Download The Respiratory System

13
The Respiratory System
Yong Jeong, MD, PhD
Department of Bio and Brain Engineering
Organs of the Respiratory System
•Nose
•Pharynx
•Larynx
•Trachea
•Bronchi
•Lungs—alveoli
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1
Nasal cavity
Nostril
Oral cavity
Pharynx
Larynx
Trachea
Right main
(primary)
bronchus
Left main
(primary)
bronchus
Left lung
Right lung
Diaphragm
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Figure 13.1
Functions of the Respiratory System
•Gas exchanges between the blood and
external environment
•Occurs in the alveoli of the lungs
•Passageways to the lungs purify, humidify,
and warm the incoming air
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The Nose
•Only externally visible part of the respiratory
system
•Air enters the nose through the external
nostrils (nares)
•Interior of the nose consists of a nasal cavity
divided by a nasal septum
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Cribriform plate
of ethmoid bone
Sphenoidal sinus
Frontal sinus
Posterior nasal
aperture
Nasal cavity
• Nasal conchae (superior,
middle and inferior)
Nasopharynx
• Pharyngeal tonsil
• Opening of
pharyngotympanic
tube
• Uvula
• Nasal meatuses (superior,
middle, and inferior)
• Nasal vestibule
• Nostril
Oropharynx
• Palatine tonsil
Hard palate
• Lingual tonsil
Tongue
Soft palate
Laryngopharynx
Esophagus
Trachea
Hyoid bone
Larynx
• Epiglottis
• Thyroid cartilage
• Vocal fold
• Cricoid cartilage
(b) Detailed anatomy of the upper respiratory tract
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Figure 13.2b
3
Anatomy of the Nasal Cavity
•Olfactory receptors are located in the mucosa
on the superior surface
•The rest of the cavity is lined with respiratory
mucosa that
•Moisten air
•Trap incoming foreign particles
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Anatomy of the Nasal Cavity
•Lateral walls have projections called conchae
•Increase surface area
•Increase air turbulence within the nasal
cavity
•The nasal cavity is separated from the oral
cavity by the palate
•Anterior hard palate (bone)
•Posterior soft palate (muscle)
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Paranasal Sinuses
•Cavities within bones surrounding the nasal
cavity are called sinuses
•Sinuses are located in the following bones
•Frontal bone
•Sphenoid bone
•Ethmoid bone
•Maxillary bone
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Paranasal Sinuses
•Function of the sinuses
•Lighten the skull
•Act as resonance chambers for speech
•Produce mucus that drains into the nasal
cavity
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Pharynx (Throat)
•Muscular passage from nasal cavity to larynx
•Three regions of the pharynx
•Nasopharynx—superior region behind nasal
cavity
•Oropharynx—middle region behind mouth
•Laryngopharynx—inferior region attached to
larynx
•The oropharynx and laryngopharynx are
common passageways for air and food
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Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
(a) Regions of the pharynx
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Figure 13.2a
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Structures of the Pharynx
•Pharyngotympanic tubes open into the
nasopharynx
•Tonsils of the pharynx
•Pharyngeal tonsil (adenoid) is located in the
nasopharynx
•Palatine tonsils are located in the
oropharynx
•Lingual tonsils are found at the base of the
tongue
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Cribriform plate
of ethmoid bone
Sphenoidal sinus
Frontal sinus
Posterior nasal
aperture
Nasal cavity
• Nasal conchae (superior,
middle and inferior)
Nasopharynx
• Pharyngeal tonsil
• Opening of
pharyngotympanic
tube
• Uvula
• Nasal meatuses (superior,
middle, and inferior)
• Nasal vestibule
• Nostril
Oropharynx
• Palatine tonsil
Hard palate
• Lingual tonsil
Tongue
Soft palate
Laryngopharynx
Esophagus
Trachea
Hyoid bone
Larynx
• Epiglottis
• Thyroid cartilage
• Vocal fold
• Cricoid cartilage
(b) Detailed anatomy of the upper respiratory tract
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Figure 13.2b
