The Respiratory System
A. Organs
1. Nose
a. Anatomy
b. Physiology
2. Pharynx
3. Larynx
4. Trachea
5. Bronchi
6. Lungs
a. Gross anatomy
b. Lobes and fissures
c. Lobules
d. Alveolar-capillary (respiratory)
membrane
e. Blood supply to the lungs
B. Physiology of respiration
1. Pulmonary ventilation
a. Inspiration
b. Expiration
c. Compliance
2. Pulmonary air volumes and
capacities
a. Pulmonary volumes
b. Pulmonary capacities
3. Exchange of oxygen and carbon
dioxide
a. Dalton's law
4. Physiology of external (pulmonary)
respiration
5. Physiology of internal (tissue)
respiration
6. Transport of oxygen and carbon
dioxide
a. Oxygen
b. Carbon dioxide
c. Summary of gas exchange in
lungs and tissues
C. Control of respiration
1. Nervous control
a. Medullary rhythmicity area
b. Pneumotaxic area
c. Apneustic area
2. Regulation of respiratory center
activity
a. Cortical influences
b. Inflation reflex
c. Chemical regulation
Overview of Respiratory System
The respiratory system has the
following functions:
1. gas exchange
2. contains receptors for the sense of smell
3. filters, warms, and moistens inspired air
4. produces sounds
5. helps eliminate wastes other than carbon
dioxide
Respiration is the exchange of gases
between the atmosphere, the blood, and
the body cells.
There are three basic processes involved:
1. pulmonary ventilation
2. external respiration
3. internal respiration
Respiratory Organs
1. upper vs lower
2. conducting vs respiratory
Nose Anatomy
1. external nose
2. internal nose
3. nasal cavity
a. mucosa
b. nasal septum
c. vestibule
d. nasal conchae
(turbinate bones)
Nose Physiology
1. filter, moisten, and warm air
2. olfaction
3. resonating chamber
Pharynx
1.
2.
3.
4.
muscular tube
location
constrictor muscles
divisions
a. nasopharynx
b. oropharynx
c. laryngopharynx
Larynx
1. nine cartilages
2. thyroid cartilage
3. epiglottis
4. cricoid cartilage
5. laryngospasm
6. mucosa
7. vestibular folds
8. vocal folds
9. glottis
10. voice production
Larynx and Voice Production
Trachea
1.
2.
3.
4.
5.
location
mucosa
submucosa
cartilage
adventitia
Bronchial Tree
1. primary bronchi
2. secondary (lobar) bronchi
( 3 right, 2 left)
3. tertiary (segmental) bronchi
(10 right, 8 left)
4. bronchioles
5. terminal bronchioles
6. respiratory bronchioles
7. alveolar ducts and sacs
8. alveoli
Bronchial Tree Con’t
1.
2.
3.
4.
5.
6.
7.
8.
primary bronchi
secondary (lobar) bronchi
tertiary (segmental) bronchi
bronchioles
terminal bronchioles
respiratory bronchioles
alveolar ducts and sacs
alveoli
Bronchial Tree (anatomical changes)
1. cartilage
Trachea – C-shaped cartilage
Bronchi – irregular plates of cartilage
Bronchioles – cartilage gone
2. smooth muscle
increases as cartilage decreases
bronchodilation vs. bronchoconstriction
3. epithelium
ciliated pseudostratified + goblet cells (trachea)
ciliated simple columnar + goblet cells
ciliated simple cuboidal + goblet cells
ciliated simple cuboidal
simple cuboidal
simple squamous (alveoli)
alveolus
Smooth muscle
Simple cuboidal
Lumen of bronchiole
Lungs
1. location
2. pleurae
a. parietal
b. visceral
3. pleural cavity
(potential space)
4. pleural fluid
Pleura
Lungs, con’t
5. apex vs base
6. hilus
7. rt. lung = 3 lobes,
2 fissures (horizontal
and oblique)
8. lt. lung = 2 lobes,
1 fissure (oblique)
Lungs, con’t
9. bronchopulmonary segments
10. lobules
11. alveolus (3 cell types)
a. squamous epithelial cell
b. macrophage (dust cell)
c. septal cell -- surfactant
Alveolar-capillary membrane
(respiratory membrane)
1.
2.
3.
4.
surfactant
alveolar epithelial cell
fused basement membrane
capillary endothelial cell
Blood supply to the lungs
1. pulmonary artery
2. bronchial artery
3. pulmonary veins
Physiology of Respiration
What is the purpose of respiration?
What three processes are necessary to
accomplish this task:
1. pulmonary ventilation
2. external respiration
3. internal respiration
Pulmonary Ventilation
(breathing)
1.
