Transcript Respiratory_system__Ch_13__S2015

The Respiratory System
Chapter 13
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Outline
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Functions of the Respiratory System
Respiratory System Anatomy
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Microscopic Anatomy of Alveoli
Mechanics of Breathing
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The Nose
The Pharynx
The Larynx
The Trachea
The Bronchi
The Lungs
Inspiration and Expiration
Lung Volumes & Capacities
Exchange of Oxygen & Carbon Dioxide
Transport of Oxygen & Carbon Dioxide
Control of Respiration
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Functions of the Respiratory System
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Gas exchange: Oxygen is brought into the body
and carbon dioxide to eliminated from the body
Helps maintain blood pH
Cleans, warms, and moistens incoming air
Provides ability to smell, protects against noxious
compounds
Provides ability to produce sounds, hence
communicate effectively within the species
Assists defense against pathogens
Aids venous blood return to the heart and
lymphatic fluid return to the cardiovascular system
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The Respiratory System
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The Respiratory System
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During inspiration or inhalation, air is
conducted toward the lungs.
During expiration or exhalation, air is
conducted away from the lungs.
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Figure 13.2 Basic anatomy of the upper respiratory tract, sagittal section.
Respiratory System Anatomy
Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
(a) Regions of the pharynx
Cribriform plate
of ethmoid bone
Sphenoidal sinus
Frontal sinus
Nasal cavity
• Nasal conchae (superior,
middle and inferior)
• Nasal meatuses (superior,
middle, and inferior)
• Nasal vestibule
• Nostril
Posterior nasal
aperture
Nasopharynx
• Pharyngeal tonsil
• Opening of
pharyngotympanic
tube
• Uvula
Oropharynx
• Palatine tonsil
• Lingual tonsil
Laryngopharynx
Esophagus
Trachea
Hard palate
Soft palate
Tongue
Hyoid bone
Larynx
• Epiglottis
• Thyroid cartilage
• Vocal fold
• Cricoid cartilage
(b) Detailed anatomy of the upper respiratory tract
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Respiratory System Anatomy (Cont.)
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The Nose
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As air moves into the nose it is cleansed (by coarse hairs,
cilia, and mucus) warmed, and moistened
Special cells in upper part of cavities detect odors; olfactory
epithelium
Involved with modifying speech sounds; areas act as
resonating chambers, e.g. paranasal sinuses
Tears drain into the nasal cavities via nasolacrimal ducts
Paranasal sinuses drain mucus into nasal cavities; additional
mucus flow
Auditory tubes (pharyngotympanic; Eustachian) lead from the
nasopharynx to the middle ears
Respiratory epithelium on bony folds (nasal conchae;
increase surface area); produce mucus; cilia move mucus to
esophagus for swallowing or spitting
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Figure 13.2 Basic anatomy of the upper respiratory tract, sagittal section.
Respiratory System Anatomy
Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
(a) Regions of the pharynx
Cribriform plate
of ethmoid bone
Sphenoidal sinus
Frontal sinus
Nasal cavity
• Nasal conchae (superior,
middle and inferior)
• Nasal meatuses (superior,
middle, and inferior)
• Nasal vestibule
• Nostril
Posterior nasal
aperture
Nasopharynx
• Pharyngeal tonsil
• Opening of
pharyngotympanic
tube
• Uvula
Oropharynx
• Palatine tonsil
• Lingual tonsil
Laryngopharynx
Esophagus
Trachea
Hard palate
Soft palate
Tongue
Hyoid bone
Larynx
• Epiglottis
• Thyroid cartilage
• Vocal fold
• Cricoid cartilage
(b) Detailed anatomy of the upper respiratory tract
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Respiratory System Anatomy (Cont.)
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The Pharynx
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The pharynx is a funnel-shaped passageway that
connects the nasal and oral cavities to the larynx.
Three sections.
 Nasopharynx - Nasal cavities open above soft palate.
 Oropharynx - Oral cavity opens.
 The tonsils (defensive lymphatic tissue containing
lymphocytes) form protective ring at junction of
oral cavity with pharynx.
 Laryngopharynx - Opens into the larynx.
In the pharynx, air and food pathways cross.
Air cleansed by cilia and mucus.