7
Larynx (Voice Box)
•Routes air and food into proper channels
•Plays a role in speech
•Made of eight rigid hyaline cartilages and a
spoon-shaped flap of elastic cartilage
(epiglottis)
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Structures of the Larynx
• Thyroid cartilage
• Largest of the hyaline
cartilages
• Protrudes anteriorly (Adam’s
apple)
• Epiglottis
• Protects the superior opening
of the larynx
• Routes food to the esophagus
and air toward the trachea
• When swallowing, the
epiglottis rises and forms a lid
over the opening of the larynx
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Structures of the Larynx
•Vocal folds (true vocal cords)
•Vibrate with expelled air to create sound
(speech)
•Glottis—opening between vocal cords
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Cribriform plate
of ethmoid bone
Sphenoidal sinus
Frontal sinus
Posterior nasal
aperture
Nasal cavity
• Nasal conchae (superior,
middle and inferior)
Nasopharynx
• Pharyngeal tonsil
• Opening of
pharyngotympanic
tube
• Uvula
• Nasal meatuses (superior,
middle, and inferior)
• Nasal vestibule
• Nostril
Oropharynx
• Palatine tonsil
Hard palate
• Lingual tonsil
Tongue
Soft palate
Laryngopharynx
Esophagus
Trachea
Hyoid bone
Larynx
• Epiglottis
• Thyroid cartilage
• Vocal fold
• Cricoid cartilage
(b) Detailed anatomy of the upper respiratory tract
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Figure 13.2b
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Trachea (Windpipe)
•Four-inch-long tube that connects larynx with
bronchi
•Walls are reinforced with C-shaped hyaline
cartilage
•Lined with ciliated mucosa
•Beat continuously in the opposite direction
of incoming air
•Expel mucus loaded with dust and other
debris away from lungs
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Posterior
Mucosa
Esophagus
Trachealis
muscle
Submucosa
Lumen of
trachea
Seromucous
gland in
submucosa
Hyaline
cartilage
Adventitia
Anterior
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Figure 13.3a
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Figure 13.3b
Main (Primary) Bronchi
• Formed by division of the
trachea
• Enters the lung at the hilum
(medial depression)
• Right bronchus is wider,
shorter, and straighter than
left
• Bronchi subdivide into
smaller and smaller
branches
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Intercostal muscle
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Lung
Trachea
Thymus
Apex of lung
Left
superior lobe
Right superior lobe
Oblique
fissure
Horizontal fissure
Right middle lobe
Oblique fissure
Right inferior lobe
Left inferior
lobe
Heart
(in pericardial cavity
of mediastinum)
Diaphragm
Base of lung
(a) Anterior view. The lungs flank mediastinal structures laterally.
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Figure 13.4a
Vertebra
Posterior
Right lung
Parietal pleura
Esophagus
(in posterior mediastinum)
Root of lung
at hilum
• Left main bronchus
• Left pulmonary artery
• Left pulmonary vein
Visceral pleura
Left lung
Pleural cavity
Thoracic wall
Pulmonary trunk
Pericardial
membranes
Heart (in mediastinum)
Anterior mediastinum
Sternum
Anterior
(b) Transverse section through the thorax, viewed from above. Lungs, pleural
membranes, and major organs in the mediastinum are shown.
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Figure 13.4b
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Lungs
•Occupy most of the thoracic cavity
•Heart occupies central portion called
mediastinum
•Apex is near the clavicle (superior portion)
•Base rests on the diaphragm (inferior portion)
•Each lung is divided into lobes by fissures
•Left lung—two lobes
•Right lung—three lobes
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Intercostal muscle
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Lung
Trachea
Thymus
Apex of lung
Right superior lobe
Horizontal fissure
Right middle lobe
Oblique fissure
Right inferior lobe
Left
superior lobe
Oblique
fissure
Left inferior
lobe
Heart
(in pericardial cavity
of mediastinum)
Diaphragm
Base of lung
(a) Anterior view. The lungs flank mediastinal structures laterally.
