Cardiovascular System: The Heart
Explain why you did this exercise. Where there any safety precautions you needed to follow? If so, what were they?
The safety precautions in this exercise were to wear goggles and gloves due to being exposed to chemicals and dissection of the sheep and cat heart. Appropriate work space was also required.
Exercise 1: Microscopic Anatomy of Cardiac Muscle
Sketch and label your slide in the space provided. Include a description of the structures you observed on the slide.
See attached picture labeled cardiac muscle
A. What are some unique structural features of cardiac muscle?
Cardiac muscle is essentially limited to the heart, though it extends slightly into the nearby blood vessels. It too, is striated, but it differs from skeletal muscle. As far as the features, the cells are much shorter, so they are called myocytes rather than fibers. Cardiac muscle is considered involuntary because it is not usually under conscious control; it contracts even if all nerve connections to it are severed.
B. What are intercalated discs and what do they do?
Intercalated disks are cross-bands that separate the opposing ends of cardiac muscle cells. These bands are the result of elaborate junctions of membranes at the cell's boundary. They help to hold adjacent cells together and transmit the force of contraction from cell to cell. Intercellular junctions between the fused membranes of the intercalated disks allow diffusion of ions between the cells. This makes it possible for muscle impulses to travel rapidly from cell to cell.
C. Why does cardiac muscle have to be both elastic and strong? Cardiac muscle has to both elastic and strong to provide physical support for the cardiac muscle fibers, blood vessels, and nerves of the myocardium, help distribute the forces of contraction, add strength and prevent overexpansion of the heart and provide elasticity that helps return the heart to its original size and shape after a contraction.
D. Which of the three layers of the heart did the tissue used to make your slide originate from?
The myocardium consists of concentric layers of the cardiac muscle tissue.
Exercise 2: The Pulmonary and Systemic Circuits Questions
A. Trace the flow of blood through the pulmonary and systemic circuits. Begin in the right atrium and end in the superior/inferior vena cava. Be sure to list every vessel, heart chamber, and heart valve the blood flows through.
Blood returns to the heart from the body via two large blood vessels, called the superior vena cava and the inferior vena cava. This blood carries little oxygen, as it is returning from the body where oxygen is used. The blood first enters the right atrium. It then flows through the tricuspid valve into the right ventricle. When the heart beats, the ventricle pushes the blood through the pulmonary valve into the pulmonary artery. The pulmonary artery carries blood to the lungs where it “picks up” oxygen, and leaves the lungs and returns to the heart through the pulmonary vein. The blood enters the left atrium, and then descends through the mitral valve into the left ventricle. The left ventricle then pumps blood through the aortic valve, and into the aorta, the blood vessel that leads to the rest of the body.
B. Explain what you learned from the online human heart dissection. I learned that the heart is not perfectly symmetrical as it looks in the pictures. It is cone shaped, more hollow and about the size of an adult fist.
Dissection and Comparison
A. Compare the structure of the cat heart and sheep heart. How are they similar? How are they different? The anatomical structure of the sheep heart is much larger in size making it easier to see...
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