Transcript blood and nerve supply

RESPIRATORY SYSTEM
RESPIRATORY
SYSTEM
LUNGS
CONTENTS:Introduction,general
organisation
Structures of respiratory system
Mechanics of respiration,
compliance
Lung volumes and capacities
Pulmonary and alveolar
ventilation
Physical principles of gaseous
exchange
 Transport of respiratory gases
Control of respiration
Pulmonary function tests.
INTRODUCTION
Respiratory system constitutes one of the
important system as it contributes the vital
provision of supply of oxygen to the body,
where cells continuously use oxygen for
metabolic reactions which in turn releases
energy.
This energy is from the nutrient molecules
which provide ATP.
DEFINITION:- Respiration is the process by
which oxygen from the lungs is carried by
the blood to the tissues and carbon dioxide
formed in the tissues by metabolic activity is
carried by the blood to the lungs and is
expired out
The PROCESS OF RESPIRATION involves
four stages:VENTILATION:-Ventilation means the
passage of air in and out of lungs during
Inspiration and expiration respectively .
INTRAPULMONARY GAS MIXING:Intrapulmonary gas mixing or distribution
of oxygen rich inspired air with the air
already present in the lungs.
DIFFUSION:- Diffusion which means gas
transfer across the alveolar capillary
membrane due to tension gradient.
PERFUSION:- Perfusion means flow of
adequate quantity of blood through the
lungs so that the diffused gases are carried
away.
FUNCTIONS OF RESPIRATION
•GAS TRANSFER:
Transfer of O2 from the alveoli to the venous blood
and CO2 in the opposite direction.
•REGULATION OF pCO2 OF BLOOD:
The most important function of respiration is to
keep the arterial pCO2 at 40 mmHg which is
essential for many vital functions of the body.
•REGULATION OF PH OF BLOOD:
By the reversible reaction, it maintains the pH of
blood
H2CO3  H+ + HCO3-
•EXCRETION OF CERTAIN VOLATILE GASES:
For example- chloroform, ether, ammonia,
etc.
•PUMPING ACTION:
The rhythmic movement of the diaphragm
and the chest wall causes rhythmic alteration of
pressure in the abdomen and chest cavity. This
assists in drawing blood from the lower part of the
body to the abdomen and then to chest and thus
helps in maintaining venous inflow to the heart.
RESPIRATORY TRACT
The whole respiratory tract is divided in two
parts :•UPPER RESPIRATORY TRACTIt extends from the nasal cavity to the vocal
cords i.e. (nose, pharynx and associated
structures)
•LOWER RESPIRATORY TRACTIt extends from the vocal cord to the alveoli i.e
(larynx, trachea, bronchi, lungs.)
STRUCTURES OF THE RESPIRATORY
TRACT
CONTENTS•Nose
• Pharynx
• Larynx
• Trachea
• Bronchi
•Lungs
CONTENTS
•POSITION AND STRUCTURE
•LINING OF THE NOSE
•FUNCTIONS OF THE NOSE(A) RESPIRATORY FUNCTIONS OF THE NOSE
(B) OLFACTORY FUNCTIONS OF THE NOSE
I. POSITION AND STRUCTURE :The nasal cavity is the main route of air
entry , and consists of a large irregular cavity
divided in to two equal passages by a septum
. The posterior bony part of the septum is
formed by the perpendicular plate of the
ethmoid bone and vomer. Anteriorly, it
consists of hyaline cartilage .
II. LINING OF THE NOSE :The nose is lined with very vascular ciliated
columnar epithelium which contains mucus
secreting goblet cells. At the anterior nares
this blends with the skin and posterioly it
extends in to the nasal part of the pharynx.
•FUNCTIONS OF THE NOSE
(A) RESPIRATORY FUNCTONS OF THE NOSE:1) WARMING:- This is due to the immense
vascularity of the mucosa. This explains the large
blood loss when a nosebleed occurs .
2) FILTERING AND CLEANING :- This occurs as
hairs at the anterior nares trap large particles.
Smaller particales such as dust and microbes settle
and adhere to the mucus. Mucus protects the
underlying epithelium from irritation and prevents
drying. Synchronous beating of the cilia wafts the
mucus towards the throat where it is swallowed or
coughed up.
3) HUMIDIFICATION:- As air travels over the
moist mucosa , it becomes saturated with water
vapour . irritation of the nasal mucosa results in
sneezing, a reflex action that forcibly expels an
irritant.
IV) OLFACTORY FUNCTIONS OF THE NOSE :The nose is the organ of the sense of smell . Nerve
endings that detect smell are located in the roof of
the nose in the area of the cribriform plate of the
ethmoid bones and the superior conchae. These
nerve endings are stimulated by airborne odours.
The resultant nerve impulses are conveyed by the
olfactory nerves to the brain where the sensation of
smell is perceived.
CONTENTS:•POSITION OF PHARYNX
•DIVISION OF PHARYNX
•BLOOD AND NERVE SUPPLY
•FUNCTIONS OF PHARYNX
1. POSITION OF PHARYNX:The pharynx is a tube 12 to14 cm long that
extends from the base of the skull to the level
of the 6th cervical vertebra.it lies behind the
nose mouth and larynx and is wider at its
upper end
2. DIVISION OF PHARYNX:(A)THE NASOPHARYNX :The nasal part of the pharynx lies behind the
Nose Above the level of the soft palate
(B) THE OROPHARYNX :The oral part of the pharynx lies behind the
Mouth extending from below the level of the soft
palate to the level of the upper part of the body
of the third cervical vertebra
(C) THE LARYNGOPHARYNX :The laryngeal part of the pharynx extends From the
oropharynx above the continues as the oesophagus
below from the level of the 3rd to the 6th cervical
vertebrae .