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Figure 13.4a
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Vertebra
Posterior
Right lung
Parietal pleura
Esophagus
(in posterior mediastinum)
Root of lung
at hilum
• Left main bronchus
• Left pulmonary artery
• Left pulmonary vein
Visceral pleura
Left lung
Pleural cavity
Thoracic wall
Pulmonary trunk
Pericardial
membranes
Heart (in mediastinum)
Anterior mediastinum
Sternum
Anterior
(b) Transverse section through the thorax, viewed from above. Lungs, pleural
membranes, and major organs in the mediastinum are shown.
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Figure 13.4b
Coverings of the Lungs
•Serosa covers the outer surface of the lungs
•Pulmonary (visceral) pleura covers the lung
surface
•Parietal pleura lines the walls of the thoracic
cavity
•Pleural fluid fills the area between layers of
pleura to allow gliding
•These two pleural layers resist being pulled
apart
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Intercostal muscle
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Lung
Trachea
Thymus
Apex of lung
Left
superior lobe
Right superior lobe
Oblique
fissure
Horizontal fissure
Right middle lobe
Oblique fissure
Right inferior lobe
Left inferior
lobe
Heart
(in pericardial cavity
of mediastinum)
Diaphragm
Base of lung
(a) Anterior view. The lungs flank mediastinal structures laterally.
© 2012 Pearson Education, Inc.
Figure 13.4a
Vertebra
Posterior
Right lung
Parietal pleura
Esophagus
(in posterior mediastinum)
Root of lung
at hilum
• Left main bronchus
• Left pulmonary artery
• Left pulmonary vein
Visceral pleura
Left lung
Pleural cavity
Thoracic wall
Pulmonary trunk
Pericardial
membranes
Heart (in mediastinum)
Anterior mediastinum
Sternum
Anterior
(b) Transverse section through the thorax, viewed from above. Lungs, pleural
membranes, and major organs in the mediastinum are shown.
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Figure 13.4b
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Bronchial (Respiratory) Tree Divisions
•All but the smallest of these passageways
have reinforcing cartilage in their walls
•Primary bronchi
•Secondary bronchi
•Tertiary bronchi
•Bronchioles
•Terminal bronchioles
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Alveolar duct
Alveoli
Respiratory bronchioles
Alveolar duct
Terminal
bronchiole
Alveolar sac
(a) Diagrammatic view of respiratory
bronchioles, alveolar ducts, and alveoli
Alveolar pores
Alveolar duct
Alveolus
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Figure 13.5a
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Respiratory Zone
•Structures
•Respiratory bronchioles
•Alveolar ducts
•Alveolar sacs
•Alveoli (air sacs)
•Site of gas exchange = alveoli only
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Alveolar duct
Alveoli
Respiratory bronchioles
Alveolar duct
Terminal
bronchiole
Alveolar sac
(a) Diagrammatic view of respiratory
bronchioles, alveolar ducts, and alveoli
Alveolar pores
Alveolar duct
Alveolus
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Figure 13.5a
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Figure 13.5b
Respiratory Membrane (Air-Blood Barrier)
•Thin squamous epithelial layer lines alveolar
walls
•Alveolar pores connect neighboring air sacs
•Pulmonary capillaries cover external surfaces
of alveoli
•On one side of the membrane is air and on the
other side is blood flowing past
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Endothelial cell
nucleus
Alveolar pores
Capillary
Macrophage
Nucleus of
squamous
epithelial cell
Respiratory
membrane
Alveoli (gas- Red blood SurfactantSquamous
cell in
secreting cell epithelial cell
filled air
capillary
of alveolar wall
spaces)
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Figure 13.6 (1 of 2)
