IRATORY SYST

ESP EM
R
RESPIRATORY SYSTEM
- provides oxygen to the body, disposes
of carbon dioxide, and helps regulate
blood pH
- gas exchange occurs in the air sacs of
the lungs, called alveoli, and at capillary
beds around the body
- share responsibility for supplying the
body with oxygen and disposing of
carbon dioxide
- respiratory system organs oversee the
gas exchanges that occur between the
blood and the external environment
RESPIRATORY SYSTEM
-using blood as the transporting fluid, the
cardiovascular system organs transport
respiratory gases between the lungs and
the cells in the rest of the body
- if either system fails, cells begin to die
from oxygen starvation and
accumulation of carbon dioxide
 FUNCTIONAL ANATOMY OF THE RESPIRATORY
SYSTEM
Upper respiratory tract - passageways
from the nose to the larynx

Lower respiratory tract - passageways

from the trachea to the alveoli
- these conducting passageways
purify, humidify, and warm incoming air
NOSE
- the only externally visible part of the respiratory
system
- during breathing, air enters the nose by
passing through the nostrils, or nares.
- interior of the nose consists of
 Nasal cavity - divided by a midline nasal
septum
Respiratory mucosa - the rest of the mucosa
lining the nasal cavity; rests on a rich network of
thin-walled veins that warms the air as it flows
past
-sticky mucus produced by mucosa’s glands
moistens the air and traps incoming bacteria
and other foreign debris
- lysozyme enzymes in the mucus destroy
bacteria chemically

- ciliated cells create a gentle current that moves

the sheet of contaminated mucus posteriorly
toward the throat (pharynx), where it is swallowed
and digested by stomach juices
CONCHAE
- lateral walls of the nasal cavity are uneven,
owing to three mucosa-covered projections, or
lobes called conchae

- greatly increase the surface area of the

mucosa exposed to the air; increases the air
turbulence in the nasal cavity

-inhaled particles are deflected onto the

mucus-coated surfaces, where they are
trapped and prevented from reaching the
lungs
NASAL CAVITY
- separated from the oral cavity below
by the palate
 Hard palate - supported by bone
 Soft palate - unsupported posterior
part
- surrounded by a ring of paranasal
sinuses located in the frontal,
sphenoid, ethmoid, and maxillary
bones
Sinuses
- lighten the skull and act as resonance
chambers for speech; produce mucus,
which drains into the nasal cavities
- suctioning effect created by nose
blowing helps to drain the sinuses
- Nasolacrimal ducts, which drain tears
from the eyes, also empty into the nasal
cavities
PHARYNX
- a muscular passageway about 13
cm (5 inches) long that vaguely
resembles a short length of red
garden hose
- commonly called the throat
- serves as a common passageway
for food and air
-continuous with the nasal cavity
anteriorly via the posterior nasal
aperture
has three regions
 Nasopharynx - superior portion where air
enters from the nasal cavity
 Oropharynx - air then descends through
 Laryngopharynx - to enter the larynx
below
- food enters the mouth, then travels along
with air through the oropharynx and
laryngopharynx
- instead of entering the larynx, food is
directed into the esophagus posteriorly by
a flap called the epiglottis
PHARYNGOTYMPANIC TUBES
- drains the middle ears
- open into the nasopharynx
- mucosae of these two regions are
continuous, so ear infections such
as otitis media may follow a sore
throat or other types of pharyngeal
infections
TONSILS
- clusters of lymphatic tissue are found in
the pharynx
- play a role in protecting the body from
infection
 Adenoid - single pharyngeal tonsil;
located high in the nasopharynx
 Two Palatine tonsils - are in the
oropharynx at the end of the soft palate
 Two lingual tonsils - lie at the base of
the tongue
LARYNX
- or voice box
- routes air and food into the proper
channels
- plays a role in speech
- located inferior to the pharynx
- is formed by eight rigid hyaline
cartilages and a spoon-shaped flap of
elastic cartilage, the epiglottis
ADAM’S APPLE
- the largest of the hyaline cartilages is the
shield
-shaped thyroid cartilage
- which protrudes anteriorly

EPIGLOTTIS
- referred to as the “guardian of the airway”
- protects the superior opening of the
larynx
- during regular breathing, it allows the
passage of air into the lower respiratory
passages
-when we swallow food or fluids,
the larynx is pulled upward, and the
epiglottis tips, forming a lid over
the larynx’s opening. This routes
food into the esophagus, which
leads to the stomach, posteriorly.

