Transcript Respiratory System Part II

Respiratory System
Part II
Respiratory Physiology





In order to supply the body with oxygen and get rid of
carbon dioxide the process of respiration MUST occur.
Pulmonary ventilation: air is moved in and out of the lungs
so that gas is exchanged and refreshed – breathing.
External respiration: gas exchange between pulmonary
blood and alveoli must take place.
Respiratory gas transport: Oxygen and CO2 must be
transported to and from the lungs and tissue cells of the
body through the bloodstream
Internal respiration: at the capillaries, gas exchanges are
made between the blood and tissue cells.
Mechanics of Breathing

Breathing/Pulmonary Ventilation:
–
–
–
Mechanical process which depends on volume
changes occurring in the thoracic cavity.
These changes can lead to pressure changes which
lead to the flow of gasses to equalize the pressure
within the lungs.
Gas always conforms to the shape of its container
filling it completely. In a large volume the gas
molecules are further apart and pressure will be low. If
the volume is reduced the gas molecules move closer
together and pressure will increase.
Inspiration –
When air flows into the lungs

Diaphragm:
–
–

External Intercostals:
–
–

Inspiratory muscles
When the diaphragm contracts it flattens inferiorly and the height
of the thoracic cavity increases.
Inspiratory muscles
Contraction of the external intercostals causes the rib cage to lift
and increases the thoracic cavity.
Intrapulmonary volume:
–
–
Volume within the lungs
As the intrapulmonary volume increases the gases in the lungs
spread to fill this larger space. The decreasing pressure then
causes a vacuum effect sucking air into the lungs. Air continues
to move into the lungs until the intrapulmonary pressure is equal
to the atmospheric pressure.
Expiration –
Exhaling


Passive process that depends on the natural
elasticity of the lungs vs. muscle contraction
When inspiratory muscles relax and resume their
normal resting lengths the thoracic and
intrapulmonary volumes decrease. When this
occurs the gasses in the lungs are forced to
move close together and intrapulmonary
pressure increases more than atmospheric
pressure and causes gasses to flow out in order
to equalize the pressures.
Expiration –
Exhaling

Normally expiration should be effortless but if
the respiratory passages are narrowed or
clogged expiration can become a forced
process. In these cases the internal
intercostals and abdominal muscles will be
forced to contract in order to exhale the air.
Expiration –
Exhaling

Intrapleural Pressure:
–
–
–

Atelactasis:
–
–

Pressure within the pleural space
This pressure is always negative protecting the lungs from collapsing
If the intraplueral space becomes equal to atmospheric pressure the
lungs will then collapse.
Collapse of the lungs
Usually occurs when air enters the pleural space through a chest wound
but may occur from a rupture of the visceral pleura allowing air to enter
directly from the respiratory tract.
Pneumothorax:
–
–
Presence of air within the intrapleural space disrupting the fluid bond
between the pleura.
It can be reversed by inserting a tube into the chest to remove the
excess fluid and allowing the lungs to attempt to function normally again
Non-respiratory Air movements

Situations other than breathing where air moves
into and out of the lungs is usually a result of
reflex activity but can sometimes be voluntarily
controlled.
–
–
–
–
Coughing & Sneezing: clear air passages of debris or
collected mucus
Laughing & Crying: reflect a persons emotions
Hiccups: involuntary reflex
Yawning: involuntary reflex
Respiratory volumes and capacities

Factors affecting respiratory capacity:
–
–
–
–
Persons size
Age
Sex
Physical condition
Respiratory volumes and capacities

Tidal Volume (TV):
–
–

Inspiratory Reserve Volume (IRV):
–
–

Normal breathing
Normally approximately 500 ml. of air are moved in and out of the
lungs with each breath.
The amount of air that can be taken in FORCIBLY over the tidal
volume.
Normally between 2100-3200 ml.
Expiratory Reserve volume (ERV):
–
–
The amount of air that can be forcibly EXHALED after tidal
expiration.
Approximately 1200 ml.
Respiratory volumes and capacities

Residual volume:
–
–

Vital Capacity (VC):
–
–

1200 ml. of air that remains in the lungs and cannot be voluntarily
expelled.
Allows gas exchange to go on continuously even between
breaths and keeps the alveoli open/inflated.
Total amount of exchangeable air
The sum of TV + IRV + ERV
Dead Space Volume:
–
–
Air enters the respiratory tract and remains in the passageways
but never reaches the alveoli.
During normal breathing the dead space volume is usually about
150 ml.
Respiratory volumes and capacities

Functional Volume:
–
–

Air that actually reaches the respiratory zone.
Approximately 350 ml.
Spirometer:
–
–
–
Device used to measure respiratory capacities
As a person breathes the volumes of air exhaled can
be read on an indicator showing the changes in air
volume inside the apparatus.
This testing is useful for evaluating losses in the
respiratory function after respiratory diseases have
been diagnosed.
Respiratory Sounds

Bronchial Sounds:
–

Vesicular Breathing:
–
–

Produced by air rushing through the large respiratory
passageways such as the trachea and bronchi.
Sounds occurring as air fills the alveoli
Sounds are soft and resemble a muffled breeze
Abnormal sounds:
–
–
–
Results of diseased respiratory tissues, mucus or pus.
Rales: rasping sounds
Wheezing: whistling sounds
Laws of Diffusion

