Anatomy and Physiology – Respiratory System

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE

Anatomy and Physiology – Respiratory System

CRT04101 · Anatomy, Physiology and Pathology

Study Anatomy and Physiology – Respiratory System using the sections below. Use the topic navigation to continue through Anatomy, Physiology and Pathology.

Anatomy and Physiology – Respiratory System

The Respiratory system:
The respiratory system (called also respiratory apparatus, ventilator
system) is a biological system consisting of specific organs and structures
used for the process of respiration in an organism. There are 3 major parts
of the respiratory system: the airway, the lungs, and the muscles of
respiration. The airway, which includes the nose,
mouth, pharynx, larynx, trachea, bronchi, and bronchioles, carries air
between the lungs and the body's exterior.
What is the respiratory system?
Your respiratory system is made up of the
organs in your body that help you to breathe.
Remember, that Respiration = Breathing. The
goal of breathing is to deliver oxygen to the
body and to take away carbon dioxide.
Parts of the respiratory system
Lungs
The lungs are the main organs of the
respiratory system. In the lungs oxygen is
taken into the body and carbon dioxide is
breathed out. The red blood cells are
responsible for picking up the oxygen in the
lungs and carrying the oxygen to all the body
cells that need it. The red blood cells drop off
the oxygen to the body cells, then pick up the
carbon dioxide which is a waste gas product
produced by our cells. The red blood cells
transport the carbon dioxide back to the lungs
and we breathe it out when we exhale.
Trachea
The trachea (TRAY-kee-uh} is sometimes called the windpipe. The
trachea filters the air we breathe and branches into the bronchi.
Bronchi
The bronchi (BRAHN-ky) are two air tubes that branch off of the trachea
and carry air directly into the lungs.
Diaphragm
Breathing starts with a dome-shaped muscle at the bottom of the lungs
called the diaphragm (DY-uh-fram). When you breathe in, the diaphragm
contracts. When it contracts it flattens out and pulls downward. This
movement enlarges the space that the lungs are in. This larger space pulls air
into the lungs. When you breathe out, the diaphragm expands reducing the
amount of space for the lungs and forcing air out. The diaphragm is the main
muscle used in breathing.
Respiration is the physiological process
supply oxygen to their cells and the cells use that oxygen to produce
high energy molecules. Respiration occurs in all types of organisms,
including bacteria, protists, fungi, plants, and animals. In higher animals,
respiration is often separated into three separate components: (a) external
respiration, the exchange of oxygen and carbon dioxide between the
environment and the organism; (b) internal respiration, the exchange of
oxygen and carbon dioxide between the internal body fluids, such as blood,
and individual cells; and (c) cellular respiration, the biochemical oxidation

of glucose and consequent synthesis of ATP (adenosine triphosphate)

. Respiration – External Respiration

External respiration, commonly known as breathing, is the exchange of
oxygen and carbon dioxide between an animal and its environment. Most
animals use specialized organs or organ systems, such as lungs, trachea, or
gills, for external respiration. In all cases, exchange of gases between the
environment and an animal occurs by diffusion through a wet surface on the

animal which is permeable to oxy…

Respiration – Internal Respiration

Internal respiration is the exchange of oxygen and carbon dioxide between
blood and cells in different tissues of an animal's body. Internal respiration
occurs in animals with a circulation system (categories 2, 4, and 5 above).
Animals with gills or lungs take up oxygen and transport oxygen-rich blood
throughout the body; they transport carbon dioxide-rich blood from the body

back into the…

Respiration – Cellular Respiration

Cellular respiration consists of many separate enzymatic reactions. The
entire process can be summarized in the chemical equation: Cellular
respiration is divided into three sequential series of reactions: glycolysis, the
citric acid cycle, and the electron transport chain. In higher organisms
(eukaryotes), glycolysis occurs in the cytosol of the cell, the aqueous region

outside the nucleus; …

Respiration – Glycolysis

Glycolysis can be defined simply as the lysis, or splitting, of sugar. More
particularly, it is the controlled breakdown of glucose, a 6-carbon
carbohydrate, into pyruvate, a 3-carbon carbohydrate. Organisms frequently
store complex carbohydrates, such as glycogen or starch, and break these
down into glucose units which can then enter into glycolysis. Two features

of glycolysis suggest that it has…

Respiration – Cirtric Acid Cycle

After pyruvate (a 3-carbon molecule) is synthesized by glycolysis, it moves
into the mitochondria and is oxidized to form carbon dioxide (a 1-carbon
molecule) and acetyl CoA (a two carbon molecule). Cells can also make
acetyl CoA from fats and amino acids and this is how cells often derive
energy, in the form of ATP, from molecules other than glucose or complex

carbohydrates. After acetyl CoA form…

Respiration – Electron Transfer Chain

The electron transfer chain is the final series of biochemical reactions in
cellular respiration. It consists of a series of organic electron carriers
associated with the inner membrane of the mitochondria. Cytochromes are

among the most important of these electron carriers. Like hemoglobin, cytochromes are colored proteins which contain iron in a nitrogencontaining heme group. The final electron…

Respiration – Anaerobic Respiration

The above reactions of cellular respiration are often referred to as aerobic
respiration because the final series of reactions, the electron transfer chain,
require oxygen as an electron acceptor. When oxygen is absent or in short
supply, cells may rely upon glycolysis alone for their supply of ATP.
Glycolysis presumably originated in primitive cells early in Earth's history
when very littl…
Respiration – Efficiency of Cellular Respiration
One can easily determine the energy efficiency of cellular respiration by
calculating the standard free energy change, a thermodynamic quantity,
between the reactants and products. On this basis, biochemists often quote
the overall efficiency of cellular respiration as about 40%, with the
additional 60% of the energy given off as heat. However, many cells
regulate the different enzymes of respirat…
The respiratory system plays a vital role in the body, by providing
your cells with much needed oxygen, as well as excreting carbon
dioxide, which can be deadly if allowed to accumulate. The three
major parts of the respiratory system are the airways, the lungs, and
the muscles of respiration. This article will explain anatomy of the
respiratory system, detailing the organs involved as well as the things
that can go wrong.
Anatomy of Respiratory System: Organs and Functions
The three major parts of the respiratory system all work together to
carry out their task. The airways (nose, mouth, pharynx, larynx etc.)
allow air to enter the body and into the lungs. The lungs work to pass
oxygen into the body, whilst removing carbon dioxide from the body.
The muscles of respiration, such as the diaphragm, work in unison to
pump air into and out of the lungs whilst breathing.
Respiratory

