Download Respiration

Respiration
Aim of Respiration
The body needs oxygen for metabolism inside all the cells and produces
CO2.The respiratory system is responsible for providing O2 and
removal of CO2 from the body as a whole.
Respiration
╩
External resp.
(Resp.at alveolar level)
Exchange of O2 and CO2 between
Alveolar air and pulmonary capillary
Blood
Internal resp.
(Resp. at the cell level)
utilization of O2 and
production of CO2
by the cells of the tissue
External respiration is divided into 4 stages:
1. ventilation( movement of air in and out between the lungs and
atmosphere)
2. diffusion( movement of oxygen from the alveoli to the
pulmonary capillary blood, and carbon dioxide in the opposite
direction)
3. transport of gases( transport of O2 & CO2 by the blood to or
from the tissues)
4. regulation( by the respiratory centers)
Respiratory system is formed of
│
│
│
┘
│
└
 Respiratory passages.
Muscles
Centers
▌
▌
╩
╩
Conducting zone
resp.zone
insp
expir.
1-16
17-23
resting Accessory
Respiratory passages:
a- conducting zone: starts from the nose- nasal cavitypharynx – larynx- trachea- rt and lt main bronchi- primary
bronchi- secondary bronchi- tertiary bronchi- terminal
bronchiol. (no gass exchange occure. It function in
filtration, humidification,warming of the inspired air,
conducts the air to the respiratory zone)
b- Respiratory zone (in which gass exchange between the air
in them and the surrounding capillary blood): includes
respiratory bronchioles- alveolar ducts- alveolar sacsalveoli.
Functions of the lung
 Respiratory functions ( O2 supply&removal of CO2).
 metabolic functions. (non-resp.functione.g synthesis of
surfactant, actvation of angiotensin I into angiotensin II).
Mechanics of pulmonary ventilation:
1. The muscles that cause lung expansion and contraction
**Inspiratory muscles
a- during resting breathing, diaphragm, external intercostal
muscles
b-During forced inspiration (e.g exercise, bronchial asthma the
accessory muscles also contract like sternomastoids muscle).
** Expiration is a passive process by elastic recoil of the lungs
so no need for muscle contraction during resting expiration. but
forced expiration occur by contraction of the abdominal muscles
& internal intercostal muscles to push the diaphragm upwards
and compress the lung to push air out.
2. Movement of air in and out of the lungs and the pressure
that cause it
-the pleural pressure and its changes during
respiration( the pleural pressure is negative ( -5cm
H2O) in between breathes. Becomes -7.5 cm H2O
during inspiration
-alveolar pressure: the pressure inside the alveoli =
zero (atmospheric= 760mmHg in between breates,
during inspiration it becomes -1cm H20, in expiration it
becomes +1cmH20) in
-Trans-pulmonary pressure is the intrapleural
pressure - the alveolar pressue.
 Inspiration is an active process by nerve discharge
from ( dorsal respiratory group of neurons)DRG
▬> phrenic nerves ▬> diaphragm
 Expiration is a passive process by elastic recoil of
lung and chest wall, but
VRG
▬>
Forced expiration
intercostals nerves
│
▼
Contraction
◄▬ intercostals muscles
Mechanics of ventilation
 How inspiration occur.
 Pressure changes as IPP, Inter-alveolar pressure.
 How expiration occur.
Respiratory volumes and capacities
(measured by spirometery)there are
4 lung volumes
4lung capacities
Diffusion:
-respiratory membrane
-transport of gases
O2 is transported in 2 forms
1-Dissolved O2 ( 1.5 %)
2- In combination with Hb,( 98.5 %) called oxy haemoglobin.
-100 ml of blood carry 20 ml O2 gives 5 ml to the tissue/min.
All the blood gives 250 ml/min.
1- {Dissolved ( 7 %)
CO2 2- { in combination with Hb ( 23 %)
3- { as bicarbonate ions (70 %)
-each 100 ml of blood carries 4 ml of CO2 from the tissues
when it passes through.
All the blood carries 200 ml of CO2.
Respiratory physiology
The major function of the respiratory system is to supply the body
with Oxygen and to dispose of carbon dioxide. To do this, at least
four distinct events, collectively called RESPIRATION, must occur:
1. Pulmonary ventilation: Air movement into and out of the
lungs. This process of pulmonary ventilation is commonly called
breathing.
2. External respiration: Gas exchange (oxygen loading and
carbon dioxide unloading) between the pulmonary blood and alveoli.
3. Respiratory gas transport: Oxygen and carbon dioxide
are transported to and from the lungs and the tissue cells.
4. Internal respiration: At systemic capillaries, gas exchanges
occur between the blood and tissue cells.
Mechanics of breathing:
Breathing or pulmonary ventilation is a mechanical process that
depends on volume changes occurring in the thoracic cavity.
