Processes within the body

The Blood Clotting Cascade

Rapid blood clotting is vital when a vessel is damaged to seal the break, limit blood loss and prevent entry of pathogens. When platelets, a type of blood cell without a nucleus, comes into contact with the damaged vessel wall they change to spheres with long, thin projections. A cascade of changes results in the formation of a blood clot: Platelets stick to the damaged wall and to each other forming a platelet plug. Thromboplastin released triggers the cascade. Thromboplastin activates an enzyme that catalyzes the conversion of prothrombin to thrombin. Vitamin K and calcium ions must be present in the blood for this to take place. Thrombin catalyzes the conversion of soluble plasma protein, fibrinogen, into the insoluble protein fibrin. A mesh of fibrin forms that traps more platelets and red blood cells to form a clot.

The process of Atherosclerosis

1. The endothelium tissue inside an artery becomes damaged and dysfunctional. This can be due to high blood pressure (obesity, bad lifestyle, bad diet, smoking) which puts a strain on the layer of cells or it can occur due to toxins from smoking in the bloodstream. Once this lining becomes damaged, an inflammatory response occurs. WBCs move to the artery wall and chemicals from the blood accumulate here, such as cholesterol. A fatty deposit form called an atheroma.  Calcium salts and fibrous tissue also builds up resulting in a plaque, therefore the artery wall loses some of its elasticity. Plaques cause the artery lumen to become narrower, this makes it harder for the body to pump blood around the body, resulting in higher blood pressure. This leads to POSITIVE FEEDBACK building up.

Determining Time Of Death

Body Temperature: Body starts to cool due to the absence of heat producing reactions. This is not extremely reliable as the body temperature is dependent on other factors such as: ambient air temperature more fat means more insulation what state, clothes or not, the body is in Not extremely reliable as the body will cool down to the ambient temperature of the surroundings

Rigor Mortis Muscle cells run out of ATP due to no respiration which causes them to stiffen. But muscle molecules then break down and the body becomes floppy again. Muscles become starved of O2 and oxygen-dependent reactions stop. This turns into anaerobic respiration which produced lactic acid. pH of cells fall, inhibiting respiration and enzymes. ATP needed for muscle contractions is not produced. Bonds between muscles then become fixed. Proteins are unable to move over one another to shorten. 

Decomposition After death, tissues in the body break down due to enzymes in, for example, the digestive tract. Autolysis is where the body's own enzymes break down cells.  There are 3 stages of decomposition: In humans, a greenish discoloration of the lower abdomen is evident. Gas/liquid blisters form due to bacteria and gasses forming in tissues.  Gas is released and the body deflates. 

Entomology and Succession Insects allow for us to make estimates on time of death. Samples of insects are taken from and around the body and 'maggot mass' is measured.  Entomologists use predictable sequences of organisms that feed on decomposing bodies to determine the time of death.