Respiratory System
Gas Exchange
Introduction
• What is our atmosphere made of?
• Nitrogen 78%, Oxygen 21%, Other 1%
• Why is breathing important?
– Exchange of O2 and CO2 b/t environment
and our bodies
• What is the O2 used for?
– All cells require O2 for cellular respiration
• energy
• Other gasses?
– CO2 + H2O
– Expelled as waste
General Functions
– Intake of oxygen
• For Cellular Respiration
– Exhale carbon dioxide
– Preservation of life
Terminology
• Breathing: to take air into
the lungs and let it out
again (inhale and exhale).
• Gas Exchange: the
process of diffusion that
allows for carbon dioxide
to leave the capillaries
surrounding the alveoli
while facilitating the
entrance of oxygen into
the capillary. (Carbon
dioxide-out: oxygen in)
• Cellular Respiration:
when cells oxidize
organic carbon to obtain
energy. This is different
from just respiration or
the respiratory system.
Note: the start product
(oxygen) and end product
(carbon dioxide)
necessitate the need for
the respiratory system.
Breathing vs. Respiration
• Breathing (Terminology)
– Intake of O2
– Exhale CO2
– Gasses exchanged in alveoli in lungs
• Respiration
– C6H12O6 + 6O2 = 6CO2 + 6H2O
– Breakdown of sugar into energy
– Takes place in all cells
• Gas Exchange:
– Diffusion allowing for carbon dioxide to leave the
capillaries and oxygen to come in. (Carbon
dioxide-out: oxygen in)
Respiratory Structures and their
Functions
• Mouth and nostrils
– Air enters respiratory system
– Allows a larger volume of air to be
transferred
• Nasal cavities
– Provide moisture
– Filter and trap particles
• Hair and mucous
Respiratory Structures and their
Functions
• Pharynx
– In mouth
– connect to the
back of the oral
and nasal cavities.
The pharynx is
also connected to
the trachea and
esophagus
– Passage for food
and air (digestion
and gas exchange
– Lined with ciliate
epithelial cells to
trap fine particles
– Contains tonsils
and adenoids
Respiratory Structures and their
Functions
• Epiglottis
– A leaf-like flap of tissue
– prevents food from entering the trachea.
Respiratory Structures and their
Functions
• Larynx
– Voice box
– Ligaments
– Air passes, vibrate
ligaments, sound
produced
• Vocal chords
Respiratory Structures and their
Functions
• Vocal chords: two elastic ligaments that
produce sounds depending on various
tensions.
Respiratory Structures and their
Functions
• Adam’s apple
– cartilage that protects
the larynx.
Respiratory Structures and their
Functions
• Trachea
– Windpipe
– Takes air into the lungs.
– Lined with cilia
• Mucus
• Filter extra particles
– Cartilage rings
• Provide support
• Keep trachea open
Respiratory Structures and Their Function
• Cilia: small hairs that trap particles. Cilia move
upwards to move particles back upwards so that
they can be spit out.
Trachea
Pharynx
Respiratory Structures and their
Functions
• Bronchi
– Two branches of the
trachea
– Contain cartilage
– Go to R & L lungs
• Bronchioles
– Smaller branches inside
each lung that are less
than 1mm in diameter
– No cartilage
– Rings of muscle –
change diameter
•
Respiratory Structures and their
Functions
Alveoli
– The point of gas exchange
– The overall purpose of alveoli is to
increase surface area for gas
exchange.
– Very thin air sacs
– Surrounded by capillaries
– Site of gas diffusion
• Concentration gradient
– One cell thick
– Each lung - ~ 150 million
– Film of lipoprotein – prevents alveoli
from sticking together
Respiratory Structures and their
Functions
• Lungs
– Two cone shaped
organs
– right has 3 lobes
– left has 2 lobes
• shares space with
heart
– Located in thoracic
cavity -base contacts
diaphragm and top
above the clavicles
Respiratory Structures and their
Functions
• Pleural Membrane
– Outer surface of
lungs
– Inner wall of chest
cavity
– Reduced friction
Respiratory Structures and their
Functions
• Diaphragm
– Band of muscle
shaped like a
dome
– Separates thoracic
cavity from
abdominal cavity
– Helps in breathing
Respiratory Structures and their
Functions
• Ribs: bones that protect the thoracic cavity.
Respiratory Structures and their
Functions
• Intercostal muscles
– muscles between the ribs that aid in breathing.
Human Gas Exchange
System
Diagram Answers
Section of head and thorax to show respiratory
system. left lung (surface) view Right lung (section)
1
Nasal cavity
2 Pharnyx
3 Epiglottis
4 esophagus
5 Cartilage rings
6 Bronchi
7 Lung
8
9
10
11
12
13
14
15
16
17
Heart
Pleural membranes
Diaphragm
Alveoli
Pleural membranes
Bronchioles
Intercostal muscles
Ribs
Trachea
Larynx
Mechanism of Breathing
BREATHING MOVEMENTS
• Oxygen continuously moves from alveoli
into blood
• Carbon dioxide from blood to alveoli
• Air in alveoli must, therefore, be
continuously replaced with fresh air
INHALATION
1. diaphragm contracts
2. intercostal muscles
contract
3. increase in lung
volume
4. environmental air
pressure is greater
than the lung
pressure
5. air rushes in to
equalize pressure
EXHALATION
1. diaphragm relaxes up
2. intercostal muscles
relax
3. decrease in lung
volume
4. lung pressure is
greater than
environmental air
pressure
5. air rushes out to
equalize pressure
Inhalation and Exhalation
Inhalation and Exhalation
Role of Diaphragm
• During inhalation
– regulates pressure in chest cavity
• Contract – flattens, moves down
• Volume increases, pressure decreases
• Air moves into lungs
• During exhalation
• Relaxes – dome shaped, moves up
• Chest volume decreases, pressure increases
• Air moves out
Role of the Intercostal
Muscles
– Intercostal muscles are located between the
ribs
– Inspiration: Muscles contract, pulls ribs up
and out
– Expiration: Muscles relax, ribs move down
Diffusion Across Alveoli
• In LUNGS –
– Higher concentration of oxygen than in blood.
