Technicians as demonstrators Demonstration: Pluck

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Poppy Holland
6 years ago
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1 Technicians as demonstrators Demonstration: Pluck The organs (offal) of the thoracic cavity of livestock are known collectively as the pluck. Plucks are available from abattoirs, butchers and suppliers such as They can be any animal that has come through these suppliers but you may want to take cultural differences into account with certain animals. Health and safety In terms of Health & Safety and disposal refer to CLEAPSS handbook or SSERC, good general hygiene is needed. Wash hands thoroughly after touching dissection material; gloves and safety specs can be worn (especially when cutting bone or cartridge etc). Equipment Have a selection of scalpels/blades, scissors, plastic or wooden dowel, tweezers, a board, Virkon or other disinfectant and a guide. Make sure you count all dissection tools used at the end of the lesson. The Pluck 1

Incisions Cut along the dotted lines this should allow you to see structure in left and right ventricles/atria.

2 What side of the heart is which? The right side should feel a lot more flexible than the left (due to the relative thicknesses in the ventricles walls on either side) the ventricles are the bottom chambers; the atria are the top. Incisions Cut along the dotted lines this should allow you to see structure in left and right ventricles/atria. (Taken from Practical Biology for Advanced Level, Michael Roberts, 1994) The lungs The lungs can be inflated using a rubber tube slotted into the trachea and firmly held in place. The lungs should be inflated by a hand or foot pump (doing it yourself can result in any content of the lungs being blown back when they deflate). The lungs may be damaged by cuts from the abattoirs if so place them in a plastic bag, over cover with cling film to eliminate spraying. 2

Comparing the structure of the lung Together, the lungs contain approximately the same length as 1500 miles (2,400 km) of airways and 300 to 500 million alveoli, having a total surface area of

With the passageways and alveoli the lungs are very spongy and light, you can compare the lung to the liver by trying to float them in water, the lung should float and the liver should sink.

3 Comparing the structure of the lung Together, the lungs contain approximately the same length as 1500 miles (2,400 km) of airways and 300 to 500 million alveoli, having a total surface area of about 70 m 2 in adults roughly the same area as one side of a tennis court. With the passageways and alveoli the lungs are very spongy and light, you can compare the lung to the liver by trying to float them in water, the lung should float and the liver should sink. Help learners make the journey from macroto micro-. Use evidence to imagine what the structure of lung must be like, and think about why. Cover a small sliver with water and use a hand lens to see bubbles on the surface. Compare to another tissue (why?). Look at a prepared (or downloaded) thin section of lung, and compare again. 3

Inside the atria and the ventricles you will see various valves and the heartstrings, which stop the valve flaps everting.

4 The Structure of the Heart Things to look out for in a heart dissection include the difference in size between the right and left ventricles. This size difference is due to the right only having to pump blood to the lungs via the pulmonary artery and the left size needs to pump to the rest of the body via the aorta. Inside the atria and the ventricles you will see various valves and the heartstrings, which stop the valve flaps everting. Using a plastic or wooden rod you can follow the blood vessels that connect to the heart. From the right atria you should be able to follow the vena cava (vein) back out (the vena cava supplies deoxygenated blood to the heart for it to be sent to the lungs). The rod should pop out of the pluck at some point (this allows you to differentiate between the vena cava and the pulmonary artery) you can cut sections of it to compare with the structure of the aorta. 4

Using the rod, follow the pulmonary artery into the lungs from the right ventricle.

All blood vessels leading away from the heart are arteries; all vessels leading to the heart are veins regardless whether or not they contain oxygenated or deoxygenated blood.

From the left atria you can follow the pulmonary vein in reverse, back to the lungs; this is transporting oxygenated blood to the heart to be pumped round the body.

5 Using the rod, follow the pulmonary artery into the lungs from the right ventricle. This artery transports deoxygenated blood to the lungs (they are the only arteries that carry deoxygenated blood, with the exception of umbilical arteries). All blood vessels leading away from the heart are arteries; all vessels leading to the heart are veins regardless whether or not they contain oxygenated or deoxygenated blood. Veins are lowpressure vessels; & vice versa. From the left atria you can follow the pulmonary vein in reverse, back to the lungs; this is transporting oxygenated blood to the heart to be pumped round the body. From the left ventricle you can follow the aorta out of the dissection (this allows you to differentiate between this and the pulmonary vein). The aorta is a very thick walled blood vessel as it has to cope with blood under enormous pressure being pumped from the left ventricle. You can follow it along and using scissors cut lengths of it to compare it with the vena cava which is a lot thinner walled as it s under low pressure. 5

Blood vessel comparisons Aorta (the thickest-walled artery, bang in the middle when you look at a heart from above

Coronary artery The coronary arteries supply blood to the heart muscle itself and are found on and below the

When dissecting the heart on the left ventricle just below the aorta you should cut though the coronary artery and

6 Blood vessel comparisons Aorta (the thickest-walled artery, bang in the middle when you look at a heart from above ) Vena cava Cut rings from each and do Hook s Law comparisons! Coronary artery The coronary arteries supply blood to the heart muscle itself and are found on and below the surface of the heart. When dissecting the heart on the left ventricle just below the aorta you should cut though the coronary artery and with care you can use a mounted needle to follow its path. This is a nice learning point as the artery is very small and if blocked causes angina, heart attacks or full scale cardiac infarction (death of zones of muscle). Simon Quinnell & Jeremy Airey STEM Learning 6

Fetal Pig Dissection Day 2 Circulatory and Respiratory Systems

Name: Date: Period: Fetal Pig Dissection Day 2 Circulatory and Respiratory Systems Dissection Roles (choose a different role from Day 1): Recorder reads directions out loud to group and records answers