L 16

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Questions and Answers

What is a characteristic feature of myocardium?

It contains intercalated discs for communication. (correct)

It consists solely of smooth muscle fibers.

It is under voluntary control.

It serves as the thickest tissue in all heart chambers.

Which chamber of the heart is the thickest part of the myocardium located?

Left atrium

Left ventricle (correct)

Right ventricle

Right atrium

What role do chordae tendinae play in the heart's function?

They facilitate the flow of blood from ventricles to arteries.

They prevent valves from opening upward into the atria. (correct)

They provide electrical impulses for heart contractions.

They connect the atria with the ventricles.

Which statement accurately describes the flow of blood through the heart?

Blood flows one way from atria to ventricles. Signup and view all the answers

What structures are responsible for supporting the heart valves?

Papillary muscles and chordae tendinae Signup and view all the answers

What significant role does the pericardium serve in relation to the heart?

It prevents over distention of the heart. Signup and view all the answers

Which structure serves as the primary pacemaker of the heart?

Sinoatrial Node Signup and view all the answers

Which of the following statements accurately describes the position of the heart?

The heart lies obliquely, more to the left. Signup and view all the answers

What complication arises from bleeding into the pericardial cavity?

Cardiac tamponade Signup and view all the answers

What is the significance of the AV nodal delay?

It ensures the atria contract before the ventricles to optimize blood flow. Signup and view all the answers

Which layer of the heart is responsible for the contraction and is the thickest?

Myocardium Signup and view all the answers

Which division of the nervous system predominantly influences the SA and AV nodes?

Parasympathetic Nervous System Signup and view all the answers

The serous membrane that secretes fluid into the pericardial cavity consists of which two layers?

Visceral and parietal layers Signup and view all the answers

What is the primary role of the Purkinje fibers in the heart?

To rapidly conduct impulses throughout the ventricles. Signup and view all the answers

How do the ventricles differ from the atria in their function?

Ventricles actively pump blood to the lungs and the body. Signup and view all the answers

Which anatomical structure is located superiorly to the heart?

Great blood vessels Signup and view all the answers

What is the main purpose of the fibrous sac of the pericardium?

To prevent over distention of the heart. Signup and view all the answers

Which of the following statements about the coronary arteries is true?

They branch from the aorta just distal to the aortic valve. Signup and view all the answers

Which structure is responsible for holding a secondary pacemaker function in case of failure of the primary pacemaker?

AV Node Signup and view all the answers

Which structures are located posteriorly to the heart?

Esophagus and descending aorta Signup and view all the answers

What role do circulating chemicals, nerve impulses, and hormones have in the heart's conducting system?

They regulate the intrinsic stimulation of cardiac muscle. Signup and view all the answers

Study Notes

Cardiovascular System Lecture Notes (L16)

The cardiovascular system is a complex system of organs responsible for transporting blood throughout the body.
The heart is a hollow muscular organ, roughly the size of the owner's fist.
The heart is located in the thoracic cavity, within the mediastinum.
It lies obliquely, positioned more towards the left side of the body.
The base of the heart is situated above, and the apex is positioned below.
The heart is positioned between the 1/3 and 2/3 of the body's long axis, from ribs 2 to 5.
Anteriorly, the heart is protected by the sternum and ribs.
Posteriorly, structures such as the esophagus, trachea, and descending aorta are situated behind the heart.
Inferiorly, the central tendon of the diaphragm is located below the heart.
Superiorly, large blood vessels like the great vessels are above the heart
Laterally, the heart is flanked by the lungs.

Heart Structure

The heart has three tissue layers: pericardium, myocardium, and endocardium.
The pericardium is a fibroserous sac, consisting of a fibrous sac (open) and a serous sac (closed).
The fibrous sac is continuous with the tunica adventitia of the great vessels and adheres to the diaphragm, preventing overdistention.
The pericardium is made of two layers - parietal (outer) and visceral (inner, or epicardium).
The fluid-filled space between the layers is called the pericardial cavity and contains serous fluid.
Serous fluid allows for smooth movement between the heart and surrounding structures.

Heart Chambers and Valves

The heart is divided into four chambers: two atria and two ventricles.
The atria are the upper chambers.
The ventricles are the lower chambers.
The heart has atrioventricular (AV) valves and semilunar valves.
AV valves are formed by double folds of endocardium strengthened by fibrous tissue which are the mitral and tricuspid valves.
The AV valves allow blood to flow from the atria to the ventricles but prevent backflow.
Semilunar valves (pulmonary and aortic valves) regulate blood flow out of the heart into arteries.

Cardiac Muscle (Myocardium)

The myocardium is specialized cardiac muscle found only in the heart.
Cardiac muscle cells are branched and contain a single nucleus.
Cardiac muscle cells are connected by intercalated discs, enabling coordinated contraction.
The myocardium is thickest at the heart's apex and thins towards the base.
Its thickness is greatest in the left ventricle.

The Conduction System of the Heart

Specialized cells within the heart form the intrinsic conduction system that automatically stimulates cardiac muscle contraction rhythmically without external impulses.
The system consists of the sinoatrial (SA) node, atrioventricular (AV) node, AV bundle (bundle of His), right and left bundle branches, and Purkinje fibers.

Nerve Supply

The vagus nerves (parasympathetic) supply the SA and AV nodes and atrial muscle.
Parasympathetic stimulation slows the heart rate and decreases the force of contraction.
Sympathetic nerves supply the SA and AV nodes and the myocardium of the atria and ventricles.
Sympathetic stimulation increases the heart rate and enhances the force of contraction.

Circulatory Pathways

Blood vessels are functionally divided into two circuits: the pulmonary circuit and the systemic circuit.
The pulmonary circuit carries blood between the heart and lungs for gas exchange (oxygenation).
The systemic circuit pumps oxygenated blood to the rest of the body from the heart.