– Lower concentration of carbon dioxide than in
blood.
Diffusion Across Alveoli
RESULTS
• Oxygen moves from the air in the lungs across
the alveoli and into the capillary where it
becomes attached to hemoglobin.
• Carbon dioxide moves from the blood across
the alveoli and into the air of the lungs.
Alveoli
• Characteristics that
facilitate diffusion:
– have thin walls
– kept moist
– richly supplied with
blood vessels
– large surface area
REGULATION & CONTROL
– Medulla Oblongata -- breathing center
• controls rate and depth of breathing
• the medulla is sensitive to CO2 levels in the blood
• If CO2 (carbonic acid) level too high...
– medulla tells diaphragm and intercostals to increase
activity
• once CO2 levels drop into normal range...
– medulla stops sending “increase activity” message
REGULATION & CONTROL
• Chemoreceptors –
– If stimulated –
• Diaphragm begins breathing movements
• More breathing, lower CO2 levels
• Can be controlled
– Medulla will take over if CO2 builds up
QUANTITIES OF AIR
• TIDAL VOLUME – amount air exchanged with
each normal breath
• INSPIRATORY RESERVE – additional air that
can be inhaled over and above the tidal volume
• EXPIRATORY RESERVE – extra air that can be
forcibly exhaled in excess of the tidal volume
QUANTITIES OF AIR
• VITAL CAPACITY – the maximum
amount of air that can be forcibly
exchanged
• RESIDUAL VOLUME – amount of air that
remains in lungs after forceful expiration.
QUANTITIES OF AIR
INSPIRATORY RESERVE
VOLUME (3 L)
VITAL
CAPACITY
TIDAL VOLUME (1/2 L)
EXPIRATORY RESERVE
VOLUME (1 L)
RESIDUAL VOLUME
(1.2L)
Transport of Gases
• OXYGEN TRANSPORT
– hemoglobin transports
about 97% of the oxygen
– 3% will diffuse into the
plasma
– the hemoglobin molecule is
composed of 4 peptide
chains with an iron center
– oxygen attaches to
hemoglobin to form
oxyhemoglobin
– oxygen is released in the
tissues
Carbon Dioxide in the Blood
• Approximately
– 64% of CO2 – bicarbonate ion in plasma
– 27% of CO2 – combines with hemoglobin
– 9% of CO2 – is dissolved in plasma
Transport of Gases
• CARBON DIOXIDE TRANSPORT
• CO2 moves away from muscle
– CO2 continually diffuses into the blood plasma.
– an enzyme (carbonic anhydrase) in red blood cells
converts some CO2 and water (from plasma) into
carbonic acid
– carbonic acid breaks into H+ and bicarbonate ions
(hydrogen carbonate)
– the H+ combines with hemoglobin
• helps avoid significant pH change in blood
– the bicarbonate ion stays in the plasma
Transport of Gases
• When this blood reaches lungs:
– new O2 will combine with hemoglobin displacing
H+ into plasma.
– H+ recombines with bicarbonate ion producing H2O
and CO2 which diffuses into alveoli to be exhaled
Factors Affecting Breathing
Rate
1. Exercise
• When exercise occurs carbon dioxide levels
accumulate faster than normal.
• As a result, your breathing rate and depth
increase.
2. Hormones
• Hormones such adrenaline increases
breathing rate
3. High Altitude
• At higher altitudes there is less oxygen present in the
atmosphere.
• This does not have a great effect on carbon dioxide
receptors.
• Receptors in the arteries will increase the breathing
rate.
4. Carbon Monoxide
• CO acts as a competitive inhibitor in the red blood
cell
• CO attaches to the hemoglobin molecule 200
times stronger (and faster) than O2 or CO2
• This makes the hemoglobin unavailable for O2 or
CO2
Holding Your Breath
• When you hold your
breath carbon dioxide
levels begin to build.
• As a result, when
breathing is resumed
it occurs at a faster
rate and with greater
depth than normal.
Hyperventilation
• When you
hyperventilate your
carbon dioxide levels
temporarily decrease.
• This temporary
carbon dioxide
decrease would allow
you to hold your
breath for longer
periods of time.
DISORDERS
Disorders
• Bronchitis
–
–
–
–
–
Inflammation of bronchioles
Air passages get smaller
Excess mucus
Harder to exhale than inhale
Can lead to asthma and emphysema
• Emphysema
– Increased resistance to airflow
– Over-inflation of the lungs
– Alveoli cannot handle pressure
• Rupture
• Less SA for gas exchange
• Lowers O2 levels
• Lung Cancer
– Uncontrolled growth of cells
– Less surface area for diffusion
– Blockages may occur
Tobacco
• People have smoked tobacco for centuries
• How is related to this class?
• Lung cancer
– Most common type of death from cancer
– 50% OF SMOKERS WILL DIE FROM
SMOKING RELATED CAUSES
Healthy vs. Unhealthy
The effects of chewing tobacco on a Man.
Other Effects of
Smoking
1. hair loss
2. cataracts
3. wrinkling
4. hearing loss :
6. tooth decay :
7. lung ailments :
9. heart disease :
16. cancer : a)of the
lungs b)of the
tongue c) of the
mouth, salivary
glands and
pharynx.