1. Respiratory System

2. Respiratory system
The primary function of respiratory system is to obtain O2 for use by the body’s cell and to eliminate CO2 the cells produced

3. Respiratory system

4. Respiratory system Non-Respiratory Functions of Respiratory system:
Route for heat and water loss from the body
Enhancement of venous return to the heart
Participates in acid base balance (through excreting CO2 which reduce acidity)
The nose acts as organ of smell
A major role in the process of vocalization

5. Major Part of Respiratory System

6. Respiratory system Alveoli : place where gas exchange occurs
300 million alveoli in both lungs
Total surface area ~ 75m²
Are surrounded by dense network of capillaries
contain two types of cells a) alveolar cell type I b)alveolar cell type II secrete surfactant

7. Respiratory System
Functionally the respiratory system consist of 2 portions:
Conducting portion:[ nose, Pharynx, Larynx, Trachea, Bronchi, bronchioles and terminal bronchioles] filter, warm and moisten air and conduct it into the lungs
Respiratory portion: where gas exchange occurs [ alveoli]  {functional unit of respiratory system}

8. Respiratory system Pleural Cavity

9. Mechanics of Respiration
Respiratory movements (Inspiration & Expiration)
are achieved by making pressure gradient between atmosphere and alveolar sacs
Air always moves from a high pressure area to a low pressure area
During inspiration air moves from atmosphere into the lungs
During expiration air moves of the lungs to atmosphere

10. Mechanics of Respiration
Three important pressure are considered in respiration :

11. Mechanics of Respiration
Intra-alveolar pressure can be changed by altering the volume of the lungs

12. Mechanics of Respiration

13. Mechanics of Respiration
During quite inspiration:
Inspiratory muscle contract →increasing thoracic volume →decreasing intra-pleural pressure →decreasing intra-alveolar pressure (become less than atmospheric pressure (-1 mmHg)→ forcing air to move into the lungs (inspiration)
Quite inspiration is an active process (need muscle contraction

14. Mechanics of Respiration

15. Mechanics of Respiration
During quite expiration:
Inspiratory muscle relax→ decreasing thoracic volume → increasing intra-pleural pressure → increasing intra-alveolar pressure (become more than atmospheric pressure (+1 mmHg)→ forcing air to move out the lungs (expiration)
Quite expiration is passive process ( doesn't need muscle contraction)
Forceful expiration is an active process

16. Respiratory Muscles Respiratory muscles two sets of muscles:
Inspiratory muscles
Expiratory muscles

17. Respiratory Muscles Inspiratory muscles: The diaphragm
The external intercostals muscles

18. Respiratory Muscles The diaphragm: Main inspiratory muscle
Seperates thoracic cavity from abdominal cavity
Skeletal muscle, supplied by phrenic nerve
During inspiration: It contracts and descends downward increasing the vertical dimension of the thorax, also it increases the anterposterior diameter of the thorax
During expiration, it relaxes and moves upward decreasing thoracic volume

19. Respiratory Muscles The External intercostals Muscles:
composed of fibers that run downward & forward between adjacent ribs
Their contraction elevates the sternum increasing the anteroposterior and lateral dimensions of the thorax (the thoracic volume is increased)
This enlarges the thoracic cavity in two dimensions: the lateral & the antero-posterior dimensions

20. Respiratory Muscles Accessory inspiratory muscles:
Sternocleidomastoid
scalenus
Deeper inspiration can be accomplished by:
Forceful contraction of both diaphragm & external intercostals
Assistance by the accessory inspiratory muscles, which lie in the neck
Contraction of accessory muscles raises the sternum & elevates the first two ribs, thus enlarging the upper portion of the thoracic cavity
This extra enlargement will be followed by a greater expansion of the lungs, & a further dropping in intra-alveolar pressure accordingly

21. Respiratory Muscles Expiratory muscles: Abdominal muscles
Internal intercostal muscles
They contract during active forced expiration
They don`t contract during quite expiration

22. Elastic behavior of the lung
Elastic recoil of the lung refer to the ability of the lung to return to its pre-inspiratory volume at the end of inspiration
Compliance of the lung refer to how much effort is required to stretch or distend the lung

23. Elastic behavior of the lung
Lung elasticity (elastic behavior) depends on two important factors:
Elastic fibers of lung tissues
Surface tension of the fluid lining the alveoli ( is a force tends to reduce the size of alveoli and to resist the expansion)

24. Surfactant Is a phospholipoprotien complex
Is produced by alveolar cell type II
Lowers the alveolar surface tension
Increases the lung compliance (facilitates lung expansion)
Reduce the work needed to inflate the lung

26. Spirometry
Measurement of the pattern of air movement into and out of the lungs during controlled ventilatory maneuvers.

28. Lung Volumes 4 Volumes 4 Capacities Sum of 2 or more lung volumes IRVIC VC
TLC TV
ERV
FRC RV RV

29. Spirometry
Measurement of the pattern of air movement into and out of the lungs during controlled ventilatory maneuvers.

30. Alveolar ventilation= (TV- dead space volume) X respiratory rate
Pulmonary ventilation: is the amount of air which breathed in or out in one minute
Pulmonary ventilation (minute ventilation)= tidal volume X respiratory rate
= 500 ml X 12 = 6000 ml/minute
Alveolar ventilation: is the amount of fresh air reached the alveoli in one minute
Alveolar ventilation= (TV- dead space volume) X respiratory rate
( ) x12 =4200 ml/min

31. Partial pressure of gases in atmospheric air
Composition of atmospheric air:
N2→78%
O2 →21%
CO2 →0.04%
Other gases → 1%
All of these gases participate to produce 760mmHg (atmospheric pressure)
Each gas exerted pressure proportional to its % this is called partial pressure (p)
N2 → pN2=78/100X760=600 mmHg
O2 → pO2=21/100X760=160 mmHg
CO2 → pCO2=.04/100X760=.3 mmHg

32. Partial pressure of O2 and CO2 in alveolar air
PO2 =100 mmHg
PCO2 =40mmHg
Partial pressure of O2 and CO2 in pulmonary capillary

33. O2 and CO2 exchange across pulmonary and systemic capillaries caused by partial pressure gradients