Transcript What are the respiratory structures that let us breath? 2/26

What are the respiratory structures that let us breath?
2/29
• Goals:
• -Describe the airway divisions that lead air to the alveoli where
most gas exchange actually occurs.
• -Describe the structure and anatomy of the lower airway anatomy
as it applies to health and disease
• -Describe gas transfer requirements as they apply to health and
disease
• Compare and contrast the atmospheric pressures found in the
lung and pleural space between the lung and the thoracic wall.
• -Describe pressure changes required for inspiration and expiration
• -Describe the implications of Boyle’s Gas Law?
• -Describe the role of surfactants with respect to alveolar surface
tension in a premature newborn and an adult
• -Describe why alveoli tend to either fully expand or fully collapse
with respect to surface tension and surfactants.
• -What are the typical lung volumes? VC, IRV, TV, ERV, RV
Anatomy and Physiology 212:
Thinking and Learning go together for Test/Quiz scores
• A lot of the time you spend
“studying” should be spend simply
“thinking” try this every night after
lecture.
On “Average” each Week (not night
before), don’t do it week before a
test:
• 3 hours study time for each hour of
lecture 3 X3 =9hours/wk
• 2 hours open lab for each hour in
lab 2 X 2 = 4hours/wk in open lab
Air Flow is distributed into tinier and tinier passages that lead to the
dead-end Alveoli where gas exchange with blood finally occurs!
• Entry: Oral Cavity/Nasal Cavity
• Pharynx
• Larynx/Glottis
• Trachea
• Primary Bronchi
• Secondary Bronchi
• Tertiary Bronchi
• End cartilaginous rings
• Bronchiole
• Terminal Bronchiole
– Above this its called Dead Space: no significant gas exchange
• ----------------------------------• Respiratory Bronchiole (Alveolar Ducts)
• Alveoli
– Most Gas Exchange is Here! IF YOU HAVE HEALTHY LUNGS!– Describe carbon dioxide and oxygen transfer to/from blood/air
Alveoli/Alveolar Sacs: Primary site of gas exchange
Distance from alveolar surface to capillary is a function of
cells in between and the depth of fluids lining the alveolus
• Distance from Alveolus to hemoglobin in a erythrocyte in a Capillary:
– mucus/membrane distance 0.5 micrometers
• Smoker vs Non-smoker difference
– More targreater mucus to clean surfacegreater distance for gas to
diffuse before reaching hemoglobinharder to oxygenate blood!
– A paradoxical difference in HEMATOCRIT is often observed!
• Remember: there are 5 plasma membranes that oxygen must pass
through before reaching hemoglobin (can you count them?)
• Gas Diffusion REQUIRES a thin film of water on alveolar surface!
• Remember that very little oxygen or carbon dioxide can directly
dissolve in water!
– Oxygen is carried by the 4 subunits of hemoglobin to improve solubility!
– Carbon Dioxide is converted to bicarbonate to improve its solubility!
The distance from the inside of the alveolus to the inside of an RBC in a capillary
is a little as 0.5 micometers. To get oxygen to hemoglobin it passes through 5
plasma membranes.
Wandering Macrophage (ma)
on Alveolar Surface destroy
bacteria and cleans the
surface.
Simple Squamous Epithelial
Tissue of Alveolus or the
Capillary (endothelium)
RBCs inside
capillaries
The alveolar sacs come in clusters where surfactants and mucus are important
for air cleaning, optimal gas exchange and lowering internal surface tension.
Alveolar macrophages are specialized monocytes (macrophages) actually leave
the blood and patrol the alveolar surface against bacteria and unwanted items.
The lung sits in a fluid filled pleural cavity that is under a slight
vacuum relative to the pressure outside the lung or in the
airways. This keeps the visceral membrane (lung) tight
against the parietal membrane (rib cage).
• Visceral and Parietal Pleural membranes: serosa
• Pleural Cavity:
• Pleural Fluid Functions:
FrictionPressure gradient/maintains suction• Pulmonary Cavity: air space inside airways (bronchialveoli)
• Pneumothorax/Atelectasis
• Pressure During Inspiration and Expiration
• Intrapulmonary vs. Intrapleural Pressures
Inspiration and Expiration require pressure gradients!
