Download Kidneys excrete excess acid or base.

Respiratory
system
Dr. Saad Kleman Abd
The main functions of the respiratory system include:
a. Exchange of O2 and CO2.
b. Voice production.
c. Regulation of plasma pH.
d. Olfaction (sensation of smell)
e. Infection (pathogen invasion) prevention.
Respiration is associated with 4 processes:
a. Pulmonary ventilation is the movement of air into/out of the lungs
b. External respiration is the movement of O2 from the lungs to the blood and CO2
from the blood to the lungs.
c. Gas transport refers to the mechanisms by which O2 and CO2 are moved through the
blood.
d. Internal respiration is the movement of O2 from the blood to the cell interior and
CO2 from the cell interior to the blood.
Cellular Respiration or Internal Respiration
 Refers to intracellular metabolic processes carried out within mitochondria to produce ATP
 Uses oxygen and produces CO2 as a by-product
 Does not use the “respiratory system”
The structures of the respiratory system:
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Respiratory
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Dr. Saad Kleman Abd
The pharynx, has three parts?
the nasopharynx, where the nasal cavities open above the soft palate; the oropharynx,
where the oral cavity opens; and the laryngopharynx, which opens into the larynx.
MECHANICS OF BREATHING
Airflow into and out of the lungs requires pressure gradients between the mouth and the alveolus,
which are created by mechanical changes in lung volume.
Breathing becomes difficult:
 if the lung or the chest wall is stiff (low compliance)
 if the resistance to gas flow along the airway is high.
Resistance; is a dynamic property determined during gas
flow.
Compliance; is referred to as an elastic property and is
measured without gas flow.
Transport of gases:
Air filtered by nasal hair, passed from the nasal passage
and pharynx where it is warmed and takes up water vapor,
the inspired air passes down the trachea and through the
bronchi, bronchioles, respiratory bronchioles and alveolar
ducts to the alveoli.
The trachea and all the bronchi have supporting cartilage
(incomplete cartilage rings) which keeps the airways open.
Respiratory system lined with ciliated mucous membrane
and some of the cells secret a sticky mucous, the micro cilia
which project from the cells beat in a synchronized fashion
and drive mucous toward the throat, the trapped particles
moves at a rate of about 2 cm/min .
Alveoli; located in clusters of air sacs (alveolar sacs) at the
end of respiratory bronchioles.
 It’s the main sites of gas exchange
 80-90% of alveoli surface area is blood vessels
 Lungs contain about 500 million alveoli, provides
huge surface area
 The alveoli are lined by Type I cells they are simple squamous epithelium cells.
 Type II cells they are thick and contain inclusion bodies, they secret surfactant.
 There are also plasma cells, mast cells and macrophages (phagocyte cells) in the lungs.
Finally the transport of oxygen from the lungs capillaries to the tissues where it will be used and
of CO2 from the tissues to the lungs occurs by the help of hemoglobin (Hb).
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Respiratory
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Dr. Saad Kleman Abd
Nervous control of respiration:
 Respiration regulated by:
I. voluntary control located in the cerebral cortex
II. automatic control located in the pones and medulla.
 Spontaneous respiration produced by rhythmic discharge of the motor neurons that
innervate the respiratory muscle, which depend on nerve impulses from the brain.
 The lungs have no muscle and therefore, there are no motor innervations.
 Sensory fibers run from stretch receptors in the lungs to the medulla via vagus nerve.
The smooth muscle of the bronchioles receives motor innervations from both branches of
autonomic nervous system; (Parasympathetic cause constriction of the bronchioles& increase
secretions, while sympathetic impulses cause dilation& decrease secretions).
The need for oxygen:
Heat and energy produced in the body by the oxidation of the carbon and hydrogen in the food
(Metabolism), the oxygen comes from the inspired air.
Carbon + oxygen
Hydrogen + oxygen
Heat& energy + CO2 (in the expired air)
Heat& energy + water (in the urine)
At rests, 250 ml of oxygen per minutes are absorbed from the inspired air to satisfy the
metabolic requirements of the body, and this figure greatly increased when exercise taken, in very
severe exercise the oxygen requirements may be as high as 5000 ml of oxygen per minute.
