Cardiovascular System Study Materials Flashcards

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Pulmonary circuit

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The pulmonary circuit carries oxygen-poor blood from the right ventricle to the lungs for gas exchange and returns oxygenated blood to the left atrium. It is a short, low-pressure circulation specialized for gaseous exchange. Pulmonary arteries carry deoxygenated blood to the lungs and pulmonary veins return oxygenated blood to the heart.

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Systemic circuit

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The systemic circuit carries oxygen-rich blood from the left ventricle through the aorta to body tissues and returns oxygen-poor blood to the right atrium. It is long and operates under higher pressure and resistance than the pulmonary circuit. The left ventricle must generate greater force, reflected in its thicker walls.

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Pericardium

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The pericardium is a double-walled sac that surrounds the heart, consisting of a superficial fibrous layer and a deep two-layered serous membrane. The fibrous pericardium protects and anchors the heart while preventing overfilling. The serous pericardium has parietal and visceral layers separated by a fluid-filled pericardial cavity to reduce friction.

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Epicardium

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The epicardium is the visceral layer of the serous pericardium that lies on the external surface of the heart. It forms the outermost layer of the heart wall and often contains fat and coronary blood vessels. It reduces friction between the heart and surrounding structures during contraction.

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Myocardium

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The myocardium is the thick middle layer of the heart wall composed of spiral bundles of cardiac muscle cells. It contains the cardiac skeleton—interlacing connective tissue that anchors fibers, supports valves and vessels, and isolates electrical signals. The myocardium is responsible for the heart's contractile force.

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Endocardium

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The endocardium is the innermost endothelial lining of the heart chambers continuous with the endothelium of blood vessels. It provides a smooth, low-friction surface for blood flow and covers the cardiac skeleton and valves. It helps prevent thrombosis within the heart.

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Atria

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Atria are the two superior, thin-walled heart chambers that receive blood returning to the heart. They contribute little to pumping force but facilitate ventricular filling and press against AV valves to help them open. The right atrium receives systemic venous blood while the left atrium receives pulmonary venous blood.

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Ventricles

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Ventricles are the two inferior, thick-walled chambers that pump blood out of the heart. The right ventricle sends blood to the pulmonary trunk, while the left ventricle sends blood into the aorta. The left ventricle has walls about three times thicker than the right to generate higher systemic pressures.

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AV valves

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Atrioventricular (AV) valves separate atria from ventricles and prevent backflow into atria during ventricular contraction. The right AV valve is the tricuspid and the left AV valve is the mitral (bicuspid) valve. Papillary muscles and chordae tendineae prevent cusps from everting during contraction.

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Semilunar valves

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Semilunar valves (aortic and pulmonary) guard the bases of the large arteries leaving the ventricles and prevent backflow when ventricles relax. They open when ventricular pressure exceeds arterial pressure and close when arterial blood flows back to fill their cusps. They operate solely by pressure changes rather than muscular attachments.

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Cardiac skeleton

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The cardiac skeleton is a crisscrossing mass of dense connective tissue that anchors cardiac muscle fibers and supports valves and great vessels. It limits the spread of action potentials to specific conduction pathways and provides structural support. This helps coordinate contraction and maintain valve integrity.

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Coronary circulation

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Coronary circulation supplies oxygenated blood to the heart muscle itself, delivered mainly during ventricular relaxation. The left ventricle receives the greatest blood supply, and arterial patterns vary between individuals. Cardiac veins drain into the coronary sinus and then into the right atrium.

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Intercalated discs

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Intercalated discs are specialized cell-cell junctions between cardiac muscle cells that include desmosomes and gap junctions. Desmosomes mechanically anchor cells during contraction while gap junctions electrically couple cells, enabling the heart to function as a syncytium. They are essential for coordinated cardiac contraction.

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Pacemaker cells

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Pacemaker cells are autorhythmic cardiac cells (around 1% of cells) that generate spontaneous action potentials and set heart rhythm without nervous input. Their pacemaker potential arises from funny channels and decreased K+ conductance, then triggers Ca2+-mediated depolarization. The sinoatrial (SA) node is the primary pacemaker.

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SA node

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The sinoatrial (SA) node is the heart's primary pacemaker located in the right atrial wall and normally fires about 75 times per minute. It depolarizes faster than other myocardial tissue and initiates the impulse that spreads across the atria. Autonomic input modulates its intrinsic rate.

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AV node

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The atrioventricular (AV) node lies in the inferior interatrial septum and delays impulses by approximately 0.1 seconds. This delay allows atrial contraction to finish before the ventricles contract. In absence of SA input, the AV node can act as a subsidiary pacemaker at about 50 times per minute.

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Capillary types

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Capillaries occur as continuous, fenestrated, or sinusoid types. Continuous capillaries have tight junctions and limited permeability, fenestrated capillaries have pores for increased exchange, and sinusoids have large gaps allowing passage of cells and large molecules. Their distribution matches tissue exchange requirements.

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MCQ request

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The user-provided text simply requested: 'prepare me mcq question.' This indicates the user asked for multiple-choice question preparation. It is the minimal user instruction forming the basis for the current task.

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Study request

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The brief text input 'prepare me mcq question' functions as a study request prompting generation of multiple-choice questions and related study materials. It represents a user instruction rather than content about cardiovascular physiology. Use it to guide task format.