minute
openings called, ‘ostia’.
 Ostia communicate with the inter-
lamellar spaces of the pulmonary
chamber.
 Inspiration & expiration of the air
in the book lungs is controlled by
action of dorso-ventral & atrial
muscles.

11. 2.1.3 Respiration in Bony fish:
2.1.3 Respiration in Bony fish: Rohu (
Rohu (Labeo
Labeo rohita
rohita)
)
 Labeo rohita (Rohu) is a
freshwater bony fish.
 Gill slits in bony fishes are
covered by a lid called,
operculum.
 Bony fish breathe by moving
water across their gills using
operculum.
 Operculum acts as a ‘trapdoor’ &
pumps the water across the gills.
 Operculum is supported by
branchiostegal rays, which acts as
a one way valve.
 Buccal cavity has 2 oral valves
which allows water to enter the
mouth but not to leave it.
 Labeo rohita (Rohu) is a
freshwater bony fish.
 Gill slits in bony fishes are
covered by a lid called,
operculum.
 Bony fish breathe by moving
water across their gills using
operculum.
 Operculum acts as a ‘trapdoor’ &
pumps the water across the gills.
 Operculum is supported by
branchiostegal rays, which acts as
a one way valve.
 Buccal cavity has 2 oral valves
which allows water to enter the
mouth but not to leave it.

12. 2.1.3 Respiration in Bony fish:
2.1.3 Respiration in Bony fish: Rohu (
Rohu (Labeo
Labeo rohita
rohita)
)
 Each gill is supported by a bony
structure i. e. gill arch.
 Gill arch provides support to hold
many comb-like structures,
called gill filaments.
 Gill filaments extend horizontally
from the gill arches.
 Each gill filament is further
divided into minute primary &
secondary lamellae.
 Secondary lamellae are highly
vascular & increase the surface
area for gaseous exchange.
 Bony projections attached to the
gill arches are called gill rakers,
which help in the fish’s feeding.
 Each gill is supported by a bony
structure i. e. gill arch.
 Gill arch provides support to hold
many comb-like structures,
called gill filaments.
 Gill filaments extend horizontally
from the gill arches.
 Each gill filament is further
divided into minute primary &
secondary lamellae.
 Secondary lamellae are highly
vascular & increase the surface
area for gaseous exchange.
 Bony projections attached to the
gill arches are called gill rakers,
which help in the fish’s feeding.

13. 2.1.3 Mechanism of Respiration in Rohu
2.1.3 Mechanism of Respiration in Rohu
 Lateral movement of operculum
brings about respiration.
 When operculum is raised, gill
apertures are closed & water
enters into the mouth by suction
action of oral valves.
 When operculum is lowered,
pressure on water in buccal
cavity & pharynx increases.
 As a result, oral valves are
closed, branchiostegal
membranes open & water is
forced out over the gills and out
of the opercular cavity.
 Exchange of gases takes place in
the gill lamellae.
 Lateral movement of operculum
brings about respiration.
 When operculum is raised, gill
apertures are closed & water
enters into the mouth by suction
action of oral valves.
 When operculum is lowered,
pressure on water in buccal
cavity & pharynx increases.
 As a result, oral valves are
closed, branchiostegal
membranes open & water is
forced out over the gills and out
of the opercular cavity.
 Exchange of gases takes place in
the gill lamellae.

14. Accessory Respiratory Organs of Fishes
 Accessory respiratory organs (ARO) are present in some
fishes along with gills.
 Found in fishes living in shallow & stagnant water and also
in hill stream fishes, where the streams dry up in summer.
 ARO enable the fish to remain out of the water for some
time or tolerate oxygen deficient water for some time.
 ARO originate from pharyngeal/branchial cavities & are
rarely found in marine fishes.
 ARO are sac like diverticulum, called as ‘opercular lungs’.
 Examples: Anabas, Clarius etc.
 Accessory respiratory organs (ARO) are present in some
fishes along with gills.
 Found in fishes living in shallow & stagnant water and also
in hill stream fishes, where the streams dry up in summer.
 ARO enable the fish to remain out of the water for some
time or tolerate oxygen deficient water for some time.
 ARO originate from pharyngeal/branchial cavities & are
rarely found in marine fishes.
 ARO are sac like diverticulum, called as ‘opercular lungs’.
 Examples: Anabas, Clarius etc.