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Figure 13.2 Basic anatomy of the upper respiratory tract, sagittal section.
Respiratory System Anatomy
Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
(a) Regions of the pharynx
Cribriform plate
of ethmoid bone
Sphenoidal sinus
Frontal sinus
Nasal cavity
• Nasal conchae (superior,
middle and inferior)
• Nasal meatuses (superior,
middle, and inferior)
• Nasal vestibule
• Nostril
Posterior nasal
aperture
Nasopharynx
• Pharyngeal tonsil
• Opening of
pharyngotympanic
tube
• Uvula
Oropharynx
• Palatine tonsil
• Lingual tonsil
Laryngopharynx
Esophagus
Trachea
Hard palate
Soft palate
Tongue
Hyoid bone
Larynx
• Epiglottis
• Thyroid cartilage
• Vocal fold
• Cricoid cartilage
(b) Detailed anatomy of the upper respiratory tract
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Respiratory System Anatomy (Cont.)
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The Larynx (Voice Box)
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The larynx serves as a passageway for air between the
pharynx and the trachea.
 When food is swallowed, the larynx moves up
against the epiglottis preventing food from passing
into the larynx.
 Food moves into the esophagus.
The larynx (voice box) houses the vocal cords which are
stretched across the glottis.
Air cleansed by cilia and mucus.
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Figure 13.2 Basic anatomy of the upper respiratory tract, sagittal section.
Respiratory System Anatomy
Pharynx
• Nasopharynx
• Oropharynx
• Laryngopharynx
(a) Regions of the pharynx
Cribriform plate
of ethmoid bone
Sphenoidal sinus
Frontal sinus
Nasal cavity
• Nasal conchae (superior,
middle and inferior)
• Nasal meatuses (superior,
middle, and inferior)
• Nasal vestibule
• Nostril
Posterior nasal
aperture
Nasopharynx
• Pharyngeal tonsil
• Opening of
pharyngotympanic
tube
• Uvula
Oropharynx
• Palatine tonsil
• Lingual tonsil
Laryngopharynx
Esophagus
Trachea
Hard palate
Soft palate
Tongue
Hyoid bone
Larynx
• Epiglottis
• Thyroid cartilage
• Vocal fold
• Cricoid cartilage
(b) Detailed anatomy of the upper respiratory tract
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Thyroid cartilage
Cricoid cartilage
Vocal fold
Arytenoid cartilage
Superior view of
cartilages and muscles
Posterior
cricoarytenoid muscle
View through a
laryngoscope
(a) Movement of vocal folds apart (abduction)
Lateral
cricoarytenoid
muscle
(b) Movement of vocal folds together (adduction)
Tongue
Epiglottis
Glottis:
Vocal folds
(true vocal cords)
Rima glottidis
Ventricular folds
(false vocal cords)
Cuneiform cartilage
Corniculate cartilage
View
Larynx
Anterior
Epiglottis
Vocal folds
(true vocal cords)
Rima glottidis
Cuneiform cartilage
Ventricular folds
(false vocal cords)
Corniculate cartilage
(c) Superior view
Posterior
Respiratory System Anatomy (Cont.)
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The Trachea
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Tube, containing C-shaped cartilage (to maintain
patency during breathing), connecting larynx to primary
bronchi; spanning open part of the C is fibromuscular
membrane containing trachealis muscle- contraction &
relaxation can change diameter slightly
Pseudostratified ciliated columnar epithelium sweeps
mucus up toward the pharynx (Mucus escalator) for
swallowing or spitting
The trachea divides into left and right primary bronchi
which eventually branch into secondary bronchi and
then into bronchioles
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Figure 13.3a Structural relationship of the trachea and esophagus.
Posterior
Mucosa
Submucosa
Esophagus
Trachealis
muscle
Lumen of
trachea
Seromucous
gland in
submucosa
Hyaline
cartilage
Adventitia
(a)
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Anterior
Figure 13.3b Structural relationship of the trachea and esophagus.
