PAG 2.1

Question 1

Aims

Answer 1

To examine the main blood vessels of the heart and the coronary arteries and to carry out a detailed examination of the differences between the heart chambers and walls between them. This will include producing scientific annotated drawings of the dissected mammalian heart.

Question 2

Equipment

Answer 2

• Heart from a mammal
• Tray lined with tissue / dissection board
• Scalpel
• Mounted needle
• Scissors
• Disinfectant in beaker for discarded dissection instruments
• Disposable gloves (non-latex)
• 30 cm ruler

Question 3

procedure

Answer 3

1. Spend some time examining the external surfaces of the heart and place your fingers inside the 4 chambers to feel the differences in the thicknesses of the walls. Do not make any cuts at this stage.
2. Identify the coronary artery on the external surface and locate where it comes from the aorta. If necessary, trim fat away using the scissors.
3. Use the information you have gained from steps 1 and 2 to position your heart on the dissecting board. Make sure you know which the left side of the heart is and which the right is.
4. Watch a demonstration from your teacher to show the location of the main cut and then use scissors to cut through the wall of the left atrium. Follow the cut down to the apex (bottom tip) of the left ventricle. Open up the left atrium and left ventricle to examine them.
5. Look for the tendinous cords (also called the heart strings) and how they are attached to the atrioventricular valve. The valve on this side has two flaps so is called the bicuspid valve.
6. It may be possible to see a different valve in the aorta. It is called the semi-lunar valve due to its half-moon shape.
7. Make a similar cut down the right side of the heart to open up the right atrium and ventricle. Spend some time examining the wall and internal structures.
8. Look for the atrioventricular valve on this side. It has three flaps so is called the tricuspid valve. Look for the semi-lunar valve.
9. Use a ruler to measure the thicknesses of the wall of the left and right atria and ventricles and record these values in a suitably designed table.
10. Produce a detailed scientific annotated drawing. Carefully arrange the dissected heart so that all the structures that you have identified can be easily seen. An annotated diagram should have detail about each structure added beside each label.

Question 4

1. Blood leaves the kidney via the renal vein and eventually returns to the heart. This blood will pass through a number of blood vessels, organs and chambers of the heart before it returns to the kidney via the renal vein. Name the blood vessels, organs and chambers of the heart, in the correct order.

Answer 4

1. Blood leaves the kidney via the renal vein and eventually returns to the heart. This blood will pass through a number of blood vessels, organs and chambers of the heart before it returns to the kidney via the renal vein. Name the blood vessels, organs and chambers of the heart, in the correct order. Renal vein à vena cava àright atrium à right ventricle à pulmonary artery à lungs à pulmonary vein à left atrium à left ventricle à aorta à renal artery.

Question 5

2. (a) Calculate how many times thicker the right ventricle is compared to the right atrium.

Answer 5

ventricle should be thicker than atrium

Question 6

(b) Calculate how many times thicker the left ventricle is compared to the right ventricle.

Answer 6

left ventricle should be thicker than the right

Question 7

(c) Explain your answers to (a) and (b).

Answer 7

(c) Atria are thinner walled as only generate enough of a force to pump blood into the ventricles below. Left ventricle needs to be thicker than the right to generate the pressure required for blood to circulate the entire systemic circulation whereas the right ventricle only needs to circulate blood to the pulmonary circulation.

Question 8

3. What is the function of the atrioventricular valves?

Answer 8

3. What is the function of the atrioventricular valves? Separate the atria from the ventricles, prevent blood from flowing back into the atria when ventricular systole occurs.

Question 9

4. (a) Describe the role of the coronary arteries.

Answer 9

(a) To deliver oxygen, glucose to the cardiac muscle for respiration.

Question 10

(b) What are the possible consequences of a blockage in a coronary artery?

Answer 10

) Blockage will cause these not to be delivered, respiration could be prevented, leading to death of cardiac muscle and even cardiac arrest.