Organs

Description Function

Nose and
Nasal
Cavity
The nose is the
primary opening
for the respiratory
system, made of
bone, muscle, and
cartilage. The
nasal cavity is a
cavity within
your nose filled
The nose is used
to inhale air into
the body. The
nasal cavity
warms the air as
it enters, acting
as filtration and
purifying the air
by removing
with mucus
membranes and
hairs.
any dust, pollen,
and other
contaminants,
before it passed
to the inner
body.
Mouth Also called the
oral cavity, the
mouth is the
secondary
exterior opening
for the respiratory
system. Most
commonly, the
majority of
respiration is
achieved via the
nose and nasal
cavity, but the
mouth can be
used if needed.
Inhaling air
through the
mouth allows
more inhalation,
as the oral
cavity is far
larger than the
nasal cavity.
The air also has
less distance to
travel, meaning
more air can
enter your body
and be used
faster. The oral
cavity has no
hairs or filtering
techniques,
meaning the air
you inhale does
not undergo the
filtration
process.
Pharynx Also called the
throat, the
pharynx is a
funnel of muscle
that extends from
the respiratory
openings to the
esophagus and
larynx.
Air that is
inhaled enters
the pharynx,
where it
descends into
the larynx via a
diversion from
the epiglottis.
As the pharynx
is used for
swallowing
food as well as
breathing, the
epiglottis
ensures that air
can pass into the
trachea, and that
food enters the
esophagus.
Larynx Also known as
the voice box, the
Aside from
allowing us the
larynx is situated
below the
pharynx, in the
anterior portion
of the neck.
ability of
speech, the
larynx also acts
as a defense
mechanism. If
any food passes
into the
esophagus when
swallowing, the
larynx produces
a strong cough
reflex.
Trachea Also known as
the wind pipe, the
trachea is a tube
made of cartilage
rings that are
lined with
pseudostratified
ciliated columnar
epithelium.
The main
respiratory
function of the
trachea is to
provide a clear
and unhindered
airway for air to
enter and exit
the lungs. Inside
the trachea,
small hairs
reside upon the
inner walls.
These hairs
catch dust and
other
contaminants
from inhaled air,
which are later
expelled via
coughing.
Bronchi The bronchi are
two tubes
stemming off of
the end of the
trachea. Each
tube is connected
to a lung.
The bronchi
connect the
wind pipe to the
lungs, allowing
air from
external
respiratory
openings to pass
efficiently into
the lungs. Once
in the lungs, the
bronchi begin to
branch out into
secondary,
smaller bronchi,
coined tertiary
bronchi.
Bronchioles Tertiary bronchi
divide to even
smaller, narrower
tubes known as
bronchioles.
lead to alveolar
sacs, which are
sacs containing
alveoli.
Alveoli Alveoli are
hollow,
individual
cavities that are
found within
alveolar sacs.
Alveoli have
extremely thin
walls, which
allows the
exchange of
oxygen and
carbon dioxide
to take place
within the
lungs. There are
estimated to be
three million
alveoli in the
average lung.
Diaphragm The diaphragm is
an important
muscle of
respiration which
is situated
beneath the lungs.
The diaphragm
contracts to
expand the
space inside the
thoracic cavity,
whilst moving a
few inches
inferiorly into
the abdominal
cavity. Whilst
this is
happening, the
intercostal
muscles also
contract, which
moves the rip
cage up and out.
The contractions
force air into the
lungs, by
creating a
negative
pressure
through
expansion.
Physiology of Gas Exchange
Anatomy of respiratory system and organ functions cannot be
complete if you don‘t understand the transition between CO2 and O2.
Once air has been inhaled, it passed through the airways until it
reaches the alveoli within the lungs.Alveolus are surrounded by
capillaries, through which the gasses enter and exit. Carbon dioxide
enters the alveolus, where oxygen is extracted and passed back into
the body. The constant blood flow prevents saturation of the blood,
allowing for optimal transfer. The following picture better illustrates
the process:
Diseases and Illnesses of the Respiratory System
With knowing the anatomy of respiratory system, you should also
know that many conditions and illnesses can affect the respiratory
system, some of the common problems include: –
Asthma – Asthma leads to a narrowing of the airways, which can
cause breathlessness and wheezing.
Bronchitis – A condition that causes inflammation of the mucus
lining within the one lung or both.
Emphysema – A disease that affects alveoli.
Influenza – An illness caused by a virus that can have a
detrimental affect on one‘s respiratory system.
Laryngitis – When one‘s vocal chords (larynx) become inflamed.
Pneumonia – When one or both lungs become inflamed.
Lung cancer – Although commonly associated with smokers, lung
cancer can also affect those who do not smoke.
Every tissue within the body requires oxygen to function. The respiratory
system, which includes air passages, pulmonary vessels, the lungs, and
breathing muscles, provides oxygenated blood to the body tissues and
removes waste gases.
The respiratory system, which includes air passages, pulmonary vessels, the
lungs, and breathing muscles, aids the body in the exchange of gases
between the air and blood, and between the blood and the body‘s billions of
cells. Most of the organs of the respiratory system help to distribute air, but
only the tiny, grape-like alveoli and the alveolar ducts are responsible for
actual gas exchange.
In addition to air distribution and gas exchange, the respiratory system
filters, warms, and humidifies the air you breathe. Organs in the respiratory
system also play a role in speech and the sense of smell.
The respiratory system also helps the body maintain homeostasis, or balance
among the many elements of the body‘s internal environment.
The respiratory system is divided into two main components:
Upper respiratory tract: Composed of the nose, the pharynx, and the
larynx, the organs of the upper respiratory tract are located outside the chest
cavity.
Nasal cavity: Inside the nose, the sticky mucous membrane lining the nasal
cavity traps dust particles, and tiny hairs called cilia help move them to the
nose to be sneezed or blown out.
Sinuses: These air-filled spaces alongside the nose help make the skull
lighter.
Pharynx: Both food and air pass through the pharynx before reaching their
appropriate destinations. The pharynx also plays a role in speech.
Larynx: The larynx is essential to human speech.
Lower respiratory tract: Composed of the trachea, the lungs, and all
segments of the bronchial tree (including the alveoli), the organs of the
lower respiratory tract are located inside the chest cavity.
Trachea: Located just below the larynx, the trachea is the main airway to
the lungs.
Lungs: Together the lungs form one of the body‘s largest organs. They‘re
responsible for providing oxygen to capillaries and exhaling carbon dioxide.
Bronchi: The bronchi branch from the trachea into each lung and create the
network of intricate passages that supply the lungs with air.
Diaphragm: The diaphragm is the main respiratory muscle that contracts

