Week 4 Flashcards
Explain the Pulmonary Ventilation
Quiet Inspiration (ACTIVE PROCESS)
-Diaphragm moves down 1cm and ribs are lifted by external and internal intercostals (intercartilagenous part) and pectoralis minor
-The lungs expand with chest wall, intrapulmonary pressure drops and air is inhaled (moves from higher pressure outside to lower pressure inside)
Explain the Pulmonary Ventilation Quiet Expiration (PASSIVE PROCESS)
-Driven by elastic recoil of lung connective tissue (1/3 contribution) and surface tension in alveoli (2/3 contribution) ~ no muscle action
-In this way, intrapulmonary pressure increases and air is pushed out (moves from higher pressure inside to lower pressure outside)
Explain Pulmonary Ventilation Forced inspiration (ACTIVE PROCESS)
- sternocleidomastoid, scalenes and pectoralis minor further lift clavicle, sternum and first rib upwards and therefore increase the volume of the thoracic cavity)
- Diaphragm can move down 13 – 14 cm!!
Explain Pulmonary Ventilation Forced expiration (ACTIVE PROCESS)
-external oblique and rectus abdominis contract, increasing pressure in the abdominal cavity which pushes diaphragm up faster and harder
-internal intercostals (interosseous part) contract to depress ribs (action opposite of external intercostals)
-intrapulmonary pressure exceeds the atmospheric by up to 30mm Hg
What is Intrapleural Pressure?
The pressure in the pleural cavity
- it is always sub-atmospheric (below atmospheric pressure) and sub-pulmonary (below pressure in lungs)
- during inspiration intrapleural pressure decreases even more due to chest cavity expansion
- this pressure keeps the parietal and visceral pleura very close together (they are not physically connected)
- A pneumothorax is when intrapulmonary and intrapleural pressures are equalcollapsed lung which cannot expand with thoracic cavity expansion
What are the 3 steps in pulmonary ventilation?
What is gas flow influenced by?
apartfrompressuredifferences,gasflowisinfluenced by airway resistance
What is airway resistance mainly affected by?
thecombined diameter of all conducting airways (itisusuallyinsignificantbecauseofthelargeairway diameters in the first part of the bronchial tree)
airway resistance is increased in ….
bronchoconstriction
Equation for Relationship between flow (F), pressure (P), and resistance (R) is:
- ∆P: pressuregradientbetweenatmosphereandalveoli (2 mm Hg or less during normal quiet breathing)
- Gasflowchangesinverselywithresistance
What is surface tension?
a thin layer of watery fluid covering alveolar wall causes an inward directed force
Where does surface tension arise?
surface tension arises at all air- water interfaces because water molecules are more strongly attracted to each other (hydrogen bonding) than to molecules of air, thus resisting expansion of alveoli during inspiration
surface tension needs to be overcome during
Inspiration
What is Surfactant?
detergent-like substance
What is surfactant a mixture of?
mixture of phospholipids and lipoproteins
What is surfacant produced by?
produced by surfactant-secreting (Type 2) cells
What lowers alveolar surface tension?
Surfactant lowers alveolar surface tension and increases↑ expandability
…… is mixed with water molecules which significantly reduces the strength of attraction between water molecules thus enabling expansion of alveoli during inspiration
Surfactant
What prevents the collapse of alveoli during expiration
Surfactant
Respiratory Volumes and Capacities graph
Respiratory Volumes and Capacities table
What is Anatomical Dead Space?
volume of air in the conducting zones that never contributes to gas exchange in the alveoli (~150ml) hence only ~350ml available for alveolar ventilation (= functional volume)
• dead space also includes non functioning alveoli
What is Alveolar Ventilation Rate (AVR)?
- This is flow of gases into and out of the alveoli during a particular time
Formulae for Alveolar Ventilation Rate (AVR)?
E.g.TheAVRforapatientwithanormalrateand depth of breathing is:
What is the Composition of Air?
