A&P 2 Ch.19 Heart notes

Afterload

Force the ventricles must develop to effectively pump blood against the resistance in the vessels.

Anastomosis

Area where vessels unite to allow blood to circulate even if there may be partial blockage in another branch.

Anterior Cardiac Veins

Vessels that parallel the small cardiac arteries and drain the anterior surface of the right ventricle; bypass the coronary sinus and drain directly into the right atrium.

Anterior Interventricular Artery (Left Anterior Descending - LAD)

Major branch of the left coronary artery that follows the anterior interventricular sulcus.

Anterior Interventricular Sulcus

Sulcus located between the left and right ventricles on the anterior surface of the heart.

Aortic Valve (Aortic Semilunar Valve)

Valve located at the base of the aorta.

Artificial Pacemaker

Medical device that transmits electrical signals to the heart to ensure that it contracts and pumps blood to the body.

Atrial Reflex (Bainbridge Reflex)

Autonomic reflex that responds to stretch receptors in the atria that send impulses to the cardioaccelerator area to increase heart rate when venous flow into the atria increases.

Atrioventricular (AV) Node

Clump of myocardial cells located in the inferior portion of the right atrium within the atrioventricular septum; receives the impulse from the SA node, pauses, and then transmits it into specialized conducting cells within the interventricular septum.

Atrioventricular Bundle (Bundle of His)

Group of specialized myocardial conducting cells that transmit the impulse from the AV node through the interventricular septum; form the left and right atrioventricular bundle branches.

Atrioventricular Bundle Branches

Specialized myocardial conducting cells that arise from the bifurcation of the atrioventricular bundle and pass through the interventricular septum; lead to the Purkinje fibers and also to the right papillary muscle via the moderator band.

Atrioventricular Septum

Cardiac septum located between the atria and ventricles; atrioventricular valves are located here.

Atrioventricular Valves

One-way valves located between the atria and ventricles; the valve on the right is called the tricuspid valve, and the one on the left is the mitral or bicuspid valve.

Atrium (Atria)

Upper or receiving chamber of the heart that pumps blood into the lower chambers just prior to their contraction

Auricle

Extension of an atrium visible on the superior surface of the heart.

Autonomic Tone

Contractile state during resting cardiac activity produced by mild sympathetic and parasympathetic stimulation.

Autorhythmicity

Ability of cardiac muscle to initiate its own electrical impulse that triggers the mechanical contraction that pumps blood at a fixed pace without nervous or endocrine control.

Bachmann’s Bundle (Interatrial Band)

Group of specialized conducting cells that transmit the impulse directly from the SA node in the right atrium to the left atrium.

Bainbridge Reflex (Atrial Reflex)

Autonomic reflex that responds to stretch receptors in the atria that send impulses to the cardioaccelerator area to increase heart rate when venous flow into the atria increases.

Baroreceptor Reflex

Autonomic reflex in which the cardiac centers monitor signals from the baroreceptor stretch receptors and regulate heart function based on blood flow.

Bicuspid Valve (Mitral Valve)

Valve located between the left atrium and ventricle; consists of two flaps of tissue.

Bulbus Cordis

Portion of the primitive heart tube that will eventually develop into the right ventricle.

Bundle of His (Atrioventricular Bundle)

Group of specialized myocardial conducting cells that transmit the impulse from the AV node through the interventricular septum; form the left and right atrioventricular bundle branches.

Cardiac Cycle

Period of time between the onset of atrial contraction (atrial systole) and ventricular relaxation (ventricular diastole).

Cardiac Notch

Depression in the medial surface of the superior lobe of the left lung where the apex of the heart is located.

Cardiac Output (CO)

Amount of blood pumped by each ventricle during one minute; equals heart rate multiplied by stroke volume.

Cardiac Plexus

Paired complex network of nerve fibers near the base of the heart that receive sympathetic and parasympathetic stimulations to regulate heart rate.

Cardiac Reflexes

Series of autonomic reflexes that enable the cardiovascular centers to regulate heart function based upon sensory information from a variety of visceral sensors.

Cardiac Reserve

Difference between maximum and resting cardiac output.