and relaxes to allow air into the lungs.

The Respiratory System

The respiratory system is made up of organs and tissues that help you
breathe. The main parts of this system are the airways, the lungs and linked
blood vessels, and the muscles that enable breathing.

The Respiratory System

Figure A shows the location of the respiratory structures in the body. Figure
B is an enlarged view of the airways, alveoli (air sacs), and capillaries (tiny
blood vessels). Figure C is a closeup view of gas exchange between the
capillaries and alveoli. CO2 is carbon dioxide, and O2 is oxygen.
Airways
The airways are pipes that carry oxygen-rich air to your lungs. They also
carry carbon dioxide, a waste gas, out of your lungs. The airways include
your:
Nose and linked air passages (called nasal cavities)
Mouth
Larynx (LAR-ingks), or voice box
Trachea (TRA-ke-ah), or windpipe
Tubes called bronchial tubes or bronchi, and their branches
Air first enters your body through your nose or mouth, which wets and
warms the air. (Cold, dry air can irritate your lungs.) The air then travels
through your voice box and down your windpipe. The windpipe splits into
two bronchial tubes that enter your lungs.
A thin flap of tissue called the epiglottis (ep-ih-GLOT-is) covers your
windpipe when you swallow. This prevents food and drink from entering the
air passages that lead to your lungs.
Except for the mouth and some parts of the nose, all of the airways have
special hairs called cilia (SIL-e-ah) that are coated with sticky mucus. The
cilia trap germs and other foreign particles that enter your airways when you
breathe in air.
These fine hairs then sweep the particles up to the nose or mouth. From
there, they're swallowed, coughed, or sneezed out of the body. Nose hairs
and mouth saliva also trap particles and germs.
Lungs and Blood Vessels
Your lungs and linked blood vessels deliver oxygen to your body and
remove carbon dioxide from your body. Your lungs lie on either side of your
breastbone and fill the inside of your chest cavity. Your left lung is slightly
smaller than your right lung to allow room for your heart.
Within the lungs, your bronchi branch into thousands of smaller, thinner
tubes called bronchioles. These tubes end in bunches of tiny round air sacs
called alveoli (al-VEE-uhl-eye).
Each of these air sacs is covered in a mesh of tiny blood vessels called
capillaries. The capillaries connect to a network of arteries and veins that
move blood through your body.
The pulmonary (PULL-mun-ary) artery and its branches deliver blood rich
in carbon dioxide (and lacking in oxygen) to the capillaries that surround the
air sacs. Inside the air sacs, carbon dioxide moves from the blood into the
air. At the same time, oxygen moves from the air into the blood in the
capillaries.
The oxygen-rich blood then travels to the heart through the pulmonary vein
and its branches. The heart pumps the oxygen-rich blood out to the body.
The lungs are divided into five main sections called lobes. Some people need
to have a diseased lung lobe removed. However, they can still breathe well
using the rest of their lung lobes.
Muscles Used for Breathing
Muscles near the lungs help expand and contract (tighten) the lungs to allow
breathing. These muscles include the:
Diaphragm (DI-ah-fram)
Intercostals muscles
Abdominal muscles
Muscles in the neck and collarbone area
The diaphragm is a dome-shaped muscle located below your lungs. It
separates the chest cavity from the abdominal cavity. The diaphragm is the
main muscle used for breathing.
The intercostals muscles are located between your ribs. They also play a
major role in helping you breathe.
Beneath your diaphragm are abdominal muscles. They help you breathe out
when you're breathing fast (for example, during physical activity).
Muscles in your neck and collarbone area help you breathe in when other
muscles involved in breathing don't work well, or when lung disease impairs

your breathing.

Breathing In (Inhalation)

When you breathe in, or inhale, your diaphragm contracts (tightens) and
moves downward. This increases the space in your chest cavity, into which
your lungs expand. The intercostals muscles between your ribs also help
enlarge the chest cavity. They contract to pull your rib cage both upward and
outward when you inhale.
As your lungs expand, air is sucked in through your nose or mouth. The air
travels down your windpipe and into your lungs. After passing through your
bronchial tubes, the air finally reaches and enters the alveoli (air sacs).
Through the very thin walls of the alveoli, oxygen from the air passes to the
surrounding capillaries (blood vessels). A red blood cell protein called
hemoglobin helps move oxygen from the air sacs to the blood.
At the same time, carbon dioxide moves from the capillaries into the air
sacs. The gas has traveled in the bloodstream from the right side of the heart
through the pulmonary artery.
Oxygen-rich blood from the lungs is carried through a network of capillaries
to the pulmonary vein. This vein delivers the oxygen-rich blood to the left
side of the heart. The left side of the heart pumps the blood to the rest of the
body. There, the oxygen in the blood moves from blood vessels into

surrounding tissues.

