Blood Structure and Function
Structure and Function
Blood consists of plasma > contains dissolved solutes.
Made in bone marrow.
Leucocytes are white blood cells.
Erythrocytes > 7um > Biconcave disk, small and flexible shape, no nucleus > haemoglobin.
Platelets > Small cytoplasm and membrane > no nucleus.
Neutrophils > 9um > Small granules of cytoplasm, lobed nucleus > Engulf microbes by phagocytosis.
Lymphoctyes > 5.5um > large nucleus, little cytoplasm, B and T > B produce antibodies, T destroy infected cells.
Monocytes > 13 - 20um > Large cells, bean shaped nucleus > Macrophages after 3 days in blood.
Macrophages > 15 - 20um > Large phagocytic cells in blood, also fixed.
Taking a Sample
- Taken from vein in arm or hand.
- Apply tourniquet > vein stands out.
- Alcohol swab cleans area.
- Sterile neelde sucks blood into syringe.
- Cotton wool applied.
- Gentle pressure stops bleeding.
- plaster applied.
Staining a Blood Smear
- Blood smear/thin film is made > spread blood across slide using second slide.
- Labelled > allowed to dry.
- Foxed using alcohol.
- Differential stain added > Left for 2 minutes (heat?)
- Washed off using water.
Using a Haemocytometer
- Slide etched with grid > total volume 0.1mm^3.
- Blood diluted to 1 in 200 dilution with blood pipette.
- Cells counted in 5 of the 0.004mm^3 squares.
- White cells > dilution factor is 1 in 20.
- Dilutin fluid > red cells burst > white cells counted.
- Larger squares used > volume of 0.1mm^3.