The respiratory system has three main functions: external respiration, the transport of gases, and internal respiration. External respiration involves extracting carbon dioxide from tissues and discharging it into the atmosphere. The air passage divides 23 times between the trachea and alveolar sacs. It can be divided into two zones: the conducting zone where no gas exchange occurs, and the respiratory zone where gas exchange takes place in the alveoli. The lungs also have non-respiratory functions like humidifying and warming air, resisting infection, and filtering the pulmonary circulation.

2. INTRODUCTION
•The main function of the respiratory is to extract from to take out CO2 from the
tissues and discharge it into the atmosphere.
•The entire respiration can be divided into 3 main divisions:
•External respiration
•Transport of gases
•Internal respiration

3. OUTLINE OF RESPIRATION

4. AIR PASSAGE
Inspired Air Trachea Bronchi Bronchioles Alveolar ducts Pulmonary Alveoli

5. TRACHEO-BRONCHIAL TREE
• WEIBEL’S LUNG MODEL :
Between the trachea and the alveolar sac, the air passage divides 23 times
•Trachea is designated as generation zero
•Bronchus constitute the first generation
•The 16th generation bronchioles are called terminal bronchioles
•The 17th generation bronchioles are called respiratory bronchioles due to
small amount of gaseous exchange
•The major amount of gas exchange takes place at 23rd generation (alveoli)

7. TRACHEO BRONCHIAL TREE AS FUNCTIONAL UNIT
• From functional point of view it can be divided into two major zones :
•CONDUCTING ZONE: This includes the portion of air passage where no
exchange of gas is possible, called dead space (from nose up to terminal
bronchioles)
•The total capacity of this zone is approximately 150 ml
•RESPIRATORY ZONE: The portion of air passage where gaseous exchange
take place (up to alveoli)
•Its volume is approximately 4litres

8. LOBES AND SEGMENTS

9. INNERVATION
• TWO BRANCHES OF AUTONOMIC NERVOUS SYSTEM (ANS)
• PARASYMPATHETIC NERVE Stimulation causes cholinergic discharge
• SYMPATHETIC NERVE Stimulated by adregenic receptors
• Non cholinergic non- adregenic nerve stimulation produces bronchodilation

10. PROPERTIES OF GASES
• PARTIAL PRESSURE : The pressure exerted by any inert gas in a mixture of gases is called its partial
pressure
• Calculation of (PGAS) : it is done by measuring the percentage of gas and total atmospheric
pressure.
• PGAS = %age OF GAS/100 x TOTAL ATMOSPHERIC PRESSURE
• DALTON’S LAW : States that the total pressure of a mixture of gases is the sum of the partial
pressures of its components: p total = p gas 1 + p gas 2 + p gas 3 .
• HENRY’S LAW : States that the amount of dissolved gas in a liquid is proportional to its partial
pressure above the liquid.

11. NON RESPIRATORY FUNTIONS
LUNG DEFENCE MECHANISM :
Humidify and cool or warm the inspired air
Helps in resisting infection and maintain the integrity of the mucosa
Prevent foreign bodies from reaching the alveoli
FUNCTION OF PULMONARY CIRCULATION :
Reservoir for left ventricle
Works as a filter
Fluid exchange and drug absorption

12. CONT…
METABOLIC AND ENDOCRINE FUNCTION :
Many vasoactive substances are inactivated, altered or removed from blood as they pass through lungs
Substances synthesized and used in the lungs i.e. surfactant
Substances synthesized and stored and released in to the blood e.g.: prostaglandin and histamine
Substances activated in the lungs e.g :
Angiotensin I Decapeptide AngiotensinII Octapeptide
Converting
enzyme

13. THANK YOU !!!