Topic 6 Flashcards
What can forensic pathologists use to estimate time of death?
Stage of decomposition, stage of succession, forensic entomology, body temperature, degree of muscle contraction
How is decomposition used to determine time of death?
Tissues break down after death due to action of enzymes. The first physical sign of decomposition is a greenish decolourisation of the lower abdomen, which darkens to reddish-green, then to purple/black. Gases like H2S, CH4, CO2, NH3, & H2 form in the intestines and the body starts to smell and become bloated
How is forensic entomology used to determine time of death?
The presence/lack of insects allows forensic entomologists to estimate the time of death, by taking samples found on, near, or under the body. Identifying the stage of development of maggots can give an estimate as to how long the body’s been dead
How is the temperature of the dead body used to determine time of death?
After death, the body begins to cool from the core body temperature of 36.2-37.6 C because of the absence of heat-producing chemical reactions. It takes about 24 hours to cool to the environmental temperature. Cooling of bodies follows a sigmoid curve
How is the degree of muscle contraction used to determine time of death?
After death, muscle cells are starved of oxygen, so respiration becomes anaerobic. Due to the lactic acid produced, the pH of cells falls and enzymes are denatured. Anaerobic respiration is inhibited, so ATP isn’t produced, fixing muscles in position, smaller ones first. Rigor mortis passes after break down of muscles.
What are pathogens?
Micro-organisms, like bacteria or viruses, that are able to cause disease
What causes TB?
A bacterium called Mycobacterium tuberculosis
What does AIDS stand for?
Acquired immune deficiency syndrome
Name the virus that causes AIDS?
HIV, human immunodeficiency virus
Why is Mycobacterium tuberculosis able to lie dormant?
It is able to survive and replicate inside phagocytes. The infected phagocytes get sealed away in tubercles by the immune system
Who are more likely to have latent TB become active?
People with weakened immune systems, like children, elderly people, and people with AIDS
How does TB progress, once it’s active?
- Initial symptoms include fever, general weakness, severe coughing
- Lungs are damaged as the disease progresses. If left untreated, it can cause respiratory failure, which can lead to death
- TB can also spread to other organs. Again, if left untreated, it can lead to organ failure, which can lead to death
How does HIV affect the immune system?
It infects and destroys T helper cells, the host cell for HIV. It replicates within T helper cells, and then spreads to others.
How is HIV spread?
It’s spread through infected bodily fluids that come into contact with mucous membranes, damaged tissue, or get into the bloodstream.
Explain how HIV replicates
1) GP120 attaches to a receptor molecule on T helper cell’s membrane
2) The capsid is released into the cell, uncoating and releasing the RNA into the cytoplasm
3) Reverse transcriptase makes complementary DNA to HIV’s RNA
4) HIV’s DNA is inserted into human DNA
5) Viral proteins are made from the vial DNA. The proteins are made into new viruses, which go on to infect other cells
