Respiratory
System
I. Respiration
A. Process filters incoming air and
transports it into the
microscopic alveoli where
gases are exchanged.
B. Consists of the following:
1. Ventilation
2. Gas exchange between
blood and lungs
3. Gas transport in the
bloodstream
4. Gas exchange between the
blood and body cells
5. Cellular respiration
II. Organs of the Respiratory
System
A. Divided into two groups:
1. Upper respiratory tract
a)Nose
b)Nasal cavity
c)Sinuses
d)Pharynx
2. Lower respiratory tract
a)Larynx
b)Trachea
c)Bronchial tree
d)Lungs
III. Upper Respiratory Tract
A.
Nose- Filters air with coarse
hairs inside the nostrils.
B. Nasal Cavity
1. Divided medially by the
nasal septum.
2. Nasal Conchae
a) Divide the cavity into
passageways
(increase surface
area)
b) Lined with mucous
membrane to warm
and filter incoming air.
III. Upper Respiratory Tract
C.
Paranasal Sinuses
1. Air-filled spaces within
the maxillary, frontal,
ethmoid, and sphenoid
bones of the skull.
2. Open to the nasal cavity
3. Lined with mucus
membrane
4. Continuous with lining of
the nasal cavity.
5. Reduce the weight of the
skull
6. Serve as a resonant
chamber to affect the
quality of the voice.
D. Pharynx- Aids in producing
sounds for speech.
IV. Lower Respiratory Tract
A.
Larynx
1. Enlargement superior to the
trachea and inferior to the
pharynx.
2. Keeps particles from entering
the trachea and also houses
the vocal cords.
3. Vocal cords.
a) The upper pair is the false
vocal cords.
b) The lower pair is the true
vocal cords.
c) During swallowing, the
false vocal cords and
epiglottis close off the
glottis.
IV. Lower Respiratory Tract
B.
Trachea
1. Extends downward from
larynx and splits into right
and left bronchi.
2. Inner wall lined with ciliated
mucous membrane (many
goblet cells) to trap
incoming particles.
3. The tracheal wall is
supported by 20 incomplete
cartilaginous rings.
IV. Lower Respiratory Tract
C.
Bronchial Tree
1. Branched tubes
leading from the
trachea to the alveoli.
2. Begins with the two
primary bronchi, each
leading to a lung.
3. Primary Bronchi 
Bronchioles 
Alveolar Ducts 
Alveoli
4. Gas exchange
between the blood
and air occurs
through the thin
epithelial cells of the
alveoli.
IV. Lower Respiratory Tract
D.
Lungs
1. Spongy, coneshaped
2. Enclosed by the
diaphragm and
thoracic cage.
3. The bronchi and
large blood vessels
enter each lung.
4. The right lung has
three lobes, the left
has two.
5. Lobes are
composed of
lobules
V. Breathing Mechanism
A.
Ventilation (breathing)composed of inspiration
and expiration.
B. Inspiration
1. Diaphragm and
intercostal muscles
contract
2. Air pressure inside the
lungs is decreased by
increasing the size of
the thoracic cavity.
3. Higher pressure air
flows in from the
outside.
C.
V. Breathing Mechanism
Expiration
1. Diaphragm
relaxes
2. Elastic recoil of
lung and muscle
tissues
3. Also from the
surface tension
within the alveoli.
4. Forced expiration
is aided by
thoracic and
abdominal wall
muscles.
VI. Respiratory Air Volumes and
Capacities
A.
B.
C.
D.
The measurement of
different air volumes is
called spirometry.
Air that enters and
leaves the lungs during
one respiratory cycle is
the tidal volume.
Maximum forced
inspiration is the
inspiratory reserve
volume.
Maximum forced
expiration is the
expiratory reserve
volume.
VI. Respiratory Air Volumes and
Capacities
E.
Vital capacity = tidal
volume + inspiratory +
expiratory reserve.
F. A residual volume always
remains in the lungs.
G. Vital capacity + residual
volume = total lung
capacity.
H. Anatomic dead space is
air remaining in the
bronchial tree.
VII. Control of Breathing
A.
Factors Affecting Breathing
1. Chemicals
2. Lung tissue stretching
3. Emotional state
B. Respiratory Center
1. Groups of neurons in the
brain stem.
2. Central chemoreceptors
a) Sensitive to changes
in the blood
concentration of CO2
and [H+]
b) CO2 or [H+]
concentrations  = 
the breathing rate
VII. Control of Breathing
C.
Peripheral
chemoreceptors
1. In the carotid sinuses
and aortic arch.
2. Sense changes in
blood oxygen
concentration.
3. Low O2 increases
breathing rate and tidal
volume increase.
4. Hyperventilation lowers
the amount of carbon
dioxide in the blood.
VII. Control of Breathing
D.
Alveolar Gas Exchanges
1. Alveoli- Tiny sacs at the
distal ends of the alveolar
ducts.
2. Respiratory Membrane
a) Components
1) Epithelial cells of the
alveolus
2) Endothelial cells of
the capillary
3) The two fused
basement
membranes of these
layers.
b) Gas exchange occurs
across this respiratory
membrane.
VIII. Gas Transport
A.
Oxygen Transport
1. Over 98% of oxygen is
carried in the blood bound
to hemoglobin, producing
oxyhemoglobin.
2. Oxyhemoglobin is
unstable and gives up its
oxygen in low O2 areas.
3. More oxygen is released
as CO2 increases, as the
blood becomes more
acidic, and as blood
temperature increases.
4. A deficiency of oxygen
reaching the tissues is
called hypoxia.
B.
VIII. Gas Transport
Carbon Dioxide Transport
1. Bound to RBC as carbaminohemoglobin
2. Dissolved in plasma as bicarbonate ions.
a) The enzyme carbonic anhydrase is in RBCs
b) Enzyme combines CO2 with water forming carbonic acid
VIII. Gas Transport
3. Carbonic acid dissociates, releasing bicarbonate and
hydrogen ions.
4. Most CO2 is transported as bicarbonate.
5. Carbaminohemoglobin releases its CO2 which diffuses out
of the blood into the alveolar air.