coplemplete respiratory system

1. Physiology
Of
Respiratory system(1)
AliShamyar
MedicalDoctor

2. contents
1)Physiological anatomy of respiratory
system
2)Mechanism of respiration
3)Pulmonary volume, capacities and
function tests
4)Transport of Gases
5)Exchange of Gases
6)Regulation of respiration
7)Applied aspects

3. 1)Physiological anatomy of respiratory system
Anatomically, respiratory
tract is divided into :
1-upper, which consist of
organs outside thorax ( nasal
cavity, pharynx
pharynx and larynx)
2-lower respiratory tract which
consist of organs within thorax
( trachea, bronchi, bronchioles,
alveolar duct and alveoli).
The discussion is mainly
concentrated on the
lower respiratory tract and the
related physiology.

4. Respieatory unit
Respiratory unit is the
terminal portion of the
respiratory tract.
It includes:
1-respiratory bronchioles
2-alveolar ducts
3-alveolar atrium
4-alveolar sac
5-alveolus
A typical pair of human lungs contain about 375-800 million alveoli,
producing 70 m2 (750 sq ft) of surface area. Each alveolus is wrapped in
a fine mesh of capillaries covering about 70% of its area.
The diameter of an alveolus is between 200 and 500 μm.

5. Water surface tension
The surface tension of water is 7.2 Pa at 25°C .
The surface tension arises from the polar nature of the water molecule

6. alveolar surface tension

7. Law of LaPlace

9. Tytpes of respirationn:
1-external respiration:
-exchange of O2 &CO2
between lungs and
blood
2-internal respirationn:
-exchange of O2 and
CO2 between blood
and tissues
discussion

10. 2)Mechanism of ventilation
Major respiratory muscles:

11. Mechanics of ventilation

12. Mechanics of ventilation
Boyle’s law states that the volume of gas is
inversely proportional to pressure (when
temperature is constant).
Therefore:
1-When the volume of the thoracic cavity
increases – the volume of the lungs increases
and the pressure within the lungs decreases.
2-When the volume of the thoracic cavity
decreases – the volume of the lungs decreases
and the pressure within the lungs increases.
Air
ouside lungs
Air
ouside lungs

13. Mechanics of ventilation

14. Mechanics of ventilation
When the plastic
wrap is pulled,
the balloon
inflates.
When the plastic
wrap is pushed,
the balloon
deflates.

15. Mechanics of ventilation
The space between the outer surface of the lungs and inner
thoracic wall is known as the pleural space.
This is usually filled with pleural fluid, forming a seal which
holds the lungs against the thoracic wall.
This seal ensures that when the thoracic cavity expands or
reduces, the lungs undergo expansion or reduction in size
accordingly.
During breathing, the contraction and relaxation of muscles
acts to change the volume of the thoracic cavity – thereby
altering the volume of the lungs, and changing
the pressure inside the lungs.

16. Basic Concepts
Elastic recoil of the chest wall,
tries to pull the chest outward
Elastic recoil of lung, creates an
inward pull
Intra-alveolar pressure P < atmospheric P Inspiration
Intra-alveolar pressure P > atmospheric P Expiration

17. Transmural( or alveolar distending Pressure )Gradient

18. Mechanics of ventilation
Inspiration is the phase of ventilation in which
air enters the lungs.
It is initiated by contraction of the inspiratory muscles:
1-Diaphragm:
- flattens, extending the superior/inferior dimension
of the thoracic cavity.
2-External intercostal muscles :
- elevates the ribs and sternum, extending the
anterior/posterior dimension of the thoracic cavity.

19. Mechanics of ventilation
The action of the inspiratory
muscles results in an
increase in the volume of
the thoracic cavity.
As the lungs are held
against the inner thoracic
wall by the pleural seal, they
also undergo an increase in
volume.

20. Mechanics of ventilation
As per Boyle’s law, an
increase in lung volume
results in a decrease in
the pressure within the
lungs.
The pressure outside
the lungs is now higher;
– and so air rushes into
the lungs, moving down
the pressure gradient.