15. Accessory Respiratory Organ in Anabas
(Climbing perch): Labyrinthine organ
 Anabus has 2 specious sac like
structures in branchial cavity, called
as ‘suprabranchial chambers’.
 Epithelial lining of these chambers
increase the respiratory area.
 Each suprabranchial chamber
contain a special rosette structure
called, ‘labyrinthine organ’.
 Labyrinthine organ consists of
number of small concentric plates.
 Plates have wavy margins & are
covered with vascular gill-like
epithelium.
 Air enters into the chamber via the
buccopharyngeal opening & goes
out through the external gill slits.
 Entrance of buccopharyngeal
chamber is controlled by valves.
 Anabus has 2 specious sac like
structures in branchial cavity, called
as ‘suprabranchial chambers’.
 Epithelial lining of these chambers
increase the respiratory area.
 Each suprabranchial chamber
contain a special rosette structure
called, ‘labyrinthine organ’.
 Labyrinthine organ consists of
number of small concentric plates.
 Plates have wavy margins & are
covered with vascular gill-like
epithelium.
 Air enters into the chamber via the
buccopharyngeal opening & goes
out through the external gill slits.
 Entrance of buccopharyngeal
chamber is controlled by valves.

16. Accessory Respiratory Organ in Clarius :
Arborescent organ
 Clarius is a catfish found in Indian &
African rivers.
 Accessory respiratory organ of
Clarius is called ‘Arborescent organ’.
 Arborescent organ consists of a pair
of suprabranchial organs present
above the gills & are divided into 2
parts.
 The organ is supported by
cartilaginous internal skeleton,
covered by vascular epithelium &
vascular sac.
 Many gills are formed by joining of
gill filaments.
 Air is taken into the mouth
continuously & Clarius can live
outside the water for several hours
and move along dump grass.
 Clarius is a catfish found in Indian &
African rivers.
 Accessory respiratory organ of
Clarius is called ‘Arborescent organ’.
 Arborescent organ consists of a pair
of suprabranchial organs present
above the gills & are divided into 2
parts.
 The organ is supported by
cartilaginous internal skeleton,
covered by vascular epithelium &
vascular sac.
 Many gills are formed by joining of
gill filaments.
 Air is taken into the mouth
continuously & Clarius can live
outside the water for several hours
and move along dump grass.

17. 2.1.4 Respiration in Frog
2.1.4 Respiration in Frog
 Frog has 3 types of respiratory surfaces for exchange of
gases: skin, lining of mouth & lungs.
 Cutaneous respiration:
 Respiration using skin as respiratory surface.
 Occurs when the frog is under water or on land.
 Skin of frog: Thin, highly vascular & permeable to water.
 Oxygen is dissolved in the film of water covering the skin &
is absorbed by the blood capillaries of the skin.
 Haemoglobin from the blood enhances the absorption of
oxygen.
 When frog is out of water, mucus glands in the skin keep
the skin moist which helps to absorb the dissolved oxygen
from air.
 Frog has 3 types of respiratory surfaces for exchange of
gases: skin, lining of mouth & lungs.
 Cutaneous respiration:
 Respiration using skin as respiratory surface.
 Occurs when the frog is under water or on land.
 Skin of frog: Thin, highly vascular & permeable to water.
 Oxygen is dissolved in the film of water covering the skin &
is absorbed by the blood capillaries of the skin.
 Haemoglobin from the blood enhances the absorption of
oxygen.
 When frog is out of water, mucus glands in the skin keep
the skin moist which helps to absorb the dissolved oxygen
from air.

