Chapter 7
The Respiratory System
Chapter 7
The Respiratory System
7.1 Structures of the Respiratory System
7.2 Breathing and Respiration
7.3 Respiratory Health
Chapter 7 The Respiratory
System
In this chapter, you will learn:
The upper respiratory tract filters, warms, and moistens oxygen-containing
air, and channels it into the lungs.
The lower respiratory tract is made up of specialized structures that
exchange oxygen for carbon dioxide in the bloodstream.
Humans ventilate their lungs by the mechanism of breathing, which involves
inspiration and expiration.
The volume of air that is taken into the lungs can increase if the need for
oxygen increases, such as during exercise.
External respiration takes place in the lungs, between the air in the alveoli
and the blood in the capillaries.
Internal respiration takes place between the blood in the capillaries and
tissue cells.
Gas exchange occurs through the processes of simple diffusion and
facilitated diffusion.
Some disorders are specific to the respiratory system. Technologies are
available to treat respiratory disorders, but they may not be able to restore
the respiratory system to optimal health.
Smoking causes respiratory diseases. Technologies can help some
symptoms of smoking, but many symptoms are untreatable.
7.1 Structures of the
Respiratory System
In this section, you will:
identify the principal structures of the
respiratory system
identify the principal functions of the
respiratory system
observe and identify the major
respiratory structures
Respiratory System
Respiration
cellular respiration
– at the cellular level involves the oxidation of glucose
respiration at the multicellular level (breathing)
– involves taking oxygen from the environment and
returning carbon dioxide to it (breathing)
– breathing is necessary to bring enough nutrients
and oxygen to all cells in a multicellular organism
(where diffusion just isn’t enough)
Respiration: Stages & Structures
• Breathing involves two basic processes:
inspiration (breathing in, or inhaling) and
expiration (breathing out, or exhaling).
Inspiration moves air from the external
environment to the lungs inside the body.
Expiration moves air from the lungs back to
the external environment.
• External respiration is the exchange of
oxygen and carbon dioxide between the air
and the blood.
• Internal respiration is the exchange of
oxygen and carbon dioxide between the
body’s tissue cells and the blood.
• Cellular respiration is the series of
energy-releasing chemical reactions that
take place inside the cells. Cellular
respiration is the final stage in respiration.
It is the sole means of providing energy for
all cellular activities, and it helps the body
maintain homeostasis.
Breathing
brings oxygen to where diffusion can take
place (bulk flow)
facilitates diffusion into the transport
system
the circulatory system brings the oxygen to
the cells (bulk flow)
oxygen is brought into cells by diffusion
across the membrane
The Respiratory System
as air passes through the nasal cavity, it is
warmed and moistened
the passages are lined with hair and later
cilia and mucous to help trap foreign
invaders and sweep them into the pharynx
where they are swallowed, sneezed or
coughed out
the warmed air passes by the epiglottis
and down the trachea which is lined with
cartilage to prevent the trachea from
collapsing or being damaged
– the opening (slit) to the trachea is called the
glottis
– the air passes by the enlargement of the
trachea, the larynx, where the vocal cords are
located
the trachea is also lined with cilia and
mucous-secreting cells
– which beat 20x per minute to move the
trapped particles up to the pharynx
Smokers cilia
just above the heart, the trachea branches
into two bronchi
Bronchi branch again into bronchioles
which branch smaller and smaller – only
the smallest of the bronchioles lack
cartilage
at the end, the terminal bronchioles (the
last ones) end at a group of alveolar ducts
and sacs called alveoli
– the specialized structures for gas exchange
the lungs are each encased in a doublemembraned sac, the pleura which allow
the lungs to expand and contract freely
the diaphragm separates the lungs (in the
thoracic cavity) from the peritoneal cavity,
where the digestive organs are located
Alveoli
are specialized for optimal diffusion
– moist membrane
– large surface area
– thin walls for diffusion (1m across)
– immediately adjacent to pulmonary capillaries,
which are just large enough for a RBC to get
through
– the inner surface of the alveoli are covered with a
single layer of lipid called surfactant
which reduces the surface tension in the alveoli allowing
them to easily expand to twice their size with each breath
when a baby is born, the first cry and
breath must expand the alveoli without the
aid of surfactant
– the lipid layer is immediately formed making
breathing easier, and oxygen diffusion more
efficient (by  surface area since surfactant
aids in the expansion of the alveoli)
– for premature babies, the lungs may not be
completely mature. Doctors must support
breathing until the baby’s lungs develop by
giving them air with a higher oxygen
concentration
-Each bronchiole ends in several clusters of alveoli.
-Surrounding each alveolus is a fine network of
capillaries from the circulatory system.
-Gas exchange occurs between the blood in the
capillaries and the air in the alveolus, so that blood
leaving the lungs has a high oxygen content.
