COMPARATIVE ANATOMY OF

RESPIRATORY SYSTEMS:

FISH, FROG, PIGEON AND

RABBIT

What is respiration?

Exchange of gases (O2 and CO2)

The process in which oxygen is taken

inside the body from the envt for

oxidation of food to release energy &

CO2 so produced is expelled out

Physiology of respiration

1. External respiration: Inspiration &

expiration

2. Exchange of gases between alveolar

air and blood

3. Internal respiration :Transportation

of O2 from blood to tissues, oxidation

of food, energy release, Co2 back to

resp. surface for expulsion

Section 37-3

Flowchart

Oxygen and

carbon dioxide

exchange at

alveoli

Oxygen-rich

air from environment

Bronchioles

Nasal

cavities

Pharynx

Trachea Bronchi

Bronchioles

Alveoli

Pharynx

Nasal

cavities

Carbon

dioxide-rich

air to the

environment

Bronchi

Trachea

Movement of Oxygen and Carbon

Dioxide In and Out of the Respiratory

System

BIG

QUESTION

… WHY DO ANIMALS BREATHE?

Why?

Just like machines, we also need energy!!!

Energy is unlocked from macromolecules

like CHO, fats & proteins by oxidation

Evolutionary significance of pharynx

Organs of resp. (both aq. &

terrestrial) are derived from

pharynx

Pharynx for food passage from

mouth to oesophagus

It opens to lungs through trachea

by means of an opening, glottis

Dorsally open to Eustachian tube

Not much used now in amniotes-

vestige

Respiration in animals

Whether they live in water or on land, all animals must respire.

◦ To respire means to take in oxygen and give off carbon dioxide.

Some animals rely of simple diffusion through their skin to respire.

While others…

Have developed large complex organ systems for respiration.

Respiratory organs

1. Gills : Fish, larval amphibians,

adult urodeles

2. Swim bladder: Fishes

3. Lungs: Tetrapods

4. Skin/ cutaneous resp:

Amphibians

The basic necessities of any

respiratory organ 1. The respiratory organs must be thin

walled so that there is easy diffusion of

gases

2. It must be richly supplied with blood

enable exchange of gases

3. It should have large area for

contraction and expansion.

I. GILLS

1. Fishes

2. Amphibian’s larva/ Tadpole

3. Adult urodelian amphibians

Gills are the respiratory

organs.

Development of gills

1. In the embryo the pharynx develops

paired pouches due to evagination

or pushing out.

2. At the same time skin develop grooves

due to invagination or pughing in

3. when the pouch and the groove meet

the membrane between the two

disentigrates and a slit develops to

form gill slit

Development of gills

4. The gill cleft or slit contains gills

which are present in a gill chamber

5. Each gill chamber has an internal

branchial aperture opening to pharynx

6. An external branchial aperture

opens to external

7. The gill chambers are separated by inter

branchial septa and supported by gill

rays

Development of gills

8. Each half of the gill filament is called

Demibranch.

9. The demibranch on either side of

interbranchial septum. gillrays, connective

tissue and associated blood vessels with

nerves form a holobranch.

10. The demibranch at the anterior end is

called pretrematic demibranch and at

the posterior end is called post trematic

demibranch.

Gills in fishes

The gills are internal and vary in number

depending on the classes they belong to.

Operculum is a bony flap like covering

that is seen over the gill slits on either

sides in bony fishes.

Aquatic Gills

Water flows through the mouth then over the gills where oxygen is removed

Carbon dioxide and water are then pumped out through the operculum

What are bony fishes and cartilaginous

fishes?