18. 2.1.4 Respiration in Frog
2.1.4 Respiration in Frog
 Buccopharyngeal respiration:
 Buccopharyngeal membrane acts as a respiratory surface.
 Buccopharyngeal respiration is predominant during rest.
 In buccopharyngeal respiration, mouth remains closed, air
is taken through the nostril & passed into the
buccopharyngeal cavity.
 Oxygen from the air, dissolves in the mucous & goes into
the blood.
 Carbon monoxide is expelled by raising the floor of
Buccopharyngeal cavity.
 Glottis remains closed to prevent entry of air in lungs.
 Buccopharyngeal respiration is the main form of breathing
at rest.
 Buccopharyngeal respiration:
 Buccopharyngeal membrane acts as a respiratory surface.
 Buccopharyngeal respiration is predominant during rest.
 In buccopharyngeal respiration, mouth remains closed, air
is taken through the nostril & passed into the
buccopharyngeal cavity.
 Oxygen from the air, dissolves in the mucous & goes into
the blood.
 Carbon monoxide is expelled by raising the floor of
Buccopharyngeal cavity.
 Glottis remains closed to prevent entry of air in lungs.
 Buccopharyngeal respiration is the main form of breathing
at rest.

19. 2.1.4 Respiration in Frog
2.1.4 Respiration in Frog
 Pulmonary respiration:
 Occurs with the help of pair of lungs.
 Pulmonary respiration occur occasionally
when need of oxygen is more.
 Lungs are thin walled sacs connected to
mouth through an opening i. e. ‘glottis’.
 Frog does not possess the trachea.
 Lungs: Delicate, thin walled, elastic sac
like structures covered by visceral
peritoneum.
 Inner surface of lungs have many
irregular & radially arranged folds.
 Space between two folds of inner
surface of lungs forms an ‘alveolus’.
 Alveoli are highly vascular & increases
the inner respiratory surface of lungs.
 Pulmonary respiration:
 Occurs with the help of pair of lungs.
 Pulmonary respiration occur occasionally
when need of oxygen is more.
 Lungs are thin walled sacs connected to
mouth through an opening i. e. ‘glottis’.
 Frog does not possess the trachea.
 Lungs: Delicate, thin walled, elastic sac
like structures covered by visceral
peritoneum.
 Inner surface of lungs have many
irregular & radially arranged folds.
 Space between two folds of inner
surface of lungs forms an ‘alveolus’.
 Alveoli are highly vascular & increases
the inner respiratory surface of lungs.

20. 2.1.4 Mechanism of respiration in frog
2.1.4 Mechanism of respiration in frog
 Air is drawn into & expelled out of the
body by action of buccal cavity muscles.
 Buccal cavity has 2 pairs of muscles:
sternohyal muscles & petrohyal
muscles.
 These muscles brings about rhythmic
lowering & raising of buccal cavity.
 By contraction of sternohyal muscles,
air comes in the buccal cavity through
the external nares.
 Tightening of jaws close the external
nares & air is trapped in the mouth.
 The glottis opens & air is pushed into
the lungs (inspiration).
 During expiration, carbon dioxide from
the lungs is expelled out of the body.
 Air is drawn into & expelled out of the
body by action of buccal cavity muscles.
 Buccal cavity has 2 pairs of muscles:
sternohyal muscles & petrohyal
muscles.
 These muscles brings about rhythmic
lowering & raising of buccal cavity.
 By contraction of sternohyal muscles,
air comes in the buccal cavity through
the external nares.
 Tightening of jaws close the external
nares & air is trapped in the mouth.
 The glottis opens & air is pushed into
the lungs (inspiration).
 During expiration, carbon dioxide from
the lungs is expelled out of the body.