Breathing Out (Exhalation)

When you breathe out, or exhale, your diaphragm relaxes and moves upward
into the chest cavity. The intercostal muscles between the ribs also relax to
reduce the space in the chest cavity.
As the space in the chest cavity gets smaller, air rich in carbon dioxide is
forced out of your lungs and windpipe, and then out of your nose or mouth.
Breathing out requires no effort from your body unless you have a lung
disease or are doing physical activity. When you're physically active, your
abdominal muscles contract and push your diaphragm against your lungs
even more than usual. This rapidly pushes air out of your lungs.
The act of breathing
The act of breathing has two stages – inhalation and exhalation
Inhalation – the intake of air into the lungs through expansion of chest
volume.
Exhalation – the expulsion of air from the lungs through contraction of
chest volume.
Inhalation and exhalation involves muscles:
1.Rib muscles = the muscles between the ribs in the chest.
2.Diaphragm muscle
Muscle movement – the diaphragm and rib muscles are constantly
contracting and relaxing (approximately 16 times per minute), thus causing
the chest cavity to increase and decrease.
During inhalation – the muscles contract:
Contraction of the diaphragm muscle – causes the diaphragm to flatten, thus
enlarging the chest cavity.
Contraction of the rib muscles – causes the ribs to rise, thus increasing the
chest volume.
The chest cavity expands, thus reducing air pressure and causing air to be
passively drawn into the lungs. Air passes from the high pressure outside the
lungs to the low pressure inside the lungs.
During exhalation – the muscles relax:
The muscles are no longer contracting, they are relaxed.
The diaphragm curves and rises, the ribs descend – and chest volume
decreases.
The chest cavity contracts thus increasing air pressure and causing the air in
the lungs to be expelled through the upper respiratory tract. Exhalation, too,
is passive. Air passes from the high pressure in the lungs to the low pressure
in the upper respiratory tract.
Inhalation and exhalation are involuntary and therefore their control
requires an effort.
The act of breathing – Illustration & Animation
The respiratory system- Illustration
Lungs and their structure and exchange of gases in the lungs:
Gas exchange is the delivery of oxygen from the lungs to the bloodstream,
and the elimination of carbon dioxide from the bloodstream to the lungs. It
occurs in the lungs between the alveoli and a network of tiny blood vessels
called capillaries, which are located in the walls of the alveoli.
Respiratory gases—oxygen and carbon dioxide—move between theair and
the blood across the respiratory exchange surfaces in the lungs. The structure
of the human lung provides an immense internal surface that facilitates gas
exchange between the alveoli and the blood in the pulmonary capillaries.
The primary function of the respiratory system is to exchange oxygen and
carbon dioxide. Inhaled oxygen enters the lungs and reaches the alveoli. The
layers of cells lining the alveoli and the surrounding capillaries are each only
one cell thick and are in very close contact with each other. This barrier
between air and blood averages about 1 micron ( 1/ 10,000 of a centimeter, or
0.000039 inch) in thickness. Oxygen passes quickly through this air-blood
barrier into the blood in the capillaries. Similarly, carbon dioxide passes
from the blood into the alveoli and is then exhaled.
Oxygenated blood travels from the lungs through the pulmonary veins and
into the left side of the heart, which pumps the blood to the rest of the body
(see Function of the Heart). Oxygen-deficient, carbon dioxide-rich blood
returns to the right side of the heart through two large veins, the superior
vena cava and the inferior vena cava. Then the blood is pumped through the
pulmonary artery to the lungs, where it picks up oxygen and releases carbon
dioxide.
Gas Exchange between Alveoli and Capillaries
To support the exchange of oxygen and carbon dioxide, about 5 to 8 liters
(about 1.3 to 2.1 gallons) of air per minute are brought in and out of the
lungs, and about three tenths of a liter of oxygen is transferred from the
alveoli to the blood each minute, even when the person is at rest. At the
same time, a similar volume of carbon dioxide moves from the blood to the
alveoli and is exhaled. During exercise, it is possible to breathe in and out
more than 100 liters (about 26 gallons) of air per minute and extract 3 liters
(a little less than 1 gallon) of oxygen from this air per minute. The rate at
which oxygen is used by the body is one measure of the rate of energy
expended by the body. Breathing in and out is accomplished by respiratory
muscles.
Gas Exchange between Alveolar Spaces and Capillaries
The function of the respiratory system is to exchange two gases: oxygen and carbon dioxid
The exchange takes place in the millions of alveoli in the lungs and the capillaries th
envelop them. As shown below, inhaled oxygen moves from the alveoli to the blood in t
capillaries, and carbon dioxide moves from the blood in the capillaries to the air in t
alveoli.
Three processes are essential for the transfer of oxygen from the outside air
to the blood flowing through the lungs: ventilation, diffusion, and perfusion.
Ventilation is the process by which air moves in and out of the lungs.
Diffusion is the spontaneous movement of gases, without the use of
any energy or effort by the body, between the gas in the alveoli and
the blood in the capillaries in the lungs.
Perfusion is the process by which the cardiovascular system pumps
blood throughout the lungs.
The body's circulation is an essential link between the atmosphere, which
contains oxygen, and the cells of the body, which consume oxygen. For
example, the delivery of oxygen to the muscle cells throughout the body
depends not only on the lungs but also on the ability of the blood to carry
oxygen and on the ability of the circulation to transport blood to muscle.
The respiratory system starts at the nose and mouth and continues through
the airways and the lungs. Air enters the respiratory system through the nose
and mouth and passes down the throat (pharynx) and through the voice box,
or larynx. The entrance to the larynx is covered by a small flap of tissue
(epiglottis) that automatically closes during swallowing, thus preventing
food or drink from entering the airways.
The largest airway is the windpipe (trachea), which branches into two
smaller airways: the left and right bronchi, which lead to the two lungs. Each
lung is divided into sections (lobes): three in the right lung and two in the
left lung. The left lung is a little smaller than the right lung because it shares
space in the left side of the chest with the heart.
Inside the Lungs and Airways
The bronchi themselves branch many times into smaller airways, ending in
the narrowest airways (bronchioles), which are as small as one half of a
millimeter across. The airways resemble an upside-down tree, which is why
this part of the respiratory system is often called the bronchial tree. Large
airways are held open by semiflexible, fibrous connective tissue called
cartilage. Smaller airways are supported by the lung tissue that surrounds
and is attached to them. The walls of the smaller airways have a thin,
circular layer of smooth muscle. The airway muscle can dilate or constrict,
thus changing airway size.
At the end of each bronchiole are thousands of small air sacs (alveoli).
Together, the millions of alveoli of the lungs form a surface of more than
100 square meters. Within the alveolar walls is a dense network of tiny
blood vessels called capillaries. The extremely thin barrier between air and
capillaries allows oxygen to move from the alveoli into the blood and allows
carbon dioxide to move from the blood in the capillaries into the air in the
alveoli.
The pleura are a slippery membrane that covers the lungs as well as the
inside of the chest wall. It allows the lungs to move smoothly during
breathing and as the person moves. Normally, the two layers of the pleura
have only a small amount of lubricating fluid between them. The two layers
glide smoothly over each other as the lungs change size and shape.
The respiratory airways include the respiratory apertures (mouth and
nose), the trachea and a branching system of long, flexible tubes
(bronchi) that branch of to shorter and narrower tubes (broncheoli)
until they end in sacs called the pulmonary alveoli.
The lungs encompass the entire system of tubes branching out from the
main bronchi to the alveoli.
Measuring the functioning of the lungs is a medical tool for diagnosing
problems in the respiratory system.
Air volume (in liters) – lung capacity
Maximum lung volume is known as TLC (total lung capacity). It can be
obtained by maximum strenuous inhalation.
The maximum lung volume of a healthy adult is up to 5-6 liters. In
children the maximum lung volume is up to 2-3 liters, depending on
age. In infants it is up to 600-1000 milliliters.
Note! Differences in lung volume can only be caused by gender, age,
and height.
Essential air volume is the maximum volume utilized by the lungs for
inhalation, also known as VC (vital capacity).
Residual volume (RV) is the volume of air remaining in the lungs after
strenuous exhalation when the lungs feel completely empty. Residual
volume prevents the broncheoli and the alveoli from sticking together.
Residual volume is approximately 1.5 liters (adults).
The differential between total lung capacity and residual volume is
the maximal volume utilized by the lungs in order to breath. It is
