Week 2: PMI, entomology and osteology
Week 2: PMI, entomology and osteology ANT3520
Popular in Skeleton Keys: Introduction to Forensic Anthropology
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AP Environmental Science
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This 8 page Class Notes was uploaded by Janaki Padmakumar on Friday July 8, 2016. The Class Notes belongs to ANT3520 at University of Florida taught by Amanda Friend in Summer 2016. Since its upload, it has received 17 views.
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Date Created: 07/08/16
Week 2 notes: Lecture 6- The postmortem interval The postmortem interval- PMI The time elapsed since death Used to examine missing persons files to look for likely matches Gives an overlap from when the person went missing; rules out people missing after PMI Target law enforcement searches Time periods First 24 hours- mortis changes (specific changes to body) Day 1-month= decomposition and insects Months to years= taphonomic changes (general damage over time) Animal scavenging Soil straining or sun bleaching Transport (rolls downhill, moved through a river) Environment is also a critical factor- changes evaluation of decomposition As time since death increases, specificity decreases (can be exact within a day, after that becomes difficult to judge time of death) First 24 hours: Determination of TOD with fleshed bodies o Algor mortis- cooling of body temperature (drops 1 degree per hour in non-climate controlled setting usually) o Livor mortis- settling of blood; causes discoloration where blood pools in the body o Rigor mortis- muscle stiffness o Vitreous humors- changes in eye fluid 24 or more hours after death: Forensic entomology Forensic botany Decomposition (two methods within the body) o Autolysis- degeneration of body tissue by digestive fluids in the intestinal tract Digests the body itself like food is digested, which then lyses/consumes internal organs (thus autolysis) Stomach and intestines are first to be decomposed o Putrefaction Breakdown of biological elements by microorganism proliferation in the body Happens because of unhindered reproduction of bacterium Digestion by bacteria causes bloating due to gases being released o Stages of decomposition: Fresh corpse Bloat Active decay Advanced decay Dry (remaining tissue is dried up bc no more consumable tissue remaining) *does not strictly correlate to a time of death regardless of stage; dependent on environment and external damage, insect activity, etc. o Factors influencing decomposition rate: Temperature, humidity and accessibility (covered/uncovered by tarp, open wounds, etc) most affect decomposition Remains in warm climates have more insect activity and decompose faster Remains in dry climates desiccate (water leaves body; quasi mummification) and decompose slower Remains in the open or with open wounds attract animals- speeds decomposition o Underwater decomposition- large environment; especially relevant in Florida Dr. Anderson- ocean forensics Higher salinity areas- less bacterial decomposition, but could be affected by fish/shrimp/scavengers o Who eats the body first? Maggots (fly larvae)- develop from eggs laid in body orifices or any open wounds Beetles- larvae eat decaying wet tissues, adults prefer drier tissues Carnivores (gnawing on bones leaves damage) Rodents (parallel striations) o Insects and the PMI Show up in predictable patterns Blowflies show up first and their lifecycle can be used to calculate PMI Use ratio of beetles to flies to look at PMI Cheese flies appear 3-6 months after death Can help determine: Time since death Season of death Geographic location (some have very specific diet/area) Personal habits of decedents (location, test larvae for chemicals) o Scavenging: Do the most actual damage; get rid of large amounts of tissue at a time No scavenging damage gives clues about PMI and how remains were handled Skeletonization Forensic taphonomy o All used by forensic anthropologists; goes in order of increasing time L7 Guest lecture from the Entomology dept. Forensic entomology- use of insects and arthropods to aid legal investigations (does not have to be only criminal procedures; FDA investigations qualify as FE) Forensic= scientific tests or techniques used in connection with detection of crime Entomology= study of insects 1 Urban entomology 1 Medico criminal entomology a What we expect forensic entomology to be; none deal with store product or urban entomology b Use of necrophorous bugs to determine time and location of death Intro to insects: Most successful organisms on the planet; over 1M described organisms are insects Some beetle families have more species than birds, mammals and fish combined Size ranges from 2mm to 9 inches All have 3 segmented bodies (head, thorax and abdomen)and 6 legs, exoskeleton, wings, open circulatory system, spiracles to breath, modified body parts (antennae) Types of insect development- three different types important to determine postmortem interval Ametabolous metamorphosis o Without change o Spring tails o Get bigger and looks exactly the same o Common only in basal bugs (not many species) Gradual metamorphosis o Gradual change from immature to adult o Cockroaches, true bugs, etc. o Immature ones called nymph; look like adults but don’t have wings Complete metamorphosis (holometabolous development) o Egg to larva to pupa to adult o Larvae very different from adults o Larvae have tiny legs and no wings; phase when they feed primarily o Larvae most common life stage found in crime investigations o Instar- developmental stage of arthropods, such as insects, between each moult (ecdysis) until sexual maturity is reached o Reach threshold weight and then pupate; change from larvae to adult (completely immobile in this phase) Have to use scientific names to document insect found; common names vary by region and are inaccurate All bugs are insects, not all insects are bugs Important stages Death- Rigor mortis- Fresh o Begins right at death o Flies start to arrive 3-4 minutes o Body temperature falls to ambient temperature o Autolysis- degradation of complex protein and carbohydrate material happens o Hematophages (lice and fleas) abandon body bc no more access to blood Bloat o Stench from gas produced by bacteria o Internal temperature rises o