lecture 2: how we can inhale and exhale a gas it's just a simple.

1. 24-9-2019

2. • During normal quite breathing the inspiratory phase is
active process and the expiratory phase is passive
process, but in heavy exercise both phases are active.
• Two mainly factors are responsible for respiration:
1- Muscles (expands and contracts the thoracic cage) which
can be divided into:
A. Inspiratory muscles also subdivided into (primary and
Accessory muscles)
B. Expiratory muscles also subdivided into (primary and
Accessory muscles).
2- Pressures (cause the movement of air in and out of the
lungs) which can be divided into:
A. Intrapleural or intrathoracic pressure.
B. Alveolar or intapulmonary pressure.
C. Transpulmonary pressure.

3. Inspiratory Muscles:
• Primary Inspiratory Muscle:
A) Diaphragm {phrenic nerve (C3 to C5)}
B) External intercostal muscles {intercostal nerves (T1
to T11)}.
• Accessory Inspiratory Muscle:
A) Sternocleidomastoid m.
B) Sclena.
C) Posterior superior serratus.
D) Levator costernum.
E) Pectoralis.
F) Interchondral part of internal intercostal muscles.

4. Expiratory Muscles:
• Primary Expiratory Muscles:
A) Internal intercostal muscles.
• Accessory Expiratory Muscle:
A) Serratus posterior inferior.
B) Abdominal muscles.
• Pulmonary movement is participated by 3 main factors:
1. The diaphragm.
2. The muscles that elevate or depress the ribs.
3. The elasticity recoil of the lungs.

5. • 3 way to increase or decrease the lung volume:
A. Vertical diameter “diaphragm”
B. Anterioposterior diameter.
C. Transverse diameter.
1- Diaphragm:
• Is the almost first methods that the normal quite breathing is
accomplished in both inspiration and expiration.
2- The muscles that are elevate or depress the ribs:
• Aids to enter or exist the air b/w the atmosphere and the
thorax.
3- The elasticity recoil of lung:
• Help the air or gases to move from lungs to the atmosphere in
normal quite respiration but in heavy expiration the
abdominal muscles will interfere.
• Two recoils of respiratory system:
A. The Lungs recoil.
B. The chest wall recoils.
“muscles that are
elevate or depress the
ribs”

7. Definitions
 Dalton Law: is the sum of all partial pressure
of gasses equal total pressure.
 Atmospheric pressure = 760 mmHg or 1
Atm.
 Pressure gradient: is movement of gases
from highest pressure to lowest pressure.
 Boyle’s law: when lung volumes increase
the pressure decrease and vice verse.

9. INTRAPLEURAL PRESSURE (intra-thoracic
pressure):
• Intra-pleural pressure is the pressure existing in pleural cavity,
that is, in between the visceral and parietal layers of pleura.
• It is exerted by the continual suction of the fluid that lines the
pleural cavity.
• Always negative.
• -4mmHg or -5mmHg or (less than atmospheric pressure).
• Importance of this pressure:
A. It prevents the collapsing tendency of lungs.
B. Responsible for venous return.

10. INTRA-ALVEOLAR PRESSURE (intrapulmonary
pressure):
• Intraalveolar pressure is the pressure existing
in the alveoli of the lungs.
• -1mmHg (inspiration), +1mmHg (expiration).
• Importance of this pressure:
A. Causes flow of air in and out of alveoli.
B. Helps in exchange of gases between the
alveolar air and the blood.

11. Transpulmonary Pressure
• Is the Difference between
Alveolar and Pleural
Pressures.
• it is a measure of the elastic
forces in the lungs that tend
to collapse the lungs at each
instant of respiration, called
the recoil pressure.

12. Mechanism of Pulmonary Ventilation:

13. Collapsing Tendency of Lungs
• Lungs are under constant threat to collapse even in
resting conditions because of certain factors.
• Factors Causing Collapsing Tendency of Lungs:
1. Elastic property of lung tissues.
2. Surface tension.
• Factors Preventing Collapsing Tendency of Lungs:
1. Intrapleural pressure.
2. Surfactant.

14. Surface tension:
• When water forms a surface with air, the water molecules
on the surface of the water have an especially strong
attraction for one another.
• This tends to force air out of the alveoli through
the bronchi and, in doing so, causes the alveoli to try to
collapse.
• In the presence of surfactant Substance reduce this surface
tension, thus prevents collapse of the alveoli.

15. Surfactant:
• Surfactant: is a complex mixture of several phospholipids,
proteins, and ions.
• The most important components are the phospholipid
dipalmitoyl phosphatidylcholine,
surfactant apoproteins, and calcium ions.
• Importance or function of surfactant:
• reduces the surface tension of water.
A. Stabilization of the alveoli.
B. Inflation of lungs after birth.
C. Defense within the lungs against infection and
inflammation.
• Pulmonary surfactant is secreted by:
I. Type II alveolar epithelial cells.
II. Bronchioles Clara cells.

16. The law of Laplace:
The law of Laplace states that the pressure tending to collapse an alveolus is directly
proportional to the surface tension generated by the molecules of liquid lining the
alveolus and inversely proportional to alveolar radius.

17. • a large alveolus (one with a large radius) will have a
low collapsing pressure and therefore will require
only minimal pressure to keep it open.
• a small alveolus (one with a small radius) will have a
high collapsing pressure and require more pressure
to keep it open.

18. Compliance of the Lungs
• Compliance: is the ability of the lungs and thorax to
expand or it is the expansibility of lungs and thorax.
• Determination of compliance is useful as it is the
measure of stiffness of lungs.
• Stiffer the lungs, less is the compliance.
• Ptp = Alveolar pressure – pleural pressure.
• If lungs could be removed from thorax, the
expansibility (compliance) of lungs alone is more and
double.
• It is because of the absence of inertia and restriction
exerted by the structures of thoracic cage, which
interfere with expansion of lungs.

19. TYPES OF COMPLIANCE:
1- Static compliance:
By measuring pressure and
volume when breathing does not
take place.
2- Dynamic compliance:
During breathing.

20. Factors determine Compliance:
A) Increase in Compliance:
1. Physiological condition: Old age.
2. Pathological condition: Emphysema.
B) Decrease in Compliance:
1. Deformities of thorax like kyphosis and
scoliosis.
2. Fibrotic pleurisy (inflammation of pleura
resulting in fibrosis)
3. Paralysis of respiratory muscles.
4. Pleural effusion.
5. Abnormal thorax such as pneumothorax,
hydrothorax, hemothorax and
pyothorax.

21. WORK OF BREATHING:
• Is work done by respiratory muscles during breathing
(inspiration) to overcome the resistance in thorax and
respiratory tract.
• Three types of resistance:
1. Airway resistance: (increases during bronchiolar
constriction).
2. Elastic resistance of lungs and thorax: (Energy is
required to expand lungs and thorax against the elastic
force).
3. Non-elastic viscous resistance: (Energy is also required
to overcome the viscosity of lung tissues and tissues of
thoracic cage).

22. • Normal quiet respiration, only 3 to 5 percent of
the total energy expended by the body is
required for pulmonary ventilation.
• During heavy exercise, the amount of energy
required can increase as much as 50-fold,
especially if the person has any degree of
increased airway resistance or decreased
pulmonary compliance.