The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary history. In land animals the respiratory surface is internalized as linings of the lungs. Gas exchange in the lungs occurs in millions of small air sacs; in mammals and reptiles these are called alveoli, and in birds they are known as atria. These microscopic air sacs have a very rich blood supply, thus bringing the air into close contact with the blood.These air sacs communicate with the external environment via a system of airways, or hollow tubes, of which the largest is the trachea, which branches in the middle of the chest into the two main bronchi. These enter the lungs where they branch into progressively narrower secondary and tertiary bronchi that branch into numerous smaller tubes, the bronchioles. In birds the bronchioles are termed parabronchi. It is the bronchioles, or parabronchi that generally open into the microscopic alveoli in mammals and atria in birds. Air has to be pumped from the environment into the alveoli or atria by the process of breathing which involves the muscles of respiration. In most fish, and a number of other aquatic animals (both vertebrates and invertebrates) the respiratory system consists of gills, which are either partially or completely external organs, bathed in the watery environment. This water flows over the gills by a variety of active or passive means. Gas exchange takes place in the gills which consist of thin or very flat filaments and lammelae which expose a very large surface area of highly vascularized tissue to the water. Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants includes anatomical features such as stomata, that are found in various parts of the plant.

1. RESPIRATORY SYSTEM
Pawan Kumar Sahu
Lecturer at
Rudauli College of Pharmacy,
Ayodhya (U.P.)

2. INTRODUCTION
Our body tissue utilize inhaled oxygen for metabolic purposes and produce carbon
di oxide in the process.
The main aim of the respiratory system is to extract oxygen from the atmosphere
and supply it to body tissues and take out CO2 from the tissues and expel it into the
atmosphere.
Respiration is thus a process, which involves exchange of gases between the
atmosphere and blood and cells.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

3. PROCESS OF RESPIRATION
Lung
expands to
take air
from the
atmosphere
(O2 rich)
O2 enters
the lungs
and
transferred
to blood in
pulmonary
capillaries
Further
blood
transfer to
the tissues.
Tissue utilize
O2 and
produce
CO2 which
passes into
the blood.
Blood rich
CO2 c/d
Venous
Blood
Venous
blood brings
CO2 to the
lungs where
CO2 diffuse
into lungs
The lungs
discharge it
into
atmosphere
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

4. FUNCTION OF RESPIRATION
Transport of oxygen
to tissues and
excretion of carbon
dioxide.
Transport of oxygen
to tissues and
excretion of carbon
dioxide.
Excretion of volatile
substances like
ammonia.
Excretion of volatile
substances like
ammonia.
Regulation of
temperature
through loss of heat
in the expired air.
Regulation of
temperature
through loss of heat
in the expired air.
Maintenance of pH
of blood.
Maintenance of pH
of blood.
Regulation of water
balance through
excretion of water
vapor.
Regulation of water
balance through
excretion of water
vapor.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

5. RESPIRATORY SYSTEM
The respiratory system consists of the following structures:
1. Nasal Cavity
1. Nasal Cavity
2. Pharynx
2. Pharynx
3. Larynx
3. Larynx
4. Trachea
4. Trachea
5. Bronchi
5. Bronchi
6. Bronchioles
6. Bronchioles
7. Alveoli
7. Alveoli
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

6. PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

7. 1. NASAL CAVITY
It is divided into right and left portions by means of nasal septum.
The nasal cavity is lined by mucous membranes.
The entrance to nasal cavity is formed by anterior nares (nostrils).
They contain small hairs which act as filters for dust.
The back of nasal cavities contain posterior nares.
They form the entrance to naso-pharynx.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

8. 2. PHARYNX
It is divided into three parts:
Laryngopharynx
Laryngopharynx
Oropharynx
Oropharynx
Nasopharynx
Nasopharynx
Which lies
behind the
nasal
cavities. It
contains
opening
for
Eustachian
tubes on
the lateral
wall.
Which lies
behind the
nasal
cavities. It
contains
opening
for
Eustachian
tubes on
the lateral
wall.
which is
continuous
in front
with mouth
and
below
with
laryngeal
part of
pharynx.
Its lateral
wall
contains
the tonsils.
which is
continuous
in front
with mouth
and
below
with
laryngeal
part of
pharynx.
Its lateral
wall
contains
the tonsils.
which is
the lowest
part. It
lies
behind the
larynx.
which is
the lowest
part. It
lies
behind the
larynx.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

9. 3. LARYNX (VOICE BOX)
It lies between pharynx above and trachea below.
It is formed by the following cartilages:
Thyroid
cartilage
Which is the
largest.
Which is the
largest.
Cricoid
cartilage
Which lies
below the
thyroid
cartilage.
Which lies
below the
thyroid
cartilage.
Two
arytenoid
Cartilages at the
back of cricoid.
Cartilages at the
back of cricoid.
Epiglottis
Attached to the
top of thyroid
cartilage.
Attached to the
top of thyroid
cartilage.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

