WARNING: The following contains spoilers for Episode 8 of Cells at Work! CODE BLACK, "Calves, Pulmonary Embolism, and Quick Thinking," now streaming on Funimation.
The Red Blood Cells have one job and one job only: deliver oxygen throughout the body. Compared to the White Blood Cells who slay all of the bad bacteria that invade the body, their job doesn't seem as hard nor does it seem as important especially in times of crisis. Episode 8 of Cells at Work! CODE BLACK is one of the darkest episodes yet, but at least the Red Blood Cells finally get a chance to shine and show why they're just as heroic as the White Blood Cells.
The Red Blood Cells' Dire Situation
Things are looking bad for the Red Blood Cells: they're dwindling in numbers, carbon monoxide is a constant danger and even the liver, where the beautiful Hepatocytes work, isn't like what it was before. AA2153 and AC1677 deliver oxygen in the calves but it's an uphill battle -- literally. For some reason, the pressure from the calves that usually push the blood forward is nowhere to be found. Suddenly, part of the blood vessel in front of them collapses, bringing down the Red Blood Cell walking ahead of them. They rush forward only to see a mass grave of Red Blood Cells at the bottom: a blood clot.
Out of nowhere, the two bullies materialize and shove AA2153 into the pit, but not before AC1677 grabs him with only his fingertips. The lead bully taunts them for giving their all for nothing. AC1677 isn't able to hang on any longer and he slips off, but U-1196 saves them in the nick of time.
The Lungs Are in Danger
With how unhealthy the host body is, it's not much of a surprise to hear that they haven't slept or moved for the past two days, explaining why the Red Blood Cells are having a hard time moving up the calves. When the pumps suddenly start moving, more problems arise: it loosens up the blood clot and sends it careening straight towards the lungs. If it gets clogged up in the pulmonary artery, no oxygen can get delivered there and the body will die soon.
AA2153 and AC1677 start tugging, hoping to dislodge the blood clot, but suddenly the hand AA2153 is holding twitches. It's the lead bully who rasps that none of the Red Blood Cells can deliver oxygen to the lungs. The bully cackles that this horrible world will finally be destroyed, bringing everyone down with it. Meanwhile, the lungs start shutting down and the cells working there begin asphyxiating.
The Red Blood Cells Rise to the Occasion
AC1677 turns to U-1196 for help since she's usually the one who pulls them out of tight spots, but this time she can't do anything. The only things that can get them out of their predicament are the Red Blood Cells. With the pulmonary artery blocking their entry, the only thing they can do is wait for the clot to dissolve, and by the time it does, it might be too late. The bully's final words don't deter AA2153. There is another way to the lungs: the bronchial arteries.
Although these vessels aren't usually made for gas exchange with the vessels being so thin, they can still be used. AA2153, AC1677 and a few other Red Blood Cells proceed through the bronchial arteries while the rest of the Red Blood Cells and U-1196 wait on the other side. When the clot dissolves, they rush in, only to find the Lung Cells lying prone on the ground. U-1196 freezes, thinking that they must have been too late, but one of the Lung Cells tells her that he's only conserving their energy while AA2153 beams at her as he holds one of the Lung Cells up.
When most people think of the heroes of the body, their first thought would be the immune system. Whenever bad things happen, these cells would be the first line of defense to protect the body. But as U-1196 says, it's a two-way street. It's only because of the Red Blood Cells that the immune system can do its job. Without the Red Blood Cells, the body wouldn't survive for very long.