Functions of the Respiratory System
 Gas exchanger
– Air goes to blood
– Blood goes to cells
 Air distributor
Other functions
1. Humidification
2. Filtering
3. Phonation
4. Warming
5. Control of pH
6. Olfaction
Respiratory System
 Primary function – Gas
exchange: to obtain oxygen
and remove carbon dioxide.
 Cells require oxygen to
break down nutrients to
release energy and produce
ATP = Cellular Respiration
 Cells must excrete carbon
dioxide that results from
cellular respiration.
Cellular Respiration - Review
 C6H12O6 (aq) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l)
 Without O2, a cell can only undergo fermentation,
resulting in a net gain of only 2 ATP for the cell.
 Why would this be a problem?
 The result of cellular respiration is carbon dioxide and
water. This carbon dioxide enters the blood stream and
there it has various functions, including:
 Regulation of blood pH
 Haldane Effect
 Bohr Effect
 Autoregulation of blood supply to tissues
Cellular Respiration
 Therefore it is incredibly important that cellular
respiration takes place, in a timely manner,
throughout the body.
 When O2 levels are limited, cellular respiration
activity slows down and the body reverts to
fermentation.
 What are the results of fermentation?
 The respiratory system allows for gas exchange
between the air and blood in the body to occur,
resulting in an intake of oxygen from the atmosphere.
Introduction to Respiration
 Respiration – gas exchange between atmosphere and





cells.
Ventilation – movement of air into and out of lungs.
Gas exchange between blood and air in lungs =
external respiration.
Gas transport in blood between lungs and body cells.
Gas exchange between blood and cells = internal
respiration.
Cellular respiration – process of oxygen utilization and
carbon dioxide production at the cellular level.
Organs Involved
 Upper Respiratory Tract
1. Nose
2. Nasopharynx
3. Oropharynx
4. Laryngopharynx
5. Larynx
 Lower Repsiratory Tract
1. Trachea
2. Bronchial Tree
3. Lungs
The Nose
• Protrudes from face
• Openings called nares
• Ala are cartilage rings or
•
•
•
•
•
flares at nares
Floor made of palatine and
maxilla
Roof formed by ethmoid
Septum made of cartilage
and bone (perpendicular
plate of ethmoid and
vomer)
Lined with mucosa
Meatuses formed cavities
Functions of the Nose
 Passageway – filters,
warms, moistens and
chemically examines air
 Smell
 Phonation
 Paranasal sinuses – air
filled spaces that reduce
weight of skull and affect
quality of voice.
The Nose
 Nostrils (nares) – are where air enters and leaves nasal
cavity.
 Nasal cavity – hollow space behind nose
 Nasal conchae – bones that divide nasal passageway.
 These support the nasal cavity and increase surface area.
 Why is this important?
 Help in nasal congestion in response to climatic changes
and needs of the body.
 Mucous membrane – epithelium rich in mucous-
secreting goblet cells that trap dust and other particles.
 How would this aid the respiratory system?
Pharynx (throat)
• Made of muscle and
mucous lining into 3
divisions
• Nasopharynx – posterior
nares to soft palate
• Oropharynx – soft palate to
hyoid bone; adenoid
tonsils
• Laryngopharynx – hyoid
bone to esophagus;
palatine and lingual tonsils
The Larynx


•
•
•
•
•
Enlargement in airway.
Houses vocal cords.
Upper end of trachea
3-6th cervical vertebrae
Made of 9 pieces of cartilage in shape of box.
Thyroid muscle – called “Adam’s apple”
Glottis – opening between vocal cords. Triangular slit.
Present during normal breathing. Muscles close glottis
when eating or drinking.
• Why would this be important?
• Prevent food and liquid from entering trachea.
The Larynx
• Epiglottis – lid. Muscle that allows air into larynx.
• Closes during eating. Why?
• Arytenoids – hold vocal cords
• Vocal cords – fibroelastic bands
stretched across
hollow interior
• Males is larger with less fat
• Function to produce voice
(pitch determined by length and tension in cords)
• Changing the shape of the pharynx and oral cavity and
using the tongue and lips transform sounds waves to words.
The Trachea
 “Windpipe” – flexible