10. 4. TRACHEA (WIND PIPE)
It is a cylindrical tube which is about 11 cm.
It begins at the lower end of pharynx.
At the level of 5th thoracic vertebra, it divides into two bronchi.
Trachea is made of sixteen to twenty C-shaped incomplete cartilages.
These cartilages are connected by fibrous tissue at the back.
The trachea is lined by mucous membrane made of ciliated epithelium.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

11. 5. BRONCHI
The trachea ends by dividing into two bronchi, namely right and left bronchi.
They pass to the corresponding lung.
The right bronchus is shorter and wider than the left.
Bronchi are made of complete rings of cartilage.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

12. 6. BRONCHIOLES
They are formed by the division of bronchi.
Bronchioles are the finest branches of bronchi.
Bronchioles do not have cartilage.
They are lined by cuboidal epithelium.
The smallest parts of these branches are called bronchioles, which are a part of
the lower respiratory system.
The terminal parts of the bronchioles contain alveoli which is the place where gas
exchange occurs.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

13. 7. ALVEOLI (AIR SACS)
They are the final terminations of each bronchus.
They contain a thin layer of epithelial cells surrounded by numerous capillaries.
Exchange of gases takes place through the walls of these capillaries.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

14. STRUCTURE OF LUNGS
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

15. THE LUNGS
These are two lungs. They are cone shaped organs that lie in the thoracic cavity.
The lungs are separated by the heart and the great blood vessels.
The space between the two lungs is called mediastinum.
Each lung has an apex and a base.
The lungs are convex on he outer surface and concave on the inner surface.
The right lung is divided into three lobes. i.e. superior lobe, middle lobe and inferior
lobe.
The left lung is divided into two lobes, i.e. superior lobe and inferior lobe.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

16. THE LUNGS
The convex surface of the lung which is called the costal surface is smooth and
follows the shape of the chest wall.
The concave surface is called the medial surface.
The lung is covered by a serous membrane known as pleura, which is composed of
epithelial cells.
The pleura are divided into two layers:-
1. Parietal
Pleura
2. Visceral
Pleura
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

17. THE LUNGS
The parietal pleura line the ribs, sternum, costal cartilage, and the intercostal muscle fibers
and also cover the superior surface of the diaphragm.
The visceral pleura are completely attached to the lungs covering the lung surface.
It also enters into fissures, assists for dividing the lungs into respective lobes.
At the base of the lung, it is reflected backward to form parietal pleura.
The flattened epithelial cells secrete a serous fluid which occupies the space between the two
layers, i.e. the pleural cavity.
This fluid reduces friction between the two membranes and allows them to slide easily over
one on another during respiration.
The internal structure of the lung shows bronchi, bronchioles, alveolar ducts, alveoli,
pulmonary artery, and bronchial artery, branches of vagus nerve, pulmonary veins, bronchial
veins and lymphatic vessels. These structures occupy the lobules of the lungs.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

18. ROOT OF THE LUNGS
The medical surface of each lung has a vertical slit called hylum.
Structures like blood vessels, nerves and lymphatics pass through the hylum.
These structures together constitute the root of the lung.
The root of lung is formed by:
1. Pulmonary arteries:- Which carry impure blood to the lungs from heart.
2. Pulmonary Veins:- Which carry oxygenated blood from lungs to the heart.
3. Bronchial Arteries:- Which are branches of thoracic aorta. They carry arterial
blood which nourishes the substance of lung tissue.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

19. ROOT OF THE LUNGS
• Which returns venous blood of lungs to superior vena
cava.
Bronchial Veins
• Which divide into bronchioles.
Bronchi
• A thin tube that carries lymph (lymphatic fluid) and white
blood cells through the lymphatic system. Also called
lymphatic vessel.
Lymphatic Vessels and
Lymph Glands
• Sympathetic and vagus nerve which supply the lungs.
Nerves
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

20. MECHANISM OF RESPIRATION
Inspiration (or breathing in):-
It is an active process. It is produced by the contraction of the following muscles:
Diaphragm, the contraction of which enlarges the chest cavity vertically (i.e., from
above downwards).
Intercostal muscles when contract produce elevation of ribs and sternum. This
enlarges the chest cavity in all the other four sides.
The lungs expand at this stage and fill this increased space. Now, the pressure in the
lungs is less than atmospheric pressure. So air flows into the lungs.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

21. MECHANISM OF RESPIRATION
Expiration (or breathing out):-
It is a passive process.
It is produced by the relaxation of diaphragm and intercostal muscles.
This produces reduction in the size of chest cavity.
So the pressure in the lungs increases which forces the air out.
The rate of respiration is 16 to 18 per minutes in adults.
The rate is higher in children.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

22. MECHANISM OF RESPIRATION
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

23. REGULATION OF RESPIRATION
Respiration is regulated by two controls:
1. Nervous Control
2. Chemical Control
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

24. NERVOUS CONTROL
It is exerted by respiratory centre present in the medulla oblongata of brain.
From this centre afferent impulses pass to:
1. Diaphragm through phrenic nerve.
2. Intercostal muscles through intercostal nerves.
These impulses cause rhythmic contraction of diaphragm and intercostal muscles.
Efferent impulses arise due to the distension of air sacs. They are carried by vagus
to the respiratory centre.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

