ANTH 2220 – Human Decomposition & Forensic Entomology
ANTH 2220 – Human Decomposition & Forensic Entomology ANTH 2220-01
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This 4 page Class Notes was uploaded by Jazmine Beckstrand on Friday October 7, 2016. The Class Notes belongs to ANTH 2220-01 at University of Utah taught by Derinna Kopp in Fall 2016. Since its upload, it has received 4 views.
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Date Created: 10/07/16
ANTH 2220 – Human Decomposition & Forensic Entomology Definitions Key Concepts Locations * = on exam Decomposition: the reduction of the body of a formerly living organism into simpler forms of matter. Begins immediately after cardio-pulmonary arrest Highly variable process, dependent on multiple factors: Temperature (colder --> slower decomposition, warmer --> faster) Climate Humidity Location Size of decedent Clothing Cause of death Process of decomposition can be divided into four stages: Fresh (autolysis) Bloat (putrefaction) Decay (putrefaction; insect/carnivore activity) Dry (diagenisis) Human decomposition may… Distort the features of true perimortem injuries Mimic antemortem diseases or perimortem trauma Obliterate markers of identity Autolysis: "self-digestion", cellular death Begins minutes after death The cells of the body are deprived of oxygen, causing carbon dioxide to build up in the blood The pH level decreases and wastes accumulate, which poisons the cell Enzymes are released from the intracellular lysomal sacs They begin to dissolve the cells from the inside out, causing them to rupture Bacteria and other microorganisms thrive on these unprotected organic component of the body Putrefaction: the cecum is an anatomical pouch located at the head of the large intestine. It is ground zero for microorganisms that naturally live in the body Bacteria Fungi Protozoa When the body is alive, the immune system keeps these microorganisms in check After death, the microorganisms break through the intestinal wall, spill into the abdomen, and drift into the circulatory system A flush of green over the lower abdomen can usually be seen first Purge fluid leaks Optimal environmental temperature for putrefaction is 70-90 degrees Putrefaction is delayed when the temperature is below 50 degrees Fahrenheit, or about 90 degrees Fahrenheit Black Putrefaction Gases and purge fluid escape as body collapses Odor of decay very strong Exposed flesh blackens Internal organs and tissues are of a creamy consistency Bloat Microorganisms produce gases as they slowly break down the unprotected organic components of the body These gases (Hydrogen, Methane, Ammonia, Sulfur Dioxide, etc.) cause all the body tissue to inflate These gases increase the internal pressure, which force fluids from the mouth and nose - purge These gases alone draw fluids into blisters that loosen and lift the skin - skin blisters The blisters will eventually drain, and the loose skin will slip off - skin slippage Butyric Fermentation Exposed flesh fermenting Slow drying of tissue Flesh is a cheesy consistency Dry Decay Flesh is drying out and is hardening to a leathery texture Skeletonization Most of the soft tissue is gone Bone is exposed Tendons, ligaments, and/or cartilage may still be intact Environmental factors will determine the process of decay in bone Degloving: skin covering the hands slips off at the scene. Important to locate this because fingerprints can still be obtained from it. Adipocere Also known as saponification In warm, moist environments a specific chemical reaction occurs during decomposition In the presence of bacterial enzymes, fats will react with water and hydrogen to produce a yellowish-white, greasy, wax-like substance Mummification: the end result of tissues that have survived the active decay process These tissues will be dehydrated and desiccated Occurs in environments with low humidity and dry heat End Stage Putrefaction Different from mummification The tissues will continue to decompose till there is nothing left but the skeleton Diagenisis: a natural process that serves to alter the proportion of organic (collagen), and inorganic (hydroxyapatite, calcium, magnesium), components of bone exposed to environmental conditions Last step in the decomposition process Embalming Will delay decomposition, but will not stop it completely. Entomology: the application of the study of insects and their arthropod relatives to legal proceedings. Entomological evidence - helps determine how long the person has been dead (PMI), as well as where and what time of year the death took place, areas of trauma on the body, and possible druge/chemical in the body Postmortem interval - two common methods used to determine the PMI: Insect succession: the idea that as each group of organisms feeds on a body, it changes the body, which then makes it attractive to another group of organisms. Rate of development: when the body is found, the stage of development for the insects found on the body can help investigators determine how long the person has been deceased. (Note: temperature is the most important factor for the rate of development). Hide Beetle - trox suberous; among the last insects attracted to a corpse and are usually found with dry remains. Life Cycle of a Blowfly (at 80 degrees F) Egg state (10-30 hrs.) 1st instar larva (11-38 hrs.) 2nd instar larva (8-54 hrs.) 3rd instar larva (20-96 hrs.) Migrating stage (40-50 hrs.) Puparial (4-18 days) Adult fly life (life span of 17-39 days) Life Cycle of Beetles Beetles go through a similar life cycle as flies Note: most insects are not found year-round, and are only found in certain geographical areas. Examples Secondary screwworm fly - most abundant in southeast US and is not cold tolerant Holarctic blow fly - most abundant in Canada and northwest US, including Alaska Relationships between corpse and insects Species that feed directly on a corpse Species that east the other insects that are feeding on the corpse Species that feed on both the corpse and other insects Species that use the corpse as a habitat Two most common insects found on a body Blowflies (family - calliphoridae) Flesh flies (family - sacrophagidea) Somatic death: when cardiac activity stops and respiration, reflexes, movement, and brain activity cease. Muscles, organs, tissues, and cells then begin to break down and die at different intervals Complex chemical reactions take place and certain enzymes are activated Blood becomes acidic and begins to clot
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