(b)
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The Trachea: Mucus escalator
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BRANCHING OF
BRONCHIAL TREE
Larynx
Trachea
Trachea
Primary bronchi
Secondary bronchi
Left lung
Right lung
Tertiary bronchi
Visceral pleura
Bronchioles
Parietal pleura
Terminal bronchioles
Pleural cavity
Location of carina
Right primary
bronchus
Left primary bronchus
Left secondary bronchus
Right secondary
bronchus
Left tertiary bronchus
Left bronchiole
Right tertiary
bronchus
Right bronchiole
Right terminal
bronchiole
Left terminal bronchiole
Cardiac notch
Anterior view
Diaphragm
Respiratory System Anatomy (Cont.)
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The Lungs
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Each bronchiole leads to an elongated space enclosed
by alveoli. The alveoli make up the lungs.
The lungs lie on either side of the heart within the
thoracic cavity.
 Right lung has three lobes and the left lung has two
lobes
 Each lobe is divided into lobules, further divided
into bronchioles serving many alveoli.
Contain large quantities of elastic fibers- permit
stretching- have a tendency to want to collapse
Gas exchange takes place in the alveoli
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Figure 13.4b Anatomical relationships of organs in the thoracic cavity.
Vertebra
Posterior
Esophagus
(in posterior mediastinum)
Root of lung at hilum
• Left main bronchus
• Left pulmonary artery
• Left pulmonary vein
Right lung
Parietal pleura
Visceral pleura
Left lung
Pleural cavity
Thoracic wall
Pulmonary trunk
Pericardial
membranes
Sternum
Heart (in mediastinum)
Anterior mediastinum
Anterior
(b) Transverse section through the thorax, viewed from above.
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Respiratory System Anatomy (Cont.)
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Lungs (Cont.)
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Microscopic anatomy
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Lobules- wrapped in elastic connective tissue with
lymphatic vessel, arteriole, venule, & a terminal
bronchiole
Terminal bronchiole lead to respiratory bronchioles (have
alveoli budding on surface), then to alveolar ducts, then to
alveolar sacs, then alveoli
All gas exchange occurs in alveoli
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MICROSCOPIC
AIRWAYS
Terminal bronchioles
Terminal
bronchiole
Respiratory bronchioles
Alveolar ducts
Pulmonary
Alveolar sacs
arteriole
Lymphatic
Alveoli
vessel
Respiratory bronchiole
Alveoli
Pulmonary
venule
Elastic
connective
tissue
Pulmonary
capillary
Visceral
pleura
Alveolar ducts
Alveolar sac
Alveoli
(a) Diagram of portion of lobule of lung
Respiratory System Anatomy (Cont.)
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Lungs (Cont.)
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Microscopic anatomy

Alveoli
 Wall composed of Type I alveolar cells- simple
squamous epithelium- main site of gas exchange
 Type II alveolar cells- produce alveolar fluid containing
surfactant- extremely important mixture of
phospholipids & lipoproteins- lower surface tension
due to hydrogen bonding of water molecules-prevents
collapse of the alveoli
 Alveolar macrophages- remove particular debris
 Respiratory membrane- type I alveolar cells, their
basement membrane; capillary basement membrane,
capillary endothelial cells
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Monocyte
Reticular fiber
Elastic fiber
Type II alveolar
(septal) cell
Respiratory
membrane
Alveolus
Type I alveolar
cell
Diffusion
of O2
Diffusion
of CO2
Alveolar
macrophage (dust cell)
Alveolus
Red blood cell
in pulmonary capillary
Red blood cell
Capillary endothelium
Capillary basement
membrane
Epithelial basement
membrane
Type I alveolar cell
Interstitial space
Alveolar fluid with surfactant
(a) Section through alveolus showing cellular components
(b) Details of respiratory membrane
Figure 13.6 Anatomy of the respiratory membrane (air-blood barrier).
Red blood cell
Capillary
Endothelial cell
nucleus
Alveolar pores
Capillary
O2
CO2
Macrophage
Nucleus of
squamous
epithelial cell
Respiratory
membrane
Alveolus
Alveolar epithelium
Fused basement
membranes
Capillary endothelium
Alveoli (gasfilled air
spaces)
Squamous
Red blood Surfactantcell in
secreting cell epithelial cell
of alveolar wall
capillary
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Ventilation: Inspiration and Expiration
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Normally there is a continuous column of air from
the pharynx to the alveoli.
Lungs lie within sealed thoracic cavity.