Cardiac Skeleton

Reinforced connective tissue located within the atrioventricular septum; includes four rings that surround the openings between the atria and ventricles, and the openings to the pulmonary trunk and aorta; the point of attachment for the heart valves.

Cardiogenic Area

Area near the head of the embryo where the heart begins to develop 18–19 days after fertilization.

Cardiogenic Cords

Two strands of tissue that form within the cardiogenic area.

Cardiomyocyte

Muscle cell of the heart.

Chordae Tendineae

String-like extensions of tough connective tissue that extend from the flaps of the atrioventricular valves to the papillary muscles.

Circumflex Artery

Branch of the left coronary artery that follows the coronary sulcus.

Coronary Arteries

Branches of the ascending aorta that supply blood to the heart

Coronary Sinus

Large, thin-walled vein on the posterior surface of the heart that lies within the atrioventricular sulcus and drains the heart myocardium directly into the right atrium.

Coronary Sulcus

Sulcus that marks the boundary between the atria and ventricles.

Coronary Veins

Vessels that drain the heart and generally parallel the large surface arteries.

Diastole

Period of time when the heart muscle is relaxed and the chambers fill with blood.

Ejection Fraction

Portion of the blood that is pumped or ejected from the heart with each contraction; mathematically represented by stroke volume divided by end-diastolic volume.

Electrocardiogram (ECG)

Surface recording of the electrical activity of the heart that can be used for diagnosis of irregular heart function; also abbreviated as EKG.

End Diastolic Volume (EDV) (Preload)

The amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction.

End Systolic Volume (ESV)

Amount of blood remaining in each ventricle following systole.

Endocardial Tubes

Stage in which lumens form within the expanding cardiogenic cords, forming hollow structures.

Endocardium

Innermost layer of the heart lining the heart chambers and heart valves; composed of endothelium reinforced with a thin layer of connective tissue that binds to the myocardium.

Endothelium

Layer of smooth, simple squamous epithelium that lines the endocardium and blood vessels.

Epicardial Coronary Arteries

Surface arteries of the heart that generally follow the sulci.

Epicardium

Innermost layer of the serous pericardium and the outermost layer of the heart wall.

Filling Time

Duration of ventricular diastole during which filling occurs.

Foramen Ovale

Opening in the fetal heart that allows blood to flow directly from the right atrium to the left atrium, bypassing the fetal pulmonary circuit.

Fossa Ovalis

Oval-shaped depression in the interatrial septum that marks the former location of the foramen ovale.

Frank-Starling Mechanism

Relationship between ventricular stretch and contraction in which the force of heart contraction is directly proportional to the initial length of the muscle fiber.

Great Cardiac Vein

Vessel that follows the interventricular sulcus on the anterior surface of the heart and flows along the coronary sulcus into the coronary sinus on the posterior surface; parallels the anterior interventricular artery and drains the areas supplied by this vessel.

Heart Block

Interruption in the normal conduction pathway.

Heart Bulge

Prominent feature on the anterior surface of the heart, reflecting early cardiac development.

Heart Rate (HR)

Number of times the heart contracts (beats) per minute.

Heart Sounds

Sounds heard via auscultation with a stethoscope of the closing of the atrioventricular valves ('lub') and semilunar valves ('dub').

Hypertrophic Cardiomyopathy

Pathological enlargement of the heart, generally for no known reason.

Inferior Vena Cava

Large systemic vein that returns blood to the heart from the inferior portion of the body.

Interatrial Band (Bachmann’s Bundle)

Group of specialized conducting cells that transmit the impulse directly from the SA node in the right atrium to the left atrium.

Interatrial Septum

Cardiac septum located between the two atria; contains the fossa ovalis after birth.

Intercalated Disc

Physical junction between adjacent cardiac muscle cells; consisting of desmosomes, specialized linking proteoglycans, and gap junctions that allow passage of ions between the two cells.

Internodal Pathways

Specialized conductile cells within the atria that transmit the impulse from the SA node throughout the myocardial cells of the atrium and to the AV node.

Interventricular Septum

Cardiac septum located between the two ventricles.

Isovolumic Contraction (Isovolumetric Contraction)

Initial phase of ventricular contraction in which tension and pressure in the ventricle increase, but no blood is pumped or ejected from the heart.

