Little Package Blog

Breathing, Part II
2001.03.13
Nursing
What makes lungs expand and contract? Are they muscles? No, the lungs aren’t muscles. *Special* respiratory muscles “make” breathing happen. Normally an involuntary act, breathing can also be consciously controlled and altered, thank goodness. Although technically many muscles of the thorax can participate in breathing, any decent yogi will tell you that the diaphragm is the prime and proper breathing muscle (Vishnudevananda 235). Here’s how to do it: Relaxed, the diaphragm is dome-shaped. Upon contraction it flattens inferiorly, expanding the thoracic cavity and lungs. This is inspiration. The muscles shown between the ribs in this illustration are the external intercostals; they aid inspiration by elevating the rib cage. In a full inspiration, the belly will protrude, the chest will expand up and out, and the shoulders may […]

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Respiration, Part I
Nursing
Breathing and respiration aren’t the same thing, but they go hand in hand. Breathing is a simple mechanical process whereby air enters and exits the lungs due to volume and hence, pressure changes. Respiration* is a more complex process of delivering oxygen to the tissues for cell metabolism and carbon dioxide to the lungs for removal. The image at left shows blood being oxygenated at the lungs (red) and traveling through the heart to the systemic circuit. The gas exchange at the alveoli/blood interface is called external respiration. Gas exchanges between blood and tissue cells is termed internal respiration. Deoxygenated blood (blue) flows from the tissues in the systemic circuit back to the heart, the lungs, and CO2 is exhaled. As seen in the illustration, the cardiovascular […]

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Respiration, Part II
Nursing
We’ve explained why air enters the lungs, what components flow in/out and why, but we still haven’t discussed internal and external respiration! Regard the image at right. Find the sad face. Here the blood is CO2 rich (45 mm Hg) and low in oxygen (40 mm Hg). This sad blood is being delivered to the lungs, where the alveolar PO2 is 104 mm Hg and the PCO2 is 40 mm Hg. See? You probably know right away that fresh oxygen will rush across the respiratory membrane into the blood and refresh its supply to 104 mm Hg. But the gradient of PCO2 is only 5 mm Hg. It would seem then that carbon dioxide would have a lesser tendency to evacuate the blood, but it turns out […]

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Respiration, Part III
Nursing
Oxygen and carbon dioxide are carried in the blood, pumped by the heart, and shifted through membranes by partial pressure gradients. Oxygen dissolves to a much smaller degree than carbon dioxide, so that at rest, the PO2 would only help provide 6% of the body’s O2 requirements. There must be another way. The hemoglobin molecule comes to the rescue. Hemoglobin is made of globin, a protein, and four heme groups consisting of an iron atom surrounded by an organic group. Four polypeptide chains make up the globin, each bearing a red-pigmented, disk-shaped heme. Each heme group binds one oxygen molecule, so each hemoglobin molecule binds four oxygens. Considering one red blood cell holds ~ 250 million Hb molecules, it can carry ~ 1 BILLION oxygen molecules (Marieb […]

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Respiration, Part IV
Nursing
Successful respiration requires a delicate acid-base equilibrium in bodily fluids. H+ concentrations, however meager they may be, significantly impact fluid pH. Furthermore, hydrogen ions are highly reactive and react with many compounds, often disrupting their shape and function. Hydrogen ion concentrations must be maintained at ~4.0 x 10-8 in order to keep blood pH at its slightly alkaline value of 7.4. Acidosis, caused by accumulation of CO2 in the blood, is a drop in blood pH. Shallow breathing may cause acidosis. The opposite condition, alkalosis, is a rise in pH due to excessive CO2 excretion. Alkalosis is commonly caused by hyperventilation, but is much less serious than respiratory acidosis. We can say that concentrations of CO2 in the blood are directly related to its pH. A pH […]

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Conclusion, Links, Sources
Nursing
In conclusion, I’ll talk about two things I’ve never even done: scuba (darn) and the bends (thank god). These underwater phenomena summarize very well the concepts I’ve outlined. As a note, this page would be set to some of my favorite music, but amazonkers.com and towersucks.com don’t have sound samples for “Underwater Love” and “The Bends.” Shucks. Back in the days when everything was still so simple, people devised novel ways of exploring the ocean floor. Take the little guy below, for example. The hood over his head connects him to surface air, and he can breathe fine, right? Wrong. We would reason that a deep diver is subjected to increased “atmospheric” water pressure, a great force pressing in on his chest. Remember, water is heavier than […]

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