Red blood cell
Endothelial cell
nucleus
Capillary
Alveolar pores
Capillary
O2
CO2
Macrophage
Nucleus of
squamous
epithelial cell
Respiratory
membrane
Alveolus
Alveolar epithelium
Fused basement
membranes
Capillary endothelium
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Figure 13.6 (2 of 2)
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Gas Exchange
•Gas crosses the respiratory membrane by
diffusion
•Oxygen enters the blood
•Carbon dioxide enters the alveoli
•Alveolar macrophages (“dust cells”) add
protection by picking up bacteria, carbon
particles, and other debris
•Surfactant (a lipid molecule) coats gasexposed alveolar surfaces
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Four Events of Respiration
•Pulmonary ventilation—moving air in and out
of the lungs (commonly called breathing)
•External respiration—gas exchange between
pulmonary blood and alveoli
•Oxygen is loaded into the blood
•Carbon dioxide is unloaded from the blood
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Four Events of Respiration
•Respiratory gas transport—transport of
oxygen and carbon dioxide via the
bloodstream
•Internal respiration—gas exchange between
blood and tissue cells in systemic capillaries
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Mechanics of Breathing
(Pulmonary Ventilation)
•Completely mechanical process that depends
on volume changes in the thoracic cavity
•Volume changes lead to pressure changes,
which lead to the flow of gases to equalize
pressure
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Mechanics of Breathing
(Pulmonary Ventilation)
•Two phases
•Inspiration = inhalation
•Flow of air into lungs
•Expiration = exhalation
•Air leaving lungs
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Inspiration
•Diaphragm and external intercostal muscles
contract
•The size of the thoracic cavity increases
•External air is pulled into the lungs due to
•Increase in intrapulmonary volume
•Decrease in gas pressure
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Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
Ribs elevated
as external
intercostals
contract
Full inspiration
(External
intercostals contract)
External
intercostal
muscles
Diaphragm moves
inferiorly during
contraction
(a) Inspiration: Air (gases) flows into
the lungs
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Figure 13.7a
Pressure relative
to atmospheric pressure
+2
+1
Inspiration
Expiration
Intrapulmonary
pressure
0
–1
–2
(a)
Volume of
breath
Volume (L)
0.5
0
–0.5
(b)
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Figure 13.8
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Expiration
•Largely a passive process which depends on
natural lung elasticity
•As muscles relax, air is pushed out of the
lungs due to
•Decrease in intrapulmonary volume
•Increase in gas pressure
•Forced expiration can occur mostly by
contracting internal intercostal muscles to
depress the rib cage
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Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral dimensions
Ribs depressed
as external
intercostals relax
External
intercostal
muscles
Expiration
(External
intercostals relax)
Diaphragm moves
superiorly as
it relaxes
(b) Expiration: Air (gases) flows out of
the lungs
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Figure 13.7b
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Pressure relative
to atmospheric pressure
+2
+1
Inspiration
Expiration
Intrapulmonary
pressure
0
–1
–2
(a)
Volume of
breath
Volume (L)
0.5
0
–0.5
(b)
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Figure 13.8
Airflow (F) is a function of the pressure differences
between the alveoli (Palv) and the atmosphere (Patm)
divided by airflow resistance (R).