21. 2.1.5 Respiration in Pigeon
2.1.5 Respiration in Pigeon
 Respiratory system is highly
developed to supply more oxygen for
aerial mode of life.
 Respiratory system is extensively
modified.
 Respiratory system has 2 unique
features:
 Presence of non-elastic, compact
& smaller size lungs.
 Possession of several air sacs to
increase functional efficiency.
 Respiratory system consists of
respiratory tract, the lungs & the air
sacs.
 Respiratory tract consists of nares,
nasal sacs, glottis, larynx, trachea &
syrinx.
 Respiratory system is highly
developed to supply more oxygen for
aerial mode of life.
 Respiratory system is extensively
modified.
 Respiratory system has 2 unique
features:
 Presence of non-elastic, compact
& smaller size lungs.
 Possession of several air sacs to
increase functional efficiency.
 Respiratory system consists of
respiratory tract, the lungs & the air
sacs.
 Respiratory tract consists of nares,
nasal sacs, glottis, larynx, trachea &
syrinx.

22. 2.1.5 Respiratory system of Pigeon
2.1.5 Respiratory system of Pigeon
 Nares & nasal sacs:
 Pair of slit like openings present
at the base of upper beak are
called, external nares.
 Nares are covered by a sensitive
pad of skin called cere.
 External nares open into the nasal
sacs which open into the pharynx
by internal nares.
 Glottis:
 Present near the base of the
tongue.
 Opens into a larynx, present at
the anterior part of trachea.
 Larynx opens into trachea.
 Nares & nasal sacs:
 Pair of slit like openings present
at the base of upper beak are
called, external nares.
 Nares are covered by a sensitive
pad of skin called cere.
 External nares open into the nasal
sacs which open into the pharynx
by internal nares.
 Glottis:
 Present near the base of the
tongue.
 Opens into a larynx, present at
the anterior part of trachea.
 Larynx opens into trachea.

23. 2.1.5 Respiratory system of Pigeon
2.1.5 Respiratory system of Pigeon
 Trachea:
 Long, cylindrical & flexible tube.
 Runs through the neck & present
ventral to the oesophagus.
 Supported by complete rings of
cartilage.
 Divides into two bronchi.
 Each bronchi enters into the lung of
its corresponding side.
 Syrinx:
 Sound producing organ of birds
present at the posterior end of
trachea where it divides into two.
 Presence of syrinx is a unique
characteristics of birds.
 Syrinx can dilate & acts as a
resonating chamber.
 Trachea:
 Long, cylindrical & flexible tube.
 Runs through the neck & present
ventral to the oesophagus.
 Supported by complete rings of
cartilage.
 Divides into two bronchi.
 Each bronchi enters into the lung of
its corresponding side.
 Syrinx:
 Sound producing organ of birds
present at the posterior end of
trachea where it divides into two.
 Presence of syrinx is a unique
characteristics of birds.
 Syrinx can dilate & acts as a
resonating chamber.

24. 2.1.5 Respiratory system of Pigeon
2.1.5 Respiratory system of Pigeon
 Lungs:
 One pair, bright red colour & spongy.
 Present in plural cavities.
 Bronchus enters into the lungs & is
known as pulmonary bronchus.
 Bronchus continues as a main trunk to
the distal end of the lungs & is known
as mesobronchus.
 Mesobronchus branches into
secondary bronchi.
 Secondary bronchi divides into tubes
with uniform diameter & are called
parabronchi.
 Parabronchi are branched fine tubules
or air capillaries.
 Parabronchi & air capillaries works as
a respiratory surface for gases
exchange.
 Lungs:
 One pair, bright red colour & spongy.
 Present in plural cavities.
 Bronchus enters into the lungs & is
known as pulmonary bronchus.
 Bronchus continues as a main trunk to
the distal end of the lungs & is known
as mesobronchus.
 Mesobronchus branches into
secondary bronchi.
 Secondary bronchi divides into tubes
with uniform diameter & are called
parabronchi.
 Parabronchi are branched fine tubules
or air capillaries.
 Parabronchi & air capillaries works as
a respiratory surface for gases
exchange.

