This ppt comprises a detailed note about mechanism of respiration in invertebrate animals .

1. PRESENTATION
ON
“MECHANISM OF RESPIRATION IN
INVERTEBRATES”
DEPARTMENT OF ZOOLOGY,
DR. HARISINGH GOUR UNIVERSITY, SAGAR
Submitted by
Siddharth rajput
MSc Zoology
Roll no. (Y21265027)
Session 2021-22

2. INTRODUCTION:-
• Respiration is the process in which oxygen is transported from
outside environment to the cells/tissues of the organism with
simultaneous transport of carbon dioxide in the opposite direction
i.e., from tissues to the environment.
• The primary function of the respiratory system is to deliver
oxygen to the cells/tissues of the organism and remove carbon
dioxide from the tissues.
• The oxygen supplied to the tissues is used up by the cells in the
breakdown of food stuff into carbon dioxide and water with the
release of energy.

3. CONTINUE...
• In higher animals, respiration occurs as- external respiration,
internal respiration and cellular respiration. External respiration
refers to the exchange of oxygen and carbon dioxide across the
respiratory surfaces such as skin, gills, lungs etc and involves two
phases- Inspiration and Expiration
• Internal respiration refers to the transport of gases to and from the
tissues by blood.
• Cellular respiration refers to the biochemical pathway by which
food molecules (glucose) are oxidized to carbon dioxide and water
in presence of oxygen with the release of energy in the form of
ATP.

4. ORGANS OF RESPIRATION
Different modes of respiration/respiratory organs are encountered
among invertebrates
• General body surface- Respiration through general body surface
occurs in protozoa, porifera, coelenterate, some annelids. It is
referred to as direct diffusione.g. Protozoa.
• Skin/integument- The respiration through skin or integument is
referred to as cutaneousrespiration. It occurs in many annelids
such as oligochaetes, hirudinarians, and some polychaetes, some
sipunculid worms, frogs, eels etc.

5. • Gills- These are present in aquatic animals. Some poycheate
worms,aquatic insects, crustaceans, molluscs etc. Different types
of gills are found among animals. In mollusks, respiration through
gills or ctenidia is called ctenidial respiration
• Lungs- Lungs include a variety of sac like structures that are
richly supplied with blood vessels. Respiration through lungs is
referred to as pulmonary respiration. In arthropods mechanism of
respiration takes place through book lungs
• Trachea- are extensive network of air tubes found in insects.
Tracheae carry air directly to the cells without blood
(trachealrespiration).
ORGANS OF RESPIRATION

6. MECHANISM OF RESPIRATION
• In simplest forms of life, the respiratory gases diffuse in and out
through the general body surface.
• Similarly, poriferans possess no respiratory organs but depend on
the water that enters their body through ostia for the exchange of
gases.
• Respiratory system is wanting in Coelenterates, Platyhelminthes
and Aschelminthes .Respiration accours through simple diffusion.
• Annelids, arthropods, molluscs and vertebrates have special
structures that carry out the function of respiration for the
animal.The main respiratory organs are gills, lungs and trachea (in
insects)

7. A) MECHANISM OF RESPIRATION IN GILLS/GILL LIKE
STRUCTURES OF INVERTEBRATES
We know that gills are found in some annelids, mollusca and
arthropoda. Let us learn about the mechanism of respiration in these
organisms.
Annelids
• In annelids some polychaetes such as Nereis, respiration occurs
through the whole-body wall and also through flattened lobes of
parapodia which possess extensive capillary network lying very
close to the surface. Blood running through them gives up CO2
collected from tissues and receives oxygen dissolved in
surrounding water. Water is constantly renewed by gentle
undulations of body

8. RESPIRATION IN NERIES THROUGH PARAPODIA

9. RESPIRATION IN SABELLA ANNELIDA
• In fan worms, Sabella and Serpula that permanently remain in their
tubes, radioles serve as the site for respirations . The pinnules of each
radioles are covered by tracts of cilia.
• Fan worms pump water through the tube by means of peristaltic
contractions of the body. The cilia of radioles generate water currents
flowing over the radioles where gaseous exchange takes place.
• There is a single branchial sinus in a radiole through which blood
flows in both directions in a tidal fashion. When the crown is
retracted inside the tube sensing some danger, the radioles cease to
function as respiratory organ.