Flies still present Decay o Bacteria and maggots break through skin o Large maggot masses; unpleasant odors o Larvae pupate o Gases lessen Post decay o Only hair, skin and bones left o Hide beetles come in o Fly population reduced Dry (skeletal) o Does not always occur especially if corpse is in a wet region o Corpse reduced to ten percent size Arthropod succession: o Necrophogous insects arrive first o Parasitoids and predators arrive second o Clean up insects are last Want negrophagous insects rather than predacious insects Evidence collection- o Collection of live and preserved insects o Seeds plants soil and pollen o Collect adult and immature o Preservation of larvae important o Collect from under the body for larvae o Use nets to collect samples from the air Live collection o Collection of live larvae for rearing o Rearing helps in identification o Adults easier to ID than larvae PMI calculations 3rd instar larval stage on a body Takes between 7-11 days at a certain temperature to reach 3rd instar phase Calculate an approximate oviposition Time taken to reach life stage calculated by Degree hours (DH) Base temp is minimum temp needed to develop from one instar to the next Take the average temperature, subtract the base temperature (DD) then add it to previous day's ADD Maggot masses Found all over a body Produce a lot of heat; affects developmental stages of insects from one phase to next Can range from 114 degrees F before maggots start dying What is bone? Two components that make it hard and elastic: o Organic and inorganic components; allows bone to react to disease and trauma; bone reproduces itself every seven years or so o Bone collagen- organic fibrous structural protein; 90% bones organic content and most common body protein; enables bone to be flexible o Hydroxyapitite- dense inorganic mineral matrix (calcium phosphate) enables bone to be strong/hard and rigid Bone cells: Osteoblasts: bone forming cell which lays down bone; evident with trauma or disease in the bone- do ossification; take calcium and phosphate and deposits it onto the bone to compose bone matrix intertwined with blood vessels Osteocyte: matured osteoblasts "trapped" in the bone Osteoclast: bone cell responsible for removal or resorption of bone cells to make space for new bone Protects vital organs, produces blood, self reproduces and restores Hydrostatic skeleton- fluid filled body cavity Exoskeletons made of chitin or calcium carbonate Endoskeleton- skeletons within bodies allow bigger size and more movement Humans have 206 bones; teeth don’t count as bone Skull composed of 8 plates; 14 facial bones Andres van Wesel-- Andres Vesalius; father of osteology, did research and found that teachings of romans concerning skeletons was grossly inaccurate; introduced human dissection- De humani corporis fabrica Most new bone tissue starts as cartilage- forms from chondrytes Matrix layer Cortical bone composes 80% mass Tribecular bone contains marrow and fat types o Hematopoesis and blood stem cells Pituitary gland controls HGH (human growth hormone) which promotes bone growth Bone remodeling- osteoblasts and osteoclasts (bone breakers); begins when osteoclasts are sent to microscopic fractures, secrete acids to break down ions, then enzymes secrete collagen; when process is complete, osteoblasts remodel bone from the cartilage Calcium reabsorbed through the body and re-laid onto bone Bone stress- fractures, exercise Ossification- intermembraneous ossification as well as cartilagenous Cortical bone- compact, long bone shafts (femur, radius, ulna, humerus etc) Outer layer is flat and irregular Trabecular (spongy/ cancellous bone) Found in the ends of long bone (acts as a shock absorber) Within flat and irregular bone Haversian systems- how compact and spongy bone works woven network of blood vessels and bones Haversian canal with both veins and arteries Volkmann's canals (transverse canals) Anatomical position importance Standard position for everyone to identify universally within the field Anatomical= hand supine position Talk in reference to skeletal right and left Sagittal plane- left and right side of body o Parasagittal- right and left but not down the middle (sagittal suture on skull) Coronal plane- front and back (through coronal suture) Transverse plane- upper and lower body Directional terms Superior- toward the head Cranial- toward the head Inferior- away from the head Caudial- toward the tail Anterior- front Posterior- back Dorsal- toward the back Ventral- towards the stomach Medial- toward midline Lateral- away from midline Proximal- closest to the torso Distal- furthest from the torso Hands and feet Palmar: palm side Plantar- sole of the foot Dorsal- top of the foot or back of the hand Cranium (specialized bone network) Ectocranial- outer surface of the cranial vault Endocranial- inner surface of the cranial vault Cranial- cranium and mandible Post cranial- all skeletal elements other than the skull Axial vs appendicular Axial are bones found on the torso o Skull, vertebrae, sacrum, ribs and sternum Appendicular are bones found in the arms and legs o Legs, arms, feet, pectoral and pelvic girdle Osteometry- measurements of human bone, used in anthropology and archaeology; determine age in young skeletons, sex, ancestry and height Osteometric devices Spreading calipers- slide out, used to measure the cranium Sliding calipers- measuring face and mandible, long bones; measure trauma like fracture lines Mandibulometer- used to measure the mandible and its angle, used to determine biological factors about an individual Osteometric board- bone length measurement Error margins present for devices Osteometric points-standardize measurements between populations Standardized points on the skull o Unpaired- found on midsagittal plane o Paired- either side of the midsagittal plane; equidistant to sagittal plane (but not every human is perfectly symmetrical) Enables comparative data and statistical analysis of different populations Anatomically determined measurements and instrumentally determined measurements (maximum lengths) Standard measurements Cranium= 24 different measurements of the cranium Mandible=10 Postcranium= 44 FORDISC (Forensic discriminant functions) 3.0 program developed by Jantz and Ousley (2005)
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