Composition of air: 78.6% nitrogen, 20.9% oxygen, 0.04% carbon dioxide, 0.5% water vapour (depending on temperature and humidity), and minor gases argon, neon, helium, ozone and methane
What is the composition of Partial Pressure?
• Dalton’s Law – the total atmospheric pressure is the sum of the contributions of the individual gases
– partial pressure – separate contribution of each gas in a mixture
– at sea level air pressure is 760 mmHg so partial pressures are:
• PN2=78.6%x760mmHg=597mmHg
• PO2=20.9%x760mmHg=159mmHg • PH2O=0.5%x760mmHg=3.7mmHg
• PCO2=0.04%x760mmHg=0.3mmHg • PN2+PO2+PH2O+PCO2=760mmHg
Composition of inspired air and alveolar air is different because of three influences:
– air is humidified by contact with mucous membranes (alveolar PH2O is more than 10 times higher than inhaled air)
– freshly inhaled air mixes with residual air left from the previous respiratory cycle
– alveolar air exchanges O2 and CO2 with the blood
The main difference between inspired air and alveolar air
PO2 of alveolar air is about 65%
that of inspired air (meaning less oxygen in the air in our lungs than the atmospheric air),
while PCO2 is more than 130 times higher (meaning more carbon dioxide in the air in our lungs compared to atmospheric air)
What is Henry’s law?
When a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure
Dissolving of gases in fluid: At equilibrium,…..
At equilibrium, the partial pressures in the two phases (alveolar air and blood) will be equal
The amount of gas that will dissolve in a liquid also depends upon its ……
The amount of gas that will dissolve in a liquid also depends upon its solubility
– CO2 is 20 times more soluble in water than O2
– very little nitrogen dissolves in water
External Respiration: Gas Exchange Process.
What is partial pressure gradient for O2?
Partial pressure gradient for O2 in the alveoli is steep
– bloodPO2=40mmHg
– alveolar PO2 = 104 mm Hg
External Respiration: Gas Exchange Process. Oxygen partial pressures in
alveolar air and blood will
equalise in …..
Oxygen partial pressures in
alveolar air and blood will
equalise in ~0.25 seconds
(about 1/3 the time a red
blood cell is in a pulmonary capillary)
External Respiration: Gas Exchange Process. Partial pressure gradient for CO2 in the lungs is….
Partial pressure gradient for CO2 in the lungs is less
steep:
– blood PCO2 = 45 mm Hg
– alveolar PCO2 = 40 mm Hg
• But CO2 diffuses much faster than oxygen so CO2 moves in
equal amounts with oxygen
External Respiration: O2 diagram
Does o2 dissolve in water easily, explain?
O2 does not easily dissolve in water - only 1.5% of O2 is transported physically dissolved in blood
What is oxyhaemoglobin?
98.5% of O2 in blood is chemically combined with iron in haemoglobin (Hb) in form of oxyhaemoglobin
Blood contains …
Bloodcontains20mLoxygenper100mL
How much Oxygen in arterial blood?
Normally in arterial blood almost all haemoglobin is saturated with oxygen (98% saturation)
What does an increase in PO2 produce?
Further increases in PO2 (e.g. breathing deeply, breathing air with greater oxygen concentration) produce minimal increases in O2 binding and dissolving in blood
What is Anaemia?
Anaemia (reduced concentration of haemoglobin)
reduces ability of blood to carry O2)
What type of o2 is allowed to diffuse into tissue?
Only the dissolved O2 can diffuse into tissues (O2 needs to be separated from haemoglobin before it can diffuse into tissues)
How much o2 is unloaded during one systemic circulation?
Only 20-25% of bound O2 is unloaded during one systemic circulation (i.e. 4-5 mL of that 20 mL oxygen per 100 mL). Thus venous blood contains a bit of oxygen
What happens when o2 levels in tissues drop?