A rule: volume
changes leads to pressure changes which
lead to the flow of gases to equalize the pressure.
A gas, like a liquid, always takes the shape of its container.
However unlike liquid, a gas fills its container.
Therefore, in a large volume, the gas molecules will
be far apart and the pressure (created by the gas
molecules hitting each other and the walls of the
container) will be low.
If the volume is reduced, the gas molecules will be
closer together and the pressure will rise.
Inspiration
When the inspiratory muscles, the diaphragm and external
intercostals, contract, the size of the thoracic cavity
increases.
Since the lungs adhere tightly to the thorax walls, they are
stretched to the new, larger size of the thorax.
As intrapulmonary volume (the volume within the lungs)
increases, the gases within the lungs spread out to fill the
larger space.
The resulting decrease in the gas pressure in the lungs
produces a partial vacuum (pressure less than atmospheric
pressure), which sucks air into the lungs.
Air continues to move into the lungs until the
intrapulmonary pressure equals atmospheric pressure.
This event is called inspiration (inhalation).
Expiration:
Expiration (exhalation) in healthy people is largely a passive
process that depends more on the natural elasticity of the
lungs than on muscle contraction.
As the inspiratory muscles relax, both the thoracic and
intrapulmonary volumes decrease, the intrapulmonary
pressure rises to a point higher than atmospheric pressure.
This causes the gases to flow out to equalize the pressure
inside and outside the lungs.
Normally expiration is effortless, but if the respiratory
passageways are narrowed by spasms of the bronchioles (as
in asthma) or obstructed with mucous or fluid (as in chronic
bronchitis or pneumonia), expiration becomes an active
process.
In such cases of forced expiration, the internal intercostals
muscles are activated to help depress the rib cage and the
abdominal muscles contract and help to force air from the
lungs by squeezing the abdominal organs against the
diaphragm.
The normal pressure within the pleural space (intrapleural
pressure) is always negative, and this is the major factor
preventing collapse of the lungs.
If for any reason the intrapleural pressure becomes equal to the
atmospheric pressure, the lungs immediately recoil completely and
collapse.
Homeostatic imbalance
During atelectasis, or lung collapse, the lung is useless for
ventilation.
This is seen when air enters the pleural space through a chest
wound.
The presence of air in the intrapleural space, which disrupts the
fluid bond between the pleurae, is referred to as pneumothorax.
Respiratory volumes and capacities
4 volumes, 4 capacities
Many factors affect respiratory capacity as a person size,
sex, age and physical condition.
Normal quiet breathing moves approximately 500 ml of air
(about a pint) into and out of the lungs with each breath.
This respiratory volume is referred to as tidal volume
(TV).
The amount of air that can be taken in forcibly over the
tidal volume is the inspiratory reserve volume (IRV),
is approximately between 2100 and 3200 ml.
The amount of air that can be forcibly exhaled after a tidal
expiration, the expiratory reserve volume (ERV) is
approximately 1200 ml.
About 1200 ml of air still remains in the lungs and cannot
be voluntarily expelled, this is called residual
volume(RV).
Residual volume air is important because it allows gas
exchange to go on continuously even between breaths and
helps to keep the alveoli open (inflated).
Lung capacities
1- Inspiratory capacity= TV+IRV
2-Vital capacity
Is the sum of the TV + IRV + ERV
The air that enters the respiratory tract and remains
in the conducting zone passage ways and never reaches
the alveoli. This is called the dead space volume.
During normal tidal breath, it amounts to about 150 ml.
3-Functional residual capacity(FRC)=
RV+ERV
4- total lung capacity= TV+IRV+ERV+RV
The functional volume: the air that actually reaches
the respiratory zone and contributes to gas exchange- is
about 350ml.
Respiratory volumes and capacities are
measured with a spirometry.
In pneumonia, inspiration is obstructed and the IRV and VC
decrease.
In emphysema, where expiration is decreased, ERV is much
lower than normal and the residual volume is higher.
External respiration, gas transport, and
internal respiration
External respiration: is the actual exchange of gases
between the alveoli and the blood (pulmonary gas exchange),
and
internal respiration: is the gas exchange process that
occurs between the systemic capillaries and the tissue cells.
It is important to remember that all gas exchange is made
according to the laws of diffusion, that is, movement
occurs toward the area of lower concentration of the
diffusing substance.
External respiration:
During External respiration , the oxygen tends to move from the
air of the alveoli through the respiratory membrane into the more
oxygen-poor blood of the pulmonary capillaries, and because the
concentration of carbon dioxide is much higher in the pulmonary
capillaries than it is in the alveolar air, it will move from the blood
into the alveoli, and be flushed out of the lungs during expiration so
the blood draining from the lungs into the pulmonary veins is
oxygen-rich and is ready to be pumped to the systemic circulation.