Breathing:
The lungs completely fill thoracic cavity, increasing and decreasing size of this cavity brings
about breathing.
The air in the lungs is termed alveolar air. It differs from room air that it contains much less
oxygen and much more carbon dioxide& it comes in contact with blood flowing through the
pulmonary capillaries.
 Alveolar air contains 14% oxygen, 80% nitrogen, 5.5-6% CO2.
 While room air contain 21% oxygen, 79% nitrogen, 0 % CO2. (CO2 about 0.04% so it
equivalent to zero).
At the end of a quite respiration, the lungs still contain a bout 3000 ml of alveolar air but only
420 ml of this is oxygen (14% of 3000ml).
Since the body requires 250ml of oxygen every minute for metabolism the reserve of oxygen in
the lungs is less than two minute supply.
So it is essential therefore to continually refresh the air in the lungs by the process of breathing,
this process must be maintained with out a break for the whole life.
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Respiratory
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Dr. Saad Kleman Abd
Boyles,s law and Breathing:
The principle of ventilation is based on Boyles,s law (If the volume changes–the pressure
changes, the smaller the volume the higher the pressure). Alternatively, the greater the volume
the lower the pressure.
The thoracic cavity moves up & out on inhalation & this increase the volume of thoracic
cavity & lungs. As the volume in the lung increases the pressure (intrapulmonary pressure) in
the lung decreases.
As a result, intrapulmonary pressure becomes less than atmospheric pressure so air flow from
high-pressure to low pressure through nose to lungs.
On expiration by returning the thoracic case to its normal size (resting position) the
intrapulmonary pressure increase & became more than atmospheric pressure so air flows from
the lung out side.
Respiratory Muscles;
Respiratory Muscles are the;
1. diaphragm
2. external intercostal muscles (inspiratory muscles)
3. internal intercostals muscles (expiratory muscles)
4. anterior abdominal wall
Movement of the diaphragm accounts for 75% of the change in intra thoracic volume during
quiet inspiration. The distance it moves ranges from 1.5 cm to as much as 7 cm with deep
inspiration.
The external intercostal muscles, which run obliquely downward and forward from rib to rib.
When contract they elevate the lower ribs. This pushes the sternum outward and increases the
diameter of the chest.
Either the diaphragm or the external intercostal muscles alone can maintain adequate
ventilation at rest.
Internal intercostals muscles are expiratory muscles when they contract they pull the rib cage
downward, leading to a decrease in intra thoracic volume and forced expiration.
Contractions of the muscles of the anterior abdominal wall also aid expiration by pulling the
rib cage downward and inward and by increasing the intra abdominal pressure, which pushes
the diaphragm upward.
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Respiratory
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Dr. Saad Kleman Abd
Inspiration: Is brought about by the contraction of the intercostal muscle, which raised the chest
wall upward, and out wards and by contraction of the diaphragm muscle which moves down
words and compresses the abdominal wall contents. (It’s an active process).
The increase in size of the chest with inspiration is quite small in quite breathing, and the volume
only increase from 3000 ml to 3500 ml.
Expiration: Is brought about by the relaxation of the intercoastal muscle, the elastic recoil of the
lungs and chest wall returns the chest to the resting respiratory level, (it’s a passive process).
Abdominal muscles are not used except in very sever exercise.
The pressure change with in the lungs is quite small during quite respiration, falling to _1mm Hg
during inspiration and rising to +1 mm Hg in expiration.
Expansion of the lungs :
The lungs are elastic structure in the thorax they are fully expanded, and completely fill the
thoracic cavity. Out side the thorax they collapse like a deflated balloon.
There is no space between the out side of the lungs and the inside of the thorax should air enter
between the out side the lungs and the inside of the thorax.
The lungs will collapse and this is called pneumo thorax and when it occur it stops lung
ventilation, it may be caused by chest injury which allow air into the chest or it may result from
a hole in the lungs.