21. Mechanics of ventilation
Expiration is the phase of ventilation in which air is expelled
from the lungs.
It is initiated by relaxation of the inspiratory muscles:
1-Diaphragm :
- returns to resting position, reducing the
superior/inferior dimension of the thoracic cavity.
2-External intercostal muscles :
- relaxes to depress the ribs and sternum, reducing the
anterior/posterior dimension of the thoracic cavity.

22. Mechanics of ventilation
The relaxation of the
inspiratory muscles
results in a decrease in
the volume of the
thoracic cavity.
The elastic recoil of
the previously
expanded lung tissue
allows them to return
to their original size.

23. Mechanics of ventilation
As per Boyle’s law, a
decrease in lung volume
results in an increase in
the pressure within the
lungs.
The pressure inside the
lungs is now higher than
outside – and so air moves
out of the lungs, down the
pressure gradient.

24. Mechanism of ventilation

25. Forced breathing
Forced breathing is an active mode of breathing which utilizes
additional muscles to rapidly expand and contract the thoracic
cavity volume. It most commonly occurs during exercise.

26. Forced breathing
Active Inspiration
Active inspiration involves the contraction of the accessory
muscles of breathing (in addition to the diaphragm and external
intercostals).
All these muscles act to increase the volume of the thoracic
cavity:
1-Scalenes – elevates the upper ribs.
2-Sternocleidomastoid – elevates the sternum.
3-Pectoralis major and minor – pulls ribs outwards.
4-Serratus anterior – elevates the ribs
(when the scapulae are fixed).
5-Latissimus dorsi – elevates the lower ribs.

27. Forced breathing
Active Expiration:
Active expiration utilises the contraction of several thoracic
and abdominal muscles.
These muscles act the decrease the volume of the thoracic
cavity:
1_Anterolateral abdominal wall – increases the intra-
abdominal pressure, pushing the diaphragm upwards into
the thoracic cavity.
2-Internal intercostal – depresses the ribs.
3-Innermost intercostal – depresses the ribs.

28. 3)Pulmonary volume, capacities and function tests

29. 500 ml

30. 2000-3000 ml

31. 800-1100 ml

32. Residual Volume(RV)
It is the volume of air remaining in the lungs after maximal exhalation.It is indirectly
measured from summation of FRC and ERV and cannot be measured by spirometry.
In obstructive lung diseases with features of incomplete emptying of the lungs and air
trapping, RV may be significantly high.
1000-1200 ml

33. Inspiratory capacity(IC)
It is the maximum volume of air that can be inhaled
following a resting state. It is calculated from the sum of
inspiratory reserve volume and tidal volume. IC = IRV+TV
2500-3500 ml

34. Vital Capacity(VC)
It is the total amount of air exhaled after maximal inhalation. The
value varies according to age and body size. It is calculated by
summing tidal volume, inspiratory reserve volume, and expiratory
reserve volume. VC = TV+IRV+ERV.
3300-4700 ml

35. Function Residual Capacity(FRC) :
It is the amount of air remaining in the lungs at the end of a normal
exhalation. It is calculated by adding together residual and expiratory
reserve volumes. FRC = RV+ERV.
1800-2200 ml

36. Total Lung Capacity(TLC)
It is the maximum volume of air the lungs can accommodate or sum
of all volume compartments or volume of air in lungs after maximum
inspiration. TLC is calculated by summation of the four primary lung
volumes. (TV, IRV, ERV, RV)
4000-6000 ml

37. Dead space

38. Dead space represents the volume of ventilated air that does
not participate in gas exchange.
The two types of dead space are anatomical dead space and
physiologic dead space:
1- Anatomical dead space is represented by the volume of
air that fills the conducting zone of respiration made up
by the nose, trachea, and bronchi.
This volume is considered to be 30% of normal tidal volume
(500 mL ); (the value of anatomic dead space is 150 mL ).
2-Alveolar dead space is the volume of air in the respiratory
zone that does not take part in gas exchange.
Physiologic or total dead space is equal to anatomic plus
alveolar dead space .

39. spirometer

40. Alveolar ventilation rate

41. Thanks for your
attention