Heart Anatomy Quiz

Heart Anatomy

• The heart is a four-chambered muscular organ located in the mediastinum, between the lungs.
• It is roughly the size of a fist and sits slightly angled.
• The heart wall consists of three layers: epicardium (outer), myocardium (middle, muscular), and endocardium (inner).
• The heart's chambers include two atria (superior) and two ventricles (inferior).
• The atria receive blood returning to the heart, and the ventricles pump blood out of the heart.
• The right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated blood from the lungs.
• The right ventricle pumps deoxygenated blood to the lungs, and the left ventricle pumps oxygenated blood to the body.
• The heart valves regulate the flow of blood through the heart: the tricuspid valve (between right atrium and ventricle), mitral valve (between left atrium and ventricle), pulmonary valve (between right ventricle and pulmonary artery), and aortic valve (between left ventricle and aorta).

Heart Valves

• Heart valves are crucial for preventing backflow of blood within the heart.
• The valves open and close passively due to pressure differences within the heart chambers.
• Atrioventricular (AV) valves (tricuspid and mitral) prevent backflow into the atria during ventricular contraction.
• Semilunar valves (pulmonary and aortic) prevent backflow into the ventricles during ventricular relaxation.
• Prolapse or stenosis of these valves can result in heart murmurs.

Heart Circulation

• The heart comprises two circulatory systems: pulmonary and systemic.
• The pulmonary circuit involves blood flow to and from the lungs, where gas exchange occurs.
• Deoxygenated blood is pumped from the right ventricle to the lungs via the pulmonary artery.
• Oxygenated blood returns to the left atrium via the pulmonary veins.
• The systemic circuit involves blood flow to and from the rest of the body.
• Oxygenated blood is pumped from the left ventricle to the body via the aorta.
• The aorta branches into smaller arteries, capillaries, and veins.
• Deoxygenated blood from the body returns to the right atrium via the superior and inferior vena cava.

Heart Conduction System

• The heart has its own electrical conduction system, which initiates and coordinates the rhythmic contractions.
• Sinoatrial (SA) node, the heart's natural pacemaker, initiates the electrical impulses.
• The impulses spread through the atria, causing atrial contraction.
• Atrioventricular (AV) node delays the impulse, allowing for complete atrial contraction before ventricular contraction.
• Bundle of His transmits the impulse to the ventricles.
• Purkinje fibers distribute the impulse throughout the ventricles, causing ventricular contraction.
• The electrical activity of the heart can be recorded using an electrocardiogram (ECG).

Cardiac Cycle

• The cardiac cycle describes the sequence of events that occur during one complete heartbeat.
• Systole is the period of ventricular contraction, during which blood is pumped out of the heart.
• Diastole is the period of ventricular relaxation, during which the heart fills with blood.
• Diastole is a passive phase where the heart chambers fill with blood.
• The length of the cardiac cycle is determined by heart rate, and varies between individuals.

Heart Physiology

• Cardiac output is the volume of blood pumped by each ventricle per minute.
• It is calculated by multiplying stroke volume (volume of blood pumped per beat) by heart rate.
• Factors affecting cardiac output include preload (venous return), afterload (resistance to ejection), and contractility (force of contraction).
• Stroke volume is influenced by preload and contractility.
• Heart rate is primarily regulated by the autonomic nervous system (sympathetic and parasympathetic).
• Sympathetic stimulation increases heart rate and contractility, while parasympathetic stimulation decreases heart rate.
• Hormones like epinephrine (adrenaline) can also increase heart rate.

Blood Pressure

• Blood pressure is the force exerted by blood against the walls of blood vessels.
• It is measured in millimeters of mercury (mmHg) and reported as systolic over diastolic pressure (e.g., 120/80 mmHg).
• Systolic pressure represents the peak pressure during ventricular contraction, while diastolic pressure represents the minimum pressure during ventricular relaxation.
• High blood pressure (hypertension) is a significant risk factor for cardiovascular disease.

Blood Vessels

• Blood vessels (arteries, veins, and capillaries) are integral parts of the circulatory system, transporting blood throughout the body.
• Arteries carry blood away from the heart, veins carry blood towards the heart, and capillaries are responsible for the exchange of nutrients and waste in the tissues.
• The walls of the different blood vessels exhibit variations to meet the specific needs of their functions.