Pneumo thorax may by unilateral due to the presence of mediastinum which separates the two
sides of the chest.
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Respiratory
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Dr. Saad Kleman Abd
Pleural membrane:
It is a thin membrane consists of two layers:
a- External layer called (parietal layer) which line the thoracic cavity and diaphragm.
b- Internal layer called (visceral layer) which covers the lungs.
The two layers are in contact with each other, but there is a small amount of fluid (pleural fluid),
between them secreted from those layers.
 The negative pressure inside the thoracic cavity at about (_2.5) mm
Hg caused by the elastic tension of the lungs and makes the two
layers in contact with each other.
 The intra pleural pressure increased negatively during inspiration up
to -6mmHg.
 The negative intrathoracic (the same intra pleural) pressure is of
importance in aspirating blood from the great veins into the heart
(thoracic pump).
 The veins, atria and lymphatic vessels are expanded with each
respiratory movement like the lungs.
 The negative intrathoracic pressure is also important in helping to
hold open all the airways and blood vessels that are embedded in the
structure of the lung.
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Respiratory
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Dr. Saad Kleman Abd
Surface tension and Surfactant:
The lung collapse for two reasons:
1- The arrangement of the elastic fibers in the lung.
2- The surface tension in the alveoli.
Surface tension produced by a thin layer of water lines the
inside of the alveolus. As water molecules pull on one
another, they tend to make the alveolus smaller (they
collapse the alveoli). The electrical attraction of the water
molecules is the surface tension.
Surfactant: which is a mixture of phospholipids and
lipoproteins, lowers the surface tension of the fluid by
interfering with the attraction between the water molecules,
(but doesn’t eliminate it) & preventing alveolar collapse.
 Without surfactant, alveoli would have to be
completely reinflated between breaths, which would
take an enormous amount of energy.
 Surfactant is important in preventing excessive
extravasations of fluid, which could cause pulmonary edema.
 Surfactant is important at birth. The fetus make respiratory movement in uterus, but the
lungs remain collapsed until birth. After birth the infant makes several strong inspiratory
movements which expand the lung, surfactant prevent the lungs from collapsing again.
 In life, the smaller the alveoli become the better they are protected from collapsing.
Structure of the Respiratory Membrane:
• The wall of an alveolus and the wall of a capillary
form the respiratory membrane, where gas
exchange occurs. Oxygen and carbon dioxide can
diffuse easily across this thin respiratory
membrane.
• The respiratory membrane is made up of two layers
of simple squamous epithelium and their basement
membranes. This membrane is extremely thin,
averaging 0.5 micrometers in width.
• In many regions of the membrane there is no interstitial fluid, because the pulmonary blood
pressure is so low that little fluid filters out of the capillaries into the interstitial space.
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Respiratory
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Dr. Saad Kleman Abd
Lungs volumes and capacities:
The volume of air that enters or leave the lungs during quite or deep respiration can be measured
using simple Spirometer.
The air that enters the lungs in a simple inspiration is known as Tidal volume (TV) under resting
conditions the tidal volume is about 500 ml. with maximal inspiration and expiration, this value
can be increased nearly ten fold, and this is the largest possible respiratory volume and is called
the vital capacity (VC) of the lungs.
The extra air that can be taken after
inspiration is known as the Inspiratory
Reserve Volume (IRV).
The extra air that can be forced out after
expiration is the Expiratory Reserve
Volume (ERV).
The larger the tidal volume, the smaller are
the inspiratory and expiratory reserve
volume.
After all the expiratory reserve volume has
been forced out, the lungs are still not empty,
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Respiratory
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Dr. Saad Kleman Abd
about 1200 ml of Residual Air (RA) remains in them. The residual air plus the vital capacity
measures the Total Lungs Capacity (TLC).
{The average values of the division of the total lungs capacities are given in the diagram.}
The volume of the lungs at the resting respiratory level (that is after a quite expiration and prior to
the next inspiration) is termed the Functional Residual Capacity (FRC) it is equal to the
expiratory reserve volume plus the residual volume.
