Uploaded by Prof.Dr.R.R.Deshpande.This is prepared by Physiologist Dr.A.R.Joshi on Respiratory System

1. RESPIRATORY
SYSTEM
Dr. A. R. JOSHI
Professor of
Physiology

2. RESPIRATORY SYSTEM
• Respiration means exchange of gases
• Types :
– External respiration at lungs
– Internal respiration at tissues

3. BASIC FUNCTIONS OF LUNGS
• Ventilation of air
– Inspiration
– Expiration
• Diffusion of gases
• Perfusion of lungs by blood through
pulmonary circulation

4. NORMAL BREATHING PATTERN
• Respiratory rate : 14 to 18 /minute
• Tidal volume: 350 to 500ml
• RMV : 6 to 8 litres/minute
• Inspiration (active) : 2.5 to 3 sec
• Expiration (passive): 2 to 2.5 sec

5. MUSCLES OF RESPIRATION
• Inspiratory Muscles
• Expiratory Muscles
• Accessary Muscles

6. INSPIRATORY MUSCLES
• Diaphragm:
– Chief muscle
– Big surface area
– Changes vertical diameter of chest
– Innervation by phrenic nerves
– No fatigue
– Works like involuntary muscle

7. INSPIRATORY MUSCLES
• External Intercostal Muscles:
• Bucket handle movement of ribs
(Lower part of chest)
• Pump handle movement of sternum
(Upper part of chest)

8. OTHER MUSCLES
• Muscles of expiration
• Work only while coughing or sneezing
• Accessary muscles of respiration
• Work during exercise or disease

9. PREVENTION OF LUNG COLLAPSE
•Role of negative intra-pleural pressure
•Role of surfactant

10. REGULATION OF
RESPIRATION
• Nervous regulation – Role of
ponto-medullary respiratory centers:
• Inspiratory Center (DRGN)
• Expiratory Center (VRGN)
• Apneustic Center
• Pneumotaxic Center

11. REGULATION OF
RESPIRATION
• Nervous regulation– Role of reflexes:
• Coughing reflex
• Sneezing reflex
• Hiccough
• Deglutition reflex

12. Chemical Regulation
Role of carbon dioxide: powerful action
1.Central action (chemo sensitive area)
2.Peripheral action (carotid and aortic
bodies)
Role of hydrogen ions
Role of lack of oxygen

13. DIFFUSION ACROSS RESPIRATORY
MEMBRANE
• Structure
• Factors affecting diffusion :
● thickness of membrane
● surface area of membrane
● pressure gradient of gas
• Diseases : Pulmonary fibrosis & oedema

14. TRANSPORT OF GASES:
OXYGEN
• Arterial O2 19 ml / 100ml of blood
• Venous O2 14 ml / 100 ml of blood
• Oxygen carried by Hb – 98%
dissolved form – 2%
• O2- Hb dissociation curve and its
significance

15. OXYGEN CONCENTRATION IN
VARIOUS TISSUES
• Alveolar PO2 : 104 mm of Hg
• Arterial PO2 : 95 mm of Hg
• Venous PO2 : 40 mm of Hg

16. O2dissociation curve…

17. O2 Dissociation Curve

18. TRANSPORT OF GASES :
CARBON DIOXIDE
• Arterial CO2level : 48 ml/100ml blood
• Venous CO2level : 52 ml/100ml blood
• Transported as:
● bicarbonates : 70%
● carbamino compounds : 23%
● dissolved state : 7%

19. CARBON DIOXIDE
CONCENTRATION IN VARIOUS
TISSUES
• Alveolar PCO2 : 40 mm of Hg
• Arterial PCO2 : 40 mm of Hg
• Venous PCO2 : 45 mm of Hg

20. HYPOXIA (Lack of Oxygen at tissue
level)
1. Hypoxic Hypoxia
• High Altitude
• Ventilatory defects like Asthma
• Diffusion defects like Pulmonary edema
• AV shunts like Fallots Tetrology
(PO2 of arterial blood is low)

21. HYPOXIA ( CONT..)
2. Anaemic Hypoxia
e.g. Anaemia
Carbon Monoxide poisoning
3. Stagnant Hypoxia
e.g. Congestive heart failure
4. Histotoxic Hypoxia
e.g. Cyanide poisoning
(Note : Oxygen therapy is useful only in
cases of hypoxic hypoxia, when PO2 of
Arterial Blood is low )

22. OXYGEN THERAPY
• Useful in hypoxic hypoxia (high altitude,
hypoventilation, impaired diffusion )
• Limited value in other types of hypoxia
• Oxygen with small quantity of Carbon
dioxide to maintain respiratory drive

23. HYPERBARIC OXYGEN
THERAPY
• Increases dissolved Oxygen –
at 2 atm.pressure - 4ml additional/dl
at 3 atm.pressure - 6ml additional/dl.
• Useful in CO poisoning, dysbarism,
acute mountain sickness, locally in
delayed wound healing & gas gangrene.

24. HAZARDS – OXYGEN THERAPY
• Irritation of airways
• Bronchopneumonia
• Retinopathy ( in premature babies )
• Derangement of cerebral activity
• Convulsions

25. ASPHYXIA
(Lack of oxygen and excess of carbon dioxide)
• Causes:
Foreign body obstruction in trachea
Strangulation
Paralysis of respiratory muscles
Drowning
Stages:
Stage of Hyperpnea
Stage of Central excitation
Stage of Central failure
Treatment:
Tracheostomy & oxygen therapy

26. For assistance in Clinical
Physiology
• Dr. A.R. Joshi
Professor of Physiology
(mobile : 9423523322)
email: aniruddharj@hotmail.com