3. BLOOD AND NERVE SUPPLY :Blood supply is by the facial artery .
Nerve supply is by the
PARASYMPATHETIC by the :- Vagus nerve and
glosso pharyngeal nerve.
SYMPATHETIC by the :- Superior cervical ganglia.
4. FUNCTIONS OF THE PHARYNX:I) WARMING AND HUMIDIFYING :- By
the same methods as in the nose the air
is further warmed and moistened as it
passes through the pharynx.
II) PASSAGE WAY FOR AIR AND FOOD:Air passes through the nasal And oral
section and food Through the oral and
laryngeal section.
POSITION :-
The larynx or voice box extends from the root of the tongue
and the hyoid bone to the trachea. It lies infront of the
laryngo pharynx at the Level of the 3rd,4th,5th and 6th
cervical vertebra
BLOOD AND NERVE SUPPLY :-
 BLOOD SUPPLY:- By the superior and inferior laryngeal
arteries.
 NERVE SUPPLY :a) PARASYMPATHETICS :- By the superior laryngeal
And recurrent Laryngeal nerves.
b) SYMPATHETICS:-Superior cervical ganglia,
FUNCTIONS : SPEECH:-
This occurs during expiration when the
sounds produced by the vocal cords are
manipulated by the tongue,cheek and lips.

PROTECTION OF THE LOWER RESPIRATORY TRACT:-
During Deglutition the larynx move upwards
occulding the opening in to it from the pharynx
and the hinged epiglottis closes over the larynx
this ensure that food passes in to the
oesophagus and not into the lower respiratory
tract.

PASSAGEWAY FOR AIR:-
This is between the pharynx and trachea
HUMIDIFYING FILTERING AND WARMING :-
This processes continue As inspired air
travel Through the larynx.
TRACHEA
CONTENTS:POSITION
STRUCTURE
BLOOD AND NERVE SUPPLY
FUNCTION
POSITION:The trachea or wind pipe is a continuation of
the larynx and Extends downwards to about
the level of the 5th thoracic Vertebra.
STRUCTURE :The trachea is a cartilaginous membranous tube
about 10 or 11cm. long it is not quite cylindrical
being flattened posteriorly.
Its external diameter from side to side is about
2cm in the adult male and 1.5 in the adult female
it is kept patent by incomplete C-shaped rings of
cartilage on its anterio lateral wall which keeps
air tubes open.
BLOOD AND NERVE
SUPPLY :BLOOD SUPPLY :-By the inferior thyroid
and bronchial arteries.
NERVE SUPPLY:a)PARASYMPATHETICS:-By the recurrent
laryngeal nerve
b)SYMPATHETICS:- By the ganglia
FUNCTIONS: SUPPORT AND PATENCY :-trachea is kept
patent by incomplete
C-shaped ring Of
cartilage on its antero tateral wall which keeps
Air tube open.
 COUGH REFLEX :-Cough is protective
reflex by means of which respiratory Passage
are kept free form foreign matter.
WARMING,HUMIDIFYING AND FILTERING :This continues as the nose, Although air is
normally Saturated and at body temperature
when it reaches the trachea.
APPLIED PHYSIOLOGY:TRACHEOSTOMY AND INTUBATION
Several condition may Block air flow by
Obstructing the trachea
FOR EXAMPLE :-The rings of cartilage that
support the trachea may collapse due to a
crushing injury to the chest inflammation of
the mucous membrane may cause it to Swell
so much that the airway closes or vomit or a
foreign object may be aspirated.
Methods are used to reestablish air flow past a
tracheal obstruction if the obstruction is
superior to the level of the larynx tracheostomy
an operation to make an opening in to the
trachea may be performed.
BRONCHI
CONTENTS:STRUCTURE
BLOOD AND NERVE SUPPLY
FUNCTIONS
STRUCTURE :The bronchi is progressively subdivided in to
bronchioles, Terminal bronchioles, respiratory
bronchioles, albeolar ducts and finally alveoli.
Situated from the superior border of the 5th
thorasic vertebra divided in to a right primary
bronchus which goes in to the right lungs and a
left primary bronchus which goes in to the left
lungs.
BLOOD AND NERVE SUPPLY:BLOOD SUPPLY :- By the right & left
Bronchial arteries
NERVE SUPPLY :-PARASYMPATHETICS &
SYMPATHETIC NERVE
3) FUNCTIONS :CONTROL OF AIR ENTRY :- The
diameter of the respiratory passages is
Altered by contraction and relaxation of
the Involuntary muscles in their walls,
thus regulating the volume of entering
the Lungs. These changes are controlled
by the autonomic nerve supply
parasympathetics causes constriction
and sympathetics stimulation dilatation .
WARMING AND HUMIDIFYING
SUPPORT AND PATENCY
REMOVAL 0F PARTICULATE MATTER
COUGH REFLEX.
LUNGS
CONTENTS: INTRODUCTION
POSITION AND STRUCTURE
COVERING OF LUNGS
LOBES, FISSURES AND LOBULES
ALVEOLI
SURFACTANT
RESPIRATORY MEMBRANE
BLOOD SUPPLY
NERVE SUPPLY
APPLIED PHYSIOLOGY
INTRODUCTION :-
The lungs (=lightweights, because they
float), are paired cone- shaped organs
in the thoracic cavity. They are
separated from each other by the heart
and other structures in the
mediastinum while thoracic Cavity &
mediastinum form two different
chambers for two lungs.