known as vital capacity(VC). In an adult, the VC is between 3.5 and 4.5
liters.
Tidal Volume or VT is the volume of air displaced between normal
inspiration and expiration. In a healthy adult the tidal volume is
approximately 500 milliliters.
Rate of airflow through the respiratory airways (into and out of the
lungs).This measures the effectiveness of airflow.
Efficiency of diffusion of oxygen from the pulmonary alveoli into the
blood (not dealt with in this unit).
TLC (total lung capacity) of children
Examining lung function
The most common, accessible and efficient method of measuring lung
function is by means of a spirometer. Its purpose is to diagnose obstructive
diseases of the respiratory system. It produces a diagram (graphic depiction)
of the volume of air expired in a given time (liter/minute)
The spirometer shows the rate at which air is expelled from the lungs. It
measures the total lung capacity up to the residual volume (this test does not
show the rate at which oxygen is absorbed).
If the airways are blocked the rate of the airflow of the lungs decreases. This
will show on the diagram and thus indicate that there is a problem in the
airways.
The most common obstruction stems from excessive phlegm, or from
swelling of the inner wall of the air ways.
The most common problem of blockage of the air ways is asthma. people
suffering from asthma it take longer to empty the lungs than healthy people.
For example, during the first second of exhalation, only half of the vital air
capacity in their lungs is expelled as opposed to 90% in healthy people. The
rest is exhaled much later.
A spirometer examination takes only a few seconds. It is completely safe but
there is a need for the patient to cooperate in order to obtain accurate results.
Stages of the examination:
1.The patient is asked to inhale as deeply as possible.
2.The patient is asked to exhale strenuously into the spirometer.
3.The patient is asked to continue to expel air for a few seconds, despite
the strong urge to breathe in.
4.The test is repeated twice or three times.
Respiratory rate
Children in the upper classes of elementary school breathe about 20 times
per minute.
Every breath causes an inhalation of approximately 7 milliliters of air
volume per kilogram of body weight.
A child who weighs 30 kilos inhales approximately 210 milliliters of air
volume (210X30). In other words, in the duration of a minute some 4200
milliliters of air volume enters and be expelled from the lungs.
Athletes breathe slightly deeper and slower. With every breath they inhale
approximately 10 milliliters of air per kilogram. Thus an athletic child who
weighs 30 kilos will only breathe 15 times in the duration space of a minute.
Each inhalation will require some 300 milliliters of air volume. In the space
of a minute 4500 milliliters of air volume will enter and be expelled from the
his lungs. We can deduce from this that athletes ventilate their airways in a
much more efficient way.
When we are under strain we breathe faster and more deeply. Since the
lungs contain a reserve of air, we do not become tired because lack of air
(oxygen) is causing respiratory restriction, but because of strain and
tiredness in our respiratory and heart muscles.
When we are under emotional stress (before an exam, in distress, or feeling
very frightened) we breathe faster, but our breathing is shallower. For
example, under stress we inhale 30 times per minute but at a rate of only 4
milliliters per kilo. In other words, overall only 3600 milliliters per minute
are passing through our airways, so we feel ―short of breath.‖
During severe asthma attacks, the breathing of asthma patients is shallower
and at a higher rate. Their breathing is thus not very efficient.
nasal cavity: Contains nasal septum, turbinates,
and cilia.
nasal septum:Divides nasal cavities into right and
left sides.
Turbinates: Bones that protrude into the nasal
cavity- they increase surface area for filtering dust
and dirt particles by the mucous membrane.
Cilia: Nose hairs, trap larger dirt particles.
Sinuses: Cavities in the skull, ducts connect them
to the nasal cavity, lined with mucous membrane
to warm and moisten the air. Give resonance to
voice.
types of sinuses: Frontal, maxillary, ethmoid, and
sphenoid.
Pharynx: Throat. Common passageway for air
and food. 5" long.
Epiglottis:When food is swallowed, this closes
over the opening to the larnyx, preventing food
from entering the lungs.
Larynx:Voice box. Triangular chamber below
pharynx. "Adam's Apple".
Glottis: Vocal cords within the larynx.
Trachea: Windpipe. 4.5" long. Walls are alternate
bands of membrane and c-shaped rings of hyaline
cartilage to keep it open. Lined with ciliated
mucous membrane. Coughing and expectoration
gets rid of dust-laden mucous.
Bronchi:Similar to trachea with ciliated mucous
membrane and hyaline cartilage. Lower end of
trachea divides into right and left this.
bronchial tubes: Cartilaginous plates (instead of
c-shaped rings of trachea).
Bronchioles: Thinner walls of smooth muscle,
lined with ciliated epithelium. Subdivision of
bronci. At the end, alveolar duct and cluster of
alveoli.
Alveoli: Composed of single layer of epithelial
tissue. Inner surfaces covered with surfactant to
keep from collapsing. Each surrounded by
capillaries. Oxygen and carbon dioxide exchange
takes place between these and capillaries.
Lungs: Fill thoracic cavity. Tissue is porous and
spongy- it floats.
Apex:Upper part of lung.
Base: Lower part of lung.
right lung: Larger and shorter (displaced by liver)
and has three lobes.
left lung:Smaller (displaced by heart) and has two
lobes.
Pleura: Thin, moist, slippery membrane that
covers lungs. Double-walled sac. Space is pleural
cavity- filled with pleural fluid to prevent friciton.
functions of the respiratory system:Respiration
(external, internal, and cellular). Production of
sound (vocal cords). Pulmonary venilation.
Inspiration (intercostal muscles lift ribs outward,
sternum rises and the diaphragm contracts and
moves downward- this increases the volume of the
lungs and the air rushes in).
pulmonary ventilation:Breathing.
respiratory movement: 1 inspiration and 1
expiration= 1 respiration. Normal adult= 14-20
respirations per minute. Increases with exercise,
body temperature, and certain diseases. Age
(newborn= 40-60 per minute). Sleep= respirations
go down. Emotion can bring respirations up or
down.
Coughing:Deep breath followed by forceful
expulsion of air to clean lower respiratory tract.
Hiccups: Spasm of diaphragm and spasmodic
closure of the glottis- irritation to diaphragm or
phrenic nerve.
Sneezing: Air forced through nose to clear
respiratory tract.
Yawning: Deep prolonged breath that fills the
lungs, increases oxygen within the blood.
neural factors of breathing control: Respiratory
center located in medulla oblongata (in the brain).
Increase in CO2 and decrease in O2 in the blood
will trigger respiratory center.
phrenic nerve: Stimulates the diaphragm.
chemical factors of breathing control: Depends
on the levels of CO2 in the blood.
Chemoreceptors in aorta and carotid arteries
sensitive to the amount of blood oxygen.
Diseases of the respiratory system
Diseases and conditions of the respiratory system fall into two
categories: Viruses such as influenza, bacterial pneumonia and the
newenterovirus respiratory virus that has been diagnosed in children; and
chronic diseases, such as asthma and chronic obstructive pulmonary disease
(COPD). According to Dr. Neal Chaisson, who practices pulmonary
medicine at the Cleveland Clinic, there is not much that can be done for viral
infections but to let them run their course. "Antibiotics are not effective in
treating viruses and the best thing to do is just rest," he said.
COPD is the intersection of three related conditions — chronic bronchitis,
chronic asthma and emphysema, Chaisson told Live Science. It is a
progressive disease that makes it increasingly difficult for sufferers to
breath.
Asthma is a chronic inflammation of the lung airways that causes coughing,
wheezing, chest tightness or shortness of breath, according to Tonya
Winders, president of the Allergy & Asthma Network. These signs and
symptoms may be worse when a person is exposed to their triggers, which
can include air pollution, tobacco smoke, factory fumes, cleaning solvents,
infections, pollens, foods, cold air, exercise, chemicals and medications.
Lung cancer is often associated with smoking, but the disease can affect
non-smokers as well. Every year, about 16,000 to 24,000 Americans die of
lung cancer, even though they have never smoked, according to the
American. Like all cancers, lung cancer is caused
growth of abnormal cells.
Mechanism of respiration (internal and external respiration)
Breathing: everyone does it, but how does it work? Most people tend to
equate breathing with respiration, assuming they are one and the same, but
really the process of respiration is a much longer, more complicated
system, of which breathing is just one of its many steps. There are also
two different types of respiration: cellular and physiological, the latter of
which concerns the process of breathing and the respiratory system.
In this guide, we‘ll cover physiological respiration, and touch a bit on
cellular respiration and its two types: aerobic and anaerobic. For some
more helpful background information, consider this introduction to
biology course.
What is Respiration?
There are two types of respiration: cellular and physiological. Before we
get into either, you might want to consider this course on medical
terminology or this course on the principles of medical language, both
of which should make understanding the processes described here much