If O2 levels in tissues drop (e.g. during increased metabolic activity as in exercise) more oxygen dissociates from haemoglobin and is used by cells
• With moderate increase in oxygen consumption respiratory rate or cardiac output need not increase
Diagram of external respiration co2
Carbon dioxide is carried by the blood in 3 ways:
– physically dissolved in blood (7%)
– combined with the globin part of haemoglobin molecule forming carbaminohaemoglobin (23%) – does not compete with oxygen (Hb can transport CO2 and O2 simultaneously)
– as part of hydrocarbonate (bicarbonate) ion HCO3- dissolved in blood (70%)
• in peripheral tissues CO2+ H2O combine to form carbonic acid that dissociates into H+ and hydrocarbonate ion
• in the lungs the process is reversed, CO2 is released and it diffuses into alveolar air
Transport of Gases in the Blood diagram
What is Internal Respiration: O2
• Opposite reaction to what occurs in the lungs
– oxygen diffuses from blood into tissue (called unloading)
What is Internal Respiration: CO2
Opposite reaction to what occurs in the lungs
– carbon dioxide diffuses out of tissue into blood (called loading)
What is internal respiration?
The rate of unloading (O2) and loading (CO2) of is regulated to ensure the adequate delivery of O2 to cells, and removal of CO2 from cells.
What does the removal of co2 from cells depend on?
PO2 (e.g. lower PO2 = more unloading of O2)
• Temperature (e.g. increased temp = more unloading of O2)
• blood pH (e.g. lower pH = more unloading of O2)
• PCO2 (e.g. higher PCO2 = more unloading of O2)
What is the unloading and loading facilitated by?
Unloading and loading is facilitated by a change in the shape of Hb
• as O2 binds, Hb affinity for O2 increases
• as O2 is released, Hb affinity for O2 decreases
What is the haldane effect?
Deoxygenation of the blood increases its ability to carry carbon dioxide; this property is the Haldane effect. Conversely, oxygenated blood has a reduced capacity for carbon dioxide. Encourages CO2 exchange in tissues and lungs
What happens when more CO2 enters blood during the haldane effect?
During the haldane effect, At tissues, as more CO2 enters blood More oxygen dissociates from haemoglobin
What happens as HbO2 releases O2 during the haldane effect?
• As HbO2 releases O2, it more readily forms bonds with CO2 to form carbaminohaemoglobin due to a change in the shape of the haemoglobin
Where are the respiratory centres located?
Located in medulla oblongata and pons
What do the respiratory centres do?
controls activity of respiratory muscles and determines respiratory pattern, and the rhythm and depth of breathing
What does the medullary respiratory centres contain?
Medullary Respiratory Centre contains:
– Ventral Respiratory Group (rhythm generation) (contains inspiratory + expiratory
neurons)
• VRG Inspiratory: stimulates phrenic nerve and intercostal
nerves contraction of inspiratory muscles
• VRG Expiratory: stimulates intercostal nerves
contraction of forced expiratory muscles
– Dorsal Respiratory Group (rhythm
modification based on peripheral input)
(contains inspiratory neurons only)
What are the Pontine Respiratory Centres (2 centres) and what are their functions?
modifies the output of medullary groups
– Apneustic centre
• Stimulates the inspiratory neurons of the DRG and VRG
– Pneumotaxic centre
• Sends inhibitory signals to the inspiratory centre of the medulla
• Controls inspiratory time
Inspiration area diagram
Forceful breathing diagram
What is activity if the respiratory centres influence by?
Activity of the respiratory centres is influenced by chemical regulation: chemoreceptors in walls of common carotid arteries and aorta) monitor levels of CO2,O2 and pH of blood – information is sent to the DRG
What is the most powerful respiratory stimulant?
high CO2 levels are the most powerful respiratory stimulant
How does blood PO2 affect breathing?
normally blood PO2 affects breathing only indirectly by influencing peripheral chemoreceptor sensitivity to changes in PCO2 but when arterial PO2 falls below 60 mm Hg, it becomes the major stimulus for respiration
Chemoreceptors diagram
What are Other factors that influence respiratory centre activity?