7.2 Breathing and Respiration
In this section, you will:
explain the mechanics of breathing
explain how gases are exchanged
between the human respiratory system
and the external environment
perform an experiment to determine your
respiratory volume
perform an experiment to examine factors
that affect the rate of respiration
Mechanics of Breathing
breathing involves two processes, inhalation
and exhalation
– Inhalation: an active process (using energy)
where one breath is drawn into the lungs with the
aid of muscle contractions
air is drawn into the lungs when the thoracic
cavity expands in size, and since the pleural
cavity is sealed, decreasing the pressure of the
cavity, which pulls air in from the environment
depending on the depth of breathing,
a number of muscles will be involved
–Diaphragm: contracts, moving
downward
–intercostal muscles (between the ribs):
contract, expanding the chest cavity
–neck muscles: contract, raising the top
two ribs
– Exhalation: generally a passive process
(unless breathing very deeply) where one
breath is expelled as the muscles above relax
as the muscles relax, the size of the
thoracic cavity is decreased, increasing the
pressure, forcing the gas out of the lungs
when breathing deeply, more air may be
exhaled with the contraction of the
abdominal muscles
The Mechanics of Breathing
Lung Volumes
the lung volume (total lung capacity) of the
average male is 5.7 L, the average female,
4.2 L, including the residual volume
residual volume is the amount of air that
remains in the lungs after maximum
expiration, keeping the lungs partially
inflated (about 1 L)
during quiet breathing, lungs generally
inflate from 2.2 L to 2.7 L (the amount of
air inhaled during quiet breathing, about
500 mL is the tidal volume)
The largest breath you can take is called
vital capacity
– involves expanding the lungs to a greater
extent than normal (recruiting the diaphragm,
intercostals and neck muscles), and exhaling
actively by recruiting the abdominal muscles
Vital capacity includes tidal volume, the
extra you can inhale (inspiratory reserve
volume) and the extra you can exhale
(expiratory reserve volume)
Of the 500 mL inhaled with every normal
breath, only about 0.35 L reaches the alveoli
(the rest fills the trachea, bronchi and
bronchioles)
– with an average respiratory rate (#
breaths/minute) of 10, the amount of air
exchanged per minute is 3.5L
Lung volumes will be affected by height and
gender in that thoracic cavity size will be
affected which affects the lung size
Exercise performed over an extended
period of time will strengthen the muscles
involved in breathing which will increase
tidal volume and vital capacity
Illness can reduce vital capacity and tidal
volume by affecting the number of alveoli
that can successfully exchange oxygen, or
by weakening the muscles in breathing
A Typical Spirograph
External vs. Internal Respiration
A) External respiration
- occurs between alveoli and the capillaries
next to them.
- As blood moves away from the body tissues,
it is oxygen-poor and carbon dioxide-rich.
- As it moves through the lung capillaries,
oxygen from the air in the alveoli diffuses into
the capillaries and carbon dioxide diffuses out
of the blood.
B) Internal respiration
- occurs between the capillaries and the body
tissues.
- Oxygen diffuses from the blood into the
oxygen-poor tissues while carbon dioxide
diffuses from the tissues into the blood.
Gas Exchange and Transport
oxygen and carbon dioxide must diffuse through the layer of
cells lining the alveolus and the layer of cells lining the
pulmonary capillary to enter/exit the blood.
The gas must also diffuse across the membrane of the RBC
to attach to a hemoglobin molecule
Oxygen
98.5% of oxygen is carried on the heme
group of the hemoglobin on the RBC
oxygen binds reversibly to hemoglobin to
form oxyhemoglobin (HbO2) in a reversible
reaction
the attaching of oxygen to hemoglobin is
affected by the following
– concentration of oxygen –  oxygen,  binding,
 oxygen,  binding (allows oxygen to be released
and diffuse into tissues over the entire capillary
length – gradually)
– pH -  pH,  binding ( pH means  CO2)
– temperature -  temp,  binding
– these conditions favour the release of oxygen in
tissues that are metabolically active (undergoing
lots of cellular respiration)
Carbon Dioxide
is transported three ways in the blood
– 7% dissolved in the blood plasma
– 23% carried on the hemoglobin molecule as
carbaminohemoglobin (HbCO2)
– 70% is carried as carbonic acid/carbonate ion
equilibrium
– Equation
CO2(g) + H2O(l) → H2CO3(aq) → HCO3-(aq) + H+(aq)
with the aid of the enzyme carbonic anydrase,
the reaction between carbon dioxide and water
is enhanced, which removes the carbon dioxide
from the plasma, maintaining the concentration
gradient from the tissues to the plasma,
ensuring diffusion
the HCO3-(aq)/ H2CO3(aq) behaves as a blood
buffer to help maintain the appropriate pH for
enzyme activity
Controlling Breathing Rate
to deliver the optimal quantity of oxygen to the tissues,
the body will  HR and alter BP (via baroreceptors
and chemosensors) but unless the breathing rate is
matched, oxygen transport will not be effective
the nervous system will match rate and magnitude of
breathing to the heart rate and blood pressure
– the medulla oblongata will control breathing rate
– the pons smoothes out the rhythm of the respiration
– chemoreceptors monitor pH ( CO2(g)  pH)
– receptors in the aorta and carotid arteries monitor
O2(g) in arterial blood
7.3 Respiratory Health
In this section, you will:
identify specific diseases that are
associated with the respiratory system
identify technologies that may be used to
treat these respiratory diseases
summarize the physiological effects of
smoking and the limitation of technologies
to address these effects
Upper Respiratory Tract Infections
Tonsillitis is an infection of the tonsils, which are located in the
pharynx. A viral infection, rather than a bacterial infection, is the
more common cause of tonsillitis. The tonsils can be removed
surgically if the infections are frequent and breathing is
impaired. In the past, many children had their tonsils removed
as a precaution, but this surgery is no longer as common. The
tonsils help to prevent bacteria and other foreign pathogens
from entering the body, so removing them can increase the
number of infections later in life.