Dead Space:
Some of the air a person breathes never reaches the gas exchange areas but simply fills
respiratory passages where gas exchange does not occur, such as the nose, pharynx, and trachea.
This air is called dead space air because it is not useful for gas exchange.
On expiration, the air in the dead space is expired first, before any of the air from the alveoli
reaches the atmosphere.
The normal dead space air in a young adult man is about 150 milliliters. This increases slightly
with age.
Anatomic & Physiologic Dead Space:
The dead space measures the volume of all the space of the respiratory system other than the
alveoli and their other closely related gas exchange areas; this space is called the anatomic dead
space.
Some of the alveoli themselves are nonfunctional or only partially functional because of absent or
poor blood flow through the adjacent pulmonary capillaries. So these alveoli must also be
considered as a dead space.
When the alveolar dead space is included in the total measurement of dead space, this is called
the physiologic dead space.
In a normal person, the anatomic and physiologic dead spaces are nearly equal because all alveoli
are functional in the normal lung, but in a person with partially functional or nonfunctional
alveoli in some parts of the lungs, the physiologic dead space may be as much as 10 times the
volume of the anatomic dead space, or 1 to 2 liters.
Pulmonary ventilation:
Under resting condition 400-500 ml of air are taken with each breath and this is termed the tidal
volume since this process is repeated 15-20 times per minute (Respiratory Rate).
Pulmonary Ventilation = Tidal Volume X Respiratory Rate.
Pulmonary Ventilation = 400 X 15=6000ml /min.
=400 X 20=8000ml/min.
It ranges from 6-8 liters /min.
In exercise, respiratory rate and tidal volume are increased markedly therefore, the pulmonary
ventilation will increase.
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Respiratory
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Dr. Saad Kleman Abd
Alveolar Ventilation:
The quality of room air that reaches the lungs per minute is less than the pulmonary ventilation
because the pulmonary ventilation includes air that only reaches the dead space.
Alveolar Ventilation = Respiratory Rate X Alveolar Tidal Volume
=Respiratory Rate X (Tidal Volume – Dead Space)
=15 X (400-150) =3750 ml/min.
Transport of O2 and CO2 in the blood:
It depends on:
 Tension: It is the force which driving the gas from one region to another, gas always
move from region of high tension to region of low tension.
 Quantity: that is how much oxygen present in the blood and it depend on hemoglobin
amount in the blood. (A person who is anemic may have the same oxygen tension in
arterial blood as a normal person, but will have much lower oxygen content).
Henry's Law:
• Within the lungs, oxygen and carbon dioxide diffuse between the air in the alveoli and the
blood that is between a gas and a liquid.
• This movement is governed by Henry's Law, which states that the amount of gas which
dissolves in a liquid is proportional to:
1. The partial pressure of the gas.
2. The solubility of the gas.
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Respiratory
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Dr. Saad Kleman Abd
Carriage of Oxygen:
When blood exposed to air, the tension of O2 (Po2) drive it into the blood.
An equilibrium is occur when tension of O2 in the blood equal to oxygen tension in the air.
Po2 = 760 X 21=159mm Hg (atmospheric partial pressure of oxygen at sea level)
Oxygen Tension:
 The blood leaves the lungs at tension of 100 mmHg, and circle through out the pulmonary
circulation and reaches the capillaries of the tissues without change in oxygen tension.
 As the blood comes in contact with tissue fluid which has much lower oxygen content 40
mm Hg due to the use of O2 in metabolism, Exchange of O2 occur and the O2 tension
decrease in the blood until equilibrium with the tissue occur 40 mmHg.
 The blood return to the heart with oxygen tension 40 mmHg then it pumped to the lung,
which have oxygen tension 100 mmHg, and oxygen exchange occur.
Oxygen Content:
The quantity of oxygen carried depend on hemoglobin (Hb),
each gram of Hb has ability to combine 1.34 ml of oxygen.
