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For my STEAM project, I chose to demonstrate the progression of decomposition of tissue, specifically in terms of decomposing outdoors. I chose to draw my project due to digital art being my typical medium, and I knew I could create something interesting to look at. In my drawing, the wolf-like creature has a section of decomposition, with each stage illustrated in a different color.
The first stage of decomposition doesn’t actually begin with the breakdown of muscle tissue, instead, it begins with the shutdown of myosin and actin units, causing a lack of calcium and adenosine triphosphate (ATP). Without calcium and ATP, there is no possibility for muscle contraction, causing the muscle fibers to contract and be unable to relax. This process is called Rigor Mortis, and typically lasts 24-48 hours.
After Rigor Mortis, the proteolytic enzymes will begin to disrupt the myosin/actin units, causing the cross linkages to break down and allow the muscles to relax. Inside the cells, the lysosome reacts to the dropped pH level due to blood cells no longer taking the carbon dioxide out of the body, which in turn causes all of the enzymes inside the lysosome to break out of their membrane. These enzymes are aggressive, and will break down every part of the cell they once inhabited. This process is called autolysis, and often begins in the stomach and liver, but will eventually affect the entire body’s tissue cells. It is quick moving once it gains access to the ulterior tissues such as the muscles, and eventually breaks through to the skin’s surface from the inside out.
Bacteria are another major piece of the decomposition process, as they are often faster at breaking down the tissues than the proteolytic enzymes released by the lysosomes. Bacteria lives within most living beings, although the function of blood pumping through the system allows the bacteria waste to be flushed out, and creates a livable ecosystem for healthy bacteria. When the blood flow stops at death, the bacteria begin to eat at the tissues of the body in order to sustain themselves, progressing the process of decomposition alongside the proteolytic enzymes.
There are a couple of different factors that can either speed up or slow down the process of decomposition. Temperature, for one, is a major factor in the process of decomposition. In a hot climate, decomposition will take place in a much quicker fashion, due to the bacteria being able to prosper off of the tissues. In a cold environment, the bacteria won’t be able to eat away at the tissues, due to the possibility of becoming too cold and dying off. This is often why scientists find preserved specimens in cold climates due to their inability to break down in the extreme temperatures. Another major player is moisture. For example, a body decomposing in a desert may not decompose completely, due to the arid environment drying up the cells and bacteria before they can complete their job of breaking down the tissues. In a wet climate, however, moisture allows bacteria to prosper, so they can continue eating away at the body.
Overall, decomposition is a fairly straightforward process, even on the molecular level. Environment, temperature, and the cause of death can tweak the outcome by only a fraction, leaving every living thing to revert back into the soil.
References:
Decomposition – Process, Factors Affecting Decomposition. (n.d.). BYJUS. https://byjus.com/biology/what-is-decomposition/
Hau, Hamzah, & Lian. (2014). Decomposition Process and Post Mortem Change: Review [Review of Decomposition Process and Post Mortem Change: Review]. https://www.researchgate.net/profile/Noor-Hazfalinda-Hamzah/publication/270236666_Decomposition_Process_and_Post_Mortem_Changes_Review_Proses_Pereputan_dan_Perubahan_Pasca_Kematian_Ulasan/links/54a3aa800cf256bf8bb0e769/Decomposition-Process-and-Post-Mortem-Changes-Review-Proses-Pereputan-dan-Perubahan-Pasca-Kematian-Ulasan.pdf
Hayman, J., & Oxenham, M. (2016). Human Body Decomposition. In Google Books. Academic Press. https://books.google.com/books?hl=en&lr=&id=q8O3CgAAQBAJ&oi=fnd&pg=PP1&dq=stage+of+decomposition+in+humans&ots=bQxYYJiq9s&sig=3PtzjnWM8Fe06x4Rkwc86Ro-eHw#v
McGill University. (2021, July 18). Office for Science and Society. https://www.mcgill.ca/oss/article/general-science/death-our-body-feasts-itself
I enjoyed your take on the body decomposition abstract. As most people choose hands or the whole person, where each finger would represent a different stage in the decomposition process. You chose to do a internally focused approach, having the decomposition progress more as from the innermost structure- the eye, to the outermost, the epidermis. Your project was organized fairly well, with there being no filler information or facts that would bloat the essay. Each stage was represented relatively clear. I had originally thought that Rigor Mortis peaked at 12 hours, then ended at 18, but I see now that it last 24-48 hours. I found myself somewhat confused on the first paragraph detailing the molecular process of rigor mortis. It says it starts with the shutdown of the myosin and actin units. which result in a lack of calcium and ATP. Later on rigor mortis is said to end by the proteolytic enzymes breaking down the myosin and actin units. breaking apart the cross bridges, ending the continuous muscle contraction. If the actin and myosin units are shut down initially, which causes rigor mortis, then how does the proteolytic enzymes break them down later on, during which they are still forming cross bridges. I thought that the last half of the essay was done well. The external factors effecting the rate of decomposition were explained well. The higher the temperature, the more bacteria are able to survive and thrive. the higher humidity and rain. The water will provide breeding grounds for the bacteria. The colder the climate, the less bacteria will be able to survive, potentially stopping the decomposition if the body is frozen fully. I was fascinated to learn about the CO2 unable to leave the body entirely, causing the lysomes to break out of their membranes and start autolysis, where they release all of their enzymes destroying the body’s tissues internally. Overall this is a well structured, entertaining project.