Blood

Blood topic

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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.
Leucocytes:
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.

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Blood Tests

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.
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Staining a Blood Smear

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.
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Using a Haemocytometer

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.
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