POSITION AND STRUCTURE
The lungs extend from the diaphragm to just
slightly superior to the clavicles and lie against
the ribs anteriorly and posteriorly.
The broad inferior portion of the lung, the base,
is concave and fits over the convex area of the
diaphragm. The narrow superior portion of the
lungs is the apex.
The surface of the lungs lying against the ribs,
called the costal surface, matches the rounded
curvature of the ribs.
Medially, the left lung also contains a concavity,
the cardiac notch, in which the heart lies
The mediastinal (medial) surface of each
lung contains the region, the hilus,
through which bronchi, pulmonary blood
vessels, lymphatic vessels, and nerves
enter and exit. These structures are held
together by pleura and connective tissue
and constitute the root of lung.
Due to the space occupied by the heart,
the left lung is about 10% smaller than
the right lung.
COVERING OF LUNGSTwo layers of serous membrane collectively
called the pleural membrane, enclose and
protect each lung.
The superficial layer lines the wall of the
thoracic cavity and is called the parietal
pleura, the deep layer, the visceral pleura,
covers the lungs themselves .
Between the visceral and parietal pleurae is a
small space, the pleural cavity.
Pleural cavity contains a small amount of
lubricating fluid secreted by the
membranes.
This fluid reduces friction between the
membranes, allowing them to slide easily
over one another during breathing.
Pleural fluid also causes the two membranes
to adhere to one another just as a film of
water causes two slides to stick together , a
phenomenon called surface tension.
LOBES, FISSURES AND LOBULES:The right lung is divided into three
lobes-superior, middle and inferior.
The left lung is smaller and is divided
into two lobes-superior and inferior.
Each lung is divided into lobes by one
or more fissures .Both the lungs have
oblique fissures . Right lung also has
horizontal fissure. The oblique fissure in
the left lung separates the superior lobe
from the inferior lobe
Each lobe receives its own secondary
(lobar)bronchus .Thus, the right
primary bronchus gives rise to three
secondary bronchi called the
superior, middle and inferior
secondary bronchi, whereas the left
primary bronchus gives rise to
superior and inferior secondary
bronchi.
Within the substance of lung, the
secondary bronchi give rise to the
tertiary bronchi. The segment of lung
tissue that each tertiary bronchus
supplies is called a “Broncho
pulmonary segment” .
ALVEOLI
Around the circumference of the alveolar
ducts are numerous alveoli and alveolar
sacs.
An alveolus is a cup-shaped outpouching
lined by simple squamous epithelium and
supported by a thin elastic basement
membrane.
An alveolar sac consists of two or more
alveoli that share a common opening.
The walls of alveoli contains two types of
alveolar epithelial cells1.)Type I alveolar cells.
2.)Type II alveolar cells.
The Type I alveolar cells, the predominant
cells, are simple squamous epithelial cells
that form a nearly continuous lining of the
alveolar wall.
The Type II alveolar cells, also called septal
cells, are fewer in number and are found in
between type I alveolar cells.
FUNCTIONS OF ALVEOLAR
CELLS:Type I alveolar cells are main sites of gaseous
exchange.
Type II alveolar cells, which are rounded or
cuboidal epithelial cells whose free surfaces
contain microvilli, secrete alveolar fluid, which
keeps the surface between cells and air moist.
Included in the alveolar fluid is SURFACTANT.
Asssociated with alveolar walls are alveolar
macrophages (dust cells), wandering
phagocytes that remove the fine dust particles
and other debris in the alveolar spaces.
SURFACTANTDEFINATION- Any surface acting material
or agent that is responsible for lowering
surface tension of fluid is called surfactant.
The surfactant present in the alveoli of
lungs is called as pulmonary surfactant.
It is a complex detergent like mixture of
phospholipids and lipoproteins. It is
secreted by Type II alveolar epithelial cells.
FUNCTIONS OF SURFACTANTThey reduces surface tension in
alveoli of lungs & prevents collapsing
tendency of lungs.
Surfactant is responsible for
stabilization of alveoli which have
tendency to deflate.
It plays an important role in
inflation of lungs during birth.
RESPIRATORY
MEMBRANEThe exchange of oxygen & carbon dioxide
between the air spaces in the lungs and
the blood capillaries takes place by
diffusion across the alveolar and capillary
walls, which together form the respiratory
membrane.
Extending from the alveolar airspace to
blood plasma, the respiratory membrane
consists of four layers:-
1) A Layer of Type I and Type II alveolar cells
and associated alveolar macrophages that
constitutes the alveolar wall.
2) An epithelial basement membrane
underlying the alveolar wall.
3) A capillary basement membrane that is
often fused to the epithelial basement
membrane.
4) The endothelial cells of the capillary.
BLOOD SUPPLY
Blood is provided to the lungs by two
sets of arteries.
Deoxygenated blood passes through
pulmonary trunk which divides into
Left And Right pulmonary artery which
enters the left & right lung respectively.
 Return of oxygenated blood to the
heart occurs by way of the four
pulmonary veins, which drain into the
left atrium.
Bronchial arteries, which branch from
the aorta, delivers oxygenated blood to
the lungs.
APPLIED
PHYSIOLOGY
PLEURISY or PLEURITISInflammation of the pleural membrane is
called pleurisy or pleuritis.
In its early stages it may cause pain due to
friction between the parietal and visceral
layers of the pleura. If the inflammation
persists, excess fluid accumulates in the
pleural space, a condition known as
PLEURAL EFFUSION.
RESPIRATORY
MOVEMENT
INTRODUCTION
During normal quiet breathing, inspiration
is the active process and expiration is the
passive process.
During inspiration, thoracic cage enlarges
and lungs expands.