2.
3.
4.
inspiration vs expiration
atmospheric pressure
intrapulmonic pressure
pressure gradient
Thoracic Cavity Dimensions
Inspiration (Active)
1.
2.
3.
4.
Boyle's law
inspiratory muscles
phrenic nerve (C3-5)
process
thoracic volume
pleural volume
intrapleural pr.
lung volume
intrapulmonic pr.
air flows into lungs
Decrease volume
increase pressure
Increase volume
decrease pressure
Inspiration (Active)
1.
2.
3.
4.
Boyle's law
inspiratory muscles
phrenic nerve (C3-5)
process
thoracic volume
pleural volume
intrapleural pr.
lung volume
intrapulmonic pr.
air flows into lungs
Expiration (passive)
1. elastic recoil
2. surface tension
3. process
thoracic volume
pleural volume
intrapleural pr.
lung volume
intrapulmonic pr.
air flows out
Forced Expiration
Compliance -- the ease with which the
lungs and thoracic wall can be expanded.
It is related to two factors:
1. elasticity
2. surface tension
Compliance is decreased with any condition that:
1. destroys lung tissue (emphysema)
2. fills the lungs with fluid (pneumonia)
3. produces a deficiency of surfactant
(premature birth, near-drowning)
4. interferes with lung expansion (pneumothorax)
Pulmonary Volumes and
Capacities
1. clinical respiration
2. tidal vol. (500 ml)
3. anatomic dead space
(150 ml)
5. inspiratory reserve volume
(3,000 ml)
6. expiratory reserve volume
(1,200 ml)
7. residual volume(1,300 ml)
8. vital capacity (4,700 ml)
Rates
maximum voluntary ventilation = TV x breaths/minute
alveolar ventilation rate = alveolar ventilation x breaths/minute
Exchange of Oxygen and Carbon
Dioxide
1. O2 flows down its concentration gradient by diffusion:
alveoli ---> blood ---> interstitial fluid ---> body cells
2. CO2 flows down its concentration gradient by diffusion:
cells ---> interstitial fluid ---> blood ---> alveoli
3. diffusion is dependent upon Dalton's law
Dalton's law = each gas in a mixture of
gases exerts its own pressure as if all of
the other gases were not present.
1. The pressure of a specific gas is known as its
partial pressure (p).
2. The total pressure of a mixture is the sum of
all the partial pressures.
3. Atmospheric air pressure = 760 mm Hg
nitrogen = 597 mm Hg +
oxygen = 159 mm Hg +
carbon dioxide = 0.3 mm Hg +
water vapor = 3.7 mm Hg
PARTIAL PRESSURES OF OXYGEN
EXTERNAL RESPIRATION
alveolar air = 104 mmHg
deoxygenated (pulmonary arterial) blood =
40 mmHg
oxygenated (systemic arterial) blood = 104 mmHg
INTERNAL RESPIRATION
interstitial fluid =
40 mmHg
cytoplasm = <40 mmHg
PARTIAL PRESSURES OF CARBON DIOXIDE
alveolar air =
40 mmHg
deoxygenated (pulmonary arterial) blood =
46 mmHg
oxygenated (systemic arterial) blood =
40 mmHg
interstitial fluid =
46 mmHg
EXTERNAL RESPIRATION
INTERNAL RESPIRATION
cytoplasm = >46 mmHg
External (Pulmonary Respiration)
1. alveoli <---> blood
a. deoxygenated --->
oxygenated blood
b. loss of CO2
2. diffusion 100% of time
3. rate dependent upon:
a. partial pr. differences
b. surface area
c. diffusion distance
d. breathing rate and depth
Internal (Tissue Respiration)
1. blood <---> tissue fluid <---> cells
a. oxygenated ---> deoxygenated
(only 25% O2 given up)
b. gains CO2
2. diffusion 100% of time
Oxygen Transport
100%
100%
oxygen released to
tissues at rest
80%
60%
40%
20%
oxygen saturation
oxygen saturation
1. 98.5% as oxyhemoglobin
2. fully saturated vs
partially saturated
3. percent saturation of HB
4. O2 - Hb dissociation curve
5. pO2 most important factor
oxygen released to
tissues during
exercise
80%
60%
40%
20%
20
20
60
100
PO2 (mmHg)
98%
75%
LUNGS
TISSUES
60
PO2 (mmHg)
100
23%
73%
98%
25%
LUNGS
TISSUES
Oxygen Transport Con’t
6. Hb saturation and pH
(Bohr effect)
7. Hb saturation and pCO2
8. Hb saturation and temperature
curve shifts to right when:
pH decreases, PCO2 increases,
temp. increases
curve shifts to left when:
pH increases, PCO2 decreases,
temp. increases
Carbon Dioxide Transport
1. 5% dissolved in plasma, 7% exhanged
