"Rigor Mortis" Lecture 1 Part 1 Medical Jurisprudence HD

"Rigor Mortis" Lecture 1 Part 1 Medical Jurisprudence Rigor Mortis: It is a Latin Term which means Rigor: Stiffness Mortis: Death Synonyms: • Cadaveric Rigidity • Post Mortem Rigor • Post Mortem Rigidity • Post Mortem Stiffening It is third stage of death and one of the recognizable signs of death, caused by chemical changes in the muscles post mortem, which cause the limbs of the corpse to stiffen. In humans, rigor mortis can occur as soon as 2-4 hours post mortem. At death skeletal muscles cannot relax without oxygen, calcium accumulates in muscle, muscle become stiff or rigid. Reason of Rigor mortis or stiffness in muscles: After death the membranes of muscle cells become more permeable to calcium ions. Living muscle cells expend energy to transport calcium ions to the outside of the cells. The calcium ions that flow into the muscle cells promote the cross-bridge attachment between actin and myosin, two types of fibers that work together in muscle contraction. The muscle fibers ratchet shorter and shorter until they are fully contracted or as long as the neurotransmitter acetylcholine and the energy molecule adenosine triphosphate (ATP) are present. However, muscles need ATP in order to release from a contracted state (it is used to pump the calcium out of the cells so the fibers can unlatch from each other). When an organism dies, the reactions that recycle ATP eventually come to a halt. Breathing and circulation no longer provide oxygen, but respiration continues anaerobically for a short time. ATP reserves are quickly exhausted from the muscle contraction and other cellular processes. When the ATP is depleted, calcium pumping stops. This means that the actin and myosin fibers will remain linked until the muscles themselves start to decompose. Reasons are given below: a. When ATP level is 85% it on set. b. ATP level 85 % is a critical level. c. When ATP level is 15-30 %, this stage of Maximum Rigidity. d. ATP is required for pumping out calcium. e. ATP is required for relaxation of muscles and not for contraction. f. When ATP level is at lower level which is required for pumping out calcium than relaxation cannot occurs. g. There is continuous and progressive hydrolysis of the ATP, when the store of ATP exhausted the muscle goes into state of contraction. h. The reduction of ATP causes stiffness and rigidity. i. Rigor Mortis starts within 2-4 hours after time of primary relaxation. The degree of rigor mortis may be used in forensic pathology, to determine the approximate time of death. A dead body holds its position as rigor mortis sets in. If the body is moved after death, but before rigor mortis begins, forensic techniques such as livor mortis can be applied. If the position in which a body is found does not match the location where it is found (for example, if it is flat on its back with one arm sticking straight up), that could mean someone moved it.