Human Heart Anatomy

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Questions and Answers

What is the primary function of the myocardium?

To provide structure to the heart

To form the innermost layer of the heart wall

To regulate body temperature

To pump blood throughout the body (correct)

What is a characteristic of cardiac muscle fibers?

Non-striated

Voluntary in nature

Involuntary in nature (correct)

Multinucleated

How many types of muscle fibers are found in the myocardium?

Two

Three (correct)

Four

Five

What is the innermost layer of the heart wall?

Endocardium Signup and view all the answers

What is a unique property of cardiac muscle?

It is striated and has intercalated discs and gap junctions Signup and view all the answers

What is the main function of capillaries?

To exchange materials between the blood and the tissues Signup and view all the answers

What are the three layers of the aorta and artery walls?

Tunica adventitia, tunica media, and tunica intima Signup and view all the answers

What is the result of stimulation of one cardiac muscle cell?

Stimulation of all cells in the heart Signup and view all the answers

What is the characteristic of arterioles?

They have more smooth muscles Signup and view all the answers

What is the main source of energy for the cardiac muscle?

Fat Signup and view all the answers

What is the name of the vessels that offer resistance to blood flow?

Arterioles Signup and view all the answers

What is the term for the functional unity of cardiac muscle cells?

Functional syncytium Signup and view all the answers

What is the diameter of venules?

20 μ Signup and view all the answers

What is the characteristic of venules?

They have thin muscular walls Signup and view all the answers

What is the name of the vessels that can hold a large quantity of blood?

Venules Signup and view all the answers

What is the diameter of superior and inferior venae cavae?

30 mm Signup and view all the answers

What is the primary function of the sinoatrial node?

To produce cardiac impulses Signup and view all the answers

What separates the two left chambers from the two right chambers in the heart?

Continuous partition Signup and view all the answers

Which of the following veins returns venous blood from the lower parts of the body?

Inferior vena cava Signup and view all the answers

What is the main difference between the musculature of the atria and ventricles?

The ventricles have thicker muscles Signup and view all the answers

What is the function of the atrioventricular node?

To conduct impulses to the ventricles Signup and view all the answers

Which side of the heart receives oxygenated blood from the lungs?

Left side Signup and view all the answers

What is the purpose of the valves in the heart?

To prevent admixture of arterial and venous blood Signup and view all the answers

Which valve separates the left atrium and left ventricle?

Mitral valve Signup and view all the answers

What percentage of caloric needs are provided by free fatty acids under basal conditions?

60% Signup and view all the answers

What is the main source of energy for skeletal muscles, especially during exercise?

Carbohydrates Signup and view all the answers

During which phase of the cardiac cycle does the left ventricle receive its blood supply?

Diastole Signup and view all the answers

Why does the left ventricle receive its blood supply only during diastole?

Due to obstruction of coronary arteries by aortic valve leaﬂets during systole Signup and view all the answers

What percentage of oxygen delivered by each unit of blood is consumed by the cardiac muscle?

70-80% Signup and view all the answers

What is the primary mechanism of energy generation in the cardiac muscle?

Aerobic metabolism Signup and view all the answers

What happens to the cardiac muscle when oxygen delivery is obstructed?

It becomes necrotic and dies Signup and view all the answers

What percentage of total energy is generated by anaerobic metabolism in the cardiac muscle?

Less than 1% Signup and view all the answers

What is the main component of the wall of capillaries?

A single layer of flat endothelial cells Signup and view all the answers

What is characteristic of sinusoids?

Relatively large caliber with irregular and tortuous walls Signup and view all the answers

What is the functional difference between systemic and pulmonary circulation?

Systemic circulation has high resistance circuit, while pulmonary circulation has low resistance circuit Signup and view all the answers

What is true about the ventricles of the heart?

They contract simultaneously Signup and view all the answers

What is the significance of the basal lamina in capillaries?

It separates the capillary endothelium from the surrounding tissue Signup and view all the answers

What is the characteristic of the walls of veins and venae cavae?

They have less elastic tissue and more smooth muscle fibers Signup and view all the answers

What is the result of any discrepancy in the time or quantitative relations of blood flow in the heart?

Heart failure Signup and view all the answers

What is the division of the circulatory system that passes through the lungs?

Pulmonary circulation Signup and view all the answers

Study Notes

Heart Structure and Function

The heart is a hollow muscular organ located between the lungs in the mediastinum.
It consists of 4 chambers: 2 atria and 2 ventricles, separated by a continuous partition (interatrial septum and interventricular septum).
The musculature is thicker in the ventricles than in the atria.
The force of contraction of the heart depends on the muscle.

Right Side of the Heart

The right side of the heart has two chambers: right atrium and right ventricle.
The right atrium is a thin-walled, low-pressure chamber that receives venous (deoxygenated) blood from the head, neck, and upper limbs through the superior vena cava, and from the lower parts of the body through the inferior vena cava.
The right atrium has the pacemaker (sinoatrial node) and the atrioventricular node that conducts impulses to the ventricles.

Left Side of the Heart

The left side of the heart has two chambers: left atrium and left ventricle.
The left atrium is a thin-walled, low-pressure chamber that receives oxygenated blood from the lungs through the pulmonary veins.
The left ventricle pumps arterial blood to different parts of the body through the systemic aorta.

Valves of the Heart

There are no admixtures between arterial and venous blood.
The myocardium forms the bulk of the heart and is responsible for the pumping action.
Myocardium has three types of muscle fibers: contractile, pacemaker, and conductive system.

Endocardium

Endocardium is the innermost layer of the heart wall, a thin, smooth, and glistening membrane.
It is formed by a single layer of endothelial cells lining the inner surface of the heart.

Properties of Cardiac Muscle

The cardiac muscle has two types of muscle fibers: cardiac muscle proper and conductive system.
It has special properties that characterize it from other types of muscles, including:
- Histology of the cardiac muscle: unlike skeletal muscle, with anatomical connections between myocardial fibers (intercalated discs and gap junctions).
- Functional syncytium: stimulation of one cardiac muscle cell results in stimulation of all cells, allowing the heart to contract as one unit.
- Main source of energy: the cardiac muscle consumes fat as the main source of energy.
- Blood flow (supply): the cardiac muscle receives its blood supply mainly during diastole.
- Oxygen extraction: the cardiac muscle extracts a higher amount of oxygen than skeletal muscle.

Blood Vessels

The circulatory system consists of:
- Aorta
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
- Venae cavae

Arterial System

The arterial system comprises the aorta, arteries, and arterioles.
Walls of the aorta and arteries are formed by three layers: tunica adventitia, tunica media, and tunica intima.
Aorta and arteries have two laminae of elastic tissues.
Arterial branches become narrower and their walls become thinner while reaching the periphery.

Venous System

The venous system starts from the capillaries and includes venules, veins, and venae cavae.
Capillaries end in venules, which are smaller vessels with thin muscular walls.
Venules are continued as veins, which have a larger diameter.
Veins form superior and inferior venae cavae, which have a larger diameter.

Capillaries

Capillaries make a connective link between the arterioles and venules.
They are linked by a single layer of flat endothelial cells.
The capillary endothelium does not directly touch the elements of other tissues and is always separated from a supporting bed of connective tissue by an intervening layer (basal lamina).

Divisions of Circulation

Blood flows through two divisions of the circulatory system:
- Systemic circulation (greater circulation with high resistance circuit)
- Pulmonary circulation (lesser circulation with low resistance circuit)
The two systems meet in the heart.

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Description

Get familiar with the structure and functions of the human heart. Learn about the atria, ventricles, and the interatrial and interventricular septum.