If a person has Hb concentration of 15gm / 100ml of blood,
he will able to carry 1.34X15 = 20ml of O2 in every 100 ml of
blood, this is termed oxygen capacity of the blood; it is the
amount of O2 carried by the blood when tension is very high
and the Hb is fully saturated with oxygen.
*In arterial blood, oxygen content is 20 ml of O2 /100 ml
blood leaving the lungs via the pulmonary veins and reaching
the arteries of the body.
* In venous blood, only 15ml of oxygen are present in every
100 ml of blood.
Therefore, it still has a low amount of O2. This is because the curve connecting the quantity of
oxygen carried and the oxygen tension is not straight line, but an S-shaped curve known as the
oxygen dissociation curve.
Carriage of carbon dioxide:
Carbon dioxide tension:
The tension of CO2 in the lung is 40 mmHg and in the tissues 46 mm Hg as the blood flows
through the tissue capillaries, the tension of CO2 in blood builds up to 46 mm Hg.
It will be noted that carbon dioxide moves in the opposite direction to oxygen because the tension
of CO2 in the tissues is higher than that in the lungs.
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Respiratory
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Dr. Saad Kleman Abd
Carbon dioxide content:
The CO2 content of the blood leaving the lungs is 46 ml CO2 / 100 ml of blood. As it passes
through the tissue capillaries, the content increases from 46 ml to 50 ml of CO2 / 100 ml blood.
As the blood passes through the lungs the content falls from 50 to 46 ml of CO2 /100 ml blood.
There are two surprising points about the carriage of CO2:
1- That blood contains very much more CO2/100 ml blood than it does oxygen. The arterial
blood contains 46 ml of CO2 but only 20 ml O2 /100ml blood.
2- As the blood passes through the lungs, it only gives up a relatively small amount of the CO 2.
The reason for this is that CO2 is more than a waste product.
An adequate level must be maintained in the blood for the proper functioning of the body.
Blood pH :
The lungs and kidneys are the organs responsible for maintaining a constant pH in the body.
 Kidneys excrete excess acid or base.
 Respiration and the carriage of CO2 are closely related with the maintenance of the correct
blood pH level.
Blood is alkaline since its pH is 7.4 and the pH must be kept between 7.0 and 7.8 for life to
continue. The pH is so important for the maintenance of proteins (enzyme) behavior. From this
equation; CO2+H2
H2CO3
H++HCO3
Any increase in H+ concentration drives the reaction from right to left and more CO2 is formed.
Increased acidity stimulates the respiratory center, which increase formation of CO2 blown from
the lungs.
Oxygen transport:
Oxygen delivery to the tissues:
The O2 delivery system in the body consists of the; lungs
and the cardio-vascular system.
The O2 delivery to a particular tissue depends on;
1- The amount of O2 entering the lungs.
2- The adequacy of pulmonary gas exchange.
3- The blood flow to the tissue.
4- The capacity of the blood to carry O2.
The blood flow depends on the degree of constriction
of the vascular bed in the tissue and the cardiac out put.
The red blood cells contain reduced hemoglobin (Hb)
Deoxyhemoglobin, which has the property of combining
loosely with O2 to from oxyhemoglobin, which can lose
this O2 and revert to Hb.
Hb + O2
HbO2
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Dr. Saad Kleman Abd
The conversion of Hb to HbO2 is oxygenation not an oxidation, it depend on partial pressure of
oxygen (PO2). Therefore, it goes from left to right in the lungs and from the right to left in the
tissues where PO2 is low.
Dissociation Curve:
Which describe the total amount of each gas present in blood
as a function of its partial pressure.
Oxygen hemoglobin dissociation Curve:
The curve relating percentage saturation of the oxygencarrying power of hemoglobin to the PO2.
It has a characteristic sigmoid shape.
This curve can be used to determine how much O2 the tissues
take up as blood flows through the capillaries.
Factors affecting the Affinity of Hb for O2:
Three important conditions affect the oxygen hemoglobin dissociation curve:
1. The pH.
The pH of blood falls as its CO2 content increase.
More hydrogen ions = lower pH (more acidic). So that when the
PCO2 raises, the curve shift to the right.
