Question

Heart valves located at the bases of the pulmonary trunk and aorta are called a. atrioventricular valves. b. semilunar valves. c. mitral valves. d. chordae tendineae.

Short answer

The correct name for the heart valves located at the bases of the pulmonary trunk and aorta is b. semilunar valves.

Step-by-step solution

Review the structure of the heart

The heart is a muscular organ that pumps blood throughout the body. It is divided into four chambers: the right atrium, right ventricle, left atrium, and left ventricle. There are four main valves in the heart that ensure one-way blood flow: the tricuspid valve, pulmonary valve, mitral (or bicuspid) valve, and the aortic valve.

Identify the function of each valve

1. Atrioventricular valves: These valves are located between the atria (top chambers) and ventricles (bottom chambers) of the heart. The tricuspid valve is between the right atrium and right ventricle, while the mitral valve is between the left atrium and left ventricle. These valves open when the heart is relaxed (diastole) to allow blood to flow into the ventricles and close during ventricular contraction (systole) to prevent blood from flowing back into the atria. 2. Semilunar valves: These valves are located at the exit points of the ventricles. The pulmonary valve is located at the base of the pulmonary trunk (which carries blood from the right ventricle to the lungs), while the aortic valve is situated at the base of the aorta (which carries oxygenated blood from the left ventricle to the rest of the body). These valves open when the ventricles contract, allowing blood to pass into the pulmonary trunk and aorta, and close when the ventricles relax to prevent blood from flowing back into the ventricles. 3. Mitral valve: Also known as the bicuspid valve, it is one of the atrioventricular valves specifically located between the left atrium and left ventricle. 4. Chordae tendineae: These are fibrous cords that attach the atrioventricular valves (tricuspid and mitral) to the ventricular muscle, preventing them from being pushed back into the atria when the ventricles contract.

Select the correct answer

Now that we have reviewed the functions of each valve and related structures, we can identify the correct option. The heart valves located at the bases of the pulmonary trunk and aorta are: a. atrioventricular valves. (Incorrect) b. semilunar valves. (Correct) c. mitral valves. (Incorrect) d. chordae tendineae. (Incorrect) So, the correct answer is option b. Semilunar valves.

Key concepts

Atrioventricular Valves

The atrioventricular valves are crucial components of the heart's anatomy, located between the atria and the ventricles. These valves ensure that blood flows correctly from the atria to the ventricles without backtracking. The human heart features two primary atrioventricular valves:

• Tricuspid Valve: Found between the right atrium and right ventricle, it prevents backflow into the right atrium during ventricular contraction.
• Mitral Valve (Bicuspid Valve): Situated between the left atrium and left ventricle, it ensures that blood doesn’t flow backward during ventricular contraction.

These valves open during the heart's relaxation phase (diastole) to allow blood to fill the ventricles. Then, as the ventricles contract (systole), the valves close tightly to avert any reverse blood flow.

Semilunar Valves

Semilunar valves are positioned at the junctions where blood exits the heart's ventricles. They are key in maintaining unidirectional flow into the arteries:

• Pulmonary Valve: Located at the exit of the right ventricle, it regulates blood flow into the pulmonary trunk, leading towards the lungs for oxygenation.
• Aortic Valve: Found at the exit of the left ventricle, it facilitates the passage of oxygenated blood into the aorta and then to the rest of the body.

These valves are unique due to their half-moon shape (hence the name "semilunar"), and they open when the ventricles contract, closing as pressure decreases in the ventricles to prevent any backflow from the arteries.

Chamber Structures of the Heart

The heart's structure comprises four chambers that work in tandem to pump blood effectively throughout the body. Each chamber serves a specified function in the cycle of blood circulation:

• Right Atrium: Receives deoxygenated blood from the body via the vena cavae and sends it to the right ventricle.
• Right Ventricle: Pumps the deoxygenated blood into the pulmonary arteries leading to the lungs to receive oxygen.
• Left Atrium: Takes oxygenated blood from the lungs through the pulmonary veins and propels it into the left ventricle.
• Left Ventricle: The strongest chamber, it pumps oxygen-rich blood into the systemic circulation via the aorta.

These chambers contract in a synchronized manner to ensure optimal blood flow, with the atria filling the ventricles during relaxation and the ventricles pumping blood during contraction.

Function of Heart Valves

Heart valves are essential in maintaining unidirectional blood flow within the heart. Each valve opens and closes in a specific sequence, driven by pressure differences between heart chambers and vessels. Their main responsibilities include:

• Preventing Backflow: Ensure that as the heart contracts and relaxes, blood moves only in the forward direction.
• Regulating Blood Flow: Open and close at precise moments to manage blood passage between different parts of the heart and the circulatory system.
• Ensuring Efficiency: Help maintain a steady cardiac cycle and optimize the heart's pumping efficiency.

In essence, heart valves act as one-way gates, orchestrating smooth transitions of blood from chamber to chamber, and helping the heart function seamlessly and efficiently.