Blood Gases

Welcome to the Blood Gases Unit! This chapter contains chapters that will help guide you through blood gas concepts in the human body. This unit will examine many different scenarios that affect our breathing and why our body reactions that way. Like, why can we hold our breath whenever we want to, but we don’t have to think about controlling our breathing when relaxed or talking? Or, how do the air molecules get into our lungs? After that, how do they get to our muscles? We will dive into this and many other examples we see in our day-to-day life throughout this unit’s chapters.

Pulmonary mechanics and respiration are the first unit and help you understand the human respiratory system’s basic structure and function. Here you will be exposed to the mechanism of how we breathe and introduced to the idea of pleural pressure, alveolar pressure, and atmospheric pressure. Understanding this first unit will set you up for further success as we progress through the rest of the blood gas unit. The second unit, pulmonary blood flow, discusses how gravity affects blood flow across the lungs and emphasizes how we regulate and change the vascular radius. In this unit, you’ll be able to make connections between the material learned and some real-life examples. The third unit, ventilation-perfusion ratio, demonstrates the importance of our VA/Q ratio and situations when this ratio can go wrong. In this unit, you will be encouraged to think about what would lead to changes in PAO2 (alveolar partial pressure of oxygen) and PACO2 (alveolar partial pressure of carbon dioxide) and how we can predict these changes using the VA/Q ratio. The fourth unit is gas exchange and transport. Here you will cover various concepts that relate to gas exchange and why our PO2 (partial pressure of oxygen) and PCO2 (partial pressure of carbon dioxide) in the alveoli do not always reflect that of our environment. This unit can be pretty tricky. Make sure you check out the additional practice questions and activities throughout to reconfirm your knowledge. The fifth and final unit covers the control and regulation of blood gases. Here we tie in multiple concepts to create a better overall understanding of blood gases as a whole and review the neural control of how we breathe. This chapter is a great place to review baroreceptors, the coordinating center, and negative feedback loops.

This chapter is designed to give you a deeper understanding of physiological blood gases, looking from the alveoli level to connections within the brain’s coordinating center. We encourage you to test your knowledge as you travel throughout the chapter with the interactive activities and application questions. As you read through this chapter, it is important to take the time to identify some reoccurring concepts that appear throughout. Write these concepts down and try to connect them to other units. Human physiology often overlaps between the systems. Findings these connections will become a great study tool and increase your overall understanding of human physiology.

Here is a list of subchapters that will direct you to the corresponding page:

  1. Pulmonary Mechanics and Respiration
  2. Pulmonary Blood Flow
  3. Ventilation Perfusion Ratio
  4. Gas Exchange and Transport
  5. Control and Regulation of Blood Gases
  6. Chapter Review

Learning Outcomes

By the end of this chapter, you will be able to:

  • Understand the main structures and function of the respiratory system. Describe the mechanism of breathing in relation to pleural, alveolar, and atmospheric pressure. Understand the changes in lung volume during breathing.
  • Understand the factors that regulate vascular radius and blood flow across the lung and the effect gravity has on blood flow across the lung.
  • Understand how real-life situations would affect the ventilation-perfusion ratio and predict how this would lead to changes in PAO2  and/or PACO2. Understand why PAO2 values are not the same as atmospheric PO2 values.
  • Understand why the PO2 and PCO2 in the alveoli do not reflect that of the environment and how oxygen (O2) and carbon dioxide (CO2) are stored in the blood. Understand how the PvCO2 (venous partial pressure of carbon dioxide) would differ during different activities. Describe the equations associated with the red blood cells and the plasma.
  • Understand the neural pathway that controls breathing and the negative feedback that exists within the pathway.
  • Review the unique roles of chemoreceptors, stretch receptors, high-pressure baroreceptors, and irritant receptors.

Blood Gases Podcast

The podcast and paired transcript for this chapter will summarize the key concepts of each subchapter and provide helpful insight as well as examples that could be useful while studying. The podcast does not describe all of the content from this chapter, but it highlights the tricky concepts to hopefully make them clearer. When learning elaborate processes like gas exchange at different tissue, it is commonly recommended to have a conversation with a classmate to gain a deeper understanding of the relationships between all the different variables. Listening to this podcast will feel like a discussion with a classmate, which could be a great way to review for tests!

 

 

“Blood Gases Podcast” by Erica Robertson and Santana Ferreira is all rights reserved.

 

The following list of hyperlinks will take you to each of the topics discussed in the podcast:

 

  1. Anatomy of Respiration, Inspiration and Expiration
  2. Respiratory Flow Section and Pressures
  3. Surfactant
  4. Tips for the Pulmonary Mechanics and Respiration Chapter
  5. Introduction to Pulmonary Blood Flow
  6. Mechanisms that Regulate Blood Vessel Radius
  7. Transmural Pressure
  8. Tips for the Pulmonary Blood Flow Chapter
  9. Example of Difference in Blood Flow in Regions of Lung
  10. Introduction to Ventilation Perfusion Ratio 
  11. Details of VA/Q Ratio
  12. Useful Tools When Studying VA/Q
  13. Real-Life Scenario Examples and Connections
  14. Introduction to Blood Gas Exchange and Transport
  15. Partial Pressures
  16. Mechanisms That Drive Changes in Partial Pressures
  17. How Gas Exchange Occurs at the Lung
  18. Transport of Gas in the Blood
  19. Gas Exchange Equations and Studying Tips 
  20. Gas Exchange at the Tissue 
  21. Introduction to the Oxygen Dissociation Curve
  22. The Meaning Behind the Oxygen Dissociation Curve
  23. Conditions that Affect the Oxygen Dissociation Curve
  24. What Might Happen During Exercise 
  25. Introduction to Control and Regulation of Blood Flow
  26. Chemoreceptors
  27. Other Receptors
  28. Involuntary Control of Breathing
  29. Voluntary Control of Breathing
  30. Example of Hyperventilation

 

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Human Physiology Copyright © by Human Physiology Students from University of Guelph is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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