2. The temperature.
A rise in temperature or fall in pH shifts the curve to right.
Therefore a higher PO2 required for Hb to bind a given amount of
O2.
3. The concentration of 2,3-diphospholglycerate(2,3-DPG).
Increased 2,3-DPG shift the reaction to the right causing more O2 to be liberated.
• All of these factors, together or individually, play a role during exercise, which decrease
hemoglobin's affinity for oxygen, causes hemoglobin to give up its oxygen to the active muscle
cells.
Boher effect: The decrease in O2 affinity of Hb, when the pH of blood falls, it related to the fact
that deoxygenated hemoglobin binds H+ more actively than does oxyhemoglobin.
Carbon dioxide transport :
CO2 is carried in three forms:
1. 70% of CO2 is carried as sodium bicarbonate HCO3– ions in plasma.
2. 5% is carried as dissolved CO2 molecules. CO2 is 20 times more soluble than O2 at body
temperature, and about 2.4 mL of CO2 is dissolved per liter of blood at a normal arterial PCO2 of
40 mm Hg.
3. 25% of CO2 is carried as carbamino compounds, which consist of CO2 bound to plasma
proteins or to hemoglobin within red blood cells.
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Dr. Saad Kleman Abd
* The CO2 that diffuses into red
blood cells is rapidly hydrated to
H2CO3 because of the presence of
carbonic anhydrase.
The H2CO3 dissociated to H+ and
HCO3- , and primarily Hb buffers the
H+.
Chloride Shift :
Since rise in the HCO3- content of
red cells is much greater than that in
plasma as the blood passes through
the capillaries. HCO3- diffuses in to
the plasma. About 70% of the HCO3- formed in the red cells enters plasma.
Normally the protein anions cannot cross the cell membrane, and the movement of Na + and K+ is
regulated by the sodium- potassium pump.
Electro chemical neutrality is maintained by diffusion of Cl- into red cells (chloride shift).
The Cl- content of red cells in venous blood is there for significantly greater than arterial blood.
The chloride shift occurs rapidly and is essentially complete in 1 second.
Control of Respiration:
Respiration is involuntary mechanism controlled by the nervous system, by certain centers in the
medulla and pones in the brain.
Respiration can be enhanced or inhibited voluntary for short periods.
 The rhythmicity center of the medulla:
 controls automatic breathing
 consists of interacting neurons that fire either during inspiration (I neurons) or
expiration (E neurons):
 I neurons - stimulate neurons that innervate respiratory muscles (to bring
about inspiration)
 E neurons - inhibit I neurons (to ''shut down'' the I neurons & bring about
expiration)
 Apneustic center (located in the pons) - stimulate I neurons (to promote inspiration)
 Pneumotaxic center (also located in the pons) - inhibits apneustic center & inhibits
inspiration
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Dr. Saad Kleman Abd
Factors involved in increasing respiratory rate:
I. Chemoreceptors - located in aorta & carotid arteries (peripheral chemoreceptors) & in the
medulla (central chemoreceptors)
Chemoreceptors stimulated more by increased
CO2 levels than by decreased O2 levels
Heavy exercise ==> greatly increases
respiratory rate.
 Conversely if the CO2 level in the blood is
too low, there is less drive on the
respiratory center and respiration is
temporarily depressed, until the CO2 in the
blood has built back to it’s original level.
II. Oxygen shortage stimulates breathing via
the chemo-receptors, when O2 content
falls, they send never impulses to the respiratory center to stimulate breathing.
 If the oxygen lack is very server, it depresses the respiratory center.
III.
The higher centers modify the respiratory center activity in :
a. Pain and strong emotions, such as fear and anxiety, act by way of the hypothalamus to
stimulate or inhibit the respiratory centers.
b. Laughing and crying also significantly alter ventilation.
The higher centers modify the breathing pattern completely when talking, singing (speaking
usually only occur during expiration).
Breathing
stops
during
swallowing to prevent food
inhalation into trachea.
