Gas Exchanges in the
Body
Internal & External Respiration
Events #2 & 4
Dalton’s Law
 Used to
determine the
individual
pressures of
each gas in a
mixture of
gases
 Based on % of
total of 760
mmHg of total
atmospheric
pressure
Dalton’s Law
 Gas exchanges that occur:




Between the blood and the alveoli AND
Between the blood and the tissue cells
Takes place by simple diffusion
Depends on partial pressures of oxygen &
carbon dioxide that exist on opposite sides of
the exchange membrane (Dalton’s law of
partial pressures)
 Always flowing from high to low
Henry’s law
states that the solubility of a gas in a liquid
is directly proportional to the pressure of
that gas above the surface of the solution
(IOW: the higher the pressure of the gas,
the more gas will be shoved into the liquid
thus increasing solubility)
Henry’s law
 Solubility (of a gas) and partial
pressure have a direct relationship
Solubility Coefficients
The solubility coefficient of the gas also affects
this process – the higher the #, the more the gas
“likes” to dissolve into a liquid (based on
molecular structure, etc.)
Each gas will dissolve in a liquid in proportion to
the ratio between its partial pressure gradient
and its solubility coefficient
 CO2 = .57
 O2 = .024
 N2 = .012
2nd Law of Thermodynamics
Solubility & temperature have an inverse
relationship.
Increase in temperature causes increase
in kinetic energy causes more molecular
motion which allows molecules to break
the intermolecular bonds and escape from
solution
And vice versa
2nd Law of Thermodynamics
Factors that Influence:
Ratio Relationships
 Partial pressure gradients
and gas solubilities
 Oxygen = has low
solubility but steep
partial pressure gradient
(105 mmHg in alveoli –
40 mmHg in blood = 65
mmHg pressure
gradient)
 Carbon dioxide = has
solubility ~20x greater
than oxygen but partial
pressure gradient is only
5 mmHg
Factors influencing internal &
external respiration
 Partial pressure gradients and gas solubilities
 Due to the ratios of solubility coefficients and
pressure gradients:
 ~Equal amounts of gases are exchanged
Factors influencing internal &
external respiration
 Thickness of respiratory membranes
 0.5 to 1.0 micrometers
 edematous (swollen) tissue can be caused by
congestion and pneumonia - hinders diffusion
leading to hypoxia
oxygen deprivation
Factors influencing internal &
external respiration
 Surface Area
 50-70 square
meters for gas
exchange
 Emphysema or
cancer
 Walls of alveoli
break down
 Less surface
area for gas
exchange
Control of Respiration
Nerves
 The phrenic &
intercostal nerves
transmit impulses to the
respiratory muscles
 Irritation to phrenic
nerve is responsible
for hiccups (spasm of
diaphragm muscle)
 Neural centers are
located in medulla &
pons
Respiration Rate Terms
 Eupnea = normal respiration rate
 Approx 12-15 breaths per min
 Hyperpnea = higher than normal rate
 Apnea = No rate
 Dyspnea = general term for abnormal rate
 Physical factors, conscious control,
emotional factors, and chemical factors all
influence rate & depth of breathing.
Hyperventilation
 Deep & rapid respiration, too much CO2 is
vented out of the body so:
 Not enough acid production
 H2O + CO2 = H2CO3 (carbonic acid)
 Respiratory alkalosis results
 Treatment: trap the CO2 and
rebreathe it till breathing returns to
normal
Hypoventilation
 Slow & shallow respiration with not adequate expiration
so CO2 is not vented out of the body
 Production of excess acid
 H2O + CO2 = H2CO3 (carbonic acid)
 Respiratory acidosis results
 Usually caused by disease process:
 COPD
 Asthma
 Obesity
 Trauma
 Pneumonia
Disorders of Respiratory
System
Chronic Bronchitis
 Symptoms: inflammation of mucosa –
chronic mucus production
 Normal
 Bronchitis
Emphysema
 Breathing is very labored due to lack
of alveolar recoil
 End stage: Alveolar walls collapse =
loss of surface area so less gas
diffusion
 Membranes thicken so decrease in
diffusion eventually
4 features in common
 Both emphysema and chronic bronchitis
have:
 Smoking history
 Dyspnea = air hunger due to dysfunctional
breathing
 Coughing & pulmonary infections
 Will develop respiratory failure, hypoxia,
acidosis
Lung Cancer
 Basic Info
 1/3 of all cancer deaths are due to lung
cancers
 90% have a smoking history
 Metastasizes VERY rapidly due to vascularity
of lungs
Metastasis
3 types of lung cancer
 Read the article in the textbook on page
420 about smoking and lung cancer.