2. 5% as carbamino-Hb, 23% exchanged
3. 90% as bicarbonate ion, (HCO3-) 70% exchanged
a. carbonic anhydrase
b. Bohr effect
c. chloride shift
CO2 + H2O
H2CO3
Carbonic anyhydrase
H+ + HCO3-
IN THE TISSUES SUMMARY
diffuses from tissues
into blood (RBCs)
CO2 + H2O
H ion binds Hb in RBC
and causes oxygen
release (Bohr effect)
H2CO3
diffuses into plasma in exchange for
chloride ions (chloride shift)
H+ + HCO3_
Systemic Gas Exchange
(in the Tissues)
IN THE LUNGS SUMMARY
diffuses into alveoli
and breathed away
CO2 + H2O
H ion released from Hb
into RBC cytoplasm
H2CO3
H+ + HCO3-
diffuses into RBC from plasma
in exchange for chloride ions
Alveolar Gas Exchange
(in the lungs)
Respiratory Centers
In the medulla
Dorsal Respiratory Group
Ventral Respiratory Group
– Inspiratory neurons
– Expiratory neurons
In the pons
Pneumotaxic Area
Apneustic Area
Control of Respiration
RESPIRATION AT REST
active
2 seconds
inactive
3 seconds
inspiratory neurons
diaphragm and external
intercostals contract
diaphragm and external
intercostals relax +
elastic recoil and surface
tension effects
normal resting inspiration
normal resting expiration
FORCED RESPIRATION
diaphragm, external intercostals, scalenes,
sternocleidomastoid contract
DRG and inspiratory
neurons active
forced inspiration
expiratory neurons of
VRG inhibited
DRG and inspiratory
neurons inhibited
inspiratory muscles
relax
active
expiration
internal intercostals and
abdominal muscles
contract
expiratory neurons of
VRG active
Control of Respiration Continued
Pons controls transition between
inhalation and exhalation
A. Pneumotaxic center (overides apneustic)
- sends inhibitory impulses to inspiratory
area which shortens duration of
inhalation before lungs get too full
B. Apneustic area
- sends stimulatory impusles to the
inspiratory area. Prolongs inhalation.
Other influences on Respiration
1. cortical influences
(chemoreceptors (Co2, H+)
2. Hering-Breuer inflation reflex
3. Proprioceptors
4. Pain receptors
cerebral cortex
limbic system
hypothalamus
sleep, exercise, vocalizations, exercise,
breath holding, emotional responses
pons respiratory group
ventral respiratory group
dorsal respiratory group
altered patterns of breathing
Hyperventilation and Hypoventilation
What would be the net effect of hyperventilation?
CO2 + H2O
H2CO3
H+ + HCO3-
reaction shifts to the left
H+ used to reform carbonic acid used to reform CO2
pH increases
increased CO2 lost from the body
What would be the net effect of hypoventilation?
CO2 + H2O
H2CO3
H+ + HCO3-
reaction shifts to the right as CO2 accumulates in the body
H+ accumulate in the body
pH decreases
Negative Feedback Control
CONTROLLED CONDITION
A stimulus or stress disrupts
homeostasis by causing a decrease in
arterial oxygen and/or increase in
hydrogen ions and/or an increase in
carbon dioxide
RETURN TO HOMEOSTASIS
Hyperventilation results in increase in
arterial oxygen and/or pH, and/or
decrease in arterial carbon dioxide
RECEPTOR
Chemosensitive neurons in medulla and
chemoreceptors in aortic and carotid
bodies respond to changes and direct
nerve impulses to the control center
CONTROL CENTER
Inspiratory neurons of medulla interpret
sensory input and generate nerve impulses
that pass ultimately to effectors
EFFECTORS
Muscles of inspiration contract more often
and more forcefully (hyperventilation)
Hypoxia and Positive Feedback
CONTROLLED CONDITION
A stimulus or stress disrupts
homeostasis by causing a decrease in
arterial oxygen below 50 mmHg
RETURN TO HOMEOSTASIS
Hypoventilation results in decreased
arterial oxygen, causing greater hypoxia.
This leads to positive feedback
RECEPTOR
Chemosensitive neurons in medulla suffer
hypoxia, resulting in the output of fewer
nerve impulses
EFFECTORS
Muscles of inspiration contract less
frequently and with less force
(hypoventilation)
CONTROL CENTER
Inspiratory neurons of medulla suffer
hypoxia, resulting in fewer nerve impulses
to the inspiratory muscles