25. CHEMICAL CONTROL
This is efferent through carbon di oxide content of blood.
An increase in the level of carbon di oxide produces stimulation of the respiratory
centre.
A decrease in carbon di oxide level produces the opposite effect.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

26. REFLEX MECHANISM
Carotid body and aortic body chemoreceptor:-
Some chemoreceptors also regulate respiration reflexly. These receptors are
present in:
oCarotid Body:- Which lies in the bifurcation of common carotid artery.
oAortic Body:- Which is at the foot of subclavian artery.
These two bodies contain the ending of sensory nerves which run in vagus nerve.
In carbon di oxide level of blood stimulate these bodies. The impulses are then
carried to the respiratory centre which is also stimulated.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

27. HERING-BREUER REFLEX
The lungs
contain
some
stretch
receptors.
Expansion
of the
lungs
stimulates
these
receptors.
These
impulses
now inhibit
the
respiratory
centre.
So
inspiration
stops.
Now the
lungs
collapse
and there
is no
stretch.
So
inhibition
of the
respiratory
centre
through
vagus also
stops.
Inspiration
starts
again.
This reflex
is called
Hering-
Breuer
Reflex.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

28. RESPIRATORY VOLUMES
The contraction of diaphragm and intercostal muscles produces
expansion of the chest cavity.
So air enters into the lungs during inspiration.
A forced inspiration can produce additional expansion.
So more air can enter the lungs.
Similarly, a forced expiration can expel an extra volume of air.
Even after a forced expiration, some air still remains in the lungs.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

29. VARIOUS RESPIRATORY VOLUME
1. Vital
Capacity
• It is defined
as the
volume of
air that can
be expelled
by a forced
expiration
after a
forced
inspiration
(Nor- mal
value is 4
litres).
2. Tidal Air
• It is the
volume of
air passing
in and out
of the lungs
with
ordinary
quiet
breathing
(Normal
value is 0.5
litres).
3. Inspiratory
Reserve
• It is the
additional
volume of
air that can
be taken in
by forced
inspiration
(Normal
value is 2.5
litres).
4. Expiratory
Reserve
• It is the
volume of
air that can
be expelled
by forced
expiration
after normal
inspiration
(Normal
value is 1
liter).
5. Residual
Volume
• It is the
volume of
air which
remains in
the lungs on
forced
expiration
after normal
inspiration
(Normal
value is 1
liter).
6. Total Lung
Capacity
• It is the sum
of vital
capacity
and residual
volume.
(Normal
value is 5
litres).
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

30. EXCHANGE OF GASES
It occurs in two stages:
Exchange between tissues and blood.
Exchange between alveoli and blood
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

31. EXCHANGE BETWEEN TISSUES AND BLOOD
This is called as tis- sue or internal respiration.
The oxygen tension of pure blood supplying the tissues is high (100 mm Hg.)
But the oxygen tension of tissues is low (40 mm Hg.).
So oxygen of blood goes to tissues.
The carbon-di-oxide tension is more in tissues than in blood.
So carbon-di-oxide goes out from the tissues to blood.
Now blood containing more carbon-di-oxide is taken back to the heart by venous
system.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

32. EXCHANGE BETWEEN ALVEOLI AND BLOOD
 It is called as pulmonary or external respiration.
The oxygen tension in the alveolar air is high (100 mm Hg).
But oxygen tension of blood in the capillaries is low.
Due to the pressure difference, oxygen of alveoli enters into blood.
Similarly carbon-di-oxide tension of capillary blood is higher than in alveoli.
So carbon-di-oxide enters into alveoli and it is breathed out through the expired air.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

33. ABNORMAL TYPE OF RESPIRATION
Apnea
• Stopping of
respiration for
short intervals.
Hyperpnea
• Increase in
depth of
respiration.
Dyspnea
• Difficulty in
breathing.
Polypnea
• Respiration
characterized
by rapid rate.
Tachypnea
• Exceedingly
high rate of
respiration.
Cheyne-
Stokes
respirations
• A rare
abnormal
breathing
pattern.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

34. ARTIFICIAL RESPIRATION
It is employed when respiration fails due to drowning, carbon monoxide poisoning
etc.
Artificial respiration must be given immediately when respiration fails.
Most methods employed are designed to increase and decrease the capacity of
thorax.
So air can be drawn into the lungs and expelled.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

35. THE FOLLOWING ARE A FEW METHODS OF
ARTIFICIAL RESPIRATION
3. Instrumental methods:
They are Drinker's method, Bragg- Paul's method and Iron lung method. These methods can be carried out only in
hospitals.
They are Drinker's method, Bragg- Paul's method and Iron lung method. These methods can be carried out only in
hospitals.
2. Mouth to mouth method:
It involves blowing air into lungs through mouth.
It involves blowing air into lungs through mouth.
1. Schafer's method and Holger Nialson method:
Both involve compression of thoracic cavity by pressure against ribs.
Both involve compression of thoracic cavity by pressure against ribs.
PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY

36. PAWAN KUMAR SAHU LECTURER AT RUDAULI COLLEGE OF PHARMACY
Thank You