VEE
voluntarily influence (voluntary alteration of breathing but not stopping until death)
– emotional factors (anxiety, excitement), body temperature and pain (all increase respiration)
– exercise leads to quicker and deeper breathing even before it causes increased level of CO2 in blood
– when the brain sends motor commands to the muscles it also sends this information to the respiratory centres
– exercise stimulates proprioceptors of the muscles and joints and they transmit excitatory signals to the brainstem respiratory centres
WHAT ARE THE 3 RESPIRATORY PATTERNS?
Hyperpnoea, hyperventilation, apnoea
What is hyperpnoea?
Hyperpnoea: increase in depth and rate of breathing in response to metabolic needs (e.g. exercise)
– PCO2, PO2, and pH remain quite constant during exercise
What is hyperventilation?
Hyperventilation: increased depth and rate of breathing that exceeds the body’s need to remove CO2 (e.g. panic
attack, when doing CPR)
What does hyperventilation result in?
results in minimal increase of amount of oxygen carried in blood but significant drop in CO2 level (hypocapnia)
– since CO2 is carried as carbonic acid in the blood, hypocapnia results in the blood becoming alkaline (alkalosis)
What is apnoea?
Apnoea: period of breathing cessation
When can apnoea occur?
can occur when CO2 is abnormally low but O2 is still not low enough (e.g. after hyperventilating) to activate respiratory centre
What is intrapleural pressure?
The pressure in the pleural cavity
What substance prevents the collapse of alveoli during expiration? Which type of cells produce it?
Surfactant. Type II alveolar cells (surfactant secreting cells)
Which gas is more soluble in fluid - O2 or CO2
CO2 (carbon dioxide)
List the 3 ways CO2 is carried by blood
-Physically dissolved in blood
-Combined with glob in part of Hb forming carbaminohaemoglobin
-As bicarbonate (hydrocarbonate/HCO3-)
Where are the respiratory centres located?
Medulla oblongata and Pons
What is vital capacity?
volume of air that can be exhaledafter maximal inspiration
Name the accessory muscles involved in forced inspiration?
Sternocleidomastoid and the scalene muscles
Thoracic vertebrae
- Name the anatomical structure enclosing the thoracic outlet and therefore separating the thoracic cavity from the abdominal cavity.
Diaphragm
- Define the difference between the true and false ribs:
True (1-7) have their own costal cartilage that attaches to the sternum, while false (8-10) have costal cartilages that indirectly articulate with the sternum.
Identify the muscles involved in respiration on the diagram
- Which thoracic dimensions are affected, and which bones are moving during the:
i) pump-handle movement:
ii) bucket-handle movement:
iii) calliper movement:
I) manubrium/sternum —> ant/post dimension
Ii) true& false ribs —> transverse (medial/lateral) dimension
Iii) floating ribs —> ant/post and transverse (med/lat) dimension
What is the bell jar lung model?
The bell jar lung model is a great way to understand how pressures are responsible for the movement of air in and out of the lungs.The bell jar represents the thoracic cavity, the flat membrane on the bottom represents the diaphragm and the balloons on the inside represent the lungs.
When the membrane (“diaphragm”) on the bottom is pulled downward:
a) What happened to the “lungs” inside the jar?
b) Why did this happen?
c) What do you think happened to the pressure inside the jar compared to the pressure outside of the jar?
d) What does this experiment represent?Diaphragmcontractingleadingtoinhalation
A) They inflated
B) Air flowed in to them from outside
C) Became lower
D) Diaphragm contracting leading to inhalation
When the membrane (“diaphragm”) is pushed upwards:
a) What happened to the “lungs” inside the jar?
b) Why did this happen?
c) What do you think happened to the pressure inside the jar compared to the pressure outside of the jar?
d) What does this experiment represent?
A) They deflated
B) Airflowed out of them to the outside
C) Became higher
D) Diaphragm relaxing leading to exhalation
What are The four ventilation processes?