tube lined with ciliated
mucous membrane tissue.
Made of smooth muscle
Contains “C” shaped rings
of cartilage
4.5 inches long
Provides passageway to
and from lungs
Splits into left and right
bronchi.
Bronchi
 Made similar to trachea
but complete rings
 Branched into primary,
secondary bronchi,
bronchioles, alveolar
ducts, alveoli
 Provide passageways and
alveoli provide gas
exchange surface
Bronchial tree
 Branched airways leading from the trachea to the air
sacs in the lungs.
 Left and right bronchi, divide into primary, secondary…
 Bronchioles – terminal bronchioles, smaller tubes. Lack
cartilage.
 Alveoli – air sacs in lungs connected to the capillary
network. Provide large surface area.
 Why is the large surface area important for alveoli?
 O2 diffuses through cell walls into blood
 Co2 diffuses through blood into cell walls.
Alveoli
 Alveolar ducts are very
thin ducts that connect
the terminal bronchioles
to the alveolar sacs.
 Alveoli lie within the
capillary network.
 Two adult lungs have
about 300 million
alveoli, providing a
surface area nearly half
the size of a tennis court.
Lungs
 3 lobes in Rt. Lung and 2 in
the left. Therefore R lung
larger than the left.
 Root of lung consists of
primary bronchus and
pulmonary arteries and
veins
 Function is to provide
rapid exchange of gases.
 Lobes connected to
lymphatic system, blood
vessels, air passages,
nerves, and connective
tissue.
Respiratory Mucosa
 Lining of entire respiratory system
 Makes mucous (sputum)
 Mucous will help clean and filter
 Make about 125 mL daily
 Moves about 1 to 2 cm per minute from lower
respiratory tract to oropharynx
 Swallow or spit out
Very short quiz over anatomy and some functions of the
respiratory system.
Breathing Mechanisms
 Inspiration – inhalation
 Atmospheric pressure, due to weight of air, is the force
that moves air into lungs.
 At sea level, the atmospheric pressure is sufficient to
support a column of mercury about 760 mm high in a
tube. Therefore, normal air pressure = 760 mmHg.
 Normal, resting inspiration – if pressure inside lungs
and alveoli decreases, atmospheric pressure will push
outside air in.
Normal, quiet Inspiration
 Diaphragm contraction (result of impulse from
•
•
•
•
•
phrenic nerves)  diaphragm moving down.
Increase in vertical diameter of thorax
Increase in transverse diameter of thorax
Alveoli air pressure decreases about 2-3 mmHg less
than atmospheric pressure.
Expansion of lungs – cohesion of visceral and parietal
pleuras
Air enters lungs = inspiration.
Normal, quiet Expiration
 Expiration – exhalation
 Force comes from elastic recoil of tissues and surface







tension (attraction of H2O molecules that make it difficult
for alveoli to inflate)
Passive process
Relaxation of inspiratory muscles
Decrease in size of thorax – elastic recoil of lung tissue
Increase in intrathoracic pressure
Decrease in size of lungs
Increase in alveolar pressure from about -3mm of Hg to +3
or +4 mm Hg (Pressure and volume in inverse relationship)
Air moves out of lungs – expiration
Respiratory Volumes
 Respiratory Cycle – 1 inspiration and following expiration.
 Tidal Volume – volume that enters during 1 resp. cycle
 Resting Tidal volume – about 500 mL of air.
 Inspiratory reserve volume (IRV) – During forced
inspiration, air in addition to resting tidal volume can
enter lungs. This maxes out at about 3,000 mL of air.
 Expiratory reserve volume (ERV) – lungs can forcefully
expel about 1,100 mL more than resting tidal volume.
 Residual volume – amount always in lungs = 1,200 mL.
Respiratory Volumes
 Because of the residual volume, new air inhaled mixes
with old air in the lungs.
 This is very important as it prevents the concentration
of O2 and CO2 in the lungs from fluctuating much
during respiration.
 Why would this be important?
• CH3CH2OH(g) + O2(g) -> HC2H3O2(g) + H2O(l)
• Ethyl alcohol and oxygen to acetic acid and water.
• The breathalyzer. No way around it!
Respiratory Capacities
 When two or more volumes are combined.
 Vital Capacity – tidal volume + ERV + IRV = 4,600 mL.
Maximum air during deepest breath possible.
 Inspiratory Capacity – Tidal volume + IRV = 3,500 mL.
Maximum amount a person can inhale after resting
expiration.
 Functional residual capacity – ERV + Residual volume
= 2,300 mL. Volume of air in lungs after resting exp.
 Total lung capacity – vital capacity + residual volume =
5,800 mL. Varies with age, sex and body size.
The didgeridoo
 Wind instrument developed by




