Lecture 5 the respiratory system

1. Chapter 18
The Respiratory
System
Copyright 2010, John Wiley & Sons, Inc.

2. Respiration: Three Major Steps
1. Pulmonary ventilation

Moving air in and out of lungs
1. External respiration

Gas exchange between alveoli and blood
1. Internal respiration

Gas exchange between blood and cells
Copyright 2010, John Wiley & Sons, Inc.

3. Organs of the Respiratory System

Upper respiratory system


Lower respiratory system


Nose and pharynx
Trachea, larynx, bronchi, bronchioles, and lungs
“Conducting zone” consists of

All airways that carry air to lungs:


Nose, pharynx, trachea, larynx, bronchi, bronchioles,
and terminal bronchioles
“Respiratory zone”

Sites within lungs where gas exchange occurs

Respiratory bronchioles, alveolar ducts, alveolar sacs,
and alveoli
Copyright 2010, John Wiley & Sons, Inc.

4. Organs of the Respiratory System
Copyright 2010, John Wiley & Sons, Inc.

5. Upper Respiratory System: Nose

Structure




External nares  nasal cavity  internal nares
Nasal septum divides nose into two sides
Nasal conchae covered by mucous membrane
Functions

Warm, humidify, filter/trap dust and microbes



Mucus and cilia of epithelial cells lining nose
Detect olfactory stimuli
Modify vocal sounds
Copyright 2010, John Wiley & Sons, Inc.

6. Upper Respiratory System: Pharynx


Known as the “throat”
Structure


Funnel-shaped tube from internal nares to larynx
3 parts
Three regions (with tonsils in the upper two)

Upper: nasopharynx; posterior to nose


Middle: oropharynx; posterior to mouth


Adenoids and openings of auditory (Eustachian) tubes
Palatine and lingual tonsils are here
Lower: laryngeal pharynx

Connects with both esophagus and larynx: food and air
Copyright 2010, John Wiley & Sons, Inc.

7. Respiratory System: Head and Neck
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8. Lower Respiratory System: Larynx


“Voice box”
Made largely of cartilage

Thyroid cartilage: V-shaped



Epiglottis: leaf-shaped piece; covers airway



“Adam's apple”: projects more anteriorly in males
Vocal cords “strung” here (and to arytenoids)
During swallowing, larynx moves up so epiglottis covers
opening into trachea
Cricoid cartilage: inferior most portion
Arytenoids (paired, small) superior to cricoid
Copyright 2010, John Wiley & Sons, Inc.

9. Lower Respiratory System: Larynx
Copyright 2010, John Wiley & Sons, Inc.

10. Voice Production

Mucous membrane of larynx forms two pairs
of folds


Upper = false vocal cords
Lower = true vocal cords
Contain elastic ligaments
 When muscles pull elastic ligaments tight, vocal
cords vibrate  sounds in upper airways
 Pitch adjusted by tension of true vocal cords


Lower pitch of male voice

Vocal cords longer and thicker; vibrate more
slowly
Copyright 2010, John Wiley & Sons, Inc.

11. Lower Respiratory System: Trachea


“Windpipe”
Location



Structure



Anterior to esophagus and thoracic vertebrae
Extends from end of larynx to primary bronchi
Lined with pseudostratified ciliated mucous
membrane: traps and moves dust upward
C-shaped rings of cartilage support trachea, keep
lumen open during exhalation
Tracheostomy: opening in trachea for tube
Copyright 2010, John Wiley & Sons, Inc.

12. Lower Respiratory System: Bronchi,
Bronchioles

Structure of bronchial tree





Bronchi contain cartilage rings
Primary bronchi enter the lungs medially
In lungs, branching secondary bronchi
 One for each lobe of lung: 3 in right, 2 in left
Tertiary bronchi    terminal bronchioles
These smaller airways


Have less cartilage, more smooth muscle. In
asthma, these airways can close.
Can be bronchodilated by sympathetic nerves,
epinephrine, or related medications.
Copyright 2010, John Wiley & Sons, Inc.

13. Lower Respiratory System: Lungs

Two lungs: left and right



Right lung has 3 lobes
Left lung has 2 lobes and cardiac notch
Lungs surrounded by pleural membrane




Parietal pleura attached to diaphragm and lining
thoracic wall
Visceral pleura attached to lungs
Pleural cavity with little fluid between pleurae
Broad bottom of lungs = base; pointy top = apex
Copyright 2010, John Wiley & Sons, Inc.