During expiration, the thoracic cage and
lungs decrease in size and attain the
preinspiratory position.
MUSCLES OF RESPIRATION
Respiratory muscles involved in inspiration
are know as inspiratory muscles.
And the muscle and the muscle involved in
expiration are called expiratory muscles.
 However, the respiratory muscles are
generally classified into primary (responsible
for change in size of thoracic cage during
normal quiet breathing) and accessory (are
put into action during forced breathing)
muscles.
PRIMARY INSPIRATORY MUSCLES :Primary inspiratory muscles are
diaphragm,which is supplied by phrenic
nerve and external intercostal muscles,
supplied by intercostal nerves.
ACCESSORY INSPIRATORY MUSCLES :Sternomastoid, scaleni, anterior serrati,
elevators of scapulae and pectorals are
the accessory inspiration muscle.
PRIMARY EXPIRATORY MUSCLES :Primary expiratory muscles are the
internal intercostal muscles, which are
innervated by intercostal nerves.
ACCESSORY EXPIRATORY MUSCLES:Accessory expiratory muscles
are the abdominal muscles.
MOVEMENT OF THORACIC CAGE :Inspiration causes enlargement of thoracic cage.
The size of the thoracic cage is increased in all
diameters.
 Increase in anterioposterior and transverse
diameters occurs due to elevation of ribs.
 The vertical diameter of thoracic cage is
increased by the descent of diaphragm.
In general the change in size of thoracic
cavity occurs because of the movement of four units
of structures.
1. Thracic lid
2. Upper costal series
3. Lower costal series
4. Diaphragm
RESPIRATORY PRESSURES
Two types of pressures are exerted in the
thoracic cavity and the lungs during the
process of respiration.
1. Intrapleural pressure Or
intrathoracic pressure.
2. Intraalveolar pressure Or
intrapulmonary pressure.
INTRAPLEURAL PRESSURE or
INTRATHORACIC PRESSURE
DEFINITIONThe intrapleural pressure is the
pressure existing in pleural cavity, that is
in between the visceral and parietal
layers of pleura. It is exerted by the
suction of the fluid that lines the pleural
cavity.
NORMAL VALUES
The respiratory pressures are always
expressed in relation to atmospheric
pressure which is 760 mm Hg.
Intrapleural pressure is always negative.
The normal values of the intrapleural
pressure in quiet breathing are:During inspiration :-6 mm Hg.
(760-6=754 mm Hg).
 During expiration :-2 mm Hg.
(760-2=758 mm Hg).
SIGNIFICANCE OF INTRAPLEURAL
PRESSURE
The intrapleural pressure has two important
functions :A. Since the intrapleural pressure is
always negative, it prevents the collapsing
tendency of lungs, which is caused by elastic
recoiling of lungs tissue .
B. Because of the negative pressure in
thoracic region, the larger veins and vena
cava are enlarged, i.e. dilated.
This acts like suction pump to pull venous
blood from lower part of the body towards
heart against gravity.
Thus,the intrapleural pressure is responsible
for venous return. So, it is called the
respiratory pump for venous return.
INTRAALVEOLAR PRESSURE OR
INTRAPULMONARY PRESSURE
DEFINATION :The pressure existing in the alveoli
of the lungs is called the intraalveoloar
pressure or intrapulmonary pressure.
NORMAL VALUES
Normally, intraalveolar pressure is
equal to the atmospheric pressure,
which is 760 mm Hg.
During inspiration, it becomes
negative. The value is -4 mm Hg
(760-4= 756 mm Hg).
During expiration, it becomes
positive. The value is +4 mm Hg
(760+4=764 mm Hg).
SIGNIFICANCE OF
INTRAALVEOLAR PRESSURE
The significance of the intraalveolar pressure
is:
A. The pressure in alveoli causes flow of air
in and out of alveoli.
During inspiration, since the pressure in the
alveoli is negative, the atmospheric air enters
the alveoli, and as the intrathoracic pressure
becomes positive during expiration, the air is
expelled out of alveoli.
B. The intraalveolar pressure also helps in
the exchange of gases between the alveolar air
and the blood.
COMPLIANCE
DEFINITION
The ability of the lungs and thorax
to expand or the expansibility of
lungs and thorax is called the
compliance.
It is defined as the change in volume per
unit change in the pressure.
The compliance can be expressed in
relation to intraalveolar pressure or
intrapleural pressure.
NORMAL VALUES
Compliance is the volume increase
in lungs per unit increase in the
intraalveolar pressure.
Compliance of lungs and thorax
together =130 ml/1 cm H2O
pressure.
Compliance of lungs alone =220
ml/1 cm H2O Pressure.
FACTOR AFFECTING
COMPLIANCE
The expansibility of thorax and the total
compliance is reduced in the following
condition:
1. Deformities of thorax like kyphosis
and scoliosis.
2. Fibrotic pleurisy
3. Paralysis of respiratory muscles
4. Pleural effusion
5. Abnormal thorax
MOTION OF THE RIBS:
The ribs are almost semicircular bones which
articulate with the vertebrae at one end with the
sternum or costal cartilages at the other
.
1. During inspiration, the sternum is elevated
and pushed forwards due to the elevation of the
shaft of the ribs, of which the sternal ends are
lower than the vertebral end during expiration.
This is caused due to the contraction of
intercostal muscles and results in an increase in
the anterioposterior diameter of the chest.
2. The rotation of the ribs around the two
points of attachment on sternum & vertebra
causes an increase in transverse diameter of
the thorax.