Quiet Inspiration and Expiration and Forced Inspiration and Expiration.
b) Oxygen, Carbon Dioxide and Nitrogen. Order these gases from most soluble to least soluble in water.
CO2, O2, N
What is partial pressure?
partial pressure – separate contribution of each gas in a mixture
What is the PO2 in the blood? What is the PO2 in the alveolus? Therefore, in which direction will O2 move?
blood PO2 = 40 mm Hg
alveolar PO2 = 104 mm Hg
Oxygen will move from higher partial pressure (alveoli) to lower partial pressure (blood) —> therefore will move into the blood from the alveoli
What is the PCO2 in the blood? What is the PCO2 in the alveolus? Therefore, in which direction will CO2 move?
blood PCO2 = 45 mm Hg
alveolar PCO2 = 40 mm Hg
Carbon dioxide will move from a higher partial pressure (blood) to a lower partial pressure (alveoli) —> therefore carbon dioxide will move out of the blood into the alveoli
Based on the PO2/PCO2 blood/alveolar gradients from questions d) and e); would you expect O2 and CO2 to exchange at the same rate?
Based on the gradients you would not expect them to exchange at the same rate. The gradient of oxygen between blood and alveoli is steep and would be a fast exchange, whereas the carbon dioxide gradient is less steep and would exchange slower. HOWEVER, carbon dioxide is 20 time more soluble than oxygen (refer to question 4.b), which balances out the differences in gradients —> oxygen and carbon dioxide exchange at the same rate.
How is O2 transported in the blood?
Physically dissolved in blood 1.5%
Combined with haemoglobin (oxyhaemoglobin) 98.5%
How is CO2 transported in the blood?
Physically dissolved in blood 7%
Combined with haemoglobin (carbaminohaemoglobin) 23% Bicarbonate/ HCO3 (as part of hydrocarbonate) 70%
What is the function of the respiratory centres?
Controls activity of respiratory muscles and determines the rhythm and depth of breathing
What are the specialised sensory receptors that influence respiratory centre activity?
CHEMORECEPTORS
Where are CHEMORECEPTORS located? What do they detect?
In the walls of the common carotid arteries and aorta. CO2,O2 and pH of blood
What is the most powerful respiratory stimulant?
High carbon dioxide levels
e) What other factors can influence respiratory centre activity?
- voluntarily influence (voluntary alteration of breathing but not stopping til death) - emotional factors (anxiety, excitement), body temperature, pain (all increase respiration)
- exercise leads to quicker and deeper breathing even before it causes increased level of CO2 in blood
- when the brain sends motor commands to the muscles it also sends this information to the respiratory centres
-exercise stimulates proprioceptors of the muscles and joints and they transmit excitatory signals to the brainstem respiratory centres
During inspiration, the diaphragm…
Is contracted and low in thoracic cage
A. Body
B. Inferior demifacet
C. Superior article facet
D.transverse process
E.transverse costal facet
F. Spinous process
A. Manubrium
B. External intercostal muscles
C. 11th rib
D.body of sternum
E. Xiphoid provess
The thoracic outlet is formed by:
The body of thoracic vertebra 12, rib 12, part of rib 11, costal cartilages of ribs 6-10 and xiphoid process
Most of the carbon dioxide transported by the blood is __________
converted to bicarbonate ions and transported in plasma
In the alveoli, the partial pressure of oxygen is __________
.
about 104 mm Hg
Which ventilation type is a passive process?
Quiet Expiration
Air moves into the lungs because __________
the gas pressure in the lungs becomes lower than the outside pressure as the diaphragm contracts
Alveolar ventilation rate is _________
the movement of air into and out of the alveoli over a period of time
Which respiratory measurement is normally the greatest?
vital capacity
Haemoglobin has a tendency to release oxygen where __________
pH is more acidic
Airway resistance is insignificant in relationship to gas flow because ______
the airways branch more as they get smaller, resulting in a huge total cross-sectional area
