Chapter 15: Respiratory
System
15-1
The Respiratory System
The respiratory system works with the
cardiovascular system to exchange gases
between the air and blood (external
respiration) and between blood and tissue
fluids (internal respiration).
Inspiration and expiration move air in and
out of the lungs during breathing.
Cellular respiration is the final destination
where ATP is produced in cells.
15-2
The respiratory tract
15-3
The Respiratory Tract
Air is cleansed, warmed, and moistened
as it passes the cilia and mucus in the
nostrils and nasal cavity.
In the nose, the hairs and the cilia act as
a screening device.
In the trachea, the cilia beat upward,
carrying dust and mucus into the
pharynx.
Exhaled air carries out heat and
moisture.
15-4
The Nose
The two nasal cavities are divided by a
septum.
They contain olfactory cells, receive tear
ducts from eyes, and communicate
with sinuses.
The nasal cavities empty into the
nasopharynx.
Auditory tubes lead from the middle ears
to the nasopharynx.
15-5
The path of air
15-6
The Pharynx
The pharynx (throat) is a passageway
from the nasal cavities to oral cavities
and to the larynx.
The pharynx contains the tonsils; the
respiratory tract assists the immune
system in maintaining homeostasis.
The pharynx takes air from the nose to
the larynx and takes food from the oral
cavity to the esophagus.
15-7
The Larynx
The larynx is a cartilaginous structure
lying between the pharynx and the
trachea.
The larynx houses the vocal cords.
A flap of tissue called the epiglottis
covers the glottis, an opening to the
larynx.
In young men, rapid growth of the larynx
and vocal cords changes the voice.
15-8
Placement of the vocal cords
15-9
The Trachea
The trachea, supported by C-shaped
cartilaginous rings, is lined by ciliated
cells, which sweep impurities up
toward the pharynx.
Smoking destroys the cilia.
The trachea takes air to the bronchial
tree.
Blockage of the trachea requires an
operation called a tracheostomy to
form an opening.
15-10
Cilia in the trachea
15-11
The Bronchial Tree
The trachea divides into right and left
primary bronchi which lead into the
right and left lungs.
The right and left primary bronchi divide
into ever smaller bronchioles to
conduct air to the alveoli.
An asthma attack occurs when smooth
muscles in the bronchioles constrict
and cause wheezing.
15-12
The Lungs
Lungs are paired, cone-shaped organs
that lie on either side of the heart and
within the thoracic cavity.
The right lung has three lobes, and the
left lung has two lobes, allowing for the
space occupied by the heart.
The lungs are bounded by the ribs and
diaphragm.
15-13
The Alveoli
Alveoli are the tiny air sacs of the lungs
made up of squamous epithelium and
surrounded by blood capillaries.
Alveoli function in gas exchange, oxygen
diffusing into the bloodstream and
carbon dioxide diffusing out.
Infant respiratory distress syndrome
occurs in premature infants where
underdeveloped lungs lack surfactant
(thin film of lipoprotein) and collapse.
15-14
Gas exchange in the lungs
15-15
Mechanism of Breathing
During breathing, air moves into the
lungs during inspiration (inhalation)
from the nose or mouth, then moves
out again during expiration
(exhalation).
A spirometer allows measurement of the
components of air during breathing.
15-16
Respiratory Volumes
Tidal volume, the normal amount of air moved
in and out of the lungs when relaxed, is
usually 500 ml.
Inspiratory reserve volume is the maximum
amount of forcibly inspired air.
Expiratory reserve volume is the maximum
amount of forcibly expired air.
Vital capacity is the maximum amount of air
moved in and out on deep breathing, and is
the sum of tidal, inspiratory reserve, and
expiratory reserve volumes.
Air that remains in the lungs is residual
volume.
15-17
Vital capacity
15-18
Inspiration and Expiration
There is a continuous column of air from
the pharynx to the alveoli, and the
lungs lie within the sealed-off thoracic
cavity.
The thoracic cavity is bounded by the rib
cage and diaphragm.
Pleural membranes line the thoracic
cavity and lungs and the intrapleural
pressure is lower than atmospheric
pressure, keeping the lobules of the
lungs from collapsing.
15-19
Inspiration
When we inhale (inspiration) impulses
from the respiratory center in the
medulla oblongata cause the rib cage
to rise and the diaphragm to lower,
causing the thoracic cavity to expand.
The negative pressure or partial vacuum
in the alveoli causes the air to come in.
Changing amounts of blood of CO2 and
H+ increase breathing rate.
15-20
Nervous control of breathing
15-21
Inspiration
15-22
Expiration
When we exhale (expiration), lack of
impulses from the respiratory center
allow the rib cage to lower and
diaphragm to resume dome shape.
Expiration is passive, while inspiration is
active.
The elastic recoil of the lungs causes
expiration.
A deep breath causes alveoli to stretch;
stretch receptors then inhibit the
respiratory center.
15-23
Expiration
15-24
Gas Exchanges in the Body
External Respiration
Individual gases exert pressure
proportional to their portion of the total
in a mixture of gases; this is called
“partial pressure”.
External respiration is the diffusion of
CO2 from pulmonary capillaries into
alveolar sacs and O2 from alveolar sacs
into pulmonary capillaries.
15-25
In both cases, diffusion occurs because
the partial pressures are higher causing
diffusion (from higher to lower
concentrations) across the capillary
wall.
Most CO2 is carried as bicarbonate ions.