Air enters the lungs when Palv < Patm
Air exits the lungs when Palv > Patm
F = Palv__-__Patm
R
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Pressure Differences in the Thoracic
Cavity
•Normal pressure within the pleural space is
always negative (intrapleural pressure)
•Differences in lung and pleural space
pressures keep lungs from collapsing
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26
Nonrespiratory Air (Gas) Movements
•Can be caused by reflexes or voluntary
actions
•Examples:
•Cough and sneeze—clears lungs of debris
•Crying—emotionally induced mechanism
•Laughing—similar to crying
•Hiccup—sudden inspirations
•Yawn—very deep inspiration
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Respiratory Volumes and Capacities
•Normal breathing moves about 500 mL of air
with each breath
•This respiratory volume is tidal volume (TV)
•Many factors that affect respiratory capacity
•A person’s size
•Sex
•Age
•Physical condition
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Respiratory Volumes and Capacities
•Inspiratory reserve volume (IRV)
•Amount of air that can be taken in forcibly
over the tidal volume
•Usually around 3100 mL
•Expiratory reserve volume (ERV)
•Amount of air that can be forcibly exhaled
•Approximately 1200 mL
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Respiratory Volumes and Capacities
•Residual volume
•Air remaining in lung after expiration
•About 1200 mL
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Respiratory Volumes and Capacities
•Vital capacity
•The total amount of exchangeable air
•Vital capacity = TV + IRV + ERV
•Dead space volume
•Air that remains in conducting zone and
never reaches alveoli
•About 150 mL
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Respiratory Volumes and Capacities
•Functional volume
•Air that actually reaches the respiratory zone
•Usually about 350 mL
•Respiratory capacities are measured with a
spirometer
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6000
Milliliters (ml)
5000
4000
Inspiratory
reserve volume
3100 ml
3000
2000
1000
Tidal volume 500 ml
Expiratory
reserve volume
1200 ml
Vital
capacity
4800 ml
Total lung
capacity
6000 ml
Residual volume
1200 ml
0
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Figure 13.9
Respiratory Sounds
•Sounds are monitored with a stethoscope
•Two recognizable sounds can be heard with a
stethoscope
•Bronchial sounds—produced by air rushing
through large passageways such as the
trachea and bronchi
•Vesicular breathing sounds—soft sounds of
air filling alveoli
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External Respiration
•Oxygen loaded into the blood
•The alveoli always have more oxygen than
the blood
•Oxygen moves by diffusion towards the area
of lower concentration
•Pulmonary capillary blood gains oxygen
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External Respiration
•Carbon dioxide unloaded out of the blood
•Blood returning from tissues has higher
concentrations of carbon dioxide than air in
the alveoli
•Pulmonary capillary blood gives up carbon
dioxide to be exhaled
•Blood leaving the lungs is oxygen-rich and
carbon dioxide-poor
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(a) External respiration in the lungs
(pulmonary gas exchange)
Oxygen is loaded into the blood
and carbon dioxide is unloaded.
Alveoli (air sacs)
O2
CO2
Loading
of O2
Hb + O2
HbO2
Unloading
of CO2
_
HCO3 + H+
(Oxyhemoglobin Bicaris formed)
bonate
ion
H2CO3
CO2+ H2O
Carbonic
acid
Water
Plasma
Red blood cell
Pulmonary capillary
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Figure 13.11a
Gas Transport in the Blood
•Oxygen transport in the blood
•Most oxygen travels attached to hemoglobin
and forms oxyhemoglobin (HbO2)
•A small dissolved amount is carried in the
plasma
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32
(a) External respiration in the lungs
(pulmonary gas exchange)
Oxygen is loaded into the blood
and carbon dioxide is unloaded.
Alveoli (air sacs)
O2
CO2
Loading
of O2
Hb + O2
HbO2
Unloading
of CO2
_
HCO3 + H+
(Oxyhemoglobin Bicaris formed)
bonate
ion
H2CO3
CO2+ H2O
Carbonic
acid
Water
Plasma
Red blood cell
Pulmonary capillary
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Figure 13.11a
Gas Transport in the Blood
•Carbon dioxide transport in the blood
•Most is transported in the plasma as
bicarbonate ion (HCO3–)
•A small amount is carried inside red blood
cells on hemoglobin, but at different binding
sites than those of oxygen
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Gas Transport in the Blood
•For carbon dioxide to diffuse out of blood into
the alveoli, it must be released from its
bicarbonate form:
•Bicarbonate ions enter RBC
•Combine with hydrogen ions
•Form carbonic acid (H2CO3)
•Carbonic acid splits to form water + CO2
•Carbon dioxide diffuses from blood into
alveoli
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(a) External respiration in the lungs
(pulmonary gas exchange)
Oxygen is loaded into the blood
and carbon dioxide is unloaded.