11. MECHANISM OF RESPIRATION IN MOLLUSC’S
GILL OR CTENIDIA
• Aquatic respiration takes place by ctenidium in molluscs which is an important
organ of the mantle cavity. In molluscs, water is drawn into the mantle cavity by
the beating of the cilia of gill epithelium or muscular pumping.
• Pila possesses monopectinate type of gill. During aquatic respiration, Pila keeps its
head and foot fully extended. Two nuchal lobes form channel like structures
facilitates the entry and exit of water current. The water enters the mantle cavity
through left nuchal lobe. This flow of water is maintained by the alternate
protrusion and retraction of the head and by the beating of cilia on the lamellae of
ctenidium.
• While water flows over the gill the exchange of gases takes place between the
water and the blood vessels of gills. The oxygenated blood in the gill filaments is
sent back to the heart through the efferent blood vessel.

13. RESPIRATION IN UNIO
• In Unio, the lateral cilia of the gill filaments and cilia lining the
mantle generate current of water under the influence which the
water enters the body of Unio through inhalant siphon.
• Thereafter the water enters the water tubes of the gill lamina
through ostia. In the water tubes, the water flows upwards to enter
the suprabranchial chambers.
• During the movement of water, exchange of gases takes place.The
water flows backwards and reaches the cloacal chambers and
moves out of the body through exhalent siphon.

15. MECHANISM OF RESPIRATION IN BOOK LUNGS
OF ARTHROPODS
• The movement of air in and out of the book lungs is controlled by the contraction
and relaxation of dorso-ventral and atrial muscles.
• When these muscles contract, book lungs are compressed and air in interlamellar
spaces is forced out into atrial chamber. From atrial chamber air is expelled to the
exterior through stigmata .
• When these muscles relax, the book lungs resume their normal shape so that fresh
air enters first into the atrial chamber and then into interlamellar spaces.
• Thus, interlamellar spaces are filled with fresh air and exchange of gases takes
place between air of interlamellar spaces and venous blood through the
membranous walls of lamellae. Blood gets oxygenated and the carbon dioxide is
passed out along the expelled air.

17. MECHANISM OF GASEOUS EXCHANGE IN THE
TRACHEAL SYSTEM OF INSECTS
• Respiratory exchange in the tracheal system occurs partly by diffusion and partly
by ventilation as found in a vertebrate lung.
• Tracheae open to exterior through spiracles.
• Through these spiracles air enters the trachea when they are open.
• After reaching tracheae, the air passively moves into the tracheoles as the partial
pressure within the tracheoles is lower than that of the trachea. From tracheoles,
air enters the tips of fine branches of tracheoles which are filled with fluids.
• This fluid takes up the oxygen and diffuses inwards to the tissues or active cells
through the tracheolar walls
• The tracheolar walls are very thin with an approximate thickness of only 40-70
nm.

18. CONTINUE...
• the gases those diffuse from tracheoles to the tissues move through the fluid
in the tracheoles, the tracheolar wall and the cell membrane ultimately to
reach cells/tissues where oxygen is utilized and carbon dioxide is produced.
• When the air is expelled outside (during expiration), the tracheolar fluid
again fills into the tracheole tips. CO2 produced mostly diffuses out through
the tracheae.
• Small insects such as Drosophila may get sufficient oxygenby diffusion alone
but forms that weigh more than 1g or that are highly active require some
degree of ventilation to fulfill their high demands for oxygen. Ventilation in
large and active insects is brought about by the changes in tracheal volume,
which in turn are caused by the movements of abdominal muscles

21. MECHANISM OF RESPIRATION IN INVERTEBRATES
HAVING LUNG OR LUNG LIKE STRUCTURES
Pulmonary sac
Aerial respiration in Pila is observed when the animal is in water or out on land. When
it is in water, it comes near to the water surface and then extends its left nuchal lobe to
form a tube-like structure, called siphon . The opening of the siphon projects above
the water surface through which air enters the pulmonary sac through pulmonary
aperture. Air always backs through this path.
To maintain the inflow and outflow, the alternate expansion and contraction of the
pulmonary sac takes place. Epitaenia is raised to push the mantle wall and hence the
air is not allowed to enter the branchial chamber. The wall of the pulmonary sac
contains blood vessels and sinuses whose blood takes up oxygen of the air and gives
out carbon dioxide.

23. Mechanism of respiration in Pulmonate lung
In terrestrial pulmonates such as Limax, mantle cavity is
transformed into a pulmonary sac or lung for aerial respiration.
Roof of the pulmonary lung is richly supplied with blood vessels.
Alternate muscular contraction and relaxation of mantle floor, lower
or raise it, causing the air to rush in and out of the mantle cavity
through pulmonary aperture. Compression of mantle cavity
increases the partial pressure of oxygen and facilitates its
absorption.

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