All gas exchanges are made by diffusion
causing movement toward the area of a
lower concentration of the diffusing
substance.
External Respiration




As dark red blood flows through the pulmonary
circuit it is then transformed to a lighter scarlet
color as it is returned to the heart.
This color change is due to the oxygen pickup
by hemoglobin in the lungs
Carbon dioxide is then removed from the blood
equally as fast as the O2 pickup
Body cells continually remove oxygen from the
blood but the alveoli continually hold more
oxygen in their sacs.
How External Respiration occurs





Oxygen moves from the air of the alveoli into the respiratory
membrane
From the respiratory membrane oxygen poor blood is then
transported to the blood of the pulmonary capillaries
As tissue removes oxygen from the blood during systemic
circulation carbon dioxide is released into the blood.
Because the concentration of CO2 is higher in the pulmonary
capillaries than in the alveolar air it leaves the blood to pass
into the alveoli and is flushed out of the lungs during
expiration.
Therefore blood that is draining from the lungs into the
pulmonary veins is oxygen rich and carbon dioxide poor and
ready for systemic circulation!
Gas Transport in the Blood

Oxygen is transported in the blood in two
ways:
–
–
Oxyhemoglobin (HbO2): oxygen attaches to
hemoglobin molecules inside the red blood cells
and produces HbO2
Dissolved in the plasma: very small amounts of
oxygen are carried this way.
Carbon dioxide transport






CO2 is transported by a Bicarbonate Ion (HC03) inside the
plasma and bound to hemoglobin.
It binds at different sites from oxygen so that it does not
interfere with the oxygen transport.
Before CO2 can diffuse out of the blood into the alveoli it
must be released from the bicarbonate form
For this to occur bicarbonate ions must combine with
hydrogen ions to form carbonic acid (H2CO3)
The carbonic acid quickly splits for form water and carbon
dioxide
The CO2 then diffuses from the blood and enters the alveoli
Internal Respiration



The exchange of gases that takes place
between the blood and the tissue cells.
Opposite of what occurs in the lungs.
It is the process of unloading oxygen and
loading CO2 into the blood.
How Internal Respiration Occurs



CO2 diffuses out of the tissue cells and
enters the blood.
When it enters blood it combines with water
to form carbonic acid
From here it releases bicarbonate ions and
diffuses out into the plasma where it is then
transported.
How Internal Respiration Occurs



At the same time oxygen is released from the
hemoglobin and the oxygen diffuses out of the
blood to enter tissue cells it causes the
exchanges in venous blood to be much more
oxygen poor and carbon dioxide rich than the
blood leaving the lungs.
Most of this conversion occurs inside the red
blood cells
RBC’s also contain carbonic anyhydrase – a
special enzyme which speeds up the reaction
time!
Impaired Oxygen Transport

Hypoxia:
–
–
–

Inadequate oxygen delivery to the body tissues
Skin becomes cyanotic (blue)
Can be the result of anemia, pulmonary disease, impaired or
blocked circulation
Carbon Monoxide Poisoning:
–
–
–
–
–
Unique type of hypoxia
Because carbon dioxide binds to hemoglobin at the same sites as
oxygen it can crowd out or displace the oxygen.
It is the leading cause of death from fire and does not produce
typical signs and symptoms of hypoxia
Victims become confused, have throbbing headache and skin
can become red in color
They must be given 100% oxygen to breathe until CO2 is cleared
from the body.
Control of Respiration

Neural Regulation:
–
–
–
–
Phrenic and Intercostal nerves control the diaphragm and
intercostal muscles used during breathing.
Self-Exciting Inspiratory center: located in the medulla and pons.
Sets the basic rhythm for breathing. Impulses going between the
two centers of the brain maintain a rate of 12-15 respirations per
minute (rpm)
Eupnea: normal respiratory rate & response
Stretch receptors: located in the bronchioles and alveoli.
Respond to extreme over inflation. Impulses are then sent from
the stretch receptors to the medulla through vegus nerves where
they will end inspiration and begin expiration.
Factors influencing respiratory rate
and depth

Physical factors:
–
–
–
–
–
Talking
Coughing
Exercise
Increased body temperature
Increased rate and depth of breathing
Factors influencing respiratory rate
and depth

Volition:
–
–

Voluntary controls of breathing is limited
Respiratory centers ignore messages from the cortex
when oxygen supply is getting low or blood Ph is
falling
Emotional factors:
–
–
–
Scared
Gasping at touching something cold, clammy or hot
Reflexes initiated by emotional stimuli from the
hypothalamus.
Factors influencing respiratory rate
and depth

Chemical Factors:
–
–
–
–
–
–
Level of O2 and CO2 in the blood
Increased CO2 and decreased blood pH = increase in rate and
depth of breathing
Decrease in O2 only become important stimuli when they are
critically low
Hyperventilation: Extremely slow or shallow breathing brought on
by anxiety dramatically decreases the amount of carbonic acid in
the blood – leads to periods of …
Apnea: cessation of breathing until CO2 builds up in the blood. If
breathing is stopped for a significant amount of time …
Cyanosis may occur. Cyanosis: insufficient oxygen in the blood