Aborigines in Australia over
1,500 years ago.
Often considered world’s oldest
wind instrument.
Termite-bored branches are
often used to make these
instruments.
Vibrations produced by the
player’s lips and the strength of
the vocal tract influence the
timbre of the sound.
The technique of circular
breathing can help.
Gas Exchange
 Respiratory membrane – walls of alveoli exchange gas





between blood and air.
Gases diffuse from regions of high pressure to regions
of low pressure.
Air = 78% N, 21% O, 0.04% CO2
Partial pressure – amount of pressure each gas
contributes to its concentration.
O2 = 160 mmHG (21% of 760 mmHg)
Gas diffuses into liquid - O2 into blood.
 Another example: CO2 into coca cola.
Gas Exchange
 Follow partial pressure gradients.
 Each gas diffuses between blood and its surroundings
from areas of higher partial pressure to areas of lower
partial pressure until the partial pressures in the two
regions reach equilibrium.
 PO2is alveoli is 105 mm of Hg while in the blood it is
only 40 mmHg. Thus O2 diffuses from the alveolar air
into the blood.
 PCO2 is 45 mmHg in blood but only 40 mmHg in
alveolar air. Therefore CO2 diffuses from the blood
into the alveoli.
Oxygen
Transport
Oxygen Transport
 98% of O2 binds with iron group of hemoglobin. 2%
dissolves in plasma.
 In lungs, combines with hemoglobin 
oxyhemoglobin.
 This is an unstable bond and as PO2 decreases, oxygen
releases and diffuses into cell to be used in cellular
respiration.
 More O2 is released from oxyhemoglobin when [CO2]
is high, when blood pH is low, and when blood
temperature is high.
 When might these conditions occur?
 Exercise, when more O2 is released to the muscles.
Carbon Dioxide Transport
 Tissues have relatively high PCO2 to blood, so CO2
rapidly diffuses into blood.
 Blood transports CO2 to lungs as CO2 in plasma,
bonded to hemoglobin, or as bicarbonate ion (HCO3-)
 CO2 bonds with the amino group of hemoglobin
forming carbaminohemoglobin, which decomposes in
areas of low PCO2 releasing carbon dioxide.
 Do you think it’s possible for both O2 and CO2 to be
bound to hemoglobin at the same time?

Yes! CO2 binds to the amino group while O2 binds to the iron
group of hemoglobin. Some exceptions…
Bohr Shift
 At lower pH (more acidic environment), hemoglobin
will bind to oxygen with less affinity = Bohr Shift
 That is, oxygen is more likely to be released from
oxyhemoglobin in a more acidic environment.
 In RBCs carbonic acid (H2CO3) dissociates into
protons (H+) and bicarbonate ions (HCO3-).
 Since CO2 is in direct equilibrium with the
concentration of protons in the blood, increasing CO2
levels leads to a decreases in pH  Bohr Shift.
Haldane Effect
 Related to the Bohr
Shift is the Haldane
Effect, which is the
phenomenon in which
oxygenated blood has
a reduced capacity for
hemoglobin to carry
carbon dioxide and
vice versa.
A short quiz over physiology and gas exchange in the
respiratory system