AP Biology : Understanding Heart Anatomy

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Heart Anatomy

Which heart chamber would you expect to have the thickest myocardial wall?

Possible Answers:

The left ventricle

The right ventricle

The left atrium

The right atrium

Correct answer:

The left ventricle

Explanation:

The left ventricle is responsible for pumping blood to all body tissues. Because it needs to pump blood a farther distance than the right ventricle (which pumps blood to the lungs), it requires a thicker myocardial wall. This provides it with a more powerful contraction in order to send blood throughout the body. The left ventriclar wall is approximately three times thicker than the right ventricular wall.

The atria generally have the thinnest myocardium, as they are only responsible for receiving blood and transferring it to the ventricles.

Example Question #2 : Understanding Heart Anatomy

Placing a blood sample in a centrifuge will cause the blood to separate into three distinct sections. What is the order of the three sections from the top of the tube to the bottom?

Possible Answers:

Plasma, buffy coat, red blood cells

Buffy coat, plasma, red blood cells

Plasma, red blood cells, buffy coat

Red blood cells, buffy coat, plasma

Correct answer:

Plasma, buffy coat, red blood cells

Explanation:

A centrifuge will organize a solution into distinct sections, separating them based on their density. The least dense sections will rise to the top, while the most dense compounds will settle at the bottom. Plasma is the least dense section, so it will rise to the top section in the tube. It will be followed by the buffy coat, and the dense red blood cells will settle at the bottom of the tube.

Plasma is composed mostly of water and proteins. The buffy coat contains most white blood cells and platelets.

Example Question #2 : Understanding Heart Anatomy

Which of the following structures connects the right atrium to the left atrium in fetal circulatory systems?

Possible Answers:

Ductus venosus

Foramen ovale

Pulmonic semilunar valve

Ductus arteriosus

Correct answer:

Foramen ovale

Explanation:

The foramen ovale is needed to shunt blood away from the lungs, which are still developing in the fetus. The ductus venosus connects the umbilical vein to the inferior vena cava, while the ductus arteriosus connects the pulmonary artery to the aorta. The pulmonic semilunar valve is used in developed circulatory systems between the right ventricle and the pulmonary artery.

Example Question #3 : Understanding Heart Anatomy

Immediately after leaving the right ventricle, blood enters which structure of the circulatory system?

Possible Answers:

The aorta

The pulmonary arteries

The right atrium

The left ventricle

The pulmonary veins

Correct answer:

The pulmonary arteries

Explanation:

When blood enters the heart from systemic circulation, it is first collected in the right atrium. It then passes through the tricuspid valve into the right ventricle. To understand where the blood travels next, we must remember that this blood is deoxygenated after its passage through the body; it must pass to the lungs for oxygenation. It does so by entering the pulmonary arteries, which carry the blood away from the heart to the lungs. The pulmonary veins later return the oxygenated blood to the left side of the heart.

Example Question #4 : Understanding Heart Anatomy

What is the function of heart valves?

Possible Answers:

Control the amount of pumped blood

Slow down blood flow

Propel blood

Keep blood moving unidirectionally

Mix blood thoroughly

Correct answer:

Keep blood moving unidirectionally

Explanation:

The major function of heart valves between the chambers of the heart is to restrict blood flow to one direction. This unidirectional flow prevents backflow and mixing of blood between chambers. This allows blood to deliver nutrients and oxygen to the peripheral tissues, return carbon dioxide to the lungs, become reoxygenated in the lungs, and maintain the circulatory system cycle without traveling backward at any point in the process. The patterns of valve opening and closing ensure that the contraction of a chamber will only expel blood in one direction, rather than allowing it to exit from both opening in the chamber.

The amount of pumped blood, also known as cardiac output, is controlled by the strength and rate of heart contractions. Since the heart valves are not constructed from muscle, they are unable to contract and propel blood. The valves are passive structures composed of connective tissue. 

Example Question #1 : Understanding Heart Anatomy

In order to pump blood efficiently, cardiac muscle cells on both the left and the right side of the heart must be stimulated simultaneously. Which of the following cellular junctions is credited with allowing cardiac muscle cells to pump simultaneously?

Possible Answers:

Gap junctions

Desmosomes

Tight junctions

Adherens junctions

Actin filaments

Correct answer:

Gap junctions

Explanation:

Gap junctions allow the same action potential to be experienced by multiple neighboring cardiac muscle cells via electrical synapses. This simultaneous electrical stimulus allows for a more unified and powerful contraction by the heart.

Intercalated discs, a unique structure to cardiac muscle, also play a key role in synchronizing contraction.

Example Question #1 : Understanding Heart Anatomy

What is the name of the valve separating the right atrium from the right ventricle?

Possible Answers:

Bicuspid valve

Mitral valve

Right semilunar valve

Tricuspid valve

None of these

Correct answer:

Tricuspid valve

Explanation:

The atria and ventricles of the heart are separated by two valves, one on each side of the heart. The left atrium and left ventricle is separated by the mitral valve, also known as the bicuspid valve. The right atrium and right ventricle is separated by the tricuspid valve, named for its three flaps that work together to form the valve.

The semilunar valves separate the aorta from the left ventricle and the pulmonary artery from the right ventricle. They are commonly called the "aortic valve" and "pulmonary valve."

Example Question #2 : Understanding Heart Anatomy

Blood pumped out of the heart circulates the body and returns to the heart. Which vessel connects directly to the right atrium?

Possible Answers:

Inferior vena cava

Aorta

Superior and inferior vena cavae

Superior vena cava

Carotid artery

Correct answer:

Superior and inferior vena cavae

Explanation:

The right atrium receives blood that is returning to the heart from the body. The vena cavae are responsible for collecting the blood from the rest of the body and depositing it in this heart chamber. The superior vena cava collects blood from the head and upper extremities, while the inferior vena cava collects blood from the lower trunk and lower extremities.

The aorta is the artery that exits the left ventricle to deliver blood back to the body's tissues. The carotid artery carries blood to the head; the left branch is derived from the aorta, while the right branch is derived from the brachiocephalic artery.

Example Question #3 : Understanding Heart Anatomy

Which of the four heart chambers is the biggest and provides the greatest contractile force? 

Possible Answers:

Aorta

Left ventricle

Right atrium

Left atrium

Right ventricle

Correct answer:

Left ventricle

Explanation:

The left ventricle is the chamber responsible for pumping oxygen-rich blood throughout the entire system, as opposed to the right ventricle, which only pumps oxygen-poor blood to the lungs. This requires the cardiac muscle that makes up the walls of the left ventricle to be much thicker, and thus stronger, than that of the rest of the heart chambers. 

Example Question #5 : Understanding Heart Anatomy

Which blood vessels supply oxygen-rich blood to the heart? 

Possible Answers:

Coronary veins

Superior vena cava

Coronary arteries

Pulmonary arteries

Aorta 

Correct answer:

Coronary arteries

Explanation:

The coronary arteries supply blood to the heart. These vessels wrap around the heart muscle. Heart attacks often occur when these blood vessels become clogged, thus inhibiting blood flow to the heart, resulting in necrosis of cardiac cells. Note that the blood in the chambers of the heart is not involved in any nutrient exchange within the heart, rather, it must be pumped through capillaries where blood can supply nutrients to cells.

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