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1. Functional Anatomy of
the Respiratory System
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2. Respiration
The goal of respiration is to provide O2 to the tissues
and to remove the CO2.
To achieve these goals ,respiration can be divided
into four major functions.
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3. Functional events of respiration
1. Pulmonary ventilation – inflow and outflow of
air between the atmosphere and the lung
alveoli.
2. Diffusion of o2 and co2 between the alveoli and
the blood.
3. Transport of o2 and co2 in the blood and body
fluids to and from the body’s tissue cells.
4. Regulation of ventilation 3

4. Principle organs of Respiratory system
• Nose /Nasal cavity
• Pharynx
• Larynx
• Trachea
• Bronchi
• Bronchioles and smaller
air passages
• Lungs
• Pleura
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5. Principle organs of Respiratory
system
• Within the lungs:
– Terminal bronchioles
– Respiratory bronchioles
– Alveolar duct
– Alveolar sac
– Alveolus
Gas exchange takes place
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6. Organization of the Respiratory System
• The respiratory system
is divided into the :
• upper respiratory tract:
– from the nasal cavity upto
the vocal folds.
– Nose,pharynx and larynx.
• Lower respiratory tract:
– below the vocal folds.
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7. Airway
branching
• Weibel’s model
• 23 generations
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8. Functional anatomy of respiratory
system
Conducting zone :
– First 16 generations.
– Transports gases from and to the exterior.
– Nose to terminal bronchioles
Respiratory zone:
– Remaining 7 generations.
– gas exchange takes place.
– Respiratory bronchiloes,alveolar ducts and alveoli.
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9. The nose
• It extends from a pair of anterior openings called nostrils or
nares, to a pair of posterior openings called posterior nasal
aperture or choanae.
• Lined by ciliated columnar epithelium which contains
mucus secreting globlet cells.
• Functions:
• Warms,moistened and filter the inhaled air.
• Projecting conchae increase the surface area spreading
inspired air.
• It detects odor in the airway.
• Serves as a resonating chamber that amplifies the voice.9

10. The Pharynx
• Muscular funnel extending
about 13 cm from the choanae
to the larynx.
1. Nasopharynx:
 Houses the pharyngeal
tonsils.
 Warms and moisten air.
 Only an air passage
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11. The Pharynx
2. Oropharynx :
– Contain palatine tonsils.
– Common passage for air
and food.
3. Laryngopharynx:
 Common passage for air and
food
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12. The Larynx
• Voice box
• Cartiligenous chamber,4 cm long
• Functions:
1. Makes air warm and moist
2. Voice production.
3. Epiglottis prevents food to
enter into the airway.
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13. The trachea(windpipe)
• Rigid tube about 12 cm long and
2.5 cm diameter
• Anterior to esophagus.
• Supported by 16 to 20 C-shaped
rings of hyaline cartilage.
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14. The trachea(windpipe)
• Function:
1. Cartilages provide support
and patency.
2. Warming,humidyfying and
filtering of the air.
3. Mucociliary escalator
– Composed of mucus secreting
globlet cells,ciliated cells.
– Mucus traps the inhaled particles
– Upward beating of cilia drives the
debris towards the pharynx.
– Swallowed
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15. Bronchi
• Two primary bronchi are formed by division of
trachea
• Right primary bronchus
– Shorter, wider and more vertical
– Enters the right lung
• Left primary bronchus
– Longer, narrower and less vertical
– Enters the left lung

16. Bronchioles
• Tertiary bronchi divide again and again to form
smaller airways, the bronchioles
• Terminal bronchiole
– The last conducting division
• Respiratory bronchiole
– Arise from the terminal bronchiole
– Respiratory zone begins
– Divide to form alveolar ducts and ultimately, end in
alveolar sacs

17. Lungs
• Two conical organs with a broad base and a blunt
apex
• Lie inside the thoracic cavity
• Rest on diaphragm
• Bronchus, blood vessels and nerves enter the lungs
through their hilum

18. Lungs
Right lung
– 3 lobes
– 2 fissures – horizontal and
oblique
Left lung
– 2 lobes
– 1 fissure – oblique
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19. Lungs
• Bronchopulmonary
segment- segment of lung
served by its own artery, vein
and receives air from an
individual segmental
( tertiary) bronchus.
• Right lung =10;Left lung=8
• Clinical significant:
• Disease is confined to one
segment, so surgical
removal is easier.
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20. Blood supply of lungs
1. Pulmonary circulation
2. Bronchial circulation
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21. Blood supply of lungs
1. Pulmonary circulation
– Blood passes via the pulmonary artery to the pulmonary
capillary bed, where it is oxygenated and returned to the
left atrium via the pulmonary veins.
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22. Blood supply of lungs
2. Bronchial circulation
– Bronchiol arteries arises from systemic arteries.
– They form capillaries which drain into bronchial veins
azygous vein.
– Anastomose with pulmonary capillaries or veins.
– Nourishes the trachea down to the terminal bronchioles
and also supplies the pleura and hilar lymphnodes.
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23. Pleura
• A closed sac of serous membrane
• Covers the lungs
Layers
• Visceral pleura
– Adherent to the lung surface
• Parietal pleura
– Adherent to the inner surface of chest wall

24. Pleura
• Pleural cavity
– A potential space in between the two pleura
– Contains a slippery pleural fluid
Function
• Reduction of friction
– Lubricant action of pleural fluid reduces the
friction during expansion and recoil of lungs

25. Functions of pleural fluid /pleura
1. Reduction of friction:
 Acts as a lubricant that enables the lungs to expand and
contract with minimal friction.
2. Creation of pressure gradient:
 Pressure in the pleural cavity is lower than the atmospheric
pressure , this assist in inflation of the lungs.
3. Compartmentalization :
 The pleura , mediastinum and pericardium
compartmentalize the thoracic organs and prevent
spreading of infection from one organ to another. 28

26. Alveoli
• Microscopic sac like structures, surrounded by
pulmonary capillaries.
• Arise from the alveolar ducts
• Actual sites of gas exchange
• 150 million alveoli in each
lungs (300 million in both)

27. LINING CELLS IN ALVEOLI
TYPE I CELLS :
 Flat cells with large cytoplasmic extensions
primary lining cells.
Approximately 95% of alveolar epithelial surface area.
TYPE II CELLS ( granular pneumocytes):
About 5% of the alveolar epithelial surface area
 Secret surfactant as well as alveolar repair.
OTHERS :
 Pulmonary alveolar macrophages, lymphocytes, plasma
cells, mast cells, neuroendocrine cells.
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28. Non-repiratory functions of lung
1. Protective function:
– Air conditioning
– Bronchial secretions help to trap the dusts and other
particles present in the inspired air.
– Pulmonary alveolar macrophages engulf foreign
particles coming with air.
– Secretion of immunoglobulin IgA provides immunity to
the respiratory mucous membrane against the
microbes coming with air.
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29. Non-repiratory functions of lung
2. Metabolic functions:
– Synthesis of protein,fat,carbohydrates.
– Various lipid(e.g., Dipalmitoylphosphatidylcholine) a
component of the pulmonary surfactant.
– Synthesis of collagen and elastic fibers.
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30. Non-repiratory functions of lung
3. The lungs contain fibrinolytic system that lyses
clots in the pulmonary vessels.
4. The angiotensin-converting enzyme(ACE)
responsible for the activation of an angiotensin I
into angiotensin II.
5. Releases substances like histamine,bradykinin
during anaphylaxis.
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31. Thankyou 36