- if anything other than air enters

the larynx, a cough reflex is
triggered to prevent the substance
from continuing into the lungs
VOCAL FOLDS
- pair of folds which forms by a part of
the mucous membrane of the larynx
- or true vocal cords
- vibrates with expelled air
- the ability of the vocal folds to vibrate
allows us to speak
- vocal folds and the slit-like passageway
between them are called the glottis
TRACHEA
- or windpipe
- air entering the trachea from the
larynx travels down its length (10–
12 cm, or about 4 inches) to the
level of the fifth thoracic vertebra,
which is approximately mid chest
- is fairly rigid because its walls
are reinforced with C-shaped
rings of hyaline cartilage
HYALINE CARTILAGE
- these rings serve a double purpose
 open parts of the rings abut the
esophagus and allow it to expand
anteriorly when we swallow a large
piece of food
 solid portions support the trachea
walls and keep it patent, or open, in
spite of the pressure changes that
occur during breathing
TRACHEALIS MUSCLE
- lies next to the esophagus
- completes the wall of the trachea posteriorly

CILIA
- trachea is lined with a ciliated mucosa
- cilia beat continuously in a superior direction
- surrounded by goblet cells that produce mucus
- propels mucus, loaded with dust particles and
other debris, away from the lungs to the throat,
where it can be swallowed or spat out
MAIN BRONCHI
- right and left main (primary) bronchi
- are formed by the division of the trachea
- right main bronchus is wider, shorter, and
straighter than the left
- more common site for an inhaled foreign
object to become lodged
- by the time incoming air reaches the bronchi,
it is warm, cleansed of most impurities, and
humid
- smaller subdivisions of the main bronchi
within the lungs are direct routes to the air
sacs
LUNGS
- are fairly large organs
- occupies the entire thoracic cavity
except for the mediastinum

MEDIASTINUM
- most central area
- houses the heart, the great blood
vessels, bronchi, the esophagus, and
other organs
APEX
- the narrow superior portion of each lung
- just deep to the clavicle
- broad lung area resting on the
diaphragm is the base
- each lung is divided into lobes by
fissures
 left lung has two lobes
 right lung has three lobes
PULMONARY PLEURA
- or visceral pleura
- a visceral serosa which covers the
surface of each lung

PARIETAL PLEURA
- lines the walls of the thoracic cavity
PLEURAL MEMBRANES
- produce pleural fluid, slippery serous fluid, which allows the lungs to
glide easily over the thorax wall during breathing and causes the two
pleural layers to cling together
- pleurae can slide easily from side to side across one another, but they
strongly resist being pulled apart
- lungs are held tightly to the thorax wall, and the pleural space is more of
a potential space than an actual one.
BRONCHIAL TREE
- after entering the lungs, the main
bronchi subdivide into smaller and
smaller branches and ending in the
smallest of the conducting passageways,
the bronchioles
- because of this branching and
rebranching of the respiratory
passageways within the lungs, the
network formed is often referred to as
the bronchial tree, or respiratory tree
- all but the smallest branches have
reinforcing cartilage in their walls.
RESPIRATORY ZONE
- is the only site of gas exchange
- includes:
 Piratory bronchioles
 Alveolar ducts
 Alveolar sacs
 Alveoli
- all other respiratory passages are
conducting zone structures that serve as
conduits to and from the respiratory zone
- lungs are mostly air spaces
Stroma
- the balance of the lung tissue, is
mainly elastic connective tissue that
allows the lungs to stretch and recoil
(spring back) as we breathe
- lungs weigh about 2½ pounds, and they
are soft and spongy
- walls of the alveoli are composed
largely of a single, thin layer of simple
squamous epithelial cells
- thinness of their walls is hard to imagine,
but a sheet of tissue paper is much
thicker
Alveolar pores connect neighboring air
sacs and provide alternative routes for air to
reach alveoli whose feeder bronchioles
have been clogged by mucus or otherwise
blocked
-gas exchange occurs by simple diffusion
through the respiratory membrane—oxygen
passes from the alveolar air into the
capillary blood, and carbon dioxide leaves
the blood to enter the alveoli
- final line of defense for the respiratory
system is in the alveoli
cuboidal surfactant-secreting cells
- these cells produce a lipid (fat)
molecule called surfactant, which
coats the gas exposed alveolar
surfaces and is very important in lung
function
RESPIRATORY PHYSIOLOGY
- major function of the respiratory system is
to supply the body with oxygen and to
dispose of carbon dioxide
- to do this, at least four distinct events,
collectively called respiration, must occur:

