Circulatory System Quiz

Ancient Greek Perspective

• Aristotle believed the heart was the center of the soul and nervous functions, viewing the brain as less important.

Heart Facts

• The heart pumps over one million gallons of blood per year.
• The American pygmy shrew has the fastest heart rate at 1,200 bpm.
• The blue whale has the largest heart.
• The average human heart beats approximately 115,000 times a day.
• Most heart attacks occur on Mondays.
• The heart is slightly larger than a clenched fist.

Heart Development

• The heart begins beating around 3-4 weeks of gestation.

Heart Function

• The heart acts as a double, self-adjusting suction and pressure pump.
• It circulates blood through both the pulmonary and systemic systems.
• It has its own pacemaker and regulatory systems.
• The heart simultaneously drains and sends blood to the periphery.

Blood Flow Through the Heart

• Oxygen-poor blood enters the right atrium from the superior vena cava (SVC) and inferior vena cava (IVC).
• Blood flows through the tricuspid valve into the right ventricle.
• The right ventricle pumps oxygen-poor blood to the lungs through the pulmonary arteries.
• In the lungs, blood picks up oxygen and releases carbon dioxide.
• Oxygen-rich blood returns to the left atrium through the pulmonary veins.
• Blood flows through the mitral valve into the left ventricle.
• The left ventricle pumps oxygen-rich blood to the body through the aorta.

Heart Location

• The heart is located in the thoracic cavity, between the second and sixth ribs (T5-T8).
• The base of the heart is posterior and superior.
• The apex of the heart is inferior and anterior, positioned at the fifth intercostal space.

Heart Size

• The heart is approximately 9 cm (roughly a hand's breadth) from the midclavicular line.

Heart Shape

• The heart has a pyramidal shape.
• It is tilted on its side.
• Its base is opposite the apex and faces posteriorly.

Heart Surfaces

• The sides of the heart include diaphragmatic, anterior (sternocostal), right pulmonary, and left pulmonary surfaces.
• The heart’s base has the right and left atrium close to the great vessels.

Heart Borders

• The heart has a right, left, superior, and inferior border.
• Examples of these borders: superior vena cava, aortic arch and the right atrium mark the right border.
• The inferior border is marked by the right ventricle and apex of the left ventricle.
• The left border is marked by the left ventricle and arch of aorta.

Heart Chambers

• The heart has four chambers: two atria (receiving chambers) and two ventricles (pumping chambers).
• The atria are marked by pectinate muscle walls.
• The ventricles have distinctive trabeculae carneae markings.

Heart Sulci

• There are grooves (sulci) on the heart's surface.
• These delineate the chambers and contain coronary vessels.
• Examples of these sulci are coronary suclus marking atrioventricular boundaries, and interventricular sulci separating the ventricles.

Heart Valves

• The heart possesses four valves that regulate blood flow.
• Atrioventricular valves (tricuspid and mitral) control blood flow between atria and ventricles.
• Semilunar valves (pulmonary and aortic) control blood flow from ventricles to arteries.

Heart Conduction System

• The heart's conducting system regulates the heart rhythm.
• It consists of the: sinoatrial (SA) node, atrioventricular (AV) node, atrioventricular bundle, right and left bundle branches, and Purkinje fibers.
• The SA node is the heart's natural pacemaker.
• The AV node is an important part of the system and delays the transmission of the signal to the ventricles allowing them to fill with blood before contracting.
• The impulse (signal) spreads throughout the ventricles causing them to contract simultaneously, which is very important for optimal blood flow.

Heart Autonomic Innervation

• Sympathetic stimulation speeds up heart rate and increases strength of contractions..
• Parasympathetic stimulation slows down heart rate and decreases contraction strength.
• Sensory information from receptors (baroreceptors and chemoreceptors) affects the function of the heart. This is delivered through the vagus nerve.

Coronary Arteries

• The coronary arteries arise from the aorta and supply the heart muscle with blood.
• The main branches originating from the aorta and wrapping around the heart include: the circumflex branch, the anterior interventricular branch, and the right coronary artery.
• The posterior interventricular branch.

Coronary Veins

• The coronary veins drain blood from the heart muscle.
• The main coronary vein is the coronary sinus and its tributaries. Examples of tributaries are great, middle, and small cardiac veins.
• The smallest cardiac veins drain directly into the atria.

Clinical Applications

• Valve stenosis (narrowing) and regurgitation (leaking) can affect heart function and usually require medical intervention.
• Myocardial infarction (heart attack) is a severe consequence of blocked coronary arteries.
• Stenting and coronary artery bypass grafting (CABG) are common procedures to address these issues.