Download The Respiratory Physiology

Respiratory System

Why is our respiratory system so
important?
 We require oxygen for cell growth and repair.

The four functions of the respiratory
system.
 Moves air through thin membrane material to
allow for rapid diffusion (take in oxygen and
release carbon dioxide).
 Provides nonspecific defenses against
pathogens
 Allows for vocal communication
 Helps control the pH level of body fluid
Parts and Functions of the
Respiratory System
The respiratory tract is divided up into
two sections.
 Conducting portion

 Begins at the entrance of the nasal cavity to
the larynx, pharynx, trachea, bronchi and
larger bronchioles

Respiratory portion
 Smallest bronchioles. The site of gas
exchange.
Nose
Most air enters here
Cilia and moisture protect from larger
particles and pathogens
 Left and right side is divided by the nasal
septum
 Air comes in turning (turbulence) which
allows the air to take longer which causes it
to warm and humidify
 Goblet cells produce mucus and are
stimulated by noxious vapors, dust,
allergens, etc….


Pharynx

Three main parts
 Nasopharynx
 Oropharynx
 Larygpharynx

Lined with cells to resist mechanical
abrasions, chemical attacks and
pathogens
Larynx
Air leaves the pharynx to enter the
larynx through the glottis
 Epiglottis closes during swallowing
 Thyroid cartilage here may form the
Adams apple.
 Vocal chords are located here.

Vocal Cords and Sound
Production
Vocal chords vibrate as air moves
through and sound moves through
 Shorter chords = higher pitch (kids and
women)
 Longer chords = lower pitch

Trachea
“Windpipe”
 Tough flexible tube (1 in wide, 11 in
long)
 Branches to form a pair of primary
bronchi
 Supported by 20 tracheal cartridges
 When this becomes blocked it can be
life threatening. If a person can talk or
breathe there is no immediate risk.

Bronchi
Right and Left primary bronchi to
secondary bronchi to tertiary bronchi
which branch repeatedly
 With each branch the tubes get smaller.
Eventually they lead to the bronchioles
(smallest tubes, 1mm)

Bronchioles
These are enflamed in an asthma attack
 They lead to the terminal bronchioles
(0.3 – 0.5 mm) which lead to lobules
 Lobules eventually branch to the gas
exchange surfaces of the lungs

Alveolar ducts and alveoli
Each lung contains approximately 150
million alveoli
 Air goes from the bronchioles to alveolar
ducts to alveolar sacs to individual alveoli
 Alveolar macrophages protect the alveoli
from pathogens, dust and debris
 Surfacant cells secrete oil to lubricate the
alveoli. This reduces surface tension to
allow for the pressure required for air
intake.

Respiratory Membrane
Gas exchange occurs across the
respiratory membrane of the alveoli
 Oxygen and carbon dioxide diffuse
across the thin membrane very rapidly
 Blood is carried into the lungs through
the pulmonary artery and is returned by
the pulmonary vein

The Lungs
The right lung has three lobes and the
left lung has two lobes
 Allows for the passage of blood vessels
to traveling to and from the heart
 Very elastic to be able to change in
volume
 Protected by the ribs

The Pleural Cavity
The thoracic cavity is cone shaped.
 The mediastanum divides the thoracic
cavity into two pleural cavities…. One
for each lung.

Respiratory Changes at Birth
First breath inflates the entire brachial
system and forces the fluid out of the
way.
 The expansion is usually an indication
used to determine if a baby took a first
breath after being born (used in cases of
infant death)

Respiratory Physiology

Four steps in the process of respiration
 Pulmonary Ventilation – physical movement of
air in and out of lungs.
 Gas diffusion across the respiratory membrane.
 The storage and transport of Oxygen and
Carbon-dioxide – this is carried through red
blood cells.
 The exchange of Oxygen and Carbon-dioxide
(between the blood and interstitial fluid) Oxygen
goes to the tissues and carries out the Carbondioxide.

Pulmonary Ventilation
 Inhalation = inspiration
 Exhalation = expiration
 The goal is to maintain adequate alveolar
ventilation (movement of air into and out of
the alveoli)
Pressure and Air Flow
Air will flow from a high pressure to a
low pressure.
 When lungs expand it creates a lower
pressure and air moves inward
(diaphragm contracts)
 When lungs contract there is a greater
pressure and air moves out of the lungs
(diaphragm relaxes)

Respiratory Volume and Rates

Tidal Volume
 The amount of air moved into and out of the
lungs in a single respiratory cycle

Expiratory Reserve Volume
 The amount of air left in your lungs after you
have exhaled. Normally we exhale about 500
ml of air. If we force out as much as possible,
we would force out about 1000ml of air.

Inspiratory Reserve Volume
 The amount of air that can be taken in over and
above the tidal volume (typically 3300ml for men
and 1900ml for female)

Vital Capacity
 The total amount of air that can be moved into
and out the lungs in a single respiratory cycle
(Tidal Volume + Expiratory and Inspiratory
reserves)

Residual Volume
 About 1200ml remains after all air has been
forced out of the lungs.

Minimal Volume
 If the chest cavity is open there is still air in the
lungs due to the surfactant cells preventing total
collapse.
Gas exchange at the respiratory
membrane
Gas will diffuse across the respiratory
membrane to a higher to a lower
concentration.
 Hemoglobin – A protein found in red
blood cells which drastically increases
the oxygen carrying capacity of RBC

 If we did not have hemoglobin we would
need 300 liters of blood instead of 6 liters of
blood to sustain everyday life.
How does Hemoglobin work
A single molecule of hemoglobin simply
has multiple attachment sites to which
oxygen atoms can combine.
 Carbon monoxide poisoning occurs when
CO enters into the lungs and binds to the
hemoglobin, (this is actually a stronger
bond than oxygen) taking up “spaces” that
are normally reserved for oxygen. So the
body basically suffocates internally due to
the lack of oxygen.

Control of Respiration

The respiratory rate is the number of
breaths per minute
 Normal adult = 12 – 18 bpm
 Normal child = 18 – 20 bpm
The respiratory rhythmicity center is located in
the medulla oblongata (stimulus such as
emotions and speech patterns can cause
the rate of change)
The two types of receptors that control
breathing automatically are
chemoreceptors and mechanoreceptors
 You can’t die from holding your breath.
The increased level of carbon di-oxide
will allert the chemoreceptors and your
body will force you to breathe.

Aging effects on the respiratory
system
Decrease the elasticity of tissues =
lower vital capacity.
 Movements of the chest cage are
restricted and therefore it limits
pulmonary ventilation (exercising is
more difficult)
 Some degree of emphysema.