– Rib cage forms top and side of the cavity, while
the diaphragm forms the floor.
Thoracic cavity and lungs are enclosed by two
membranes, pleura.
– Visceral pleura surround the lungs
– Parietal pleura sticks to the rib cage and
diaphragm.
– Fluid separates these two. Pressure in fluid is
normally negative due to lungs trying to collapse
(elastic recoil).
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Inspiration
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A respiratory center located in the brain
triggers inspiration.
Inspiration is the active phase of breathing.
– The diaphragm and the rib muscles
(intercostals) contract, intrapleural
pressure decreases, the lungs expand,
and air rushes in.
 Creation of a partial vacuum in the
alveoli causes air to enter the lungs.
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Inspiration Versus Expiration
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Figure 13.7 Rib cage and diaphragm positions during breathing.
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral
dimensions
Ribs elevated
as external
intercostals
contract
External
intercostal
muscles
Full inspiration
(External
intercostals contract)
Diaphragm moves
inferiorly during
contraction
(a) Inspiration: Air (gases) flows into the lungs
Ribs depressed
as external
intercostals relax
External
intercostal
muscles
Diaphragm moves
superiorly as
it relaxes
(b) Expiration: Air (gases) flows out of the lungs
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Expiration
(External
intercostals relax)
Pressure relative
to atmospheric pressure
Figure 13.8 Changes in intrapulmonary pressure and air flow during inspiration and expiration.
+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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Expiration
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When the respiratory center stops sending
signals to the diaphragm and the rib cage,
the diaphragm relaxes.
– Abdominal organs press up against the
diaphragm, and the rib cage moves down
and inward.
Expiration is usually passive as the
diaphragm and intercostal muscles are
relaxed and the lung tissue recoils.
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Inspiration Versus Expiration
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Figure 13.7 Rib cage and diaphragm positions during breathing.
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral
dimensions
Ribs elevated
as external
intercostals
contract
External
intercostal
muscles
Full inspiration
(External
intercostals contract)
Diaphragm moves
inferiorly during
contraction
(a) Inspiration: Air (gases) flows into the lungs
Ribs depressed
as external
intercostals relax
External
intercostal
muscles
Diaphragm moves
superiorly as
it relaxes
(b) Expiration: Air (gases) flows out of the lungs
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Expiration
(External
intercostals relax)
Pressure relative
to atmospheric pressure
Figure 13.8 Changes in intrapulmonary pressure and air flow during inspiration and expiration.
+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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Lung Volumes & Capacities
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Spirometer- generates spirogram
1.
2.
3.
4.
5.
6.
7.
Tidal volume (TV)= mL/breath
Anatomic dead space- 30% of TV
Inspiratory reserve volume (IRV)
Expiratory reserve volume (ERV)
Residual volume
Vital capacity (VC)
Total lung capacity
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Figure 13.9 Idealized tracing of the various respiratory volumes of a healthy young adult male.
6,000
Milliliters (ml)
5,000
4,000
Inspiratory
reserve volume
3,100 ml
3,000
2,000
1,000
0
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Tidal volume 500 ml
Expiratory
reserve volume
1,200 ml
Residual volume
1,200 ml
Vital
capacity
4,800 ml
Total lung
capacity
6,000 ml
Exchange of Oxygen & Carbon Dioxide
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Gas laws: Dalton’s law & Henry’s law
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Dalton’s law- each gas in a mixture exerts it’s own pressure
independent of the other gas- this pressure is called it’s
partial pressure (in mmHg)
Henry’s law- quantity of a gas that will dissolve in a liquid is
proportional to the partial pressure of the gas & to it’s
solubility- solubility of CO2 is 24 times greater than the
solubility of O2 in water
External & internal respiration- exchange of gases
between alveolar air & blood
– Dependent on
1.
Partial pressure difference of the gases- the larger the partial
pressure difference of O2 in alveolar air vs. partial pressure in
the blood, the greater the rate of diffusion; the larger the
partial pressure of CO2 in the blood vs. the partial pressure in
the alveolar air, the greater the rate of diffusion
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Exchange of Oxygen & Carbon Dioxide (Cont.)
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External & internal respiration (Cont.)
2.
