In the Aliens franchise, the facehugger places what an alien embryo (ie chestburster) inside of the host, where the chestburster quickly grows and eventually emerges from the chest of its host. My question is: where does this gestation take place? Is it the esophagus or the trachea or the stomach or some other place?


The creature lies snugly nestled between the soft organs of the abdomen until it has a final growth spurt, taps the main veins and arteries from the heart to maximize growth and escapes through the chest cavity of the victim.

The movie industries lack of scientific acumen makes the Alien franchise, particularly the chestburster alien, both disturbing but scientifically difficult to swallow (pardon the pun).

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  • Given the size of the creature from this first time Hallmark moment from Aliens, it is hard to see where the creature might be housed in the human abdomen which would not cause excruciating pain for the host, even before it decided it was time to relocate.

After attaching itself to a vein and gestating in the chest cavity, Xenomorph infants - called Chestbursters - push and chew through the host's chest, causing severe pain, blood loss, and shock. The host's rib cage is cracked open, bones bent outward. No one has survived this process.

  • Given the creature has to penetrate the rib cage (or perhaps chooses to) implies it must be residing in a space near or behind the sternum (central chest bone). Hard to believe considering you already have lungs in that spot. If this thing were sitting where one of your lungs might be, it should surely be causing pressure on the lung.

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Let's instead assume the creature is has two properties which we already know to be true:

  • It grows very fast. But this growth allows it to remain very soft and able to lie between the very snug fitting internal organs of the chest cavity, tap into a vein and dine happily until a few days before its explosion of muscular activity.

  • The last hours of growth may be what the host experiences as tightness in the chest as the creature's presence begins pressing on organs around it and in its last growth spurt gives it the muscular ability allowing it to crack the bony sternum, push up from between the organs in a burst of muscular activity and liberate itself from the host.

  • For most of the gestation, I suspect it lies wrapped around the liver and underneath a lung, maneuvering for position to increase its ability to gain access to blood. This may explain why it has to escape the chest of prey, using its final hours to maximize its use of the host's biological system for its final growth spurt.

  • I disagree. This isn't the Hulk coming up with extra mass from nowhere... even as it gets bigger, it's feeding off the host making it smaller. This means that at most we might see some abdomen swelling, for instance. Tumors happen all the time, truly huge ones where despite their size the person still survives as their internal organs are displaced. The only difference here is the rapidity of the process. – John O Feb 6 '13 at 1:05
  • Feeding off the host making it smaller? It isn't eating the host directly. It is likely metabolizing what it needs from the blood stream like any good parasite. We know the xenomorph is super-efficient in its metabolic process. It isn't eating the person from within (until it is leaving) and probably needs a bit of mass for energy until it can find food. It is growing the same way any creature grows, it eats (likely the protein-blood) until it is ready to leave. – Thaddeus Howze Feb 6 '13 at 1:30
  • It doesn't have to eat the host directly. If it's ingesting or absorbing nutrients from the host, those molecules don't materialize out of thin air. They're subtracted from the host. – John O Feb 6 '13 at 3:04

The first movie made it sound as if the alien gestates in between organs rather than in the stomach (Ash mentions that the thing shifted and forced organs into unnatural locations). If true, this tells us several things:

  1. It must have caused a lesion through the wall of the stomach/esophagus, a small one (and maybe even anesthetizes the host, since even small ulcers hurt like hell).
  2. It most likely puts pressure downward, as any upward could impact diaphragm or heart function, killing the host.
  3. It's probably using acid to make its way out of the chest (rather than physically ripping its way out), since it would have little leverage outside of the upper ribcage.

Of course, this doesn't work completely... you call it a chestburster (as everyone does) because it seems to come out right at the sternum. No one calls it an abdomenburster, though this seems a more natural exit point.

We can rule out the suggestions you've made:

  • Trachea - would impact breathing too greatly, and cause visible bulges in the neck as it matured
  • Esophagus - would have impacted swallowing and eating/drinking, and been obvious well before the thing rips out of his chest
  • Stomach - would impact eating/drinking as above, and caused him to have little appetite (he makes mention that he's hungry, does he not?)

As established in new canon, the Facehugger does not put an embryo into someone, but a mutagenic fluid that is a variaton to the black goo from Prometheus. The mutagen actually transforms some of the hosts own flesh into the chestburster, therefore, like a tumor, it can grow out anywhere within the host's body, in between the organs.

  • 1
    Hi, welcome to SF&F. While this is a reasonable answer, you could make it quite a good one if you find a quote or two to back it up. Anything from the transcript of a movie, a novelization or sanctioned book, or even a quote from one of the creators. – DavidW Feb 14 at 1:43
  • Yeah I found out about it by searching on google, I have no idea where exactly did I find this explanation. Most likely a Wiki article about the Xenomorph's lifecycle. – Kutsera Richárd Feb 18 at 7:20

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