During expiration both intercostal muscles
which are responsible for movement of the
ribs and sternum relaxes, the size of the
thorax decreases in anterio-posterior and in
transverse diameter , the lungs volume
consequently decreases.
Lung volume are of four types:
1.Tidal volume.
2. Inspiratory reserve volume.
3. Expiratory reserve volume.
4. Residual volume.
1.TIDAL VOLUME (TV):
It is the amount of air which passes
into and out of the lungs during each
cycle of quiet breathing.
It is about 500 ml= 0.5 litres.
2.INSPIRATORY RESERVE VOLUME
(IRV) :
It is the maximum volume of air that
can be inhaled into the lungs after
normal tidal inspiration
It is about 3300 ml= 3.3 litres.
3.EXPIRTORY RESRVE VOLUME
(ERV):
It is the largest volume of air which
can be expelled from the lungs after
normal expiration.
It is about 1000 ml = 1 litre.
4.RESIDUAL VOLUME(RV):
It cannot be directly measured but is
the volume of air remaining in the
lungs after forced expiration.
It is about 1200 ml =1.2 litres.
Two or more lung volumes are together called
lung capacities .
There are four lung capacities:1.Inspiratory capacities
2.Vital capacity
3.Functional residual capacity
4.Total lung capacity
1. INSPIRATORY CAPACITIES:
It is the maximum volume of air that
can be inspired from end expiratory
position. Inspiratory capacity
includes TV and IRV.
IC = TV +IRV
2. VITAL CAPACITY(VC):
It is the maximum amount of air that
can be expelled out forcefully after a
maximal inspiration. vital capacity
includes IRV and TV and ERV
VC =IRV +TV +ERV
3. FUNCTIONAL RESIDUAL CAPACITY (FRC):
It is the volume of air remaining in the lungs
after normal expiration . Functional residual
capacity includes ERV and RV.
FRC = ERV +RV
4. TOTAL LUNG CAPACITY(TLC):
It Is the amount of air present in the lungs
after a maximal inspiration .This includes
all the volumes.
TLC =IRV+ TV+ ERV +RV
RESPIRATORY DEAD
SPACE
DEFINITION:The air which remains confined in the
upper respiratory tract with each
inspiration and is not available for gaseous
interchange constitutes what is known as
‘DEAD SPACE’.
Dead space is of two types:1. Anatomical dead space
2. Physiological dead space
PULMONARY
VENTILATION
DEFINATION:Pulmonary ventilation is a cyclic
process by which fresh air enters the
lungs and an equal volume of air leaves
the lungs. It is the volume of air
moving in and out of lungs per minute
in quiet breathing.
It is also called respiratory minute
volume.
NORMAL VALUE AND
CALCULATION
NORMAL VALUE:Normal value of pulmonary ventilation is
6000 ml (6 litres/min)
CALCULATION:Pulmonary ventilation is the product of
the Tidal volume and rate of respiration.
It is calculated by formula:PULMONARY VENTILATION
=Tidal volume x respiratory rate
=500 ml x12/min.
=6000ml/min.
ALVEOLAR VENTILATION
DEFINITION:The alveolar ventilation is defined as the
amount of air utilize for gaseous exchange
every minute.
The alveolar ventilation is different from
pulmonary ventilation. It indicates only
the volume of air that is utilized for
gaseous exchange. Some amount of air
trapped in dead space is not utilised for
gaseous exchange.
NORMAL VALUE AND
CALCULATION:-
NORMAL VALUE:-Normal value of alveolar
ventilation is 4200ml/min.
CALCULATION:- It is calculated by the
formula given below:Alveolar ventilation
=(Tidal volume-dead space volume) x
Respiratory rate
=(500-150)x12
=4200ml(4.2lit.)/min.
DIFFUSION OF GASES
Diffusion means movement of a substance from
an area of high concentration to an area of low
concentration.
In the present context the diffusion of O2 from
alveoli to pulmonary capillaries and of CO2 in
the reverse direction is to be considered.
The following points are to be noted in this
connection:
Gases in the alveoli are dissolved in small quantity of
alvoelar fluid and are in equilibrium with partial
pressure of the respective gases in alveolar air.
Gases in the blood of pulmonary capillaries are also
dissolved in water of the plasma where these exert a
tension.
EXTERNAL RESPIRATION:External respiration or pulmonary gas exchange
is the diffusion of O2 from air in the alveoli of the
lunga to blood in pulmonary capillaries and the
diffusion of CO2 in the opposite direction.
External respiration in the lungs converts
deoxygenated blood (depleted of some O2) coming
from the right side of the heart into oxygenated
blood that returns to the left side of the heart. As
blood flows through the pulmonary capillaries, it
picks up O2 from alveolar air and unloads CO2 into
alveolar air.
Although this process is commonly called an
“exchange”of gases, each gas diffuses
independently form the area where its partial
pressure is higher to the area where its partial
pressure is lower.
INTERNAL RESPIRATION :
The left ventricle pumps oxygenated blood into
the aorta and through the systemic arteries to
systemic capillaries. The exchange of O2 and
CO2 between systemic capillaries and tissue
cells is called internal respiration or systemic
gas exchange.
As O2 leaves the blood stream, oxygenated
blood is converted into deoxygenated blood.
Unlike external respiration, which occurs only
in the lungs, internal respiration occurs in
tissues throughout the body.
The rate of pulmonary and systemic gas
exchange depends on several factors:1. Partial pressure difference of the
gasesAlveolar Po2 mustbe higher than blood
Po2, for oxygen to diffuse from alveolar
into the blood. The rate of diffusion is
faster when the difference between Po2 in
alveolar air and pulmonary capillary
blood is larger.