Surface area available for gas exchange- normally 750
ft2 ; any disorder that decreases functional surface area
decreases rate of exchange (e.g. emphysema; destruction
of alveolar walls
3.
Diffusion distance- respiratory membrane very thin (just
two cells thick); RBCs moving through capillaries in single
file; slow blood flow through capillaries; any disease that
builds up interstitial fluid slows rate of exchange (e.g.
asthma, pulmonary edema)
4.
Molecular weight & solubility of the gases- O2 is smaller
but CO2 is 24 times more soluble- net is that CO2 diffusion
is ~20 times faster than O2 ; thus in disease states hypoxia
comes before hypercapnia
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CO2 exhaled
O2 inhaled
Atmospheric air:
PO2 = 159 mmHg
PCO2 = 0.3 mmHg
Alveoli
Alveolar air:
PO2 = 105 mmHg
PCO2 = 40 mmHg
CO2 O
2
Pulmonary capillaries
To lungs
(a) External respiration:
pulmonary gas
exchange
To left atrium
Deoxygenated blood:
PO2 = 40 mmHg
PCO2 = 45 mmHg
Oxygenated blood:
PO2 = 100 mmHg
PCO2 = 40 mmHg
To right atrium
To tissue cells
(b) Internal respiration:
systemic gas
exchange
Systemic capillaries
CO2
O2
Systemic tissue cells:
PO2 = 40 mmHg
PCO2 = 45 mmHg
Figure 13.10 Gas exchanges in the body occur according to the laws of diffusion.
Inspired air:
Alveoli
of lungs:
CO2 O2
O2 CO2
O2 CO2
External
respiration
Pulmonary
arteries
Alveolar
capillaries
Blood
leaving
tissues and
entering
lungs:
Pulmonary
veins
Blood
leaving
lungs and
entering
tissue
capillaries:
Heart
O2 CO2
Tissue
capillaries
Systemic
veins
Internal
respiration
Systemic
arteries
CO2
O2
Tissue
cells:
O2 CO2
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O2 CO2
Transport of Oxygen & Carbon Dioxide
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Oxygen transport- hemoglobin (Hb)
– Hb + O2 = Hb-O2 (oxyhemoglobin); reversible

Relationship between hemoglobin & oxygen partial
pressure
 As partial pressure of O2 increases have rapid
binding to Hb but then binding plateaus & reaches
saturation
 At 100 mmHg, 100% saturation of Hb
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Transport of Oxygen & Carbon Dioxide (Cont.)
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Carbon dioxide transport
1.
2.
Dissolved CO2 – 7% is dissolved in plasma
Carbamino compounds- 23% bound to Hb; higher the
partial pressure of CO2 the greater the binding

Hb + CO2 = Hb-CO2 ; reversible

Binds to terminal amino acids of globin portions of Hb
3.
Bicarbonate ions- 70%- generated by equation belowcarried inside RBCs
CA
Hydrogen
Ion
Bicarbonate
Ion
Carbonic
Acid
Carbon
Dioxide
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Figure 13.11 Diagrammatic representation of the major means of oxygen (O 2) and carbon dioxide (CO2) loading and unloading in the body.
(a) External respiration in the lungs
(pulmonary gas exchange)
Oxygen is loaded into the blood
and carbon dioxide is unloaded.
(b) Internal respiration in the body tissues
(systemic capillary gas exchange)
Oxygen is unloaded and carbon
dioxide is loaded into the blood.
Alveoli (air sacs)
Tissue cells
O2
Loading
of O2
Hb + O2
HbO2
(Oxyhemoglobin
is formed)
CO2
CO2
Loading
of CO2
Unloading
of CO2
HCO3− + H+ H2CO3
CO2 + H2O
BicarCarbonic
Water
bonate
acid
ion
O2
Unloading
of O2
CO2 + H2O H2CO3
H++ HCO3−
Water Carbonic
Bicaracid
bonate
ion
Plasma
HbO2
Hb + O2
Plasma
Red blood cell
Systemic capillary
Pulmonary capillary
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Red blood cell
Control of Respiration
•
Respiratory Center- control rate & depth of breathing
–
Three important areas in brain stem
1.
2.
3.
1.
