Take rings of artery and vein tissue. Load and unload with 10 g masses and hence assess differences in elasticity. Consider how the elastic properties suit the different functions of artery and vein in the circulatory system.

Lesson organisation

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This will depend on the availability of suitable material to work with. If material is limited, you could carry it out as a demonstration with students in turn loading and unloading the material and collating the results as a group. If so, students could be fully occupied investigating the histology of arteries and veins using microscope slides while the demonstration is under way and then work together processing the results.

Apparatus and Chemicals

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Health & Safety and Technical notes

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Eye protection is needed when stretching blood vessels in case of ‘flyback’ of bits of animal tissue if the tissue breaks.

Clear the work area before the procedure to avoid contaminating personal items, and disinfect the work area after the procedure. Careful hand washing is important to reduce the risk of possible infection from the animal material.

Decide how you will collect all the animal material and dispose of it. Make the system clear to the students.

1 You can collect material for this activity by cutting and freezing suitable rings of blood vessel tissue each time you have material for a heart/ lung dissection. Talk to your local butcher or abattoir about your needs. A ‘pluck’ – with heart and lungs still attached to one another – will provide greater lengths of blood vessels.

2 Wash and disinfect any apparatus that has come into contact with the blood vessel tissue.

3 Suitable disinfectants include sodium chlorate(I) (hypochlorite) at a concentration of at least 100 000 parts per million available chlorine, or VirKon used according to manufacturer’s instructions. Refer to the CLEAPSS Hazcard, Recipe card, and the Laboratory Handbook Section 7, pp742-743).

4 Some groups have found that some samples will support a total mass of up to 300 g.

Ethical issues

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The animal material used has not been produced for the purpose of the investigation – it is a regular by-product of the meat industry, available for consumption from some butchers, or part of the waste stream.

Some students may be sensitive to the use of any animal product in this way, or to the very fact that we breed, raise and kill animals for human consumption.

Some students may have religious objections to handling dead animal material, particularly pigs and cows, or to the method used to slaughter the animal.

Procedure

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SAFETY: Wear eye protection while stretching blood vessels.

Clean the bench thoroughly with 1% VirKon or other suitable disinfectant (Note 3).

Wash your hands thoroughly before leaving the laboratory.

Preparation

a Cut rings of similar width (about 2 mm) of artery and vein tissue (Note 1).

b Make hooks from paperclips or other suitably strong wire. Fasten a piece of tough cotton thread to them if necessary. Make sure the cotton is neither stretchy nor easily broken.

Investigation

a Take a close look at the artery and vein material. Make notes on their appearance and how each feels to the touch.

b Set up a box filled with crumpled paper beneath the apparatus to catch the masses if the tissues break.

c Suspend a ring of blood vessel from a paperclip hook on a clamp stand. Attach a mass carrier to the bottom end of the ring. Use a ruler to record the length of the ring of blood vessel with the mass carrier attached. This is the ‘original length’ for the calculation below.

d Attach a 10 g mass and record the new length of the blood vessel ring in a suitable table. (See Standard procedures.)

e Remove the mass (but not the mass carrier) and record the length of the ring.

f Repeat steps f and g using 20 g, 30 g, 40 g and 50 g masses.

g Repeat steps e to g for the other kind of blood vessel.

h Calculate percentage change in length as shown here.

i Plot suitable graphs of percentage change in length against mass for each blood vessel as it was loaded, and as it was unloaded.

j Use larger masses until the vessel does not return to its original length after loading. (Note 4.)

Teaching notes

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Have a text-based version of this activity available for students who have objections to handling the material.

Relate the observations from this investigation to information about the fibres making up the walls of arteries and veins. Gather this from texts or observations of stained microscope slides of artery and vein transverse sections. Relate the presence and proportion of elastic fibres, collagen and muscle fibres to the elastic properties of the different vessels.

If you cannot acquire suitable samples of vein, here is a sample set of results for a vein approximately 2 mm in width.

Mass	Length of vein (mm)
	Vein with mass	Vein without mass
0 (original length)	21	21
10	36	36
20	38	37
30	40	39
40	41	39
50	41	41

Downloads

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Download the student sheet  Elastic recoil in arteries and veins (64 KB) with questions and answers.

Thanks to Salters-Nuffield Advanced Biology (SNAB) for permission to use this procedure
Here are the original SNAB documents:   

Elastic recoil in arteries and veins Technician notes (45 KB)
Elastic recoil in arteries and veins Student sheet (107 KB)

Related experiments

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Modelling effect of aspirin on blood clots

Web links

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BioEthics Education Project: beep
Visit this site for definitions and guidance on evaluating the data from this investigation.
www.beep.ac.uk – How Science Works section, Reliability, accuracy and validity.

(Website accessed October 2011)