1. Chapter 7 The Respiratory System
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2. Respiration: Three Major Steps
Pulmonary ventilation
Moving air in and out of lungs
External respiration
Gas exchange between alveoli and blood
Internal respiration
Gas exchange between blood and cells
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3. Organs of the Respiratory System
Upper respiratory system
Nose and pharynx
Lower respiratory system
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
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4. Organs of the Respiratory System
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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
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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
Adenoids and openings of auditory (Eustachian) tubes
Middle: oropharynx; posterior to mouth
Palatine and lingual tonsils are here
Lower: laryngeal pharynx
Connects with both esophagus and larynx: food and air
The adenoid, also known as a pharyngeal tonsil or nasopharyngeal tonsil, is a mass of lymphatic tissue situated posterior to the nasal cavity,
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9. Respiratory System: Head and Neck
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10. Lower Respiratory System: Larynx
“Voice box”
Made largely of cartilage
Thyroid cartilage: V-shaped
“Adam's apple”: projects more anteriorly in males
Vocal cords “strung” here (and to arytenoids)
Epiglottis: leaf-shaped piece; covers airway
During swallowing, larynx moves up so epiglottis covers opening into trachea
Cricoid cartilage: inferior most portion
Arytenoids (paired, small) superior to cricoid
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11. Lower Respiratory System: Larynx
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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
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13. Lower Respiratory System: Trachea
“Windpipe”
Location
Anterior to esophagus and thoracic vertebrae
Extends from end of larynx to primary bronchi
Structure
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
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14. 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.
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15. 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
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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
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Lung Lobes
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18. 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
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Lobule of the Lung
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Lobule of the Lung
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21. Structure of an Alveolus
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22. Respiration Step: 1. Pulmonary Ventilation
Air flows: atmosphere   lungs due to difference in pressure related to lung volume
Lung volume changes due to respiratory muscles
Inhalation: diaphragm + external intercostals
Diaphragm contracts (moves downward)   lung volume
Cohesion between parietal-visceral pleura   lung volume as thorax volume .
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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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24. Muscles of Inhalation and Exhalation
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25. Muscles of Inhalation and Exhalation
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26. 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
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27. Volume-Pressure Changes in Lungs
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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
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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)
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Lung Capacities
Inspiratory capacity = TV + IRV
Functional residual capacity (FRC) = RV + ERV
Vital capacity (VC) = IRV + TV + ERV
Total lung capacity (TLC) = VC + RV
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Lung Capacities
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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 ~ mm Hg)
Meanwhile “blue” blood (PCO2 ~45) diffuses to alveolar air (PCO2 ~40) (Partial pressure gradient = 5 mm Hg)
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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
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34. Internal and External Respiration
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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)
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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
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37. Transport of Oxygen and Carbon Dioxide
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38. Control of Respiration
Medullary rhythmicity area in medulla
Contains both inspiratory and expiratory areas
Quiet breathing
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
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39. Control of Respiration
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40. Control of Respiration
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42. Regulation of Respiratory Center
Cortical input: voluntary adjustment of patterns
For talking or cessation of breathing while swimming
Chemoreceptor input will override breath-holding
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43. 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
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44. Regulation of Respiratory Center
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45. Other Regulatory Factors of Respiration
Respiration can be stimulated by
Limbic system: anticipation of activity, emotion
Proprioception as activity is started
Increase of body temperature
Sudden pain can  apnea: stop breathing
Prolonged somatic pain can increase rate
Airway irritation cough or sneeze
Inflation reflex
Bronchi wall stretch receptors inhibit inspiration
Prevents overinflation
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46. 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
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