2.Surface area available for gas exchange- the
surface area of alveoli is very huge. Any
pulmonary disorder that decreases the functional
surface area of the respiratory membrane
decreases the rate of external respiration.
3.Diffusion distance- the respiratory membrane
is very thin, so diffusion occurs very quickly. Also,
the capillaries are so narrow that the red blood
cells must pass through them in single file, which
minimize the diffusion distance from an alveolar
space to haemoglobin inside red blood cells.
4.Molecular weight and solubility of gasesbecause O2 has a lower molecular weight than
CO2,it could be expected to diffuse across the
respiratory membrane about 1.2 times faster.
TRANSPORT OF OXYGEN
Oxygen is transported by the blood from
alveoli to the tissues. The volume of oxygen in
arterial blood is 19 ml% and ,the partial
pressure of oxygen is 95mm of Hg. In venous
blood the volume of oxygen is 14ml% and
partial pressure is 40mm of Hg.
Oxygen is transported in blood in two forms:As simple physical solution.
In combination with haemoglobin.

Oxygen is dissloves in water of plasma and is
transported in this physical form.The amount
of oxygen transported in this way is very
negligible.It is only 0.3ml per 100ml of
plasma.It is about 3% of total oxygen in blood.
Hb + O2
HbO2
Oxygen combines with haemoglobin in blood and is
transported as oxyhaemoglobin.The transport of
oxygen in this form is important because maximum
amount(97%) of oxygen is transported by this
method.Oxygen combines the iron in heme part of
haemoglobin.Each molecules of haemoglobin
contains 4 atoms of iron One gram of haemoglobin
carries 1.34ml of oxygen.The normal haemoglobin
content in blood is 15 gm%.So the blood with 15
gm% of Hb must carry 20.1 ml% of oxygen i.e 20.1ml
of oxygen in 100 ml of blood.
OXYGEN HAEMOGLOBIN
DISSOCIATION CURVE
INTRODUCTION:The relationship between the the
partial pressure of oxygen and the %
saturation Hb with oxygen can be
explained graphically and the graph
is called “OXYGEN Hb
DISSOCIATION CURVE
Normally in blood ,Hb is saturated with
oxygen only upto by 95%. The
saturation of Hb with oxygen depends
upon partial pressure of oxygen. When
the partial pressure of oxygen is less,
Hb accepts oxygen and when the partial
pressure of oxygen is less, Hb releases
oxygen.
Under normal conditions ,the oxygen
Hb dissociation curve is “S” shaped or
sigmoid shaped. The lower part
indicates dissociation of oxygen from
Hb. The upper part of curve indicates
the acceptance of oxygen by Hb
depending upon the partial pressure of
oxygen.
FACTORS AFFECTING
OXYGEN DISSOCIATION
CURVE
The oxygen Hb dissociation curve is
shifted to right by left by various factors:Shift to left indicates acceptance of
oxygen by Hb.
Shift to right indicates dissociation
oxygen from haemoglobin.
Shift to right:The oxygen Hb dissociation curve is shifted
to right in following conditions:Decrease in partial pressure of oxygen
Increase in partial pressure of co2
Increase in hydrogen ion concentration and
decrease in pH
Increased in body temp.
Excess of DPG(2,3-Di phospho glycerate)
Shift to left:-
Shift of oxygen Hb dissociation
curve to left occurs in following
conditions:In fetal blood :because fetal Hb
has got more affinity for oxygen
than adult Hb
Decrease in hydrogen ion
concentration and increase in PH.
In the tissues due to continous metabolic
activities, partial pressure of CO2 is very high and
partial pressure of oxygen is low. Due to pressure
gradient CO2 enters the blood and oxygen is
release from blood to the tissues. The presence of
CO2 decreases the affinity of Hb for oxygen .It
enhances further Release of oxygen to tissues and
oxygen dissociation curve is shifted to right. It is
known as BOHR’S EFFECT.
All the factors which shift the oxygen dissociation
curve to right enhance bohr’s effect.
CO2 is transported by blood from tissues to
alveoli. In the arteriole blood the volume of
CO2 IS 48ml% and partial pressure of CO2 is
40mm Hg.In venous blood volume of CO2
52ml% and partial pressure is 46 mm of Hg.
CO2 is transported in 4 ways:•As dissloved form-7%
•As carbonic acid-negligible
•As bicarbonates-63%
•As carbamino compounds-30%
CO2 diffuses into blood into and dissolves in
fluid of plasma forming a simple solution.
Only about 3ml per 100ml of plasma of CO2
is transported as dissolved state. It is about
7% of total CO2 in blood.
Part of dissolved CO2 in plasma combines
with water to form carbonic acid.
Though CO2 is transported in this form,
this reaction is very slow and it is
negligible.
About 63% of CO2 is transported as bicarbonate
from plasma,the CO2 enters the RBCs. In the RBCs
,CO2 combines with water to form carbonic
acid.The reaction inside RBCs very rapid,Due to
presence of carbonic anhydrase enzyme.Carbonic
anhydrase is present only inside the RBC not in
plasma. i.e why the carbonic acid formation is
atleast 200-300 times more in RBCs than in
plasma.
The carbonic acid is very unstable.Almost all
carbonic acid formed in RBCs dissociates into
bicarbonate and hydrogen ions .The increased
concentration of bicarbonate inside the RBCs
causes diffusion of bicarbonate ions through cell
CHLORIDE SHIFT/HAMBURGER
PHENOMENON
In plasma plenty of NaCl is present.It
dissociates into Na+ and ClWhen negatively charged bicarbonate
ions moved out of RBCs into plasma, to
maintain the electrolyte equlibrium the
negatively charged ions Cl- ions moved
into RBC and it is called chloride shift or
hamberger’s phenomenon.
