Week 10: Oxygenation Flashcards
What is pressure?
Force exerted on surfaces gas molecules are in contact with
What is partial pressure?
Pressure of single type of gas in a mixture
What is Total Pressure?
Sum of all partial pressures of gaseous mixture
What is Dalton’s Law?
Total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in a mixture
What is Henry’s Law?
Concentration of gas in a liquid is directly proportional to the solubility and Px of the gas
What is the relative concentration of gases?
Nitrogen > Oxygen > Water Vapour > Carbon Dioxide
Is the amount of water vapour greater in the alveolar air or in the atmospheric air?
Alveolar air
What is Ventilation?
Movement of air into and out of the lungs
What is Perfusion?
Flow of blood in pulmonary capillaries
For gas exchange to be efficient, volumes involved in Ventilation/Perfusion should be …..
Compatible
Factors that can lead to ventilation/perfusion imbalance:
- Regional gravity effects on blood
- Blocked alveolar ducts
- Disease
What is the Px of O2 in alveolar air?
104mmHg
Sufficient Ventilation means that O2 enters alveoli at high rate, Px remains high, which means what?
Adequate gas exchange occurs
Poor Ventilation means that Px of O2 in alveoli drops, which means what?
Inadequate gas exchange occurs
What is a Compensatory mechanism for Ventilation and Perfusion?
Body will redirect blood flow (constriction of pulmonary arterioles) to alveoli that are receiving sufficient ventilation; pulmonary arterioles at these sites will vasodilate increasing blood flow
Ventilation is regulated by…
The diameter of the airways
How does the diameter of the airways impact Ventilation?
A greater Px of CO2 in alveoli and decrease level of O2 in alveolar blood supply cause bronchioles to dilate, causing CO2 to be exhaled at greater rate
Perfusion is regulated by…
The diameter of blood vessels
How does the diameter of the blood vessels impact Perfusion?
Greater Px of O2 in alveoli cause pulmonary arterioles to dilate, increasing blood flow
What are the 2 sites where Gas Exchange occurs?
The lungs and the tissues
Where in Gas Exchange is O2 picked up and CO2 is released at the respiratory membrane?
The Lungs
Where in Gas Exchange is O2 released and CO2 is picked up?
The Tissues
What is External Respiration?
Exchange of gases with EXTERNAL environment (alveoli of lungs)
What is Internal Respiration?
Exchange of gases with INTERNAL environment (tissues)
How does the exchanging of gases occur?
Diffusion, molecules follow pressure gradients and there is no energy required
Explain the Overview of Perfusion/Gas Exchange
- Pulmonary artery carries deoxygenated blood from the heart to lungs.
- Blood branches from arterioles into pulmonary capillaries, forming the respiratory membrane with alveoli.
- Gas exchange occurs in the capillary network.
- O2 binds to hemoglobin in red blood cells; some dissolves in plasma.
- Oxygenated blood appears bright red and returns to the heart via pulmonary veins. (note: deoxygenated blood is dark red (burgundy).
- CO2 is released from blood to alveoli, some carried by hemoglobin, in plasma, or converted.
When does External Respiration occur?
Occurs as a function of Px differences in O2 and CO2 between alveoli and blood in pulmonary capillaries
When does Internal Respiration occur?
Like external respiration, internal respiration occurs as simple diffusion due to Px gradient
What are O2 and CO2 like in Internal Respiration?
Px of O2 in tissues is LOW
Px of O2 in blood is HIGH
Px of CO2 in tissues is HIGH
Px of CO2 in blood is LOW
Is Oxygen very soluble or not very soluble?
Not very soluble
The majority of O2 molecules are carried to and from lungs to the tissues via what?
Erythrocytes (RBCs)
What do RBCs contain that binds O2 molecules to them?
Hemoglobin (Hb)
What part of hemoglobin is the portion that binds to O2?
Heme as it contains iron
Each molecule of Hb contains how many heme molecule?
4
Each hemoglobin molecule can carry how many O2 molecules?