 Then continue on to the next slides to
learn about:
 Squamous cell carcinoma
 Adenocarcinoma
 Oat cell (small cell) carcinoma
 Be sure you learn where these cancers
begin and what they look like
 (test question diagrams!)
Squamous cell carcinoma
Begins in larger
bronchi &
bronchioles
Forms masses that
have bleeding
cavities within
them
Adenocarcinoma
Nodules that
develop in
peripheral
areas of lung
Develop from
alveolar cells &
bronchial
glands
Small cell
carcinoma
Originate in primary
bronchi
Grow into small grape like
clusters in mediastinum
Very aggressive cancer
Treatments
 Resection of diseased portion of lung
(thoracotomy)
 Radiation therapy
 Chemotherapy
Thoracotomy/lung resection
Cystic Fibrosis
• Genetic disorder – recessive
• Causes oversecretion of thick mucus that
clogs respiratory passages
• Impairs food digestion by clogging ducts
that secrete enzymes
• Multiple other organs are affected
Cystic Fibrosis
SIDS - Sudden Infant Death Syndrome
• Sudden, unexplained death of an infant
less than 1 year old
• Possibly caused by brain abnormalities
that control respiration, heart rate, or
consciousness
• Environmental factors to reduce risks –
sleep on back not on stomach, firm crib
with no blankets or stuffed animals or
pillows
• Sudden infant death syndrome (SIDS):
Risk factors - MayoClinic.com
Asthma
• Chronically inflamed hypersensitive
bronchial passageways
• Bronchoconstriction of passageways in
response to allergen, temperature
changes, & exercise
• Can be managed with medication
Hyperbaric Conditions
 Hyperbaric
oxygen chambers
– designed to
force greater
amounts of
oxygen into
patient’s blood
 Treats tissues
affected by poor
circulation
How Hyperbaric Treatment
Works
 Patient breathes in regular air while body
is under pressure
 Increased pressure means increased
solubility of gases (incl oxygen)
 More oxygen in blood benefits treatment
of certain conditions
HBOT used to treat:
Tetanus
Gangrene
Migraines
Slow healing wounds
Burns/skin grafts
Stroke
Autism
Traumatic Brain Injury
Decompression
Sickness
Cerebral Palsy
Multiple Sclerosis
Fibromyalgia
Many other conditions
Scuba Diving
The Physics of Diving - Scuba Gas Laws
• As you go down in depth, the water puts
pressure on your body
• Increased pressure = increased solubility
of inhaled gases into the blood
Scuba Diving
• As you come up at the correct rate, the
pressure decreases slowly
• So the solubility decreases slowly
• So the gases come out of the blood
• And you can exhale them
Scuba Diving
• If you come up too rapidly, the pressure
decreases rapidly
• So the solubility decreases rapidly
• So the gases come out of the blood too
fast to exhale them properly
• The excess gas bubbles can collect in
joint spaces, arteries, tissues, etc.
causing coronary, pulmonary, or brain
embolisms
Nitrogen Narcosis
• As you descend under the water, the
pressure on your body increases, so more
nitrogen and oxygen dissolve in your
blood. Most of the oxygen gets consumed
by your tissues, but the nitrogen remains
dissolved.
• Excess nitrogen causes a feeling of
euphoria similar to laughing gas – impairs
judgement
Decompression Sickness
• DCS arises when the pressure gradient
for nitrogen leaving the tissues is so great
that large bubbles form in venous
circulation
• DCS symptoms are wide-ranging: from
skin mottling to mild tingling in the hands
or feet to shock and death
• Recompression in hyperbaric chamber is
only effective treatment
High Altitude Sickness
• The higher the altitude, the less the
amount of oxygen present in the air.
• Headache and difficulty breathing are
initial symptoms.
• HA pulmonary edema and HA cerebral
edema are life threatening symptoms.
• Body responds over time by increasing
erythropoiesis to give body greater
oxygen carrying capacity.