Cartilaginous fishes

(Elasmobranches or Chondrichthyes)

Bony fishes

(Teleosts/ Osteichthyes)

1. 5 pairs of gill slits 1. 4 pairs of gill slits

2. A pairs of spiracle in front of the

hyomandibular arch

2. No Spiracles

3. Operculum is absent 3. Operculum present

4. Gills open to the exterior by inter

branchial aperture

4. Gills open to the opercular

chamber

5. No opercular chamber 5.Opercular chamber is present

6. 1 demibranch & 5 Holobranches 6. 4 holobranch, the

demibranch of the first gill is

lost

GILLS IN AMPHIBIANS

Amphibian tadpoles are purely aquatic,

they need to utilize oxygen in the water-

help of gills.

Initially 3 pairs of external gills (gills

that are constantly bathed in water)-

internal gills-Lungs

Only in Urodeles like Salamanders and

Necturus, 3 pairs of external gills

persist through out the life.

Anya

ANURA

Urodeles?

SWIM BLADDER/ AIR BLADDER-

Development

Swim bladder or air bladder are paired or

unpaired structures arise from the

pharynx or oesophagus of bony fishes

The air bladder arise as an outgrowth of

the pharynx on either side, initially

lateral in position then becomes dorsal

It is below vertebral column and

outside Coelom.

SWIM BLADDER/ AIR BLADDER

Connection between b/w the pharynx and

airbladder is called pneumatic duct.

SB serves both as respiratory and

hydrostatic organ.

Richly supplied with blood capillaries

In lung fishes the SB resembles the lungs &

makes respiration more effective

eventhough they have lesser no of

demibranches

SWIM BLADDER/ AIR BLADDER- How is it

working?

When the fish gulps in air, it enters

through mouth, pharynx, pneumatic duct

Oesopharyngeal pumb forces air into

pneumatic duct

When air bladder is compressed, gas

exchange & CO2 is expelled through the

mouth as bubbles.

Section 33-3

Salamander Lizard Pigeon Primate

Nostrils, mouth, and throat

Trachea

Lung

Air sac

Figure 33–10: Vertebrate Lungs

Section 37-3

Figure 37-13 The Respiratory System

The Human Respiratory System

Lungs

From amphibians to mammals all terrestrial

org. has lungs

Formation of lungs

1. Lungs develop from the floor of pharynx

at its posterior end as a small bud called

lung bud single through single

evagination.

2. The lung bud slightly elongates &

bifurcates into two

3. The opening of lung bud into the pharynx

develops a small slit & form the glottis.

4. The part after glottis forms the larynx

(voice box)

5. The elongated part of the lungs before

bifurcation forms Trachea (air pipe)

6. The bifurcated part becomes the bronchi

7. The ends of bifurcated parts of the lung

buds expand to form lungs.

8. The lungs push backwards & come to lie

on either side of the heart.

9. Lungs get surrounded by coelomic

epithelium

LARYNX

TRACHEA

AIRSACS IN BIRDS

LUNGS

LARYNX

Part between glottis and upper end of

trachea, well developed in tetrapods

Larynx in Amphibia

a. In anurans there is a laryngo-tracheal

chamber for production of sound

(urodeles and apodans do no not produce

sound)

b. Laryngo-tracheal chamber: 3

cartilaginous structure to keep it

stretched-one ring like cricoid cartilage

and two semicircular arytenoids

cartilage

Larynx in Reptiles

Similar as in frog.

Has well developed hyoid cartilage to

hold larynx in position

Larynx in Birds

Simple

Another organ for sound Production-

Syrinx

Larynx in Mammals

Highly developed-3 cartilages

Thyrenoid/ thyroid cartilage: @ ant end of

larynx

Dorsal to thyroid cartilage is the arytenoids

Below arytenoids is the crinoids, followed by

trachea.

Epiglottis (fold of mucous membrane of

pharynx)-@ ant to glottis

Erect while breathing, close the glottis while

eating

Sound: a pair of vocal cords b/w thyroid &

arytenoids cartilages

TRACHEA

A duct that connect pharyngeal cavity to

lungs

Trachea bifurcates into - two bronchi –

Each bronchus enter to lungs –

bronchioles (pimary, secondary , tertiary

and terminal)