|MadSci Network: General Biology|
Hello Jay! Thank you for your question. ***DO NOT TRY THIS AT HOME*** :) If it were ethically and legally possible to cut someone open and remove their heart for the heck of it, the heart would truly beat for only a few seconds. This is because the tissue starts to die as cells are deprived of oxygen and the electrochemical gradient across the membranes are disrupted. Atrial and ventricular fibrillation will continue for maybe 3-5 minutes more, but fibrillations do not look like true heartbeats that one would see in a movie (ex. Indiana Jones and the Temple of Doom, where the evil guy rips out the other guy's heart and it beats away like crazy). Fibrillations are disorganized electrical impulses scattering throughout the heart. These are really cool to see --- they move like little ripples along the heart. Now, what I just described above assumes you took the heart out and just left it sitting on a table somewhere. The heart can survive for longer periods of time outside the body if conditions are carefully controlled. During transplants, for example, the heart is not only kept on ice (or iced saline), but it is perfused with a special solution (very cold as well) containing adenosine, magnesium sulfate, potassium, starches, sugars... this solution helps to maintain cell viability so that the heart will survive to function properly upon implantation. Administering the cold preservation solution to the heart stops the heart from beating, which is a good indicator of how well the heart is preserved. If, during implantation, the new heart starts to beat a little before surgeons are finished sewing it in (it may be warming up from the surgery lights aimed on it), the surgeons may apply some more iced saline directly onto the heart or run another bag of preservation solution to cool it back down. Organ preservation solutions, as amazing as they are, are still only a temporary means of protecting the cells and tissue. That is why during transplants, even though the heart is protected by the cold environment and the preservation solution, the donor team (they go to retrieve the healthy organ) still moves very quickly, very efficiently, as they only have a few hours to excise the donor heart and get it to the recipient before it is no longer viable. ***For information on preservation solutions, check out http://users.surgery.wisc.edu/~southard/uwsolution.html This solution, UW, is one of the most widely used preservation solutions*** Just for an interesting tidbit, there is a very common technique for researching organs removed from the body called the Langendorff model. Basically, you perfuse organ you're interested in (let's use the heart for now) with your particular preservation solution, completely cut out the organ from the body, and connect it to this Langendorff apparatus. This setup is made up of a complex system of plastic tubing, pressure transducers, a reservoir of preservation solution, a place for oxygen to be added to the preservation solution, bubble traps (don't want to pump air into the coronary arteries or create an air lock in your tubing), filters, flowprobes, a roller pump for moving the preservation solution through the tubing, and a little place to connect your excised heart to the system. Often, researchers will crush the SA node (the natural pacemaker of the heart) and connect their own pacing wires to the heart so that they can control the heart rate for their study (this is useful in studying the heart, because changes in rhythm can alter the particular data you're collecting). The heart can continue beating for a few hours completely removed from the body via this setup. Even after a few hours, though, the heart begins to contract out of synch with the pacing, and it eventually dies simply because of the artificial environment it is in (a happy heart would much rather be in someone's chest). ***For information on the Langendorff model, check out www.quantametrics.com/exp-prod05b.htm and www.kentscientific.com/2000updatedpages/28.html These sites show diagrams of Langendorff setups and how the heart connects to them. Hope this information is helpful to you. Feel free to email me at firstname.lastname@example.org if you have more questions. Sincerely, G. Monreal
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