Heart Structure, Blood Flow, and Cardiac Cycle

What are the two major circuits of the cardiovascular system?

Pulmonary circuit and systemic circuit.

What is the primary function of the pulmonary circuit?

Releases CO₂ and absorbs O₂ in the lungs.

What is the primary function of the systemic circuit?

Delivers O₂ to body tissues and picks up CO₂.

Where is the heart located?

In the mediastinum, the region of the chest cavity between the lungs.

What is the approximate size of the heart?

About the size of a closed fist.

What is the apex of the heart?

The pointed, inferior portion directed toward the left side.

What structure separates the right and left atria?

Interatrial septum.

What are the two types of heart valves?

Atrioventricular (AV) valves and semilunar valves.

What is the function of heart valves?

Prevent blood from flowing backward and ensure blood moves in one direction.

What is the role of the myocardium?

It is the middle layer of the heart wall responsible for the heart's contractions.

What is the pericardium?

The protective covering surrounding the heart.

What is the function of the coronary arteries?

They provide the heart muscle with its own blood supply.

What is the pathway of deoxygenated blood through the heart?

Superior/inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk → lungs.

What is the pathway of oxygenated blood through the heart?

Pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta.

What is the significance of the coronary sinus?

It returns blood from the cardiac muscle to the right atrium.

What are pectinate muscles?

Muscular ridges inside the atria.

What are trabeculae carneae?

Muscular ridges inside the ventricles.

Which valve is located between the left atrium and left ventricle?

Left AV (mitral) valve.

What happens to the AV valves during ventricular systole?

They close.

What happens to the semilunar valves during ventricular diastole?

They close.

What is the role of papillary muscles?

They help prevent AV valve cusps from turning backward into the atria during ventricular contraction.

What is a myocardial infarction?

A heart attack caused by the death of heart muscle tissue due to inadequate blood supply.

What is the difference between pulmonary arteries and pulmonary veins?

Pulmonary arteries carry deoxygenated blood; pulmonary veins carry oxygenated blood.

What is the epicardium?

The outermost layer of the heart wall, a serous membrane attached to the heart's surface.

What is the endocardium?

The innermost layer of the heart, a simple squamous epithelial lining of the heart chambers.

What is the cardiac conduction system?

A system of specialized noncontractile cells that generate and conduct electrical signals to coordinate heart contractions.

What is the function of the Sinoatrial (SA) node?

It is the natural pacemaker of the heart that initiates electrical impulses.

What role does the Atrioventricular (AV) node play?

It receives electrical excitation from the atria.

What is the AV bundle (bundle of His) responsible for?

Conducting electrical signals toward the ventricles.

What do the right and left bundle branches do?

They carry electrical signals toward the ventricular apex.

What is the purpose of Purkinje fibers?

They distribute excitation through the ventricular myocardium.

What is the sequence of the cardiac electrical conduction pathway?

SA node fires → Excitation spreads through atrial myocardium → AV node receives excitation → AV bundle → bundle branches → Purkinje fibers excite ventricular myocardium.

What are cardiac muscle cells called?

Cardiomyocytes.

What are intercalated discs?

Specialized connections that join adjacent cardiac muscle cells.

What is the difference between desmosomes and gap junctions?

Desmosomes provide mechanical connections, while gap junctions provide electrical connections.

How does the autonomic nervous system (ANS) affect the heart?

The ANS regulates the heart's intrinsic activity, with the sympathetic division stimulating the heart and the parasympathetic division slowing it.

What occurs during systole?

Contraction of a heart chamber.

What occurs during diastole?

Relaxation of a heart chamber.

What does an electrocardiogram (ECG/EKG) record?

The heart's electrical activity.

What does the P wave in an ECG represent?

Atrial depolarization.

What does the QRS complex in an ECG indicate?

Ventricular depolarization.

What does the T wave in an ECG signify?

Ventricular repolarization.

When does the heart begin to beat during embryonic development?

Around the fourth week of embryonic development.

What is the function of the foramen ovale before birth?

It diverts blood away from pulmonary circulation.

What does the ductus arteriosus connect?

It connects the pulmonary trunk to the aorta, bypassing the lungs.

What happens to the foramen ovale after birth?

It seals and becomes the fossa ovalis.

What is coronary atherosclerosis?

Plaque buildup in the coronary arteries.

What is a congenital heart defect?

A structural heart abnormality present at birth.

What is myocardial hypertrophy?

Abnormal thickening/enlargement of heart muscle.

What is pericarditis?

Inflammation of the pericardium.

What is myocarditis?

Inflammation of the myocardium.

What is endocarditis?

Inflammation of the endocardium.

What is a valvular defect?

An abnormality of a heart valve.