Alveoli (air sacs)
O2
CO2
Loading
of O2
Hb + O2
HbO2
Unloading
of CO2
_
HCO3 + H+
(Oxyhemoglobin Bicaris formed)
bonate
ion
H2CO3
CO2+ H2O
Carbonic
acid
Water
Plasma
Red blood cell
Pulmonary capillary
© 2012 Pearson Education, Inc.
Figure 13.11a
34
Internal Respiration
•Exchange of gases between blood and body
cells
•An opposite reaction to what occurs in the
lungs
•Carbon dioxide diffuses out of tissue to
blood (called loading)
•Oxygen diffuses from blood into tissue
(called unloading)
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(b) Internal respiration in the body tissues
(systemic capillary gas exchange)
Oxygen is unloaded and carbon
dioxide is loaded into the blood.
Tissue cells
CO2
O2
Loading
of CO2
CO2+ H2O
H2CO3
Unloading
of O2
H++ HCO3_
Water Carbonic Bicaracid bonate
Plasma
ion
HbO2
Hb + O2
Systemic capillary
Red blood cell
© 2012 Pearson Education, Inc.
Figure 13.11b
35
Inspired air:
Alveoli
of lungs:
CO2 O2
O2 CO2
O2 CO2
External
respiration
Pulmonary
arteries
Alveolar
capillaries
Pulmonary
veins
Blood
leaving
lungs and
entering
tissue
capillaries:
Blood
leaving
tissues and
entering
lungs:
Heart
O2 CO2
Tissue
capillaries
Systemic
veins
Internal
respiration
O2 CO2
Systemic
arteries
CO2
O2
Tissue cells:
O2 CO2
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Figure 13.10
Change of Hb Saturation
Chemical and thermal factors that
alter hemoglobin’s affinity to bind
oxygen alter the ease of “loading”
and “unloading” this gas in the
lungs and near the active cells.
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36
Neural Regulation of Respiration
•Activity of respiratory muscles is transmitted to
and from the brain by phrenic and intercostal
nerves
•Neural centers that control rate and depth are
located in the medulla and pons
•Medulla—sets basic rhythm of breathing and
contains a pacemaker called the selfexciting inspiratory center
•Pons—appears to smooth out respiratory
rate
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Neural Regulation of Respiration
•Normal respiratory rate (eupnea)
•12 to 15 respirations per minute
•Hyperpnea
•Increased respiratory rate often due to extra
oxygen needs
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Brain
Breathing
control
centers
Pons
centers
Medulla
centers
Afferent
Impulses to
medulla
Efferent nerve impulses from
medulla trigger contraction of
inspiratory muscles
Phrenic
Breathing control centers
nerves
stimulated by:
CO2 increase in blood
(acts directly on medulla
centers by causing a
drop in pH of CSF)
CSF in
brain
sinus
Nerve impulse
from O2 sensor
indicating O2
decrease
Intercostal
nerves
Intercostal
muscles
O2 sensor
in aortic body
of aortic arch
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Diaphragm
Figure 13.12
Non-Neural Factors Influencing
Respiratory Rate and Depth
•Physical factors
•Increased body temperature
•Exercise
•Talking
•Coughing
•Volition (conscious control)
•Emotional factors
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Non-Neural Factors Influencing
Respiratory Rate and Depth
•Chemical factors: CO2 levels
•The body’s need to rid itself of CO2 is the
most important stimulus
•Increased levels of carbon dioxide (and thus,
a decreased or acidic pH) in the blood
increase the rate and depth of breathing
•Changes in carbon dioxide act directly on
the medulla oblongata
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Non-Neural Factors Influencing
Respiratory Rate and Depth
• Chemical factors:
oxygen levels
• Changes in oxygen
concentration in the
blood are detected
by chemoreceptors
in the aorta and
common carotid
artery
• Information is sent to
the medulla
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Control by PO2
A severe reduction in the arterial concentration of
oxygen in the blood can stimulate hyperventilation.