About 30% of CO2 is transported as
carbamino compounds CO2 is
transported as blood in combination
with Hb and plasma proteins. CO2
Combines with Hb to form carbamino
Hb, and it combines with plasma
proteins .
CO2 DISSOCIATION CURVE
CO2.The relationship between the
partial pressure of CO2 and the
quantity of CO2 that combines with
blood is demonstrated by a graph called
CO2 dissociation curve.
NORMAL CO2 DISSOCIATION CURVE:The normal CO2 dissociation curve shows that
the CO2 content in the blood is 48% when
partial pressure of CO2 is 40mm of Hg and it
is 52ml% when partial pressure of CO2 is 48
mm Hg .The CO2 content becomes
70ml%.When partial pressure is about
100mm Hg.
FACTORS AFFECTING CO2
DISSOCIATION CURVE
Combination of more amount of oxygen
with Hb displaces CO2 from Hb. This effect
is called haldane’s effect.
So the excess of oxygen content in blood
causes shift of CO2 dissociation curve to
right.
CAUSES OF HALDANE’S
EFFECT:Due to combination with oxygen, the Hb
becomes strongly acidic. It causes
displacement of CO2 from Hb in two ways:The highly acidic Hb has low tendency to
combine with CO2 So CO2 is displaced from
blood.
Because of acidity, hydrogen ions are
released in excess. The hydrogen ions bind
with bicarbonate ions to form carbonic acid.
Carbonic acid in turn dissociates into water
and CO2. The CO2 is released from blood and
alveoli.
SIGNIFICANCE OF HALDANE’S
EFFECT:-
The release of
co2 from blood
into alveoli
lungs.
Uptake of
oxygen by
blood.
INTRODUCTION
Respiration is a reflex process. Voluntary
control of respiration is possible but only for
a short period of about 40 seconds.
The pattern of respiration is regulated by 2
mechanism:NERVOUS MECHANISM
CHEMICAL MECHANISM
A}.NERVOUS
MECHANISM :-
It regulates respiration by reflex process .
It includes: respiratory centres,
 afferent nerves and
efferent nerves.
Respiratory centres:-
These are group of neurons, which control the
rate rhythm and force of respiration. These
centers situated in reticular formation of
brainstem on either side.
Depending upon situation in the brainstem the
respiratory Centres are classified into 2 groups:•Medullary centres
•Pontine centres
Medullary centres:-1}.Inspiratory centre
2}.Expiratory centre
Pontine centres:- 3}.Pneumotaxic centre
4}.Apneustic centre
1}.Inspiratory centre:-It situated in upper part
of medulla oblongata. It is formed by
inspiratory neurons which are otherwise called
dorsal group of respiratory organs.
Function:-Inspiratory centre concerned with
inspiration.
Effect of stimulation:- Electric stimulation of
inspiratory centre in animals by using needle
electrode causes contraction of inspiratory
muscles and prolonged inspiration.
2}.Expiratory centre:-It situated in medulla
oblongata and lateral to the inspiratory centre.
It is formed by expiratory neurons; which are
otherwise called ventral group of respiratory
neurons.
Function:-Normally expiratory centre is
inactive during quiet breathing and it becomes
active during forced breathing or when
inspiratory centre is inhibited. During quiet
breathing expiration is a passive process due
to recoiling property of thoracic cage.
3}.Pneumotaxic centre:-It situated in
dorsoventral part of reticular formation in
upper pons. The neurons of this centre
form nucleus parabrachialis.
Function:-The primary function of
pneumotaxic centre is to control
medullary respiratory centres,particularly
the inspiratory centre through apneustic
centre. It always controls activity of
inspiratory centre so that duration of
inspiration is controlled. Indirectly the
pneumotaxic centre increases respiratory
rate by reducing duration of inspiration.
4}.APNEUSTIC CENTRE:-It is situated in
reticular formation of lower pons.
Function:-The centre increases depth of
inspiration by acting directly on
inspiratory centre.
Effect of stimulation:-The stimulation
increases the duration of inspiration with
short expiratory gasp.so respiration is
called gasping type of respiration.
Impulses from higher centres
Impulses from stretch receptors of lungs
Impulses from ‘j’ receptors of lungs
Impulses from irritant receptors of lungs
Impulses from baroreceptors
Impulses from chemoreceptors
Impulses from proprioreceptors
Impulses from thermoreceptors
Impulses from pain receptors cough
reflex
Sneezing reflex
Deglutition reflex.
B}.CHEMICAL
MECHANISM :Certain chemical stimuli modulate how
quickly and how deeply we breathe.
Sensory neurons that are responsive to
chemicals are termed
CHEMORECEPTORS.
There are two types of chemoreceptors:-
CENTRAL
CHEMORECEPTORS
These are located in the medulla
oblongata in the central nervous system.
They respond to changes in H+
concentration or pCO2, or both, in
cerebrospinal fluid.
CO2 + H2O  H2CO3
 H+ + HCO3-
PERIPHERAL
CHEMORECEPTORS
These are located in the aortic bodies,
clusters of chemoreceptors located in
the walls of the arch of the aorta, and in
the carotid bodies, which are oval
nodules in the wall of the left and right
common carotid arteries where they
divide into the internal and external
carotid arteries.
Pulmonary function tests provide a
quantitative and objective
assessment of the physiological
derangement associated with
pulmonary diseases.