25. 2.1.5 Respiratory system of Pigeon
2.1.5 Respiratory system of Pigeon
 Air sacs:
 Presence of air sacs is an important
feature of respiratory system of birds.
 Secondary bronchi pass through the
walls of lungs to form air sacs.
 Air sacs: Bladder-like, thin walled,
membranous, non-muscular & non-
vascular structures.
 Air sacs are present in communication
with pneumatic cavities of bones.
 9 air sacs of 5 different types are
present in Pigeon.
 Air sacs are accessory respiratory
organs used as reservoir of gases.
 Acts as balloons giving buoyancy
during flight.
 Air sacs:
 Presence of air sacs is an important
feature of respiratory system of birds.
 Secondary bronchi pass through the
walls of lungs to form air sacs.
 Air sacs: Bladder-like, thin walled,
membranous, non-muscular & non-
vascular structures.
 Air sacs are present in communication
with pneumatic cavities of bones.
 9 air sacs of 5 different types are
present in Pigeon.
 Air sacs are accessory respiratory
organs used as reservoir of gases.
 Acts as balloons giving buoyancy
during flight.

26. 2.1.5 Types of Air Sacs in Pigeon
2.1.5 Types of Air Sacs in Pigeon
 Interclavicular:
 Unpaired & median air sac of
large size.
 Has two ducts, one opening into
each lung.
 Each side of this sac gives off 2
extensions: clavicular air sac &
humeral air sac.
 Cervical:
 Paired air sacs present near the
base of the neck & in front of the
lungs.
 Each sac sends diverticula into
the cervical vertebra & the skull.
 Interclavicular:
 Unpaired & median air sac of
large size.
 Has two ducts, one opening into
each lung.
 Each side of this sac gives off 2
extensions: clavicular air sac &
humeral air sac.
 Cervical:
 Paired air sacs present near the
base of the neck & in front of the
lungs.
 Each sac sends diverticula into
the cervical vertebra & the skull.

27. 2.1.5 Types of Air Sacs in Pigeon
2.1.5 Types of Air Sacs in Pigeon
 Anterior thoracic:
 Paired & present at the ventral
side of lungs.
 Present in close contact with ribs.
 Posterior thoracic:
 Paired & overlap the posterior end
of the corresponding lung.
 Abdominal:
 Paired & arise from distal end of
the lung.
 Present along dorsal wall of the
abdomen.
 Present ventral to kidneys & in
close contact with small intestine.
 Anterior thoracic:
 Paired & present at the ventral
side of lungs.
 Present in close contact with ribs.
 Posterior thoracic:
 Paired & overlap the posterior end
of the corresponding lung.
 Abdominal:
 Paired & arise from distal end of
the lung.
 Present along dorsal wall of the
abdomen.
 Present ventral to kidneys & in
close contact with small intestine.

28. Mechanism of Respiration in Pigeon
Mechanism of Respiration in Pigeon
 At rest, inspiration is brought about
by intercostal muscles.
 By contraction of these muscles,
pressure on lungs is reduced & air is
drawn in into the lungs & air sacs.
 Exchange of gases takes place in the
capillaries.
 Expiration is brought about by
movements of thoracic & abdominal
muscles.
 By compression of air sacs, fresh air
goes into the capillaries.
 During flight, movement of sternum
& vertebral column, helps in
respiration.
 Rate of respiration is rapid when the
bird moves faster.
 At rest, inspiration is brought about
by intercostal muscles.
 By contraction of these muscles,
pressure on lungs is reduced & air is
drawn in into the lungs & air sacs.
 Exchange of gases takes place in the
capillaries.
 Expiration is brought about by
movements of thoracic & abdominal
muscles.
 By compression of air sacs, fresh air
goes into the capillaries.
 During flight, movement of sternum
& vertebral column, helps in
respiration.
 Rate of respiration is rapid when the
bird moves faster.

29. Thank you