easier.

 Cellular Respiration

The process of converting molecules into energy through oxidization. This
is the opposite of photosynthesis, the biochemical process used by plants
and some types of bacteria to convert light energy into chemical
energy. Learn more about photosynthesis in this guide.
In terms of cellular respiration, there are two types: aerobic and anaerobic.
In short, the process of aerobic respiration requires oxygen, while the
process of anaerobic respiration does not require oxygen. Learn a bit

more about both aerobic and anaerobic respiration in this guide.

 Physiological Respiration

The process involving absorption of oxygen in the air into the cells of an
organism, with the output of carbon dioxide back into the environment. It
is a cycle between the organisms that breath oxygen and the organisms
that breath carbon dioxide.
There are two types of physiological respiration in animals: internal
respiration, and external respiration. Internal respiration is the process of
cells in the body exchanging gases, while external respiration is the
process of respiration that actually takes place within respiratory organs
like the lungs. This is the actual exchange of oxygen and carbon dioxide
between an organism and its environment, which involves the process of
breathing directly.
It‘s important to work out and learn proper breathing techniques to
maintain a strong cardiovascular and respiratory system.
Process of Respiration: Physiological
For humans and other oxygen-breathing vertebrates, the process of
respiration takes place within the lungs, driven by a series of mechanics
called inhalation and exhalation. These are the biological mechanisms that
make up breathing. We breathe in to take in oxygen, and breathe out to
expel carbon dioxide! There‘s more involved with the process of
respiration than just the lungs, though. The entire process uses the nasal
cavity, the mouth, the larynx, the trachea, and the bronchial tubes of the

lungs as well.