Medullary rhythmicity area- medulla oblongata
Pneumotaxic area- upper pons
Apneustic area- lower pons
Medullary rhythmicity area- controls the basic rhythm of
respiration
2.
Pneumotaxic area- sends inhibitory signals to the
inspiratory area of the medulla oblongata; prevents over
expansion of lungs
3.
Apneustic area- sends stimulatory signals to the inspiratory
area of the medulla oblongata; activates it; prolongs
inhalation, result is long deep inhalations; overridden by the
pneumotaxic area when active
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Figure 13.12 Breathing control centers, sensory inputs, and effector nerves.
Breathing control centers:
• Pons centers
• Medulla centers
Efferent nerve impulses from
medulla trigger contraction
of inspiratory muscles.
• Phrenic nerves
• Intercostal nerves
Afferent
impulses to
medulla
Breathing control centers
stimulated by:
CO2 increase in blood
(acts directly on medulla
centers by causing a
drop in pH)
Nerve impulse
from O2 sensor
indicating O2
decrease
Intercostal
muscles
Diaphragm
O2 sensor
in aortic body
of aortic arch
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Control of Respiration (Cont.)
•
Respiratory Center (Cont.)
–
Regulation of the respiratory center
1.
2.
3.
4.
5.
Cortical influence on respiration
Chemoreceptor regulation of respiration
Proprioceptor stimulation of respiration
The inflation reflex
Other influence on respiration
a)
b)
c)
d)
e)
f)
Limbic system stimulation
Temperature
Pain
Stretching of the anal sphincter
Irritation of airways
Blood pressure
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Control of Respiration (Cont.)
•
Respiratory Center (Cont.)
–
Regulation of the respiratory center (Cont.)
1.
2.
Cortical influence on respiration- cerebral cortex
connected to the respiratory center- can voluntarily alter
breathing patterns- provides voluntary protect effect;
input from hypothalamic & limbic systems- emotional
stimuli can alter breathing, e.g. laughing & crying
Chemoreceptor regulation of respiration- very sensitive
to CO2 & O2 levels

Two locations
a)
Central chemoreceptors- in medulla oblongatarespond to changes H+ & partial pressure of CO2
b)
Peripheral chemoreceptors- PCO2 , H+ , PO2


Carotid bodies- most sensitive to PCO2
Aortic bodies- most sensitive to PCO2
49
Figure 13.12 Breathing control centers, sensory inputs, and effector nerves.
Breathing control centers:
• Pons centers
• Medulla centers
Efferent nerve impulses from
medulla trigger contraction
of inspiratory muscles.
• Phrenic nerves
• Intercostal nerves
Afferent
impulses to
medulla
Breathing control centers
stimulated by:
CO2 increase in blood
(acts directly on medulla
centers by causing a
drop in pH)
Nerve impulse
from O2 sensor
indicating O2
decrease
Intercostal
muscles
Diaphragm
O2 sensor
in aortic body
of aortic arch
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Medulla oblongata
Sensory axons in
glossopharyngeal nerve
(cranial nerve IX)
Internal carotid
artery
External carotid
artery
Carotid body
Carotid sinus
Sensory axons in vagus nerve
(cranial nerve X)
Common carotid
artery
Arch of aorta
Aortic bodies
Heart
Some stimulus disrupts
homeostasis by
Increasing
Arterial blood PCO2 (or
decreasing pH or PO2)
Receptors
Central
Chemoreceptors
in medulla
Peripheral
chemoreceptors
in aortic
and
carotid
bodies
Nerve
impulses
Input
Control center
Inspiratory area in
medulla oblongata
Output
Nerve
impulses
Effectors
Muscles of
inhalation and
exhalation
contract more
forcefully and
more frequently
(hyperventilation)
Decrease in arterial blood
PCO2, increase in pH, and
increase in PO2
Return to homeostasis
when response brings
arterial blood PCO2 ,
pH, and PO2 back to
normal
Control of Respiration (Cont.)
•
Respiratory Center (Cont.)
–
Regulation of the respiratory center (Cont.)
3.
4.
