Answer to Question #150304 in General Chemistry for sally

Question

Explain the mechanisms causing algor mortis, livoe mortis, and rigor mortis.

Answer 1

Immediately after death, the muscles relax, passive movements in all joints become fully possible. After 1-3 hours, the muscles contract, become dense, attempts to open the mouth, bend or straighten the limbs are very difficult. These changes are called rigor mortis.

Rigor mortis also covers the smooth muscles of the internal organs. Rigor of the muscle of the heart is clearly visible. Lifetime total compaction of all smooth and skeletal muscles is impossible, therefore rigor mortis is an absolute sign of death.

There is still no unified theory explaining this phenomenon. Difficulties in explaining the mechanism of rigor mortis are largely due to the fact that after biological death, on the one hand, muscle tissue retains some physiological properties (for example, mechanical and electrical excitability) for many hours, and on the other, biochemical processes that regulate its activity are sharply disorganized. It is believed that the excitement and contraction of muscle tissue is associated with the breakdown of adenosine triphosphate (ATP), and muscle relaxation - with its resynthesis. During the first hour after death, the level of ATP rises, which is explained by a decrease in the activity of adenosine triphosphatase due to changes in pH and massive glycogenolysis (muscles are relaxed). By the end of the first hour, a decrease in the ATP level begins, which at first occurs gradually, and then is progressive (the muscles become denser). There are no conditions for the synthesis of ATP in a corpse, so muscle contraction becomes irreversible. According to modern concepts, the essence of rigor mortis is expressed in a strong polymerization of high-molecular actomyosin structures (actin and myosin molecules), provided that plastic ATP disappears from the muscles.