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Chapter 11; Blood

Chapter 11; Blood. Serology; the study of bodily fluids. Living portion of blood is: Erythrocytes (red blood cells…RBCs) Leukocytes (white blood cells) Platelets. Liquid part of the blood with no cells in it is called the plasma. (Mostly water with salts, ions, proteins.) .

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Chapter 11; Blood

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  1. Chapter 11; Blood

  2. Serology; the study of bodily fluids

  3. Living portion of blood is: • Erythrocytes (red blood cells…RBCs) • Leukocytes (white blood cells) • Platelets Liquid part of the blood with no cells in it is called the plasma. (Mostly water with salts, ions, proteins.) Separation of blood

  4. BLOOD TRANSFUSIONS were not working! OUTLAWED IN MOST COUNTRIES IN EARLY 1900’S

  5. ABO Blood Typing (Karl Landsteiner – 1901) A classification of blood: A, B, AB, O Rhesus monkey factor (Rh) discovered in 1940. If you have it, you’re Rh+ and if you don’t you’re Rh-

  6. Theoretically, no two people have the same combination of blood factors and it should be possible to individualize evidence using blood, but in reality this is not the case. Testing for every factor on RBCs in not practical, and many factors break down as blood dries and ages. Blood is still important in forensics because testing can be done on both whole blood and dried bloodstains quickly and inexpensively.

  7. Antigens and antibodies

  8. Each antibodybinds to a specific antigen; an interaction similar to a lock and key. The antibody destroys the antigen

  9. THE CLUMPING TOGETHER OF RED BLOOD CELLS AGGLUTINATION

  10. Uses antibody-antigen reactions to test for blood types Lattes slide method

  11. Varies by country, ethnic group, etc.

  12. Blood typing can be used to: -show that two samples had different origins (exclude a suspect) -determine the probability of an individual having a particular blood type

  13. What is the probability that an American has type AB- blood? 4/100 x 15/100 = 60/10,000 or 0.6%

  14. Blood Tests Determines whether a substance is blood or not, but does NOT distinguish between human and animal blood. Hemastix test

  15. LUMINESCES WITH BLOOD OR SEMEN LUMINOL TEST

  16. Determines if blood is human • An animal (mammal) is injected with sample. If human, animals produce antibodies. PRECIPITIN TEST

  17. Oval red blood cells with a visible nucleus Non-mammals

  18. Circular red-blood cells • No nucleus Mammals

  19. 80 % of population • Blood type antigens are secreted in bodily fluids (saliva, semen, perspiration, gastric and vaginal secretions) Secretors

  20. Proteins that regulate chemical reactions Blood enzymes

  21. Protein components into which enzymes can be separated (1) PGM – an enzyme that has 10 variations (2) importance- allows forensic scientists to reduce the number of possible sources Iso-enzymes

  22. BLOOD SPATTER

  23. HEIGHT OF FALL • ANGLE OF IMPACT • SURFACE ON WHICH THE DROPS LAND SIZE AND SHAPE OF DROPSARE AFFECTED BY:

  24. Shape is determined by the impact angle

  25. Measure the length and width of the stain Determination of Impact Angle

  26. Divide the width by the length to get arc sine of the impact angle Width / Length = arc sine of impact angle Ex: width = 2.4 cm length = 3.1 cm Ratio of width/length = 2.4 cm / 3.1 cm = .77419

  27. Enter: “sin -1 (.77419)” Answer: 50.7 degrees 50.7 Use your calculator to get the impact angle

  28. 1. Height of drops vs. drop size 2. Angle of drop vs. drop shape 3. Surface texture vs. drop size and shape Blood spatter labs

  29. The Nobel Prize in Physiology or Medicine – Educational(Blood type simulation)

  30. American Justice; Jeffrey MacDonald

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