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Hyperventilation and Hypoventilation
•Hyperventilation
•Results from increased CO2 in the blood
(acidosis)
•Breathing becomes deeper and more rapid
•Blows off more CO2 to restore normal blood
pH
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Control by PCO2
Small changes in the
carbon dioxide content
of the blood quickly
trigger changes in
ventilation rate.
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Hyperventilation and Hypoventilation
•Hypoventilation
•Results when blood becomes alkaline
(alkalosis)
•Extremely slow or shallow breathing
•Allows CO2 to accumulate in the blood
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Respiratory Disorders: Chronic
Obstructive Pulmonary Disease (COPD)
•Exemplified by chronic bronchitis and
emphysema
•Major causes of death and disability in the
United States
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Respiratory Disorders: Chronic
Obstructive Pulmonary Disease (COPD)
•Features of these diseases
•Patients almost always have a history of
smoking
•Labored breathing (dyspnea) becomes
progressively more severe
•Coughing and frequent pulmonary infections
are common
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Respiratory Disorders: Chronic
Obstructive Pulmonary Disease (COPD)
•Features of these diseases (continued)
•Most victims are hypoxic, retain carbon
dioxide, and have respiratory acidosis
•Those infected will ultimately develop
respiratory failure
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Respiratory Disorders: Chronic Bronchitis
•Mucosa of the lower respiratory passages
becomes severely inflamed
•Mucus production increases
•Pooled mucus impairs ventilation and gas
exchange
•Risk of lung infection increases
•Pneumonia is common
•Called “blue bloaters” due to hypoxia and
cyanosis
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Respiratory Disorders: Emphysema
•Alveoli enlarge as adjacent chambers break
through
•Chronic inflammation promotes lung fibrosis
•Airways collapse during expiration
•Patients use a large amount of energy to
exhale
•Overinflation of the lungs leads to a
permanently expanded barrel chest
•Cyanosis appears late in the disease;
sufferers are often called “pink puffers”
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Figure 13.13
44
Lung Cancer
•Accounts for one-third of all cancer deaths in
the United States
•Increased incidence is associated with
smoking
•Three common types
•Squamous cell carcinoma
•Adenocarcinoma
•Small cell carcinoma
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A Closer Look: Lung Cancer
Figure 13.14
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Developmental Aspects of
the Respiratory System
•Lungs are filled with fluid in the fetus
•Lungs are not fully inflated with air until two
weeks after birth
•Surfactant is a fatty molecule made by alveolar
cells
•Lowers alveolar surface tension so that lungs
do not collapse between breaths
•Not present until late in fetal development and
may not be present in premature babies
•Appears around 28 to 30 weeks of pregnancy
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Developmental Aspects of
the Respiratory System
•Homeostatic imbalance
•Infant respiratory distress syndrome
(IRDS)—surfactant production is inadequate
•Cystic fibrosis—oversecretion of thick
mucus clogs the respiratory system
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Developmental Aspects of
the Respiratory System
•Respiratory rate changes throughout life
•Newborns: 40 to 80 respirations per minute
•Infants: 30 respirations per minute
•Age 5: 25 respirations per minute
•Adults: 12 to 18 respirations per minute
•Rate often increases somewhat with old age
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Developmental Aspects of
the Respiratory System
•Sudden Infant Death Syndrome (SIDS)
•Apparently healthy infant stops breathing
and dies during sleep
•Some cases are thought to be a problem of
the neural respiratory control center
•One third of cases appear to be due to heart
rhythm abnormalities
•Recent research shows a genetic
component
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Developmental Aspects of
the Respiratory System
•Asthma
•Chronic inflamed hypersensitive bronchiole
passages
•Response to irritants with dyspnea,
coughing, and wheezing
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Developmental Aspects of
the Respiratory System
•Aging effects
•Elasticity of lungs decreases
•Vital capacity decreases
•Blood oxygen levels decrease
•Stimulating effects of carbon dioxide
decrease
•Elderly are often hypoxic and exhibit sleep
apnea
•More risks of respiratory tract infection
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