1. PULMONARY VENTILATION
- air must move into and out of the lungs so
that the gases in the alveoli of the lungs are
continuously refreshed
- process is commonly called breathing
2. EXTERNAL RESPIRATION
- gas exchange (oxygen loading and carbon
dioxide unloading) between the pulmonary
blood and alveoli must take place
- in external respiration, gas exchanges are
being made between the blood and the
body exterior

3. RESPIRATORY GAS TRANSPORT

- oxygen and carbon dioxide must be
transported to and from the lungs and
tissue cells of the body via the bloodstream
4. INTERNAL RESPIRATION
- at systemic capillaries, gas exchange
occurs between the blood and cells inside
the body
- although only the first two processes are
the special responsibility of the respiratory
system, all four processes are necessary
for gas exchange to occur
- cellular respiration, the use of oxygen to
produce ATP and carbon dioxide, is the
cornerstone of all energy-producing
chemical reactions and occurs in all cells
MECHANICS OF BREATHING
- breathing, or pulmonary ventilation, is
a mechanical process that depends on
volume changes occurring in the
thoracic cavity
- Rule: Volume changes lead to
pressure changes, which lead to the
flow of gases to equalize the pressure
1. INSPIRATION (INHALATION)
- when air is flowing into the lungs
- when the inspiratory muscles, the diaphragm
and external intercostals, contract, the size of
the thoracic cavity increases.

2. EXPIRATION (EXHALATION)
- when air is leaving the lungs
- as the inspiratory muscles relax and resume
their initial resting length, the rib cage
descends, the diaphragm relaxes superiorly,
and the lungs recoil
RESPIRATORY VOLUMES AND
CAPACITIES
- many factors affect respiratory capacity
 Person’s size
 Sex
 Age
 Physical condition
TIDAL VOLUME (TV)
- the respiratory volume
- normal quiet breathing moves
approximately 500 ml of air (about a pint)
into and out of the lungs with each breath
-the amount of air that can be taken in
forcibly above the tidal volume is the
inspiratory reserve volume (IRV), which is
around 3,100 ml.
the amount of air that can be forcibly exhaled
beyond tidal expiration, the expiratory
reserve volume (ERV), is approximately 1,200
ml
RESIDUAL VOLUME
- even after the most strenuous
expiration, about 1,200 ml of air still
remains in the lungs and cannot
voluntarily be expelled
- residual volume air is important because
it allows gas exchange to go on
continuously even between breaths and
helps to keep the alveoli open (inflated)
VITAL CAPACITY (VC)
- the total amount of exchangeable air
(around 4,800 ml in healthy young
men and 3,100 ml in healthy young
women)
- the sum of the tidal volume plus the
inspiratory and expiratory reserve
volumes
DEAD SPACE VOLUME
- some of the air that enters the respiratory
tract
remains in the conducting zone passageways
and never reaches the alveoli
- during a normal tidal breath is about 150 ml.