14. Lung Lobes



Divided into lobules fed by tertiary bronchi
Further divisions  terminal bronchioles
 Respiratory bronchioles




Lined with nonciliated epithelium
 Alveolar ducts
 Alveolar sacs
 Surrounded by alveoli
Copyright 2010, John Wiley & Sons, Inc.

15. Lung Lobes
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16. Lower Respiratory System: Alveoli


Cup-shaped outpouchings of alveolar sacs
Alveoli: composed of three types of cells


Lined with thin alveolar cells (simple squamous);
sites of gas exchange
Scattered surfactant-secreting cells. Surfactant:




Lowers surface tension (keeps alveoli from collapsing)
Humidifies (keeps alveoli from drying out)
Alveolar macrophages: “cleaners”
Respiratory membrane: alveoli + capillary

Gases diffuse across these thin epithelial layers:
air  blood
Copyright 2010, John Wiley & Sons, Inc.

17. Lobule of the Lung
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18. Lobule of the Lung
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19. Structure of an Alveolus
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20. Respiration Step: 1. Pulmonary Ventilation

Air flows: atmosphere   lungs due to
difference in pressure related to lung volume


Inhalation: diaphragm + external intercostals


Lung volume changes due to respiratory muscles
Diaphragm contracts (moves downward)  ↑ lung
volume
Cohesion between parietal-visceral pleura 
↑ lung volume as thorax volume ↑.
Copyright 2010, John Wiley & Sons, Inc.

21. Exhalation

Exhalation is normally passive process due
to muscle relaxation



Diaphragm relaxes and rises  ↓ lung volume
External intercostals relax  ↓ lung volume
Active exhalation: exhale forcefully


Example: playing wind instrument
Uses additional muscles: internal intercostals,
abdominal muscles
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22. Muscles of Inhalation and Exhalation
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23. Muscles of Inhalation and Exhalation
Copyright 2010, John Wiley & Sons, Inc.

24. Volume-Pressure Changes in Lungs

Volume and pressure are inversely related




As ↑ lung volume ↓ alveolar pressure
As ↓ lung volume ↑ alveolar pressure
Contraction of diaphragm  lowers diaphragm
 ↑ lung volume ↓ alveolar pressure so it is <
atmospheric pressure  air enters lungs =
inhalation
Relaxation of diaphragm  raises diaphragm 
↓ lung volume  ↑ alveolar pressure so it is >
atmospheric pressure  air leaves lungs =
exhalation
Copyright 2010, John Wiley & Sons, Inc.

25. Volume-Pressure Changes in Lungs
Copyright 2010, John Wiley & Sons, Inc.

26. Air Flow Terms


Frequency = breaths/min; normal: 12
Tidal volume (TV) = volume moved in one
breath. Normal ~ 500 ml




About 70% of TV reaches alveoli (350 ml)
Only this amount is involved in gas exchange
30% in airways = anatomic dead space
Minute ventilation (MV) = f x TV = 6000
mL/min
Copyright 2010, John Wiley & Sons, Inc.

27. Lung Volumes

Measured by spirometer



Inspiratory reserve volume (ERV) = volume of air
that can be inhaled beyond tidal volume (TV)
Expiratory reserve volume (IRV) = volume of air
that can be exhaled beyond TV
Air remaining in lungs after a maximum expiration
= residual volume (RV)
Copyright 2010, John Wiley & Sons, Inc.

28. Lung Capacities




Inspiratory capacity = TV + IRV
Functional residual capacity (FRC) =
RV + ERV
Vital capacity (VC) = IRV + TV + ERV
Total lung capacity (TLC) = VC + RV
Copyright 2010, John Wiley & Sons, Inc.

29. Lung Capacities
Copyright 2010, John Wiley & Sons, Inc.

30. Breathing Patterns

Eupnea = normal breathing



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Highly variable in pattern
Costal breathing: shallow with rib movements
Diaphragmatic breathing: deep breathing
Special modifications for speech and
emotional responses
Also variations for coughing and sneezing to
clear airways

See Table 18.1
Copyright 2010, John Wiley & Sons, Inc.

31. Nature of Air




Mixture of gases (N2, O2,, CO2, H2O, and
others)
Each gas has own partial pressure, such as
PO2 or PN2
Sum of all partial pressures = atmospheric
pressure
Each gas diffuses down its partial pressure
gradient
Copyright 2010, John Wiley & Sons, Inc.