Isovolumic Ventricular Relaxation Phase

Initial phase of the ventricular diastole when pressure in the ventricles drops below pressure in the two major arteries, the pulmonary trunk, and the aorta, and blood attempts to flow back into the ventricles, producing the dicrotic notch of the ECG and closing the two semilunar valves.

Left Atrioventricular Valve (Mitral Valve)

Valve located between the left atrium and ventricle; consists of two flaps of tissue.

Marginal Arteries

Branches of the right coronary artery that supply blood to the superficial portions of the right ventricle.

Mesoderm

One of the three primary germ layers that differentiate early in embryonic development.

Mesothelium

Simple squamous epithelial portion of serous membranes, such as the superficial portion of the epicardium and the deepest portion of the pericardium.

Middle Cardiac Vein

Vessel that parallels and drains the areas supplied by the posterior interventricular artery; drains into the great cardiac vein.

Mitral Valve (Bicuspid Valve)

Valve located between the left atrium and ventricle; consists of two flaps of tissue.

Moderator Band

Band of myocardium covered by endocardium that arises from the inferior portion of the interventricular septum in the right ventricle and crosses to the anterior papillary muscle; contains conductile fibers that carry electrical signals followed by contraction of the heart.

Murmur

Unusual heart sound detected by auscultation; typically related to septal or valve defects.

Myocardial Conducting Cells

Specialized cells that transmit electrical impulses throughout the heart and trigger contraction by the myocardial contractile cells.

Myocardial Contractile Cells

Bulk of the cardiac muscle cells in the atria and ventricles that conduct impulses and contract to propel blood.

Myocardium

Thickest layer of the heart composed of cardiac muscle cells built upon a framework of primarily collagenous fibers and blood vessels that supply it and the nervous fibers that help to regulate it.

Negative Inotropic Factors

Factors that negatively impact or lower heart contractility.

P Wave

Component of the electrocardiogram that represents the depolarization of the atria.

Pacemaker

Cluster of specialized myocardial cells known as the SA node that initiates the sinus rhythm.

Papillary Muscle

Extension of the myocardium in the ventricles to which the chordae tendineae attach.

Pectinate Muscles

Muscular ridges seen on the anterior surface of the right atrium.

Pericardial Cavity

Cavity surrounding the heart filled with a lubricating serous fluid that reduces friction as the heart contracts.

Pericardial Sac (Pericardium)

Membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium.

Pericardium (Pericardial Sac)

Membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium.

Positive Inotropic Factors

Factors that positively impact or increase heart contractility.

Posterior Cardiac Vein

Vessel that parallels and drains the areas supplied by the marginal artery branch of the circumflex artery; drains into the great cardiac vein.

Posterior Interventricular Artery (Posterior Descending Artery)

Branch of the right coronary artery that runs along the posterior portion of the interventricular sulcus toward the apex of the heart and gives rise to branches that supply the interventricular septum and portions of both ventricles.

Posterior Interventricular Sulcus

Sulcus located between the left and right ventricles on the posterior surface of the heart.

Preload (End Diastolic Volume)

Amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction.

Prepotential Depolarization (Spontaneous Depolarization)

Mechanism that accounts for the autorhythmic property of cardiac muscle; the membrane potential increases as sodium ions diffuse through the always-open sodium ion channels and causes the electrical potential to rise.

Primitive Atrium

Portion of the primitive heart tube that eventually becomes the anterior portions of both the right and left atria, and the two auricles.

Primitive Heart Tube

Singular tubular structure that forms from the fusion of the two endocardial tubes.

Primitive Ventricle

Portion of the primitive heart tube that eventually forms the left ventricle.

Pulmonary Arteries

Left and right branches of the pulmonary trunk that carry deoxygenated blood from the heart to each of the lungs.

Pulmonary Capillaries

Capillaries surrounding the alveoli of the lungs where gas exchange occurs: carbon dioxide exits the blood and oxygen enters.

Pulmonary Circuit

Blood flow to and from the lungs.

Pulmonary Trunk

Large arterial vessel that carries blood ejected from the right ventricle; divides into the left and right pulmonary arteries.

Pulmonary Valve

Valve at the base of the pulmonary trunk that prevents backflow of blood into the right ventricle; consists of three flaps.