FUNCTIONAL VOLUME
- air that actually reaches the respiratory zone
and contributes to gas exchange
- is about 350 ml.
SPIROMETER
- measures respiratory capacities
- Spirometer testing is useful for evaluating
losses in respiratory functioning and in
following the course of some respiratory
diseases
- Example:
 In pneumonia, inspiration is obstructed,
and the IRV and VC decrease.
 In emphysema, where expiration is
hampered, the ERV is much lower than
normal, and the residual volume is higher.
NONRESPIRATORY AIR MOVEMENTS

1. COUGHS AND SNEEZES

- clear the air passages of debris or collected
mucus

2. LAUGHING AND CRYING

- reflect our emotions
- these nonrespiratory air movements are a
result of reflex activity, but some may be
produced voluntarily
RESPIRATORY SOUNDS
- as air flows into and out of the respiratory
tree, it produces two recognizable sounds
that can be picked up with a stethoscope
- bronchial sounds are produced by air
rushing through the large respiratory
passageways (trachea and bronchi)
- Vesicular breathing sounds occur as air
fills the alveoli
- vesicular sounds are soft murmurs that
resemble a muffled breeze
EXTERNAL RESPIRATION
- is the actual exchange of gases between the
alveoli and the blood (pulmonary gas exchange)
-oxygen tends to diffuse from the air of the alveoli
through the respiratory membrane into the more
oxygen-poor blood of the pulmonary capillaries
- as tissue cells remove oxygen from the blood in
the systemic circulation, they release carbon
dioxide into the blood
-because the concentration of carbon dioxide is
much higher in the pulmonary capillaries than it is in
the alveolar air, it will diffuse from the blood into
the alveoli and be flushed out of the lungs during
expiration

- blood draining from the lungs into the

pulmonary veins is rich in oxygen and poor in
carbon dioxide
GAS TRANSPORT IN THE BLOOD
- Oxygen is transported in the blood in two ways
-a very small amount of oxygen is carried
dissolved in the plasma
- Carbon dioxide is twenty times more soluble
in plasma compared to oxygen
-Carbon dioxide is enzymatically converted to
bicarbonate ion within red blood cells; then the
newly formed bicarbonate ions diffuse into the
plasma
-Carbon dioxide binds to hemoglobin at a
different site from oxygen, so it does not
interfere with oxygen transport
-Carbonic acid quickly splits to form water
and carbon dioxide, and carbon dioxide
then diffuses from the blood into the alveoli
INTERNAL RESPIRATION
- the gas exchange process that occurs
between the blood and the tissue cells
(systemic capillary gas exchange)
- oxygen leaves and carbon dioxide enters the
blood
- in the blood, carbon dioxide combines with
water to form carbonic acid (H2CO3), which
quickly releases bicarbonate ions then the
bicarbonate ions diffuse out into plasma,
where they are transported
- Oxygen is released from hemoglobin, and the
oxygen diffuses quickly out of the blood to
enter the cells
- as a result of these exchanges, venous blood
in the systemic circulation is much poorer in
oxygen and richer in carbon dioxide than blood
leaving the lungs
1. NEURAL REGULATION: SETTING THE
BASIC RHYTHM

- the activity of the respiratory muscles,

the diaphragm and external
intercostals, is regulated by nerve
impulses transmitted from the brain by
the phrenic nerves and intercostal
nerves
- Neural centers that control respiratory
rhythm and depth are located mainly in
the medulla and pons
A brief summary of what we know follows:
 The medulla contains two respiratory
centers.
 The other medullary center, the dorsal
respiratory group (DRG), integrates sensory
information from chemoreceptors and
peripheral stretch receptors.
 The pons respiratory centers, which also
communicate with the VRG, help to smooth
the transitions (modify timing) between
inhalation and exhalation during activities
such as singing, sleeping or exercising.
-the bronchioles and alveoli have stretch
receptors that respond to extreme
overinflation (which might damage the
lungs) by initiating protective reflexes

- example of DRG integration during

respiratory control:
 In the case of overinflation, the vagus
nerves send impulses from the stretch
receptors to the medulla; soon thereafter,
inspiration ends and expiration occurs
 YPERPNEA During exercise, we breathe more

H vigorously and deeply because the brain

centers send more impulses to the
respiratory muscles

- after strenuous exercise, expiration

becomes active, and the abdominal
muscles and any other muscles capable of
depressing the ribs are used to aid
expiration
 NONNEURAL FACTORS INFLUENCING
RESPIRATORY RATE AND DEPTH
PHYSICAL FACTORS