Proprioceptor stimulation of respiration- start exercising
get increase in respiration depth & rate before changes
in PCO2 , H+ , PO2 , due to input from proprioceptors
directly into inspiratory area of medulla oblongata
The inflation reflex- stretch receptors in bronchi &
bronchioles- overinflation causes signals to inspiratory &
apneustic areas, inhibition of both areas, exhalation
begins- protects from overinflation (not part normal
regulation)
53
Control of Respiration (Cont.)
•
Respiratory Center (Cont.)
–
Regulation of the respiratory center (Cont.)
5.
Other influence on respiration
a)
Limbic system stimulation- emotional anxiety resulting in
excitatory stimuli- rate & depth of breathing go up
b)
Temperature- increase temperature increase rate; decrease
temperature decrease rate
c)
d)
e)
f)
Pain- sudden severe pain can stop breathing briefly
(apnea); prolonged somatic pain increases rate; visceral
pain can slow rate
Stretching of the anal sphincter- increases rate
Irritation of airways- chemical or physical irritation of
pharynx or larynx cause immediate cessation of breathing
Blood pressure- carotid & aortic baroreceptors for blood
pressure control have small effect on breathing rate; rise
in blood pressure decrease rate; drop in pressure
increases rate
54
Need to Know
Functions of the Respiratory System
1.
a)
b)
c)
d)
e)
Gas exchange: oxygen in, CO2 out
Aids venous and lymph return
Assists defense
Cleans, warms, moistens air
Help maintain pH
Components of the Respiratory System
2.
a)
b)
c)
d)
Nose: cleans, warms, moistens air, detects odors
Pharynx: connects nose, mouth, larynx; tonsils aid
defense; food and air paths cross
Auditory tube (Eustachian): tube from middle ear to
pharynx; equalizes air pressure on both sides of eardrum
(covered in Sensory Mechanisms Chap. 12)
Larynx: voice box, allows speech; closes off during
swallowing
55
Need to Know (Cont.)
Components of the Respiratory System (Cont.)
2.
e)
f)
g)
h)
Trachea (C-shaped cartilage holds this tube open),
bronchi (has smooth muscle), bronchioles (little smooth
muscle): tubes conducting air to alveoli; mucus escalator
in trachea aids in defense
Alveoli: area of gas exchange
Capillaries lay right up against the walls of the alveoli;
walls of the alveoli are only one cell thick
Exchange of gases

Oxygen diffuses through the alveoli walls and the walls
of the capillaries (which are also only one cell thick)
and enters into red blood cells and then binds to
hemoglobin

Carbon dioxide, carried mostly inside RBC as
bicarbonate ion; small amount of CO2 carried on
hemoglobin; bicarbonate ion converted to CO2 which
then diffuses out of the capillaries and enters into the
air in the alveoli to be expelled
56
Need to Know (Cont.)
Inspiration and Expiration
3.
a)
b)
c)
d)
Negative pressure in thoracic cavity due to elastic
tissue in lungs tending to collapse the lungs
Parietal pleura (membrane; epithelial cell layer) on
wall of thoracic cavity
Visceral pleura (membrane; epithelial cell layer) on
surface of lung tissue
Fluid layer between the two pleural membranes;
prevents collapse of lung due to hydrogen bonding of
the water molecules in the fluid to each membrane
surface
57
Need to Know (Cont.)
Inspiration and Expiration (Cont.)
3.
e)
Inspiration: active process; rib cage lifted up and out
by intercostal muscles while diaphragm (large muscle
that makes up the floor of the thoracic cavity) flattens,
pushing the abdominal cavity downward; result is
large increase in size of the cavity with the lung stuck
to it by hydrogen bonding of water molecules; air is
now in larger space thus pressure of the air in the
lungs decreases; air from outside then rushes in to
equalize the pressure
58
Need to Know (Cont.)
Inspiration and Expiration (Cont.)
3.
Expiration: mostly passive; intercostal muscles relax,
diaphragm relaxes, thus rib cage gets smaller,
diaphragm now moves back up into the thoracic
cavity; air in lungs is now in smaller space then before
thus pressure increases and then it moves out of the
lungs
Control of Respiration
a)
Know that the principal mechanism for control of
respiration is the chemoreceptors in the carotid &
aortic bodies and the amount of CO2 in the blood and
the blood pH, which is directly related to the amount of
CO2 in the blood
f)
4.
59