It can be because the blood is dirty
He or his nurse can draw blood for a test. If you want to donate blood, he doesn't do that.
To test you before the doctor comes
as the blood enters it collects oxeyen, vitamins , minerals waste and sugars .
Most blood tests are taken by a Nurse and analysed in a Lab, a Surgeon may refer to the results but would rarely take the test sample.
Blood that has perfused the lungs and is now oxygenated collects into the pulmonary veins to travel back to the heart. Once reaching the heart, oxygenated blood from the lungs enters the left atrium. The left atrium collects blood from the lungs
There is a bedside version of the test in which the doctor collects four or five drops of blood in a small tube, cools the tube in ice water for 30-60 seconds, and looks for clumping of red blood cells.
No, as the nurse will just take blood instead.
the lung collects oygenation blood
Blood banks, and the Red Cross which collects blood for blood banks, do not accept blood from people who have HIV, and they also test the blood that they collect in case it has infections that they were not warned about. Every effort is made to keep HIV out of blood that will be used for transfusions.
i have no clue
It collects oxygen
Collects fluid lost from the blood