- physical factors such as talking, coughing, and

exercising can modify both the rate and depth
of breathing
- increased body temperature also causes an
increase in the rate of breathing
VOLITION (CONSCIOUS CONTROL)
- during singing and swallowing, breath control is
extremely important, and many of us have held
our breath for short periods to swim
underwater
- voluntary control of breathing is limited, and
the respiratory centers will simply ignore
messages from the cortex when the oxygen
supply in the blood is getting low or blood pH is
falling
EMOTIONAL FACTORS

- these examples result from reflexes initiated

by emotional stimuli acting through centers in
the hypothalamus:
1. Watched a horror movie with bated (held)
breath or been so scared by what you saw that
you were nearly panting
2. Touched something cold and clammy and
gasped
CHEMICAL FACTORS
- an increased level of carbon dioxide and a
decreased blood pH are the most important
stimuli leading to an increase in the rate and
depth of breathing
- an increase in the carbon dioxide level can
cause a decreased blood pH because high CO2
results in more carbonic acid, which lowers
blood pH
- a low blood pH could also result from metabolic
activities independent of breathing.
-when oxygen levels are low, these same
chemoreceptors are also able to detect high
carbon dioxide levels the body’s need to rid itself
of carbon dioxide that is the most important
stimulus for breathing.
-A decrease in the oxygen level becomes an
important stimulus only as carbon dioxide or other
sources of acids begin to accumulate in the blood
and tissues, and pH starts to drop, you begin to
breathe more deeply and more rapidly
HYPERVENTILATION
- is an increase in the rate and depth of
breathing that exceeds the body’s need to
remove carbon dioxide
- during hyperventilation, we exhale more CO2
than we should, resulting in elevated blood pH
(there is less carbonic acid)
- when blood starts to become slightly alkaline,
or basic, breathing slows and becomes shallow
- slower breathing allows carbon dioxide to
accumulate in the blood and brings the blood
pH back into the normal range
HYPOVENTILATION
- extremely slow or shallow breathing
- hypoventilation or hyperventilation can
dramatically change the amount of carbonic
acid in the blood
 Carbonic acid increases dramatically during
hypoventilation
 Carbonic acid decreases substantially during
hyperventilation
- in both situations, the buffering ability of the
blood is likely to be overwhelmed; the result is
acidosis or alkalosis
 - exemplified by chronic bronchitis and
CHRONIC OBSTRUCTIVE emphysema
PULMONARY DISEASE - a major cause of death and disability in the
(COPD) United States
 Patients almost always have a history of
smoking
 Dyspnea, difficult or labored breathing,
often referred to as “air hunger,” occurs
and becomes progressively worse
 Coughing and frequent pulmonary
infections are common
 Most COPD victims are hypoxic, retain
carbon dioxide and have respiratory
acidosis, and ultimately develop respiratory
failure
LUNG CANCER
- the leading cause of cancer death for
both men and women in North America
- causing more deaths than breast,
prostate, and colorectal cancer combined
- nearly 90 percent of lung cancers result
from smoking
- is aggressive and metastasizes rapidly
and widely, so most cases are not
diagnosed until they are well advance
 three most common types of lung cancer:
LUNG CANCER
1. ADENOCARCINOMA (40 PERCENT OF
CASES)
- which originates as solitary nodules in
peripheral lung areas and develops from
bronchial glands and alveolar cells

2. SQUAMOUS CELL CARCINOMA (25–30

PERCENT)
- which arises in the epithelium of the larger
bronchi and tends to form masses that hollow
out and bleed
LUNG CANCER
3. SMALL CELL CARCINOMA (ABOUT 20
PERCENT)
- which contains lymphocyte-like cells that
originate in the main bronchi and grow
aggressively in small grapelike clusters
within the mediastinum
- most effective treatment for lung cancer is
complete removal of the diseased lung
lobes in an attempt to halt metastasis.
However, removal is an option only if
metastasis has not already occurred.
 REFERENCE:
Essentials of Human Anatomy & Physiology 12th
Edition. Marieb, E.N & Keller, 2016. S.M. Boston :
Pearson. (PDF)