Laryngitis is an inflammation of the larynx. Recall that the
larynx contains the vocal cords. The most common cause of
laryngitis is a viral infection; allergies and overstraining of the
voice can also lead to laryngitis. When the larynx is inflamed,
the vocal cords are not able to vibrate as they normally do. This
reduces the ability to speak in a normal voice or even to speak
at all. Symptoms of laryngitis include a sore throat and
hoarseness.
Lower Respiratory Tract Infections
Bronchitis is a disorder that causes the bronchi to become inflamed and filled
with mucus, which is expelled by coughing.
Pneumonia is a disease that occurs when the alveoli in the lungs become
inflamed and fill with liquids. This interferes with gas exchange, and the body
becomes starved for oxygen.
Pleurisy is a lung disorder that is caused by the swelling and irritation of the
pleura, the membranes that surround the lungs.
Emphysema is an obstructive respiratory disorder in which the walls of the
alveoli break down and lose their elasticity. This reduces the surface area for
gas exchange and causes oxygen shortages in the tissues.
Cystic fibrosis is a serious genetic condition that affects the lungs. Cystic
fibrosis is caused by an abnormal gene that disrupts the function of the cells
lining the passageways of the lungs.
Asthma is a chronic obstructive lung disease that affects the bronchi and
bronchioles, making breathing difficult or impossible because of reduced air
flow.
Lung cancer is the uncontrolled and invasive growth of abnormal cells in the
lungs. It is the leading cause of cancer deaths for men and women in Canada.
Lower Respiratory Tract
Disorders
Normal Lungs vs. Diseased Lungs
(A) These normal lungs have healthy red tissue. (The heart
is visible near the lower centre.) (B) These diseased lungs
have black tissue caused by heavy smoking. The white
areas are tumours, or carcinomas.
Carcinoma of the Lung
The large ball of cells in the centre of the image is a
carcinoma that has developed from the interior
surface cells of the human lung. The carcinoma
continues to grow and invade surrounding tissues,
including the lymphatic and blood vessels in the
lung. The lymphatic and blood vessels circulate
through the body and carry the cancerous cells, or
metastatic cells, to new locations where they can
grow and invade new tissues.
Chapter 7 Review
Create a flowchart or diagram showing the
path of oxygen through the respiratory
system.
Explain how each of the major respiratory
structures function.
What is cellular respiration?
Compare and contrast a normal lung with
smoker’s lung.
Identify three respiratory diseases. Briefly
describe their symptoms and how they are
diagnosed.
Concept Organizer
Chapter 7 Summary
Respiration enables the body to take
oxygen from the external environment and
process it for delivery to the cells and, at
the same time, rid itself of carbon dioxide.
Chapter 7 Summary
Oxygen is delivered to the cells and carbon dioxide is
removed from the cells and the body in a number of
exchanges.
Inspiration (breathing in, inhaling) and expiration
(breathing out, exhaling) exchange air between the
environment and the lungs.
External respiration exchanges oxygen and carbon
dioxide between the air in the lungs and the blood.
Internal respiration exchanges oxygen and carbon
dioxide between the blood and the body’s tissue cells.
Cellular respiration is the final step, when the oxygen
delivered to the cells is used to provide the energy for
all cellular activities; carbon dioxide is the waste
product of cellular respiration.
Chapter 7 Summary
The respiratory tract is the passageway for air to move
from the external environment into the lungs.
The upper respiratory tract begins at the nostrils and
includes the nasal passages, pharynx, larynx, and
trachea.
These passageways all clean and warm the air as it
passes through.
The lower respiratory tract consists of two bronchi that
each lead to a lung.
Within the lungs are small, fine tubes called
bronchioles, where the air continues to be cleaned
and warmed.
The exchange of gases takes place in a cluster of tiny
sacs at the end of each bronchiole, called alveoli,
where the oxygen diffuses through the membranes of
the alveoli into the capillaries of the circulatory system.
Chapter 7 Summary
A number of disorders of the respiratory
tract can impair the delivery of oxygen to
the cells, including bronchitis, pneumonia,
pleurisy, emphysema, cystic fibrosis,
asthma, and lung cancer.
These are all disorders of the lower
respiratory tract.
Infections of the upper respiratory tract,
such as tonsillitis and laryngitis are short
term infections that do not obstruct
breathing.