 External Respiration

To breathe in and breathe out, we use our intercostals muscles, the muscle
group that lies between our ribs. When we breathe in through the nose or
mouth, these intercostals muscles contract, our sternum moves up and out
along with our ribs, and our diaphragm flattens. The diaphragm is a sheet
of muscle that lies across the bottom of the rib cage, and it is vital for
proper respiration. When the diaphragm contracts, this allows the volume
in our thoracic cavity to expand, thus reducing pressure and enabling us to
draw air into our lungs. With the help of our diaphragm and thoracic
cavity, our body creates a literal suction.
Similarly, when we exhale, our intercostals muscles and our diaphragm
relax. This causes the volume of the thoracic cavity to decrease and the
pressure inside to increase, which expels the air in what is called an

exhalation.

 Internal Respiration

What is actually happening inside the body between the inhale and the
exhale? That‘s where internal respiration comes in. Internal respiration
occurs after and during the process of external respiration, and it‘s when
the gases in the air we‘ve drawn into our lungs can be sorted out, the
oxygen absorbed in our blood and the carbon dioxide removed.
This happens because our heart is pumping oxygen-low blood through the
pulmonary arteries and into the lungs. At the ends of the pulmonary
arteries are small blood vessels called capillaries, which wrap like a net
around the alveoli. The alveoli is where our bronchial tubes transport the
air we inhale. They are the round, clustered, and sac-like tips of the
respiratory tree where gas exchange occurs.
Inside the alveoli, the oxygen rich air we‘ve inhaled is pumped into the red
blood cells located in the surrounding capillaries, enriching the blood with
much needed oxygen. In exchange, the red blood cells expel the carbon
dioxide they‘re carrying into the alveoli.
Carbon dioxide is a waste product created through the process of
metabolism, and too much of it in our blood can cause harm to our body. It
can raise the levels of acidity in your blood, which is damaging to your

heart, and even cause suffocation! When you hold your breath by inhaling and then not immediately exhaling, the reason you begin to feel lightheaded is not actually due to the sudden lack of oxygen intake, but the excess of carbon dioxide built up in your body. Of course, both are just as important, so make sure to practice proper breathing techniques!

Once the air in your alveoli are enriched with carbon dioxide from the
newly oxygen riched red blood cells, this air travels back up the bronchial
tubes and out the nose or mouth, in a process called exhalation. At the
same time, the pulmonary veins transport the oxygen rich blood back to
the heart to be distributed throughout the body.
There is a big difference between external and internal respiration. External
respiration is basically the transfer of gas between respiratory organs such as
lungs and the outer environment. It takes place prior to internal respiration.
Internal respiration is the transfer of gas between the blood and cells.
External respiration also known as breathing refers to a process of inhaling
oxygen from the air into the lungs and expelling carbon dioxide from the
lungs to the air. Exchange of gases both in and out of the blood occurs
simultaneously. External respiration is a physical process during which
oxygen is taken up by capillaries of lung alveoli and carbon dioxide is
released from blood.
Internal respiration or tissue respiration/cellular respiration refers to a
metabolic process in which oxygen is released to tissues or living cells and
carbon dioxide is absorbed by the blood. Once inside the cell the oxygen is
used for producing energy in the form of ATP or adenosine triphosphate.
Lung capacity: The inspiratory capacity plus the functional
residual capacity; the volume of air contained in the lungs at the end of a
maximal inspiration; also equals vital capacity plus residual volume.
The average total lung capacity of an adult human male is about six liters of
air, but only a small amount of this capacity is used during normal breathing.
Tidal breathing is normal, resting breathing; the tidal volume is the volume
of air that is inhaled or exhaled in a single such breath.
The lung capacities are measurements of two or more volumes. The
vital capacity (VC) measures the maximum amount of air that can be inhaled
or exhaled during a respiratory cycle. It is the sum of the expiratory
reserve volume, tidal volume, and inspiratory reserve volume.
Lung volumes and lung capacities refer to the volume of air associated
with different phases of the respiratory cycle. Lung volumes are directly
measured; Lung capacities are inferred from lung volumes. The average total
lung capacity of an adult human male is about 6 liters of air, but only a small
amount of this capacity is used during normal breathing.
Tidal breathing is normal, resting breathing; the tidal volume is the volume
of air that is inhaled or exhaled in only a single such breath.
The average human respiratory rate is 30-60 breaths per minute at
birth, decreasing to 12-20 breaths per minute in adults.
A person who is born and lives at sea level will develop a slightly smaller
lung capacity than a person who spends their life at a high altitude. This is
because the partial pressure of oxygen is lower at higher altitude which, as a
result means that oxygen less readily diffuses into the bloodstream. In
response to higher altitude, the body's diffusing capacity increases in order
to process more air.
When someone living at or near sea level travels to locations at high
altitudes (e.g., the Andes; Denver, Colorado; Tibet; the Himalayas) that
person can develop a condition called altitude sickness because their lungs
remove adequate amounts of carbon dioxide but they do not take in enough
oxygen. (In normal individuals, carbon dioxide is the primary determinant of
respiratory drive.)
Specific changes in lung volumes also occur during pregnancy. Functional
residual capacity drops 18–20%, typically falling from 1.7 to 1.35 liters, due
to the compression of the diaphragm by the uterus. The compression also
causes a decreased total lung capacity (TLC) by 5% and
decreased expiratory reserve volume by 20%.Tidal volume increases by 30–
40%, from 0.5 to 0.7 liters, and minute ventilation by 30–40% giving an
increase in pulmonary ventilation. This is necessary to meet the increased
oxygen requirement of the body, which reaches 50 mL/min, 20 mL of which
goes to reproductive tissues. Overall, the net change in maximum breathing
capacity is zero.
Lung Volumes and Capacities
Different animals exhibit different lung capacities based on their activities.
For example, cheetahs have evolved a much higher lung capacity than
humans in order to provide oxygen to all the muscles in the body, allowing
them to run very fast. Elephants also have a high lung capacity due to their
large body and their need to take up oxygen in accordance with their body
size.
Human lung size is determined by genetics, gender, and height. At maximal
capacity, an average lung can hold almost six liters of air; however, lungs do
not usually operate at maximal capacity. Air in the lungs is measured in
terms of lung volumes and lung capacities . Volume measures the amount of
air for one function (such as inhalation or exhalation) and capacity is any
two or more volumes (for example, how much can be inhaled from the end
of a maximal exhalation).
Human lung volumes and capacities
The total lung capacity of the adult male is six liters. Tidal volume is the
volume of air inhaled in a single, normal breath. Inspiratory capacity is the
amount of air taken in during a deep breath, while residual volume is the

amount of air left in the lungs after forceful respiration.

