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
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
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
red blood cells (RBCs) (also, erythrocytes) one of the formed elements of blood that transports oxygen
thoroughfare channel continuation of the metarteriole that enables blood to bypass a capillary bed and flow directly into a venule, creating a vascular shunt
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)
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