Cardiovascular System and

Diffusion

Katerina LinKiran PandherRachel Gibbs

Group 5

Goals Explain how gas exchange takes place at the

cellular level. What prevents gas from being exchanged in

non-optimal places?

An Overview:The Respiratory System Respiratory system: takes oxygen from

the air into the body and releases CO2, the waste product.

Gas exchange occurs because of partial pressure gradients (oxygen and CO2). Higher pressure = more diffusion. Lungs: Gases pass through capillaries and

alveoli down partial pressure gradients. Capillaries and alveoli share a membrane (Starr).

Body: Gases diffuse through capillaries.

Oxygen… Simple diffusion Lungs: oxygen flows from the

alveoli (high) to the bloodstream (low) (“Respiration”). More pressure/higher temp/lower

pH = more oxygen diffuses (Starr).

Most (98.5%) of the oxygen flowing into the bloodstream binds onto the hemoglobin in RBCs (Starr).

Oxygen does not dissolve well in blood so needs help from hemoglobin (Starr).

Carbon Dioxide… Simple diffusion Body: diffuses from interstitial fluid (high)

into capillaries and carried in blood (low): 10%: dissolves in blood 30%: binds to hemoglobin (carbamino hemoglobin) 60%: becomes bicarbonate (HCO3

-) when CO2 dissociates in water or with enzyme (carbonic anhydrase)

Lung: from the bloodstream (high) to alveoli (low) (“Respiration”).

CO2 is released from the CO2 bound to hemoglobin and HCO3

- dissolved in the blood (Freudenrich).

Diffusion of Carbon Dioxide

What prevents gas from being exchanged in non-optimal places? Surface areas and rates of flow

influence gas exchange The more surface area and larger the

partial pressure gradient, the faster diffusion will occur (Fick’s law) (Starr).

Alveoli sacs provide a lot of surface area for optimum diffusion.

Gas exchange is most efficient when the rate of air coming into the body equals blood flow (Starr).

What prevents gas from being exchanged in non-optimal places? Different parts of body have

characteristics that help create optimal gas exchange.

Capillaries Very small and only one cell

thick (“Capillaries”). Network throughout body Blood flow slows down

Alveoli respiratory surface: thin

layer of epithelium/other tissue that is moist at all times gas molecules can diffuse only when dissolved in a liquid (Starr).

Quick diffusion because very thin and a lot of surface area (Starr).

Electron Micrograph of a Capillary

Gas Exchange Simulation!

References “Capillaries: Connecting Arteries and Veins.” 1996-2009. The

Franklin Institute. 10 Nov. 2009. <http://www.fi.edu/learn/heart/vessels/capillaries.html>.

Freudenrich, Craig. “How Your Lungs Work.” 30 Oct. 2008. How Stuff Works. 8 Nov. 2009. <http://health.howstuffworks.com/lung2.htm#>.

<http://i.ehow.com/images/GlobalPhoto/Articles/5159074/266617_Full.jpg>.

<http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/images/12188b.jpg>.

<http://www.cdli.ca/~dpower/resp/exchange.htm>. <http://www.health.com/health/static/hw/media/medical/hw/

n5551117.jpg>. “Human Physiology: Respiration.” 7 Nov. 2009.

<http://people.eku.edu/ritchisong/RITCHISO//301notes6.htm>. Starr, Cecie, and Ralph Taggart. Biology: The Unity and Diversity

of Life. 9th ed. United States: Brooks/Cole, 2001.

Note: pictures are also cited throughout this powerpoint in the “Notes” section at the bottom of the screen.