IV. Stretch receptors in the
lungs
send
sensory
information up the vagus
nerve to the respiratory
center, without these
receptors the respiration
would much deeper than
it is, there is also stretch
receptor
in
skeletal
muscle and joint they
stimulated during exercise and though relay impulses directly or indirectly to the
respiratory center.
V. Sensory fibers from a variety of receptors in all parts of the body relay impulses to the
respiratory center some cause excitation and other inhibition.
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Asphyxia: A state when there is oxygen lack and excess carbon dioxide in the body. It stimulate
respiratory center.
Hypercapnia: A state when there is too much CO2 only in the body occur by breathing a gas
mixture which contains high percentage of CO2.
Anoxia or Hypoxia: A shortage of oxygen alone, it produces stimulation of respiration via
chemo receptors. Anoxia has been divided into four different types:
1- Anoxic Anoxia or Hypoxic Hypoxia: Due to a shortage of oxygen in inspired air or due to
lung disease.
2- Anemic Anoxia: Due to deficiency of hemoglobin or due to carbon monoxide poisoning,
carbon monoxide (CO) is a gas that has a great affinity for hemoglobin. By forming
carboxy hemoglobin it make the Hb no longer available for the carriage of O2.
3- Stagnant Anoxia: Due to slow flowing of the blood though the circulation, so insufficient
oxygen is supplied to the tissue although the lungs, oxygen tension and content are
normal.
4- Histo Toxic Anoxia: Due to the failure of the cell to extract oxygen from the blood it occur
in cyanide poisoning.
Cyanosis:A blue color of the skin & mucous membrane due to low concentration of the oxygen
in the blood. It seen in anoxic anoxia and stagnant anoxia.
Oxygen Excess:
The tension of O2 in the blood may be increased by breathing pure O2. Oxygen content of the
blood will not be increased largely because the hemoglobin is very nearly saturated when
breathing room air at see level. However, there will be a small increase in the dissolved oxygen in
the plasma.
Oxygen under high pressure is a poisonous gas and produce irritation of the lungs and toxic
effects on the enzymes of the body. Therefore, Care must be taken to persons taken high oxygen
tension for long periods.
Carbon dioxide lack :
CO2 can be reduced by voluntarily hyperventilation.
 If one breathes deeply and rapidly through the mouth for period of two minute the CO2
tension in the blood can be reduced to about one half of its normal value, the effect of this
washing out of the acid gas (carbon dioxide) is to produce alkalosis of the blood (PCO2 is
less than 35 mm Hg and the pH is greater than 7.45).
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Dr. Saad Kleman Abd
 This will lead to increases excitability of the nerves and muscles of the body, particularly
those of the arms and legs, [slight pressure on the nerve bring about muscular contraction
and the muscle may go into spontaneous spasm (tetany) ] .
Non-Respiratory air movements:
Coughing and sneezing:
When a large amount of mucous collects in the large airways by the action of cilia it is removed
by coughing. A cough is produced by making a forced expiratory effort against a closed larynx
after a large inspiration. A very high pressure is built up in the lungs and thorax. The larynx is
then open releasing a blast of air with a very high velocity that both narrows but at the same time
clears the large airways of mucus and foreign particles, coughing clear lower respiratory
passages it not clear smaller airways or alveoli.
The sneeze reflex is quite similar to the cough reflex, but impulses are initiated in the nose and
movements of the palate force the air through the nose rather than the mouth, thus clearing the
nasal passages. It clears the nasal passages.
Laughing/Crying; Cause the release of the breath in short bursts of air, it occurs in emotional
responses.
Yawing: It is a deep inhalation with widely opened jaws. It needed for increasing oxygenation
of a large number of alveoli.
Hiccuping: Sudden inhalation of the air in response to spasm of diaphragm, since the glottis is
closed. During hiccuping ;The inhalated air hits the tissue of the closed glottis, this create the
characteristic hiccupping sound.(it has no function).
Speaking: Air is forced through the vocal cords of the larynx causing the vocal cords to vibrate.
This creates a sound .The sound is formed into words by the lips, tongue & the oral cavity. (It
needed for communication).
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