COAS Biology 1 Teacher ResourcesOriginal material © Cambridge University Press 20081
5 Practical 1
Heart dissection
Safety
At the end of the practical, the hearts and any material cut from them should be wrapped up and disposed of safely. Students should wash their hands thoroughly with soap and hot water. Dissection instruments and boards should be washed with disinfectant.
Apparatus and materials
•pig or sheep heart / •blunt seeker•dissection board / •scalpel
•scissors / •surgical gloves
•forceps / •disinfectant
Introduction
In this practical, you will:
•identify the structures visible on the surface of the heart
•trace the pathway taken by blood as it flows through the heart
•dissect the heart to show how its structure enables it to carry out its function as a pump.
Procedure
1Place the heart on a dissection board with the coronary vessels on the upper side. You should be looking at the heart as seen from the front of the animal (a ventral view), as shown in Figure 5.6 on page 65 of Biology 1. Check that the left ventricle is on the right-handside – it will feel solid when pressed. The right ventricle feels softer.
2Use the photographs and drawings on page 65 of Biology 1 to help you identify the following structures:
•left and right ventricles
•left and right atria
•aorta
•pulmonary artery
•vena cava
•pulmonary veins
•coronary arteries.
Cut away any surplus fat to expose the major blood vessels at the top of the heart.
3 Make a drawing of the heart to show the main external features. Draw a ventral view, with the apex at the bottom of the drawing. Label and add a scale your drawing.
4Cut into the vena cava and then through the right atrium. From there cut into the wall of the right ventricle down to its base. Clear out any clotted blood. Open up the chambers and wash out with water if necessary.
5Examine the valve between the right atrium and the right ventricle. Measure the thickness of the walls of the two chambers.
6Trace the pathway taken by blood as it leaves the right ventricle through the pulmonary artery.
7Cut down the pulmonary artery to expose the semilunar valves.
8Make a drawing of your dissection of the right side of the heart. Label the drawing. Use annotations to describe the appearance of the structures you have drawn and their functions. Add a scale to your drawing.
9Cut into the left atrium and then into the left ventricle as far as the apex of the heart. Open the chambers and clean out as before.
10Examine the valve between the left atrium and the left ventricle. Measure the thickness of the walls of the two chambers.
11Trace the pathway of blood as it leaves the left ventricle through the aorta.
12Cut down the aorta to expose the semilunar valves. Find the origin of the coronary arteries in the aorta.
13Make a drawing of your dissection of the left side of the heart. Label the drawing. Use annotations to describe the appearance of the structures you have drawn and their functions. Add a scale to your drawing.
14Record all your measurements of wall thickness in a suitable way.
15If there are any spare hearts that have not been dissected, make some cross-sections by cutting across the hearts at different depths from top to apex. This will help you to appreciate the differences in the thickness of the chambers.
16When you have finished, dispose of the dissected material as instructed, wash the dissection board and place the instruments into disinfectant. Wash your hands thoroughly.
17aDraw up a table to compare the structure and appearance of the four chambers of the heart.
bIn one complete circuit through the heart, how does the output of blood from any one of these chambers compare with that from the other chambers?
cExplain how the valves you have displayed in your dissection ensure that blood flows through the heart.
dCalculate the ratio between the thickness of the wall of the left ventricle and that of the wall of the right ventricle.
COAS Biology 1 Teacher ResourcesOriginal material © Cambridge University Press 20081