Practical - Examination of artery and vein using a light microscope

Aim

To observe a cross section of artery and vein and to draw a labelled scientific diagram.

Method

  1. Collect a prepared slide of a transverse section (T.S.) of artery and vein.
  2. Use a light microscope to observe the slide under low power. Calculate the total magnification: eyepiece lens magnification × objective lens magnification.
  3. Draw a low power plan of artery and vein. Take care to represent the distribution of the different tissue layers in the correct proportions.
  4. In each vessel label the:
    • tough outer coat
    • muscle layer
    • endothelium
    • lumen

Example results - drawn

A student drew the low power plan shown here:

Student sketch of a cross section of an artery and vein

Analysis

A student was told that the actual diameter of the artery she observed was 5 mm.

The student drew a line across the diameter of the image of the artery she had drawn, as shown in the diagram (line A). She then measured this line as 70 mm.

Question

Using the equation:

\text{magnification} = \frac{\text{image size}}{\text{actual size}}

Calculate the magnification of the image she had drawn.

\text{magnification} = \frac{70~\text{mm}}{5~\text{mm}} = 14

The diameter of the image drawn was 14 times bigger than the actual artery diameter.

Question

Give one obvious difference shown in the diagram between the artery and the vein and explain why this would be an advantageous adaptation.

The muscle wall of the artery is much thicker than the muscle wall of the vein.

The artery needs this to withstand the higher pressure of the blood in the artery than in the vein.

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