1. Human Respiratory System 2

3. Airways in lung 23 generations of branching Trachea (2 cm2) Bronchi
first 11 generations of branching
Bronchioles (lack cartilage)
Next 5 generations of branching
Respiratory bronchioles
Last 4 generations of branching
Alveolar ducts give rise to alveolar sacs which give rise to alveoli
300 million with surface area M2

5. Respiratory airways Anatomical classification:
*Nose ,pharynx, ( upper resp. tract)
*Larynx, trachea, bronchi, bronchioles terminal bronchiols, respiratory bronchiols, alveolar duct ,sacs and alveoli ( lower resp. tract)

6. Physiological classification
Nose ,pharynx, Larynx, trachea, bronchi, bronchioles terminal bronchiols( conducting zone )(16 times).
respiratory bronchiols, alveolar duct ,sacs and alveoli( respiratory zone)( 7 times )
These 23 division greatly increase the total cross sectional area

7. Conducting Zone Conducting zone:
Includes all the structures that air passes through before reaching the respiratory zone.
Mouth, nose, pharynx, glottis, larynx, trachea, bronchi.

8. Conducting Zone Conducting zone
Warms and humidifies until inspired air becomes:
37 degrees
Saturated with water vapor
Filters and cleans:
Mucus secreted to trap particles
Mucus/particles moved by cilia to be expectorated.

9. Respiratory Zone Respiratory zone
Region of gas exchange between air and blood
Respiratory bronchioles
Alveolar ducts, Alveolar Sacs and
Alveoli

10. Respiratory Zone

11. Upper respiratory tract functions
Passageway for respiration
Receptors for smell
Filters incoming air to filter larger foreign material
Moistens and warms incoming air
Resonating chambers for voice
When a person breathes air through a tube directly into the trachea (as through a tracheostomy), the cooling and especially the drying effect in the lower lung can lead to serious lung crusting and infection.

13. Components of the lower respiratory tract

14. Lower Respiratory Tract
Functions:
*Larynx: maintains an open airway, routes food and air appropriately, assists in sound production
*Trachea: transports air to and from lungs
*Bronchi: branch into lungs
*Lungs: transport air to alveoli for gas exchange

15. Lungs and Pleura
Around each lung is a flattened sac of serous membrane called pleura
Parietal pleura – outer layer
Visceral pleura – directly on lung
Pleural cavity – slit-like potential space filled with pleural fluid
Lungs can slide but separation from pleura is resisted (like film between 2 plates of glass)
Lungs cling to thoracic wall and are forced to expand and recoil as volume of thoracic cavity changes during breathing

16. Functions of the Respiratory Passageways
To keep the trachea from collapsing, multiple cartilage rings extend about five sixths of the way around the trachea.
In the walls of the bronchi, less extensive curved cartilage plates also maintain a reasonable amount of rigidity and allow sufficient motion for the lungs to expand and contract.

18. Posterior open parts of tracheal cartilage abut esophagus
Trachealis muscle can decrease diameter of trachea
Esophagus can expand when food swallowed
Food can be forcibly expelled
Wall of trachea has layers common to many tubular organs – filters, warms and moistens incoming air

19. The bronchioles which usually have diameters less than 1
The bronchioles which usually have diameters less than 1.5 millimeters The walls of the bronchioles are almost entirely smooth muscle are kept expanded mainly by the same transpulmonary pressures that expand the alveoli. That is, as the alveoli enlarge, the bronchioles also enlarge.

20. Terminal bronchiole, respiratory bronchiole wall mainly pulmonary epithelium and underlying fibrous tissue plus a few smooth muscle fibers.
Many obstructive diseases of the lung result from narrowing of the smaller bronchi and larger bronchioles, often because of excessive contraction of the smooth muscle itself.

21. Under normal respiratory conditions, air flows through the respiratory passageways so easily that less than 1 centimeter of water pressure gradient from the alveoli to the atmosphere is sufficient to cause enough airflow for quiet breathing.
The greatest amount of resistance to airflow occurs not in the minute air passages of the terminal bronchioles but in some of the medium size bronchioles and bronchi near the trachea.

22. Yet in disease conditions, the smaller bronchioles
often play a far greater role in determining airflow
resistance because of their small size and because they are easily occluded by (1) muscle contraction in their walls,
(2) edema occurring in the walls,
or (3) mucus collecting in the lumens of the bronchioles

23. The minute respiratory volume :
The total amount of new air moved into the respiratory passages each minute
minute respiratory volume =tidal volume X the respiratory rate per minute
= 500 milliliters X 12 breaths per minute
= averages about 6 L/min.
(A person can live for a short period with a minute respiratory
volume as low as 1.5 L/min and a respiratory rate of
only 2 to 4 breaths per minute).

24. The respiratory rate occasionally rises to / minute, and the tidal volume can become as great as the vital capacity, about 4600 milliliters in a young adult man.
This can give a minute respiratory volume greater than 200 L/min, or more than 30 times normal.
Most people cannot sustain more than one half to two thirds these values for longer than 1 minute.

25. Alveolar ventilation
The rate at which new air reaches the alveoli, alveolar sacs, alveolar ducts, and respiratory bronchioles is called alveolar ventilation

26. Rate of Alveolar Ventilation
Alveolar ventilation per minute: is the total volume of
new air entering the alveoli and adjacent gas exchange
areas each minute.
It is equal to the respiratory rate X the amount of new air that enters these areas with each breath.
Va = Freq. X (Vt – Vd)
where Va = the volume of alveolar ventilation per minute, Freq.= is the frequency of respiration per minute,
Vt is the tidal volume, and Vd is the physiologic
dead space volume.

27. With a normal tidal volume of 500 milliliters, a
normal dead space of 150 milliliters, and a respiratory rate of 12 breaths per minute, alveolar ventilation equals
12 x (500 – 150), or 4200 ml/min.
Alveolar ventilation is one of the major factors
determining the concentrations of oxygen and carbon
dioxide in the alveoli.

28. Dead Space
Some of the air never reaches the gas exchange areas but fills respiratory passages ( nose, pharynx, and trachea). This air is called dead space air because it is not useful for gas exchange.
On expiration, the air in the dead space is expired
first, before any of the air from the alveoli reaches the atmosphere. Therefore, the dead space is very disadvantageous for removing the expiratory gases from the lungs.

29. *The normal dead space air in a young adult man is about 150 milliliters.
*This increases slightly with age.
*This nose, pharynx, and trachea are called anatomical dead space.

30. Physiologic Dead Space
Some of the alveoli are nonfunctional or only partially functional because of absent or poor blood flow through the adjacent pulmonary capillaries, this is called the physiologic dead space.