Gas transport in the blood
Oxygen is transported in the
blood in two ways. Most attaches to hemoglobin molecules
inside the RBCs to form oxyhemoglobin,a very small
amount of oxygen is carried dissolved in the plasma.
Most carbon dioxide is transported in plasma as the
bicarbonate, which play a very important role in the blood
buffer system.20 to 30 % of CO2 is carried inside the RBCs
before CO2 can diffuse out of the blood into the alveoli. It must
first be released from its bicarbonate ion form.
Bicarbonate ions must combine with hydrogen ions(H+) to
form carbonic acid(H2CO3).carbonic acid quickly splits to form
water and carbon dioxide, and carbon dioxide then diffuses
from the blood and enters the alveoli.
Internal respiration.
The exchange of gases that takes place between the blood and tissue
cells.
In which oxygen is unloaded and carbon dioxide is loaded into the
blood.
Carbon dioxide diffusing out of tissue cells enters the blood. In the
blood, it combines with water to form carbonic acid, which quickly
releases the bicarbonate ions.
Most conversion of carbon dioxide to bicarbonate ions actually
occurs inside the RBCs, where a special enzyme (carbonic
anhydrase) is available. Then the bicarbonate ions diffuse out into
plasma, where they are transported.
At the same time, oxygen is released from hemoglobin, and the
oxygen diffuses quickly out of the blood to enter the tissue cells.
Homeostatic imbalance
 Inadequate oxygen delivery to body tissues is called
hypoxia.
 Carbon monoxide poisoning represents a type of hypoxia.
 CO is odorless, colourless gas that competes vigorously with
oxygen for the same binding sites on hemoglobin.
 Carbon monoxide poisoning is the leading cause of death
from fire.
 Treatment of those with CO poisoning is to give 100%
oxygen until CO has been cleared from the body.
Control of respiration
Regulation
Normal regulation
Medulla
DRG
VRG
Pons
Pneumotaxic
Apneustic
Neural regulation: setting the basic rhythm
The activity of the respiratory muscles, the diaphragm and external
intercostals, is regulated by nerve impulses transmitted to them
from the brain by the phrenic and intercostal nerves.
The neural centers that control respiratory rhythm and depth are
located in the medulla and pons.
The medulla, which sets the basic rhythm of breathing, contains a
self-exciting inspiratory center (DRG).
The pons centers appear to smooth out the basic rhythm of
inspiration and expiration set by the medulla.
Normal respiratory rate is 12-15 respiration /min.
Factors influencing respiratory rate and depth:
Chemical factors:
Increased levels of carbon dioxide and decreased blood
PH are the most important stimuli leading to increased rate
and depth of breathing
Changes in oxygen concentration in the blood are detected
by chemoreceptor regions in the aorta (aortic arch) and
carotid artery (carotid body).these send impulses to the
medulla when blood oxygen levels are drooping.
Decreases in oxygen levels only become important stimuli
when they are dangerously low.
As carbon dioxide or other sources of acids begin to
accumulate in blood and blood PH starts to drop, you begin
to breathe more deeply and more rapidly. This breathing
pattern is called hyperventilation.
 Hypoventilation or hyperventilation can dramatically
change the amount of carbonic acid in the blood.
Carbonic
acid increases dramatically during
hypoventilation and decreases during
hyperventilation.
Lung cancer:
the facts behind the smoke screen
 Lung cancer account for one third of all cancer
deaths in the United States.
 Over 90% of lung cancer patients are smokers.
 Cigarette increases one’s heart rate, constricts the
peripheral blood vessels, disrupts the flow of air in
the lungs, and affects one´brain and mood.
 Long-term smoking contributes to atherosclerosis
and heart disease, strokes, cataracts, and early onset
of osteoporosis.
 Secondhand tobacco smoke causes 3000 lung cancer
deaths among non-smokers in the USA.
 Sticky mucous and the action of cilia do a fine job of
protecting the lungs from chemical and biological
irritants.
Smoking slows the movements of cilia that clear this
mucus and depresses the activity of the lung macrophages.
Pooling of mucus in the lower respiratory tree and an
increased frequency of pulmonary infections including
pneumonia and COPD.
The most effective treatment of lung cancer is:
-complete removal of the diseased lung in an attempt to halt
metastasis
-radiation
-chemotherapy.
 Only small cell carcinoma responds to
chemotherapy.
Bronchial astma :
increased air way resistance( spasm of
bronchial muscles) due to allergic condition leading to diffculty of
breathing, wheezes, cough, dyspnea.
Pneumonia:-Inflammatory condition leading to accumulation
of blood cells and fluids in some or all of the alveoli i(
consolidation).
(infection by viruses or bacterial or other organisms that leads to
Emphysema (COPD):
prolonged smoking leads to
infections and cough which after long time cause
obstruction of the small air ways by mucus and destruction
of the wall of the alveoli, leading to diffculty of breathing,
hypoxia(decreased O2) and hypercapnia(increased CO2)