Forensic Pathology - Forensic Pathology Definition of Death...

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Forensic Pathology Definition of Death A person is dead if: He has suffered irreversible cessation of circulatory and respiratory functions Or, he as suffered irreversible cessation of all functions of the entire brain, including the brain stem Brain death: Coma and cerebral unresponsiveness, Apnea, Dilated pupils, Absent cephalic (brainstem)reflexes, Electrocerebral silence Reversibility of Death Dependent upon capability of tissues to recover from anoxia Resistance of organs variable CNS has high sensitivity Approx. 4-6 min. between loss of oxygen and irreversible brain damage With cutting edge techniques may be 15-16 minutes Age and temperature cause variability-- up to 30 min. Brain Death Physical characteristics: Grayish appearance, marked swelling, herniation, anoxic damage, liquefaction Brain death changes become apparent 12-16 hrs. after end of cerebral circulation Persistent Vegetative State (PVS) Different from brain death Total permanent and total destruction of frontal lobe Postmortem Changes Once dead, bodily functions cease and body begins to break down Circulation stops, chemical composition of body fluids changes, digestion ends, natural bacteria in gut takes over, animals begin to feed on body Happens in particular order--“postmortem clock” Algor Mortis Body cools to ambient temperature Cools at rate of 1.5o F to 2o F per hour Skin cools fastest, and isn’t used in body
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temp determination Body core temps used--rectum, liver, brain Rate of cooling changes with clothing, body fat, air currents, immersion in water, size Ocular Changes Eyes show some of the earliest postmortem changes Settling of rbc’s in capillaries Thin film on cornea within 2-3 minutes, cloudiness within 2-3 hours If open, exposed areas develop tache noire (black spot) Intraocular fluid--dries up in about 4 days Vitreous Potassium Potassium levels in the eye much higher than potassium levels in the blood Due to the sodium-potassium pump After death pump no longer works, so postassium diffuses out Known rate: (7.14 x K+ concentration) - 39.1 = hours since death Livor Mortis Purplish-blue discoloration due to settling of blood by gravitational forces within capillaries May be evident as early as 20 min. after death Fixed after 8-12 hours Rigor Mortis Right after death, muscles flaccid Ca still present, but ATP no longer produced Ca binds to troponin, actin/myosin form cross bridges As body proteins decompose, bridges break Rule of thumb: takes 12 hours to appear fully, lasts 12 hours, takes 12 hours to disappear Variable: previous exercise, convulsions, electrocution, heat Cadaveric Spasm
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