1. Respiratory System

2. Non-respiratory functions of the system:
1-water loss and heat elimination, also keeps alveoli wet
2-inhances venous return
3-acid-base balance
4-enables speech
5-defends against foreign inhaled matters.
6-removes, modifies, & activate or inactivate materials “prostglandins”
7-smelling
8-shape of the chest
9-protects heart & vessels
10-aireate the blood between respiratory phases

3. Respiratory Physiology
Structure :
Air conducting channels
Respiratory spaces
 lungs float in the thoracic cavity + pleura

4. Respiratory passages comprises two portions A- Conducting part
1- Nose and mouth
2- Nasal cavity
3- Pharynx
4- Larynx
5- Trachea
6- Bronchi and Bronchioles
Inside lungs
B- Respiratory part
1- Alveolar ducts, Alveolar
Sacs and alveoli inside
lungs
Larynx

5. Respiratory Physiology
Steps:
1- pulmonary ventilation: air flow between the atmosphere and the lungs.
2- diffusion of gasses between the alveoli and the blood.
3- transport.
4- regulation.

6. Steps of external respiration
Atmosphere
Steps of external respiration 1
Ventilation or gas exchange between
the atmosphere and air sacs (alveoli)
in the lungs O2
CO2
Alveoli of lungs 2
Exchange of O2 and CO2 between air
in the alveoli and the blood
CO2 O2
Pulmonary
circulation 3
Transport of O2 and CO2 between the
lungs and the tissues
FIGURE 12-1: External and internal respiration. External respiration encompasses the steps involved in the exchange of O2 and CO2 between the external environment and tissue cells (steps 1 through 4). Internal respiration encompasses the intracellular metabolic reactions involving the use of O2 to derive energy (ATP) from food, producing CO2 as a by-product.
Systemic
circulation
CO2 O2 4
Exchange of O2 and CO2 between the
blood and the tissues
Food + O2
CO2 + HO2 + HTP
Internal respiration
Tissue cell
Fig. 12-1, p. 366

7. Mechanics of ventilation
1.By down word and upward movement of the diaphragm  lengthen or shorten(Normal)
2.By elevation and depression of the ribs (anteropost ) ribs and sternum moves away from the spine (20% more)

8. Mechanics of ventilation
Muscles :
1- Inspiratory : -
Diaphragm
External intercostals
Sternocloidomastoid Sternum - Scalini (2 ribs)
Anterior serrati

9. Mechanics of ventilation
2- Expiratory muscles : -
internal intercostals
Abdominal recti

10. Accessory muscles of inspiration
Internal
intercostal
muscles
Sternocleidomastoid
Scalenus
Muscles
of active
expiration
Sternum
Ribs
External
intercostal
muscles
FIGURE 12-10: Anatomy of the respiratory muscles.
Diaphragm
Abdominal
muscles
Major
muscles of
inspiration
Fig , p. 373

11. Respiratory muscles

12. Airway resistance.. Due to friction when air moves through airways.
Medium-sized bronchi contribute most of the resistance.
Small airways contribute 20 %.

13. Factors responsible for elastic recoil of lungs
Elastic fibers in the lungs & chest wall.
The surface tension in the fluid lining the alveoli.

14. Cont… At end of quit exp-5 cm H2o. At end of quit insp -8 cm H2o.
More (-) during maximal inspiration.
Becomes (+) during maximal expiration.

15. Lollipop “Lung” “Pleural sac”
Water-filled
balloon
“Pleural sac”
Right pleural sac
Left pleural sac
FIGURE 12-4: Pleural sac. (a) Pushing a lollipop into a water-filled balloon produces a relationship analogous to that between each double-walled, closed pleural sac and the lung that it surrounds and separates from the thoracic wall. (b) Schematic representation of the relationship of the pleural sac to the lungs and thorax. One layer of the pleural sac closely adheres to the surface of the lung, then reflects back on itself to form another layer, which lines the interior surface of the thoracic wall. The relative size of the pleural cavity between these two layers is grossly exaggerated for the purpose of visualization.
Parietal pleura
Right
lung
Left
lung
Thoracic wall
Visceral pleura
Pleural cavity
filled with
intrapleural fluid
Diaphragm
Pleural cavity
filled with
intrapleural fluid
Fig. 12-4, p. 369

16. Respiratory pressure 1- Pleural pressure: fluid pressure
slight suction that helps the lungs to open at rest .
(-5 to -7.5)cm H2O, during normal inspiration.

17. Cont… At end of quit exp-5 cm H2o. At end of quit insp -8 cm H2o.
More (-) during maximal inspiration.
Becomes (+) during maximal expiration.

18. Respiratory pressure A- Glottis open, no air flow 0 cm H2O
2- Alveolar pressure :
the pressure Inside the Alveoli:
A- Glottis open, no air flow 0 cm H2O
B- Inward flow sub atmospheric (-1 cm H2O) within 2s
C- Outward flow positive (1 cm H2O) within 2-3s.

19. Atmospheric pressure (the pressure exerted by the
weight of the gas in the
atmosphere on objects on the Earth’s surface—760 mm Hg at sea level)
Atmosphere
760 mm Hg
Airways
Thoracic wall
Intra-alveolar pressure (the pressure within
the alveoli—760 mm Hg when equilibrated
with atmospheric pressure)
Plural wall
FIGURE 12-5: Pressures important in ventilation.
Lungs
Intrapleural pressure (the pressure within the pleural sac—the pressure exerted outside the lungs within the thoracic cavity, usually less than atmospheric pressure at 756 mm Hg)
756 mm Hg
Fig. 12-5, p. 370

20. Respiratory pressure 3- Transpulmonary pressure :
Pressure difference between the alveolar pr. and pleural pr. [pr.differ. b/w alveoli and outer surfaces of the lungs]
it measures elastic forces that tend to collapse the lungs each point of expansion [recoil pressure] .