4
What is the term used for when hemoglobin has O2 bound to it?
Oxyhemoglobin (HbO2)
What is the term used for when hemoglobin does NOT, or has less oxygen bound to it?
Deoxyhemoglobin
What are considered normal Hb saturation levels?
95-99%
What is the Oxygen-hemoglobin dissociation curve?
Graph describes relationship of Px to the binding and dissociation of O2 to heme
What happens to the affinity of O2 to heme when it increases as more O2 molecules are bound?
- As Px O2 increases, greater # of O2 molecules bound to heme
- As Px O2 decreases, so does # of O2 molecules bound to hem
Is deoxygenated blood (venous) completely free of oxygen bound to hemoglobin?
No, O2 is often still bound to hemoglobin in its red blood cells
What are some factors that can affect O2 affinity and dissociation to and from heme?
Temperature
Hormones
pH
What are the 3 methods of CO2 transport in the blood?
Transport by blood plasma
Transport in form of bicarbonate (HCO3–)
Transport via erythrocytes
What is the Chloride-Bicarbonate Exchange (Chloride Shift)?
As CO₂ enters RBC from tissues, bicarbonate builds up in cells; To maintain electrical neutrality, chloride ions (Cl⁻) move into RBCs from the plasma in exchange for bicarbonate ions.
What is the reverse of the Chloride-Bicarbonate Exchange (Chloride Shift)?
In the lungs, the process reverses: bicarbonate ions re-enter RBCs in exchange for chloride ions.
CO2 binds to amino acid moieties on globin portion of Hb to form…
Carbaminohemoglobin
What is the Haldane Effect?
Relationship b/w Px O2 and affinity of Hb for CO2
Hyperpnea is…
Increased depth & rate of ventilation to meet increase in O2 demand (exercise/disease)
Hyperventilation is…
Increased ventilation rate, independent of cellular O2 needs
What are some factors that affect both Hyperpnea and Hyperventilation?
Low O2
High CO2
pH
What happens to Hb saturation in high altitudes?
Hb saturation is lower at high altitudes due to decreased partial pressure gradient; less O2 crossing resp. membrane leads to less O2 available to bind to Hb
What is Acute Mountain Sickness (AMS) or Altitude Sickness?
Acute exposure to high altitudes;
Result of low blood O2-body has difficulty adjusting to low Px of O2
How would you treat Acute Mountain Sickness (AMS)?
Descending to lower altitude, supplemental O2
How does one prevent Acute Mountain Sickness (AMS)?
Prevented by ascending SLOWLY (allows body to acclimate), hydration also important
What is Acclimatization?
Process of adjustment the resp. system makes due to chronic exposure to high altitude
When does a Fetus’ respiratory system begin to develop?
~4 weeks
When has a Fetus’ lungs matured enough (has enough alveoli) that it can breathe on its own if born early?
By 28 weeks
When does the respiratory system fully mature (full complement of functional alveoli)?
~ 8 Years old
What are the 5 phases of development the respiratory system in an embryo?
- Embryonal phase
- Pseudoglandular phase
- Canalicular phase
4/5. Saccular/Alveolar phase
When can fetal breathing movements be observed?
Weeks 20-21
What happens to a fetus’ lungs prior to birth?
Prior to birth the lungs are filled with amniotic fluid, mucus, surfactant
What happens to the fluids in the lungs of the fetus when it move into the birth canal?
The fluids are expelled when the thoracic cavity is compressed
When does the first inhalation occur after birth?
10 seconds
What is the purpose of the first breath after birth?
To inflate the lungs
Why is a pre-term baby born before 26 weeks often given a low chance of survival?
It has insufficient amount of surfactant produced and not enough surfaces for gas exchange not adequately formed
What is RDS?
Respiratory distrass syndrome
What sort of treatments are used for RDS?
- Resuscitation/intubation (mechanical ventilation) if infant does not breath on their own
- If spontaneous breathing-continuous positive airway pressure (CPAP)
- Pulmonary surfactant administered
