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Copyright 2010, John Wiley & Sons, Inc.
ANATOMY on
The Respiratory System
JAY P. JAZUL, RPh, MSc.,CPSUniversity of Santo Tomas Faculty of Pharmacy
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Respiration: Three Major Steps1. Pulmonary ventilation
Moving air in and out of lungs
2. External respiration Gas exchange between alveoli and blood
3. Internal respiration Gas exchange between blood and cells
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Organs of the Respiratory System Upper respiratory system
Nose and pharynx Lower respiratory system
Trachea, larynx, bronchi, bronchioles, and lungs
Chapter 22, Respiratory System 4
Respiratory System
Consists of the respiratory and conducting zones
Respiratory zone Site of gas exchange Consists of bronchioles, alveolar ducts, and
alveoli
Chapter 22, Respiratory System 5
Respiratory System
Conducting zone Provides rigid conduits for air to reach the sites of
gas exchange Includes all other respiratory structures (e.g.,
nose, nasal cavity, pharynx, trachea) Respiratory muscles – diaphragm and other
muscles that promote ventilation
Chapter 22, Respiratory System 6
Major Functions of the Respiratory System To supply the body with oxygen and dispose
of carbon dioxide Respiration – four distinct processes must
happen Pulmonary ventilation – moving air into and out of
the lungs External respiration – gas exchange between the
lungs and the blood
Chapter 22, Respiratory System 7
Major Functions of the Respiratory System
Transport – transport of oxygen and carbon dioxide between the lungs and tissues
Internal respiration – gas exchange between systemic blood vessels and tissues
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Organs of the Respiratory System
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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
NASAL CAVITY
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Chapter 22, Respiratory System 12
Nasal Cavity
Vestibule – nasal cavity superior to the nares Vibrissae – hairs that filter coarse particles from
inspired air Olfactory mucosa
Lines the superior nasal cavity Contains smell receptors
Chapter 22, Respiratory System 13
Nasal Cavity
Respiratory mucosa Lines the balance of the nasal cavity Glands secrete mucus containing lysozyme and
defensins to help destroy bacteria
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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
Upper Respiratory System: Pharynx
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Respiratory System: Head and Neck
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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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Lower Respiratory System: Larynx
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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
Larynx
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Copyright 2010, John Wiley & Sons, Inc.
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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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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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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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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Structure of an Alveolus
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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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Muscles of Inhalation and Exhalation
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Muscles of Inhalation and Exhalation
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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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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
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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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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)
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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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Internal and External Respiration
Leaving the alveolar capillaries:•PO2 = 100 mm Hg•PCO2 = 40 mm Hg
As blood travels through arteries and arterioles, no gas exchange occurs
Entering the systemic capillaries:•PO2 = 100 mm Hg•PCO2 = 40 mm Hg
Leaving the systemic capillaries:•PO2 = 40 mm Hg
•PCO2 = 45 mm Hg
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Copyright 2010, John Wiley & Sons, Inc.
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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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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Transport of Oxygen and Carbon Dioxide
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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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Control of Respiration
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Control of Respiration
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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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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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Regulation of Respiratory Center
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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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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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End of Chapter 18
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