While these tests do not give a
specific etiological or pathological
diagnosis, the reasons for pulmonary
function testing are:-
a) Identification of cause of respiratory
symptoms.
b) Diagnosis of functional abnormalities.
c) Diagnosis of severity of dysfunction,
including subclinical abnormalities.
d) Identification of and screening of
unsuspected diseases.
e) Assessment of reversibility of airway
obstruction.
f) Assessment of airway sensitivity.
g) Evaluation of effectiveness of shortterm and long-term therapy.
h) Long-term follow up.
On the basis of these requirements the
various pulmonary function test can be
broadly classified into three groups:Tests to assess ventilatory functions of
lungs;
Tests to assess gaseous exchange
across the lungs;
Tests to assess transport of gases in
the body;
TESTS TO ASSESS VENTILATORY FUNCTIONS OF
LUNGS:-
(A) Assessment of the expansion of lungs
and chest wall:1.Measurement of pressure changes
during ventilation. For example:
Intra pulmonary (intra alveolar)
pressure.
Intra pleural (intra thoracic ) pressure.
2.Measurement of compliance
Compliance of lungs and chest wall
Compliance of lungs alone.
(B)Assessment of restrictive and
obstructive ventilatory defects
1.)Measurement of static and dynamic
lung volumes and capacities by ‘
spirometry ’ .
2.)Measurement of airways resistance.
These provide a fairly good idea of
the physical fitness in normal and the
type and the extent of derangement of
lung functions in lung patients.
TEST TO ASSESS GASEOUS
EXCHANGE ACROSS THE LUNGS:-
1. Measurement of ‘functional
residual capacity’- FRC.
2. Measurement of ‘dead space’
and uniformity of ‘alveolar
ventilation’.
3. Measurement of diffusion
capacity of lungs.
TEST TO ASSESS TRANSPORT OF GASES
IN THE BODY
1. Measurement of gas tension, for
example, pO2 and pCO2 in
inspired, expired and alveolar air.
2. Measurement of gas tension and
acid-base status of the blood.
HYPOXIA
DEFINITION:Hypoxia is a condition characterised by
inadequate or decreased supply of oxygen to
the lungs because of extrinsic reasons. The
term anoxia is used synonymously with the
hypoxia.
Based on the cause, we can classify hypoxia
into following types:1. HYPOXIC HYPOXIA OR ARTERIAL
HYPOXIAIt is caused by a low Po2 in arterial blood
as a result of high altitude, airway
obstruction, or fluid in the lungs.
2. ANEMIC HYPOXIA-
IN this type, too little functioning hemoglobin is
present in blood, which reduces o2 transport in
tissue cells. Among the causes are haemorrhage,
anemia, and failure of hemoglobin to carry its
normal complement of o2, as in carbon monoxide
poisoning.
3.ISCHEMIC HYPOXIAin this the blood flow to a tissue is so reduced
that too little o2 is delivered to it, even though po2
and oxyhaemoglobin level are normal.
4.
HISTOTOXIC HYPOXIAIn this the blood delivers adequate o2 to
tissues, but the tissues are unable to use it
properly because of the action of some toxic
agent. One cause is cyanide poisoning, in
which cyanide blocks an enzyme needed for
o2 utilization during ATP synthesis.
5.STAGNANT HYPOXIAthis type is characterised by decreased rate
of flow of blood through the tissues. the
oxygenncontent and tension of the arterial
blood is normal but that of the venous is
abnormally low due to sluggish circulation.
ACCLIMATISATION
( Compenstory changes at moderately high altitude or
low atmospheric pressure)
DEFINITION :The term acclimatisation means the adjustment of
the human body to suit the climate at a higher
altitude. It includes various physiological
readjustments and compensatory mechanisms
that reduces the effects of hypoxia in permanent
residents at high altitude.
Some of the changes are immediate while others
are a little delayed.
CHANGES IN ACCLIMATISATION
 ON
RESPIRATION:-
a) Vital capacity of lungs increases in those
people .
b) Diffusing capacity for O2 through the alveolo
capillary membrane increases.
The factor responsible for these changes are :1. Expansion and dilatation of pulmonary
capillaries
2. Increased blood volume
3. Increased lung volume
4. Elevated pulmonary arterial pressure
5. The apical part of the lungs which is normally
under perfused is adequately perfused during
anoxic acclimatisation .
ON CIRCULATION:The right heart hypertrophies so that blood
can be effectively pumped through the
expanded capillary bed of the lung.
There occurs temporary increase in cardiac
output. blood flow through the heart, brain,
muscles and other organs isincreased at the
expense of blood flow through the skin and
kidneys.
The blood capillaries exposed to anoxia for
long time get dilated to accommodate the
extra blood.
CYANOSIS:DEFINITION:
Cyanosis is the bluish discolouration of the skin and
/or mucus membrane due to the presence of at least
5 gm of reduced haemoglobin per 100 ml of blood in
the capillaries.
SITESCyanosis is commonly seen at the sites where the
skin is thin. for eg:
1. Mucus membrane of under surface of tongue.
2. lips
3. Ear lobes
4. Nail beds
5. Tip of nose
DYSPNOEA
DEFINITION:-
Dyspnoea means difficulty in breathing
associated with a sense of distress.
It is to be differentiated from hypernoea
which simply means hyperventilation, as
occurs in muscular exercise, and is
usually not associated with sense of
distress, unless, of course, the exercise
very severe.
ASPHYXIA
DEFINITION:
Improper aeration of blood, if
continued for some time in an intact
animal, produces a series of
pathological manifestations and
ultimately death. these manifestations
are collectively called asphyxia.
CLASSIFICATION:Asphyxia may be classified as
1.GENERAL
2.LOCAL