32. Respiration Step 2: Pulmonary Gas
Exchange: External Respiration

Diffusion across alveolar-capillary membrane

O2 diffuses from air (PO2 ~105 mm Hg) to
pulmonary artery (“blue”) blood (PO2 ~40 mm Hg).
(Partial pressure gradient = 65 mm Hg)


Continues until equilibrium (PO2 ~100-105 mm Hg)
Meanwhile “blue” blood (PCO2 ~45) diffuses to
alveolar air (PCO2 ~40) (Partial pressure gradient =
5 mm Hg)
Copyright 2010, John Wiley & Sons, Inc.

33. Respiration Step 3: Systemic Gas Exchange:
Internal Respiration




Occurs throughout body
O2 diffuses from blood to cells: down partial
pressure gradient
PO2 lower in cells than in blood because O2
used in cellular metabolism
Meanwhile CO2 diffuses in opposite direction:
cells  blood
Copyright 2010, John Wiley & Sons, Inc.

34. Internal and
External
Respiration
Copyright 2010, John Wiley & Sons, Inc.

35. Transport of Oxygen within Blood

98.5% of O2 is transported bound to
hemoglobin in RBCs




Binding depends on PO2
High PO2 in lung and lower in tissues
O2 dissolves poorly in plasma so only 1.5% is
transported in plasma
Tissue release of O2 to cells is increased by
factors present during exercise:



High CO2 (from active muscles)
Acidity (lactic acid from active muscles)
Higher temperatures (during exercise)
Copyright 2010, John Wiley & Sons, Inc.

36. Transport of Carbon Dioxide

CO2 diffuses from tissues into blood 

CO2 carried in blood:



Some dissolved in plasma (7%)
Bound to proteins including hemoglobin (23%)
Mostly as part of bicarbonate ions (70%)


CO2 + H2O  H+ + HCO3-
Process reverses in lungs as CO2 diffuses
from blood into alveolar air  exhaled
Copyright 2010, John Wiley & Sons, Inc.

37. Transport of
Oxygen and
Carbon Dioxide
Copyright 2010, John Wiley & Sons, Inc.

38. Control of Respiration

Medullary rhythmicity area in medulla


Quiet breathing






Contains both inspiratory and expiratory areas
Inspiratory area  nerve signals to inspiratory
muscles for ~2 sec 
Inspiration 
Inspiration ends and muscles relax 
Expiration 
Expiratory center active only during forceful
breathing
Two areas in pons adjust length of inspiratory
stimulation
Copyright 2010, John Wiley & Sons, Inc.

39. Control of Respiration
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40. Control of Respiration
Copyright 2010, John Wiley & Sons, Inc.

41. Regulation of Respiratory Center

Cortical input: voluntary adjustment of
patterns


For talking or cessation of breathing while
swimming
Chemoreceptor input will override breath-holding
Copyright 2010, John Wiley & Sons, Inc.

42. Regulation of Respiratory Center

Chemoreceptor input to  increase
ventilation



Central receptors in medulla: sensitive to ↑ H+ or
PCO2
in CSF
Peripheral receptors in arch of aorta + common
carotids: respond to ↓ PO2 as well as ↑ H+ or
PCO2 in blood
Blood and brain pH can be maintained by
these negative feedback mechanisms
Copyright 2010, John Wiley & Sons, Inc.

43. Regulation of
Respiratory Center
Copyright 2010, John Wiley & Sons, Inc.

44. Other Regulatory Factors of Respiration

Respiration can be stimulated by



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Sudden pain can  apnea: stop breathing

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Limbic system: anticipation of activity, emotion
Proprioception as activity is started
Increase of body temperature
Prolonged somatic pain can increase rate
Airway irritation cough or sneeze
Inflation reflex


Bronchi wall stretch receptors inhibit inspiration
Prevents overinflation
Copyright 2010, John Wiley & Sons, Inc.

45. Aging and the Respiratory System

Lungs lose elasticity/ability to recoil  more
rigid; leads to




Decrease in vital capacity
Decreased blood PO2 level
Decreased exercise capacity
Decreased macrophage activity and ciliary
action 

Increased susceptibility to pneumonia, bronchitis
and other disorders
Copyright 2010, John Wiley & Sons, Inc.

46. End of Chapter 18

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