Part 2: Sheep Heart Dissection
The human heart beats about 100,000 times a day, pushing blood through 60,000 miles of vessels. One blockage in the wrong place and the whole system fails. Yesterday you read Marco's vitals. Today you go inside a real heart, trace the blood flow, and see exactly why his blockage is so dangerous. Everything you find goes in your Casebook.
You work in pairs at a shared tray. This is a real animal heart, so treat it the way you would treat any specimen in a lab: with focus and respect. A few habits keep everyone safe:
- Safety glasses on, gloves on, before you open the tray.
- Cut away from your hand, and keep the tip of every tool pointed down at the tray.
- The specimen and tools stay on the tray, never near your face.
- Follow the clean up steps at the end exactly. Your facilitator will walk you through disposal.
Knowing the anatomy is not optional here. It is the difference between catching Marco's problem and missing it. Watch how the heart works, then read his cardiology report.
- Why do doctors call the LAD the widow maker?
- If Marco's artery is 85 percent blocked, what happens to his heart during exercise?
- What do you expect to find when you dissect the heart?
Time to open it up. Go slow, make clean cuts, and compare what you see to Marco's blocked artery as you go.
Watch the tutorial all the way through before you make a single cut, then follow the same steps on your specimen.
- External anatomy. Before any cuts, examine the outside. Find the coronary arteries, the thin vessels on the surface that feed the heart muscle itself. Find the deep groove between the ventricles. Identify the great vessels: the thick aorta leaving the top, the vena cava, the pulmonary arteries.
- Open the right side. Make a careful cut down the right side. Find the tricuspid valve, three thin flaps built for the low pressure trip to the lungs. Notice how thin the wall is. This chamber has an easy job.
- Open the left side. Open the left side and find the mitral valve, two tough flaps. Then the left ventricle. Compare its wall to the right side. It is 2 to 3 times thicker, because this muscle pushes blood to every cell in your body.
- Trace the blood flow. With the probe, follow the full circuit: vena cava into the right atrium, through the tricuspid into the right ventricle, out the pulmonary artery to the lungs, back through the pulmonary veins to the left atrium, through the mitral valve into the left ventricle, and out the aorta to the body.
- Measure the walls. With your ruler, measure the wall thickness of the right ventricle and the left ventricle. Record both on your Casebook. The left should be 2 to 3 times thicker. That is why an LAD blockage, which starves the left ventricle, is so dangerous: the hardest working muscle loses its blood supply.
The human heart generates enough pressure to squirt blood about 30 feet across a room. The left ventricle you are dissecting is the powerhouse behind that force.
When you finish, follow your facilitator's disposal steps exactly. Place the heart back in its container, put gloves and paper towels in the marked waste bag, wipe your tray and tools with disinfectant, and wash your hands well with soap and water.
You held the real thing. Now lock it in. Your Casebook has a labeled heart diagram. Use it to confirm every part you found in the specimen.
- Label all four chambers, both valves you opened, and the great vessels. Match each one to what you held in your hands. If anything feels unfamiliar, go back to your specimen and find it.
- Draw the blood flow arrows through the full circuit. Your probe path should match exactly.
- In 2 to 3 sentences, explain why the left ventricle wall is thicker than the right. What does that tell you about the work each chamber does?
You have seen the anatomy up close. Now connect it to Marco's real situation.
- Based on your dissection, why is the left ventricle the most dangerous place for a blockage?
- Marco's blockage is 85 percent. What symptoms would you expect at 50 percent? At 100 percent?
- If you were Marco's cardiologist, what treatment would you recommend, and why?
On your Casebook heart diagram, find the LAD and mark it at 85 percent blocked. Predict before you shade: which wall loses its blood supply, and what happens to the heart's pumping pressure? Shade that wall and write your prediction. This is exactly how a cardiologist reads an angiogram.
- What surprised you most about the inside of the heart?
- How did holding a real heart change your understanding of heart disease?
- What would it be like to be the person who first sees an 85 percent blockage on the screen?
Someone found Marco's blockage on a screen before any surgeon touched him. That is a whole set of Valley careers, and they start closer to home than you think. Watch, then talk it over with your partner.
Valley first step: the hospital based Adult Cardiac Sonography program at Community Regional Medical Center in Fresno, one of the few in California.
Pay, roughly: around $90K and up in California.
Valley first step: a cardiovascular or allied health associate's degree, then hospital cath labs across Fresno.
Pay, roughly: around $65K and up.
Valley first step: Fresno City College nursing or a Fresno State BSN, then a cardiac or ICU unit.
Pay, roughly: around $120K and up in California.
Valley first step: a bachelor's, then medical school and a cardiology fellowship. Central Valley doctors train at UCSF Fresno.
Pay, roughly: $300K and up.
Pick the two careers that pull at you. Which one could you start the fastest? Write one step you could take while you are still in high school, then share one with the class.
You dissected a real heart, traced the full circuit of the blood, and read Marco's blockage like a cardiologist. Most people never see this in their lives. Next you scrub in and learn to close a wound.