Lung Volumes

The volume in the lung can be divided into four units: tidal volume,
expiratory reserve volume, inspiratory reserve volume, and residual volume.
Tidal volume (TV) measures the amount of air that is inspired and expired
during a normal breath. On average, this volume is around one-half liter,
which is a little less than the capacity of a 20-ounce drink bottle. The
expiratory reserve volume (ERV) is the additional amount of air that can be
exhaled after a normal exhalation. It is the reserve amount that can be
exhaled beyond what is normal. Conversely, the inspiratory reserve volume
(IRV) is the additional amount of air that can be inhaled after a normal
inhalation. The residual volume (RV) is the amount of air that is left after
expiratory reserve volume is exhaled. The lungs are never completely
empty; there is always some air left in the lungs after a maximal exhalation.
If this residual volume did not exist and the lungs emptied completely, the
lung tissues would stick together. The energy necessary to re-inflate the lung
could be too great to overcome. Therefore, there is always some air
remaining in the lungs. Residual volume is also important for preventing
large fluctuations in respiratory gases (O2 and CO2). The residual volume is
the only lung volume that cannot be measured directly because it is
impossible to completely empty the lung of air. This volume can only be
calculated rather than measured. .
Lung volumes are measured by a technique called spirometry. An important
measurement taken during spirometry is the forced expiratory volume
(FEV), which measures how much air can be forced out of the lung over a
specific period, usually one second (FEV1). In addition, the forced vital
capacity (FVC), which is the total amount of air that can be forcibly exhaled,
is measured. The ratio of these values (FEV1/FVC ratio) is used to diagnose
lung diseases including asthma, emphysema, and fibrosis. If the FEV1/FVC
ratio is high, the lungs are not compliant (meaning they are stiff and unable
to bend properly); the patient probably has lung fibrosis. Patients exhale
most of the lung volume very quickly. Conversely, when the FEV1/FVC
ratio is low, there is resistance in the lung that is characteristic of asthma. In
this instance, it is difficult for the patient to get the air out of his or her lungs.
It takes a long time to reach the maximal exhalation volume. In either case,

breathing is difficult and complications arise.

Lung Capacities

The lung capacities are measurements of two or more volumes. The vital
capacity (VC) measures the maximum amount of air that can be inhaled or
exhaled during a respiratory cycle. It is the sum of the expiratory reserve
volume, tidal volume, and inspiratory reserve volume. The inspiratory
capacity (IC) is the amount of air that can be inhaled after the end of a
normal expiration. It is, therefore, the sum of the tidal volume and
inspiratory reserve volume. The functional residual capacity (FRC) includes
the expiratory reserve volume and the residual volume. The FRC measures
the amount of additional air that can be exhaled after a normal exhalation.
The total lung capacity (TLC) is a measurement of the total amount of air
that the lung can hold. It is the sum of the residual volume, expiratory
reserve volume, tidal volume, and inspiratory reserve volume.
The following terms describe the various lung (respiratory) volumes:
The tidal volume (TV),about 500 mL, is the amount of air inspired
during normal, relaxed breathing.
The inspiratory reserve volume (IRV), about 3,100 mL, is the
additional air that can be forcibly inhaled after the inspiration of a
normal tidal volume.
The expiratory reserve volume (ERV), about 1,200 mL, is the
additional air that can be forcibly exhaled after the expiration of a
normal tidal volume.
Residual volume (RV), about 1,200 mL, is the volume of air still
remaining in the lungs after the expiratory reserve volume is exhaled.
Summing specific lung volumes produces the following lung capacities:
The total lung capacity (TLC), about 6,000 mL, is the maximum
amount of air that can fill the lungs (TLC = TV + IRV + ERV + RV).
The vital capacity (VC), about 4,800 mL, is the total amount of air
that can be expired after fully inhaling (VC = TV + IRV + ERV =
approximately 80 percent TLC). The value varies according to age
and body size.
The inspiratory capacity (IC), about 3,600 mL, is the maximum
amount of air that can be inspired (IC = TV + IRV).
The functional residual capacity (FRC), about 2,400 mL, is the

amount of air remaining in the lungs after a normal expiration (FRC =

RV + ERV).

Some of the air in the lungs does not participate in gas exchange. Such air is
located in the anatomical dead space within bronchi and bronchioles—that
is, outside the alveoli.
Tidal volume: Tidal volume is the lung volume representing the
normal volume of air displaced between normal inhalation and exhalation
when extra effort is not applied. In a healthy, young human adult, tidal
volume is approximately 500 mL per inspiration or 7 mL/kg of body mass.
Tidal volume plays a significant role during mechanical ventilation to ensure
adequate ventilation without causing trauma to the lungs. Tidal volume is
measured in milliliters and ventilation volumes are estimated based on a
patient's ideal body mass. Measurement of tidal volume can be affected
(usually overestimated) by leaks in the breathing circuit or the introduction
of additional gas, for example during the introduction of nebulizer drugs.
Ventilator-induced lung injury such as ALI/ARDS can be caused by
ventilation with very large tidal volumes in normal lungs, as well as
ventilation with moderate or small volumes in previously injured lungs, and
research shows that the incidence of ALI increases with higher tidal volume

settings in non neurologically-impaired patients.