21. Numbers are mm Hg pressure.
Airways
Pleural cavity
(greatly exaggerated)
Lung wall
Lungs (alveoli)
Thoracic wall
FIGURE 12-7: Transmural pressure gradient. Across the lung wall, the intra-alveolar pressure of 760 mm Hg pushes outward, while the intrapleural pressure of 756 mm Hg pushes inward. This 4-mm Hg difference in pressure constitutes a transmural pressure gradient that pushes out on the lungs, stretching them to fill the larger thoracic cavity.
Transmural pressure gradient
across lung wall =
intra-alveolar pressure minus
intrapleural pressure
Transmural pressure gradient
across thoracic wall =
atmospheric pressure minus
intrapleural pressure
Numbers are mm Hg pressure.
Fig. 12-7, p. 371

22. Inspiration Expiration
Intra-alveolar
pressure
Atmospheric
pressure
Transmural pressure
gradient across the
lung wall
Intraplural
pressure
FIGURE 12-13: Intra-alveolar and intrapleural pressure changes throughout the respiratory cycle.
Fig , p. 375

24. 760 760 760 760 760 756 756 Traumatic pneumothorax
Puncture wound
in chest wall
760
760
760
760
756
756
FIGURE 12-8: Pneumothorax. (a) Traumatic pneumothorax. A puncture in the chest wall permits air from the atmosphere to flow down its pressure gradient and enter the pleural cavity, abolishing the transmural pressure gradient.
Traumatic pneumothorax
(Continue to the next slide)
Numbers are mm Hg pressure.
Fig. 12-8a, p. 371

25. Spontaneous pneumothorax Numbers are mm Hg pressure.
760
Hole in lung
760
760
760
760
756
756
FIGURE 12-8: Pneumothorax. (c) Spontaneous pneumothorax. A hole in the lung wall permits air to move down its pressure gradient and enter the pleural cavity from the lungs, abolishing the transmural pressure gradient. As with traumatic pneumothorax, the lung collapses to its unstretched size.
Spontaneous pneumothorax
Numbers are mm Hg pressure.
Fig. 12-8c, p. 371

26. (Continue to the next slide) Numbers are mm Hg pressure.
760
760
760
760
760
760
756
FIGURE 12-8: Pneumothorax. (b) When the transmural pressure gradient is abolished, the lung collapses to its unstretched size.
Collapsed lung
(Continue to the next slide)
Numbers are mm Hg pressure.
Fig. 12-8b, p. 371

27. Compliance of the lungs
Expandability of the lungs
 stretch ability of the lungs.
The extent to which the lungs will expand
for each unit increase in transpulmonary pr.
total compliance of both lungs is around 200 ml/cm H2O transpulmonary pressure .

28. Compliance of the lungs
The extent to which the lungs expand for each unit increase in transpulmonary pressure.
Compliance=
Normal value= 200 ml/cm H2O V P

29. Chest wall compliance Chest wall is an elastic structure.
Compliance of the respiratory sys is a combination of both, lung & chest wall compliance.

30. Compliance of the lungs
A. the curves in the figure above depend on the
elastic forces of the lungs :
1) elastic forces of the lung tissue (elastin and collagen fibres) (1/3 of the total force)
2) Surface tension of the fluid (2/3 of the total force)
Surface tension is huge when surfactant is absent : H2O molecules on the surface of the water have an extra strong attraction for one another attempting to contract and collapse the alveoli.

31. Compliance of the lungs
B. Surfactant :
surface-active agent in water secreted by type II alveolar epithelial cells (10% of surface area of alveoli).
Phospholipids, dipalmitoylphosphotidylcholine (DPPC)
proteins (apoprotein), and ions (calcium) that help in spreading phospholipids

32. Compliance of the lungs
Without surfactant
With surfactant
Surface tension
50 dynes/cm
5-30 dynes/cm
Collapsing pressure
In one alveoli
18 cm H2O
4 cm H2O

33. Compliance of the lungs
Pressure generated by S.T = 2x S.T.
Radius
Effect of size of the alveoli on collapsing pr.:
The Radius is inversely proportional to coll. pr. So smaller alveoli have greater pr. than the larger ones.
premature babies have small alveolar radius and less surfactant  tendency for lung collapse is 6-8 times greater than in adults  Respiratory distress syndrome of the newborn

34. The Relationship Between Pressure & Surface Tension in Alveolus
Laplace’s law

36. Rule of surfactant…
The tension is decreased with decrement of radius therefore the pressure kept constant.
Causes surface tension to vary with surface area of the alveolus.

37. Physiological advantage of surfactant
Increase lung compliance.
Prevents collapsing tendency of the alveoli.
Decrease surface tension.

38. Compliance of the lungs
-Compliance of thorax and lungs : 110 ml/cm H2O pr.
- At high volume or compressed to low volumes, the compliance can be as little as one-fifth that of lungs alone .

39. Work of breathing -Work of breathing:
1.work required to expand the lungs against the lung and chest elastic forces (compliance work)
2.work required to overcome the viscosity of the lung and chest wall (tissue resistance work)
3. work required to overcome airway resistance (airway resistance work)

41. Energy required for respiration: 3-5% of total body energy and can increase to 50 fold during heavy exercise and some obstructive diseases.