The enzyme carbonic anhydrase, in red
blood cells, speeds up the conversion of
bicarbonate and H+ to H2O and CO2; CO2
enters alveoli and is exhaled.
Hemoglobin (Hb) takes up oxygen from
alveoli and becomes oxyhemoglobin
(HbO2).
15-26
Internal Respiration
Internal respiration is the diffusion of O2
from systemic capillaries into tissues
and CO2 from tissue fluid into systemic
capillaries.
Oxyhemoglobin gives up O2, which
diffuses out of the blood and into the
tissues because the partial pressure of
O2 of tissues fluid is lower than that of
the blood.
15-27
After CO2 diffuses from tissue cells into
the blood, it enters red blood cells
where a small amount is taken up by
hemoglobin, forming
carbaminohemoglobin.
Most of the CO2 combines with water to
form carbonic acid (H2CO3), which
dissociates to release hydrogen ions
(H+) and bicarbonate ions (HCO3-); the
enzyme carbonic anhydrase speeds
this reaction.
15-28
The globin portion of hemoglobin
combines with excess hydrogen ions to
become reduced hemoglobin or HHb;
this helps maintain a normal blood pH.
Blood leaving capillaries is a dark
maroon color because red blood cells
contain reduced hemoglobin.
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External and internal respiration
15-30
Binding Capacity of Hemoglobin
The partial pressure of gases,
temperature, and pH affect binding
capacity of hemoglobin.
The high pressure of oxygen, the low
temperature and low pH aid the binding
of oxygen to hemoglobin in the lungs;
the opposite is true in the tissues.
In both cases, environmental conditions
are favorable to the uptake of the
appropriate gases.
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Saturation of Hb relative to
temperature
15-32
Saturation of Hb relative to pH
15-33
Respiration and Health
The presence of disease in the upper or
lower respiratory tract means that
homeostasis is threatened.
Upper Respiratory Tract Infections
These infections involve the nasal
cavities, pharynx, or larynx.
Some infections, such as “strep throat”,
can lead to systemic body infection.
15-34
Sites of upper respiratory
infections
15-35
Sinusitis
Sinusitis is infection of the cranial
sinuses within the facial skeleton that
drain into nasal cavities.
It occurs when nasal congestion blocks
the sinus openings and is relieved
when drainage is restored.
Pain and tenderness over the lower
forehead and cheeks, and toothache,
accompany this condition.
15-36
Otitis Media
Otitis media is bacterial infection of the
middle ear.
Children suffer when a nasal infection
spreads to the middle ear by way of the
auditory tube and antibiotics are
usually used to clear the infection.
Sometimes drainage tubes (called
tympanostomy tubes) are inserted into
the eardrums of children with recurrent
infections.
15-37
Tonsillitis
Tonsillitis is infection of tonsils and
recurrent infections that make
breathing or swallowing difficult may
be relieved by a tonsillectomy.
Laryngitis
Laryngitis is an infection of the larynx
and usually results in a loss of voice.
Persistent hoarseness is a warning sign
of cancer.
15-38
Lower Respiratory Tract
Disorders
Lower respiratory infections include:
1) acute bronchitis, an infection of
primary and secondary bronchi;
2) pneumonia involving a bacterial or
viral infection of the lungs; and
3) pulmonary tuberculosis (infection
caused by tubercle bacillus).
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Restrictive Pulmonary Disorders
In restrictive pulmonary disorders, vital
capacity is reduced because the lungs
have lost their elasticity due to inhaled
particles such as silica, coal dust, or
asbestos.
Fibrous connective tissue builds in the
lungs in pulmonary fibrosis, caused by
exposure to inhaled particles, including
those of fiberglass.
15-40
Obstructive Pulmonary
Disorders
In obstructive pulmonary disorders, air
does not flow freely in the airways, and
inhalation and exhalation are difficult.
Chronic bronchitis with inflamed airways,
emphysema where alveolar walls break
down, and asthma with constricted
bronchioles obstruct the airways and
tend to get progressively worse or
recur.
15-41
Lower respiratory tract disorders
15-42
Lung Cancer
Lung cancer follows this sequence of
events: thickening of airway cells, loss
of cilia on the lining, cells with atypical
nuclei, tumor development, and finally
metastasis.
Removal of a lobe or lung, called
pneumonectomy, may remove the
cancer.
Smoking, whether active or passive, is a
major cause of lung cancer.
15-43
Normal lung versus cancerous
lung
15-44
Chapter Summary
Air passes through a series of tubes
before gas exchange takes place
across an extensive moist surface in
the alveoli of the lungs.
Respiration comprises breathing,
external and internal respiration, and
cellular respiration.
15-45
During inspiration, the pressure in the
lungs decreases and air comes rushing
in; during expiration, increased pressure
in the thoracic cavity causes air to leave
the lungs.
External respiration occurs in the lungs
where oxygen diffuses into the blood and
carbon dioxide diffuses out of the blood.
Internal respiration occurs in the tissues
where oxygen diffuses out of the blood
into tissue cells and carbon dioxide
diffuses into the blood.
15-46
The respiratory pigment hemoglobin
transports oxygen from the lungs to the
tissues and aids in the transport of
carbon dioxide from the tissues to the
lungs.
The respiratory tract is especially subject
to disease because it is exposed to
infectious agents; also, cigarette
smoking contributes to two major lung
disorders—emphysema and cancer.
15-47