Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

18. The Heart

Cardiac Cycle

Anatomy & Physiology

18. The Heart

Cardiac Cycle

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Problem L21a

Textbook Question

A birth defect called transposition of great vessels results in the pulmonary trunk emanating from the left ventricle and the aorta stemming from the right ventricle.
Which ventricle is thicker-walled, and why?

Verified step by step guidance

Understand the anatomy of the heart: The heart has four chambers—two atria and two ventricles. The left ventricle pumps oxygenated blood to the entire body via the aorta, while the right ventricle pumps deoxygenated blood to the lungs via the pulmonary trunk.

Recognize the functional differences between the ventricles: The left ventricle must generate higher pressure to push blood through the systemic circulation, which includes all the organs and tissues of the body. The right ventricle, on the other hand, only needs to pump blood to the lungs, which is a much shorter and lower-pressure circuit.

Relate the structural adaptation to function: Because the left ventricle needs to generate higher pressure, its walls are thicker and more muscular compared to the right ventricle. This structural difference allows the left ventricle to handle the demands of systemic circulation.

Apply this knowledge to the defect described: In transposition of the great vessels, the pulmonary trunk is connected to the left ventricle, and the aorta is connected to the right ventricle. Despite the abnormal connections, the left ventricle remains thicker-walled because its structure is determined by its role in generating high pressure, not by the vessels it is connected to.

Conclude the reasoning: The left ventricle is thicker-walled because it is designed to pump blood under high pressure to the systemic circulation, which requires more muscular walls to overcome the resistance of the entire body’s blood vessels.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ventricular Structure

The heart consists of four chambers, with the left and right ventricles being responsible for pumping blood to different parts of the body. The left ventricle has a thicker muscular wall compared to the right ventricle because it needs to generate higher pressure to pump oxygenated blood throughout the systemic circulation, while the right ventricle pumps deoxygenated blood to the lungs at lower pressure.

Pressure Dynamics in the Heart

The pressure dynamics in the heart are crucial for understanding the function of the ventricles. The left ventricle must overcome the systemic vascular resistance to deliver blood effectively, resulting in a thicker wall to withstand and generate this higher pressure. In contrast, the right ventricle operates against the lower resistance of the pulmonary circulation, allowing it to have a thinner wall.

Transposition of Great Vessels

Transposition of the great vessels is a congenital heart defect where the positions of the pulmonary artery and aorta are switched. This condition leads to two separate circulatory systems: one for oxygen-poor blood and another for oxygen-rich blood, which can cause significant physiological challenges. Understanding this defect is essential for grasping the implications of ventricular wall thickness and function in this context.

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Related Practice

Textbook Question

More than one choice may apply.

Soon after the onset of ventricular systole, the

a. AV valves close.

b. semilunar valves open.

c. first heart sound is heard.

d. aortic pressure increases.

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Textbook Question

The pericardial cavity is located between:

a. The parietal pericardium and the fibrous pericardium.

b. The fibrous pericardium and the myocardium.

c. The parietal pericardium and the visceral pericardium.

d. The epicardium and the endocardium.

Which of the following statements is true?

a. The tricuspid valve is located between the right atrium and the right ventricle.

b. The mitral valve is located between the pulmonary veins and the left atrium.

c. The pulmonary valve is located between the pulmonary artery and the pulmonary veins.

d. The aortic valve is located between the right ventricle and the aorta.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

The heart consists of two superior ventricles and two inferior atria.

As Cara worked at her dissection, she became frustrated that several of the structures she had to learn about had more than one common name. Provide another name for each of these structures:

a. Atrioventricular groove

b. Tricuspid valve

c. Bicuspid valve (give two synonyms)

d. Atrioventricular bundle

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Textbook Question

The chordae tendineae:

a. The atrioventricular valves

b. Prevent the AV valve flaps from everting

c. Contract the papillary muscles

d. Open the semilunar valves