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Blood!!!

2010-11-13 · Hank · watch on YouTube · Science & nature · explainer learning

On his way to give blood, Hank explains the human circulatory system by following the life of one red blood cell, 'Arby', from its creation through the lungs and back, and urges viewers to give blood.

What is said

00:00:00 — Greeting; on the way to the blood bank as a universal donor; how to start a video on a circulatory system with no beginning or end

  • ★★ Hank says he is on his way to the Western Montana Blood Bank to give blood, calling himself a universal donor they can't get enough of. (playful) — 00:00:00
  • ★★ Hank says the circulatory system has no beginning or end except birth and death, so he tells it from the perspective of one red blood cell's life. — 00:00:00

00:00:29 — The red blood cell 'Arby' (from RBC); erythropoiesis; losing nucleus and organelles; 270 million hemoglobin molecules

  • ★★ Hank says you have trillions of red blood cells delivering oxygen wherever it is needed; that is all they do, and if they stopped you would die instantly. — 00:00:29
  • ★★ Hank says making a red blood cell is called erythropoiesis, from erythrocytes and 'poiesis', Latin for to make, which is also the root of 'poetry'. — 00:00:58
  • ★★★ Hank says near the end of its creation a red blood cell expels its nucleus and organelles, and by then holds 270 million hemoglobin molecules. — 00:00:58
  • ★★ Hank says hemoglobin is a protein complex with four heme molecules, each an organic compound with an iron center that bonds very well to oxygen. — 00:00:58

00:01:27 — Heme and iron bond oxygen; comic analogies; hemoglobin prefers carbon monoxide

  • ★★ Hank says hemoglobin actually prefers to bind carbon monoxide, which is why breathing in too much carbon monoxide kills you. — 00:01:27

00:01:56 — The journey: vena cava, right heart, pulmonary arteries, lung capillaries and alveoli, oxygen loading down its gradient, back through the left heart

  • ★★ Hank traces a cell made in, say, the femur up the inferior vena cava, the largest vein, into the right atrium; the right ventricle pumps it through the pulmonary arteries. — 00:01:56
  • ★★ Hank says arteries carry blood away from the heart and veins carry it to the heart, so the pulmonary artery carries deoxygenated blood, which is not weird at all. — 00:01:56
  • ★★ Hank says lung capillaries, on the alveolar sacs, are narrower than the cell; without its nucleus the cell, holding 230 million hemoglobin molecules, can fold to squeeze through. — 00:02:26
    • number check: 230 million — doubtful
  • ★★★ Hank says oxygen moves from the alveoli down its concentration gradient into the hemoglobin, which keeps soaking it up so oxygen keeps flowing in until it is full. — 00:02:55
  • ★ Hank says the oxygenated cell returns to the heart through the pulmonary vein, enters the left atrium and ventricle, and is pumped out into the body. — 00:03:24

00:03:53 — How hemoglobin knows where to unload oxygen: carbonic anhydrase, acidity and carbon dioxide

  • ★★★ Hank explains that carbonic anhydrase turns carbon dioxide and water into carbonic acid, which releases protons; hemoglobin reacting with them lets go of oxygen. — 00:03:53
  • ★★ Hank says this makes sense, since wherever work produces carbon dioxide oxygen is needed, and he finds the mechanism beautiful and elegant, dork or not. — 00:04:22

00:04:52 — The cell's ~100-day life ends in the liver; give blood; sign-off; post-donation coda and comment question

  • ★★ Hank says the cell repeats the circuit every 20 seconds for about a hundred days until the liver filters it out (helping make poop brown); bleeding or giving blood is the only other exit. — 00:04:52
  • ★★★ Hank hopes viewers are giving blood and ends with an appeal: give blood, it saves lives. — 00:04:52
  • ★★ After donating, Hank says he hadn't given blood in a long time and found it really easy; he asks commenters when they last gave blood and what they thought. — 00:04:52

Humor (significant)

  • Hank says the circulatory system has no beginning or end except birth and death, and death makes it uninteresting. — 00:00:00 > «If you're a zombie, I don't think it would be interesting to you either.»
  • Hank names his red blood cell Arby, after biochem shorthand RBC. — 00:00:29 > «we're calling him Arby not because he was created from the meat of a roast beef sandwich»
  • Hank says the cell holds 270 million hemoglobin molecules. — 00:00:58 > «I know this because I counted.»
  • Hank ranks hemoglobin's skill at bonding oxygen: the Clash of punk rock, the Cristiano Ronaldo of soccer. — 00:01:27 > «If it was being delicious, hemoglobin would be corndogs.»
  • At the end of its hundred days the cell is filtered out by the liver. — 00:04:52 > «and yes, helps to make your poop brown.»
  • Just after giving blood, Hank notes he has said Arby about 25 times. — 00:04:52 > «So now I really, really, really want a roast beef sandwich.»

Threads in this video

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