These gradients can be very slight because air offers little resistance to flow!
PRESSURE IN AND AROUND THE LUNG CAN BE
DESCRIBED USING BOYLE’S GAS LAW.
• “Pressure is inversely proportional to volume if temp
same”
SO: +P>>-V and +V>>-P
• 1 Atmosphere is equal to: 760 mmHg
• Pressure inside an alveoli: Intrapulmonary P
• Pressure inside pleura: Intrapleural P
• Intrapulmonary/Intrapleural pressure difference:
• Transpulmonary Pressure- determines if lung inflates (mmHg) or deflates (+mmHg).
• Circulatory rules also apply to air in lung: Q=ΔP/R
• What are some pathological sources of increased airway
resistance?
HOW/ WHY DOES AIR MOVE IN/OUT OF THE LUNGS?
• Insipiration: diaphragm contracts and pulls down and/or
External intercostal muscles contract +Volume and -Pressure
(↑Vol ↓Press) ….air sucked into lung
• Expiration: relax diaphragm (contract internal intercostals)
• If pressure inside lung is more than outside then pressure
gradient favors air moving out!
• Generally: expiration is a passive process (ELASTIN)
• 75% breathing work is from diaphragm
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•
•
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Forced Expiration: METABOLICALLY EXPENSIVE
Contact abdominals and internal intercostals
Required with increased airway resistance: asthma
You only do this if you have too….heavy exercise or if you have
respiratory disease
• If you have emphysema forced expiration is required for even
tidal breathing……very expensive indeed.
HOW IS TENSION CREATED/REDUCED IN THE LUNG?
• Elastin in lung tissue and surfactant in alveoli conserves energy!
• Surface Tension (hydrogen bonds) of fluid lining alveoli critical
• Law of Laplace: Force= 2 Tension/radius
•
As the radius is increased the force to inflate is reduced
•
Energy is required to pull volume open
• Surfactant: is a phospholipid/protein mix that reduces surface
tension in alveoli Critical for infants and adults alike!
– Repulsion: negative repels negative
– Lipid-PO4--  --PO4-Lipid
– Attraction: water attached to PO4 pulls them together if they
are far apart
• Often premature infants lack sufficient surfactant: results in
Sudden Infant Death Syndrome.
• Surfactant also improves gas diffusion to/from blood
Water molecules create surface tension in the alveoli: 1) it causes small
alveoli to collapse, and 2) it causes air to be diverted to the larger of any
two alveoli because larger alveoli are easier to keep inflated. Surfactants
are phospholipids that help prevent complete alveolar collapse due to the
compaction of strong opposing negative charges on the phosphates!
They also provide elasticity to help the lung work passively, this adds to
the effect of elastin proteins found in the lung tissue itself!
A Spirometer is used to measure Breathing Patterns and Lung Volumes:
Reduce these values about 20% in females.
Approximate Volumes: memorize these numbers:
Total Lung Capacity: TC=5-6 Liters
Vital Capacity: VC=5 L…its what you can manipulate
Tidal Volume: TV=500 ml
Typical size of a typical resting breath
• Inspiratory Reserve Volume: IRV=3L
Air added to a tidal volume with Max Inspiration
• Expiratory Reserve Volume: ERV=1.5L
Amount you can exhale after a typical Tidal Exhalation
• Residual Volume: RV=1L
Air that’s left in Trachea, Bronchi, etc after a max. expiration
In our Respiratory Physiology lab we will use an electronic
spirometer that converts air velocity and flow into
respiratory volumes using a set of computer algorithms.
Old School
Spirometer
Could you answer these questions?
1 Where does most gas exchange occur in the lung?
2 How far apart is the inside of an alveolus from the
inside of a red blood cell?
3 What are the methods used to clean the alveolus and
larger bronchi? Are they the same?
4 How do pleural and pulmonary cavities differ?
5 What are the typical pressures in the atmosphere,
airway and pleural space during inspiration?
5 What is Boyle’s Law?
6 Do surfactants contain lipids, phosphates or both?
7 What do surfactants do?