58 Glossary: The Circulatory System

Glossary

albumin  most abundant plasma protein, accounting for most of the osmotic pressure of plasma

anastomosis  (plural = anastomoses) 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  (also, left anterior descending artery or 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

antibodies  (also, immunoglobulins or gamma globulins) antigen-specific proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses

aortic valve  (also, aortic semilunar valve) valve located at the base of the aorta

arteriole (also, resistance vessel) very small artery that leads to a capillary

arteriovenous anastomosis short vessel connecting an arteriole directly to a venule and bypassing the capillary beds

artery blood vessel that conducts blood away from the heart; may be a conducting or distributing vessel

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  (plural = atria) upper or receiving chamber of the heart that pumps blood into the lower chambers just prior to their contraction; the right atrium receives blood from the systemic circuit that flows into the right ventricle; the left atrium receives blood from the pulmonary circuit that flows into the left ventricle

auricle extension of an atrium visible on the superior surface of the heart

bicuspid valve (also, mitral valve or left atrioventricular valve) valve located between the left atrium and ventricle; consists of two flaps of tissue

blood  liquid connective tissue composed of formed elements—erythrocytes, leukocytes, and platelets—and a fluid extracellular matrix called plasma; component of the cardiovascular system

buffy coat  thin, pale layer of leukocytes and platelets that separates the erythrocytes from the plasma in a sample of centrifuged blood

capacitance ability of a vein to distend and store blood

capacitance vessels veins

capillary smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid

capillary bed network of 10–100 capillaries connecting arterioles to venules

cardiac notch  depression in the medial surface of the inferior lobe of the left lung where the apex of the heart is located

cardiac skeleton (also, skeleton of the heart) 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

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 

continuous capillary most common type of capillary, found in virtually all tissues except epithelia and cartilage; contains very small gaps in the endothelial lining that permit exchange

coronary arteries branches of the ascending aorta that supply blood to the heart; the left coronary artery feeds the left side of the heart, the left atrium and ventricle, and the interventricular septum; the right coronary artery feeds the right atrium, portions of both ventricles, and the heart conduction system

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

elastic artery (also, conducting artery) artery with abundant elastic fibers located closer to the heart, which maintains the pressure gradient and conducts blood to smaller branches

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

external elastic membrane membrane composed of elastic fibers that separates the tunica media from the tunica externa; seen in larger arteries

fenestrated capillary type of capillary with pores or fenestrations in the endothelium that allow for rapid passage of certain small materials

fibrinogen  plasma protein produced in the liver and involved in blood clotting

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

formed elements  cellular components of blood; that is, erythrocytes, leukocytes, and platelets

fossa ovalis oval-shaped depression in the interatrial septum that marks the former location of the foramen ovale

globulins  heterogeneous group of plasma proteins that includes transport proteins, clotting factors, immune proteins, and others

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

hematocrit  (also, packed cell volume) volume percentage of erythrocytes in a sample of centrifuged blood

hypertrophic cardiomyopathy pathological enlargement of the heart, generally for no known reason

immunoglobulins  (also, antibodies or gamma globulins) antigen-specific proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses

inferior vena cava large systemic vein that returns blood to the heart from the inferior portion of the body

interatrial septum cardiac septum located between the two atria; contains the fossa ovalis after birth

internal elastic membrane membrane composed of elastic fibers that separates the tunica intima from the tunica media; seen in larger arteries

interventricular septum cardiac septum located between the two ventricles

left atrioventricular valve (also, mitral valve or bicuspid valve) valve located between the left atrium and ventricle; consists of two flaps of tissue

lumen interior of a tubular structure such as a blood vessel or a portion of the alimentary canal through which blood, chyme, or other substances travel

marginal arteries branches of the right coronary artery that supply blood to the superficial portions of the right ventricle

mesothelium simple squamous epithelial portion of serous membranes, such as the superficial portion of the epicardium (the visceral pericardium) and the deepest portion of the pericardium (the parietal pericardium)

metarteriole short vessel arising from a terminal arteriole that branches to supply a capillary bed

microcirculation blood flow through the capillaries

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

mitral valve (also, left atrioventricular valve or 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
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

nervi vasorum small nerve fibers found in arteries and veins that trigger contraction of the smooth muscle in their walls

packed cell volume (PCV)  (also, hematocrit) volume percentage of erythrocytes present in a sample of centrifuged blood

