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Dissection Tools & Kits
Sheep have a four-chambered heart, just like humans. By studying the anatomy of a sheep's heart, you can learn about how your own heart pumps blood through your body and keeps you alive! Use this as a dissection guide complete enough for a high school lab, or just look at the labeled images to get an idea of what the heart looks like. If you do the dissection yourself, you will need a preserved sheep heart.
Observation: External Anatomy
Most heart diagrams show the left atrium and ventricle on the right side of the diagram. Imagine the heart in the body of a person facing you. The left side of their heart is on their left, but since you are facing them, it is on your right.
2. Turn the heart so that the right side is on your right, as if it were in your body. Examine the flaps of darker tissue on the top of the heart. These ear-like flaps are called auricles. Find the large opening at the top of the heart next to the right auricle. This is the opening to the superior vena cava, which brings blood from the top half of the body to the right atrium (the atria are the top chambers in the heart). Stick a probe down this vessel. You should feel it open into the right atrium.
3. Sticking straight up from the center of the heart is the largest blood vessel you will see. This is the aorta, which takes oxygenated blood from the left ventricle to the rest of the body (the ventricles are the lower chambers of the heart). The aorta branches into more than one artery right after it leaves the heart, so it may have more than one opening on your heart specimen. Look carefully at the openings and you should be able to see that they are connected to each other.
4. Behind and to the left of the aorta there is another large vessel. This is the pulmonary artery which takes blood from the right ventricle to the lungs.
Dissection: Internal Anatomy1. Insert your dissecting scissors or scalpel
2. Insert your probe into the pulmonary artery and see it come through to the right ventricle. Make an incision down through this artery and look inside it for three small membranous pockets. These form the pulmonary semilunar valve which prevents blood from flowing back into the right ventricle.
3. Insert your dissecting scissors or scalpel into the left auricle at the base
4. Insert a probe into the aorta and observe where it connects to the left ventricle. Make an incision up through the aorta and examine the inside carefully for three small membranous pockets. These form the aortic semilunar valve which prevents blood from flowing back into the left ventricle.
Now consider all the parts you've found and how the blood flows through them. Draw a diagram of the heart and use red and blue arrows to show the flow of blood:
→ deoxygenated blood
Blood from the tissues → superior and inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary artery → lungs → pulmonary veins → left atrium → bicuspid (mitral) valve → left ventricle → aortic semilunar valve → aorta → body tissue.
Label the Parts of a Sheep Heart
Print out these diagrams and fill in the labels to test your knowledge of sheep heart anatomy.
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