{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter 18 Notes - Gas Exchange & Transport

Chapter 18 Notes - Gas Exchange & Transport -...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Oxygen and carbon dioxide can diffuse freely (i.e. through simple diffusion) across cell layers (between alveoli and pulmonary capillaries, or between systemic capillaries and cells) - Obeys Fick’s Law Fick’s Law: rate of diffusion α ( surface area of t h e membrane x concentration ) gradient x membrane permeability membrane t h ickness Note: Membrane permeability α lipid solubilitymolecular size Along with the three factors that influence diffusion in the lungs (according to Fick’s law), there is a fourth: diffusion distance - Diffusion is most rapid over short distances. - Diffusion distance, surface area and membrane thickness are kept constant in the body (usually maximized to facilitate diffusion) - The most important factor is thus concentration gradients that drive gas exchange . The movement of gas molecules from air into liquid is directly proportional to the pressure gradient of the gas, the solubility of the gas in the liquid, and the temperature . - Recall from general chemistry: the solubility of a gas decreases with increasing temperature (Why? think about boiling water: the liquid molecules will want to vaporize and become gas molecules: therefore increasing the temperature will decrease the solubility of a gas in a liquid) Gases flow from areas of higher pressure to areas of lower pressure. An increase in temperature causes an increase in pressure (Charles’ Law) General overview of gas exchange: oxygen exchange occurs at the alveolar-capillary interface (oxygen comes into the alveoli from the air, and carbon dioxide comes into the alveoli from the blood in order to be exhaled). Oxygen is transported via systemic circulation to the tissues, where cellular respiration occurs and produces carbon dioxide. Carbon dioxide is picked up by the venous blood, and returned to the heart. The cycle begins again when the blood enters pulmonary circulation. Carbon dioxide is much more soluble in water than is oxygen – we have evolutionarily developed to overcome this obstacle. - The low oxygen solubility in water implies that at chemical equilibrium (between oxygen molecules in air and oxygen molecules in water), the amount of oxygen per liter of fluid is more in air than it is in fluid. The normal alveolar P oxygen is roughly 100 mm Hg, and the P oxygen of systemic venous blood arriving at the lungs is 40 mm Hg Oxygen will move down its concentration gradient from the lungs into the blood.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern