9. Máu

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Testing blood
Use a syringe to take some blood from a vein in the patient's arm. Put the blood into a test tube. Then, use a pipette to put a drop of the blood onto a slide. Examine it under a microscope.



Blood types
Instructor: I want to show you what happens if you mix the wrong types of blood. Now , in front of you you've got test tubes with different types of blood in them. The blood in one test tube is type A. Now who can receive blood type A?
Students 1: A patient with blood type AB.
Instructor: Right So AB can receive type A. But can B receive A? What happens if you give type A to type B? Now there's some type B blood in the second test tube. If you add a drop of type A, you'll see how they react together. Now put a drop of the blood on a slide and look at it through the microscope.
Students 2: The red blood cells are joining together.
Instructor: Yes , that’s right. We call that' clumping Now the blood stops moving if the red cells clump. And of course , if the blood stops moving the patient dies. Now if we put a little of blood type O into more type A we'll see the difference.
Students 1: The red blood cells are moving. The blood looks OK
Instructor: Right. You can give type O blood to all the other blood types. So, if we have an emergency, we usually use type O. It's the universal donor.



A blood test
Nurse: How do you feel ?
Patient: Tired all the time , really - I never have any energy.
Nurse: Have you had a blood test before?
Patient: No, I haven't , no. How much blood will you take ?
Nurse: Oh , just enough to fill the syringe. — just five millilitres . Well we’ve got the results of your blood test. As I thought, you're a little bit anaemic.
Patient: Is that bad?
Nurse: No , not necessarily It just means that your red blood cell count is a little on the low side A normal count is about 4.2 to 5.4 million red blood cells per microlitre of blood , and yours was 3.9.
Patient: Oh dear - what does that mean?
Nurse: Don't worry - anaemia's very common in women. If you take iron supplements your red cell count should soon go up. The cells are normal in size and shape, so that looks good. Your white cells are a little high, but you've just had a sore throat, haven't you?
Patient: Yes .
Nurse: Well , that's just a sign that your body's been fighting the infection, so that's fine. And platelets were normal.
BLOOD PATTERN ANALYSIS
Even a tiny drop of blood at the scene of a violent crime can give important information to the police. Blood is there either because it has dripped out of a small wound, sprayed out from an artery, oozed out through a large wound, or flowed off a weapon. Using blood pattern analysis, police can learn a lot about what happened from the shape of the blood drops.
Sometimes a murderer cleans the crime scene very carefully and if detectives cannot see any blood, they spray a chemical called Luminol across the scene. This makes it possible to see the blood in the dark. Luminol can show up very small drops of blood.
From blood at the scene of a crime, police can learn about the person the blood came from. They can tell the person's blood type and, because male and female blood cells are different, they can also work out if the blood comes from a man or woman. Also, 80% of us are 'secretors', which means our blood type is contained in other bodily fluids. This can also help identify suspects
In 1984 a man, Graham Backhouse, was found injured near his home with deep cuts across his face and chest. A neighbour lay dead nearby. Backhouse said the neighbour attacked him and so he shot the neighbour to defend himself. But the shape of the blood drops showed that Backhouse was standing still when he was wounded, and there was also no blood from Backhouse on his gun or near the victim. Police were sure Backhouse shot his victim and then wounded himself. He was FOUND guilty of murder.