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
perfusion distribution of blood into the capillaries so the tissues can be supplied
pericardial cavity cavity surrounding the heart filled with a lubricating serous fluid that reduces friction as the heart contracts
pericardial sac (also, pericardium) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium
pericardium (also, pericardial sac) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium

plasma  in blood, the liquid extracellular matrix composed mostly of water that circulates the formed elements and dissolved materials throughout the cardiovascular system

platelets  (also, thrombocytes) one of the formed elements of blood that consists of cell fragments broken off from megakaryocytes

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 (also, 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 anterior surface of the heart
precapillary sphincters circular rings of smooth muscle that surround the entrance to a capillary and regulate blood flow into that capillary
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 (also, pulmonary semilunar valve, the pulmonic valve, or the right semilunar valve) valve at the base of the pulmonary trunk that prevents backflow of blood into the right ventricle; consists of three flaps
pulmonary veins veins that carry highly oxygenated blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and to the many branches of the systemic circuit

red blood cells (RBCs)  (also, erythrocytes) one of the formed elements of blood that transports oxygen

right atrioventricular valve (also, tricuspid valve) valve located between the right atrium and ventricle; consists of three flaps of tissue
semilunar valves valves located at the base of the pulmonary trunk and at the base of the aorta
septum (plural = septa) walls or partitions that divide the heart into chambers
septum primum flap of tissue in the fetus that covers the foramen ovale within a few seconds after birth
sinusoid capillary rarest type of capillary, which has extremely large intercellular gaps in the basement membrane in addition to clefts and fenestrations; found in areas such as the bone marrow and liver where passage of large molecules occurs
small cardiac vein parallels the right coronary artery and drains blood from the posterior surfaces of the right atrium and ventricle; drains into the great cardiac vein
sulcus (plural = sulci) fat-filled groove visible on the surface of the heart; coronary vessels are also located in these areas
superior vena cava large systemic vein that returns blood to the heart from the superior portion of the body
systemic circuit blood flow to and from virtually all of the tissues of the body

thoroughfare channel continuation of the metarteriole that enables blood to bypass a capillary bed and flow directly into a venule, creating a vascular shunt

trabeculae carneae ridges of muscle covered by endocardium located in the ventricles
tricuspid valve term used most often in clinical settings for the right atrioventricular valve

tunica externa (also, tunica adventitia) outermost layer or tunic of a vessel (except capillaries)

tunica intima (also, tunica interna) innermost lining or tunic of a vessel

tunica media middle layer or tunic of a vessel (except capillaries)

valve in the cardiovascular system, a specialized structure located within the heart or vessels that ensures one-way flow of blood

vasa vasorum small blood vessels located within the walls or tunics of larger vessels that supply nourishment to and remove wastes from the cells of the vessels

vascular shunt continuation of the metarteriole and thoroughfare channel that allows blood to bypass the capillary beds to flow directly from the arterial to the venous circulation

vasoconstriction constriction of the smooth muscle of a blood vessel, resulting in a decreased vascular diameter

vasodilation relaxation of the smooth muscle in the wall of a blood vessel, resulting in an increased vascular diameter

vasomotion irregular, pulsating flow of blood through capillaries and related structures

vein blood vessel that conducts blood toward the heart

venous reserve volume of blood contained within systemic veins in the integument, bone marrow, and liver that can be returned to the heart for circulation, if needed

ventricle one of the primary pumping chambers of the heart located in the lower portion of the heart; the left ventricle is the major pumping chamber on the lower left side of the heart that ejects blood into the systemic circuit via the aorta and receives blood from the left atrium; the right ventricle is the major pumping chamber on the lower right side of the heart that ejects blood into the pulmonary circuit via the pulmonary trunk and receives blood from the right atrium

venule small vessel leading from the capillaries to veins

white blood cells (WBCs)  (also, leukocytes) one of the formed elements of blood that provides defense against disease agents and foreign materials

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