cardiovascular system

• Heart


  • Hollow, cone-shaped
  • Approximately the size of a person's fist
  • Weighs less than a pound
  • Snugly enclosed within the inferior mediastinum
  • Apex directed toward the left hip and rests on the diaphragm
  • Base points toward the right shoulder and lies beneath the second rib
  • Enclosed in a double-walled sac called the pericardium
• Fibrous pericardium


  Loosely fitting superficial part of the pericardial sac that helps protect the heart and anchors it to surrounding structures
• Serous pericardium


  Deep to the fibrous pericardium, the two-layer serous pericardium where the parietal layer lines the interior of the fibrous pericardium
• Layers of the heart


  • Epicardium
  • Myocardium
  • Endocardium
• Epicardium


  The visceral and outermost layer of the heart wall
• Myocardium


  The thick bundles of cardiac muscle that contract
• Endocardium


  The thin, glistening sheet of endothelium that lines the heart chambers
• Chambers of the heart

  • Atria (receiving chambers)
  • Ventricles (discharging chambers)
• Septum


  The wall that divides the heart longitudinally, either the interventricular septum or the interatrial septum
• Great vessels associated with the heart

  • Superior and inferior vena cava
  • Pulmonary trunk and pulmonary arteries
  • Pulmonary veins
  • Aorta
• Heart valves


  • Atrioventricular (AV) valves (bicuspid/mitral and tricuspid)
  • Semilunar valves (pulmonary and aortic)
• Coronary arteries


  Arteries that branch from the aorta and encircle the heart, supplying it with blood
• Cardiac veins


  Veins that drain the myocardium and empty into the coronary sinus
• Tunics of blood vessels


  • Tunica intima
  • Tunica media
  • Tunica externa
• Tunica intima


  The thin, innermost layer of endothelium lining the vessel lumen
• Tunica media


  The bulky middle coat consisting mostly of smooth muscle and elastic fibers
• Tunica externa


  The outermost layer composed largely of fibrous connective tissue
• Major arteries of the systemic circulation

  • Arterial branches of the ascending aorta (coronary arteries)
  • Arterial branches of the aortic arch (brachiocephalic trunk, left common carotid, left subclavian)
  • Arterial branches of the thoracic aorta (intercostal arteries)
  • Arterial branches of the abdominal aorta (celiac trunk, superior mesenteric, renal, gonadal, lumbar, inferior mesenteric, common iliac)
• Major veins of the systemic circulation

  • Veins draining into the superior vena cava (radial, ulnar, cephalic, basilic, median cubital, subclavian, vertebral, internal jugular, brachiocephalic)
• The heart is the size of a person's fist and weighs less than a pound
• The heart is snugly enclosed within the inferior mediastinum, the medial cavity of the thorax, and is flanked on each side by the lungs
• The heart's apex is directed toward the left hip and rests on the diaphragm, approximately at the level of the fifth intercostal space
• The heart's broad posterosuperior aspect, or base, from which the great vessels of the body emerge, points toward the right shoulder and lies beneath the second rib
• The heart is enclosed in a double-walled sac called the pericardium, with the loosely fitting superficial part referred to as the fibrous pericardium
• The slippery, two-layer serous pericardium is deep to the fibrous pericardium, with its parietal layer lining the interior of the fibrous pericardium
• The epicardium is the visceral and outermost layer of the heart wall
• The myocardium consists of thick bundles of cardiac muscle twisted and whirled into ringlike arrangements, and it is the layer that actually contracts
• The endocardium is the thin, glistening sheet of endothelium that lines the heart chambers
• The two superior atria are primarily the receiving chambers, while the two inferior, thick-walled ventricles are the discharging chambers or actual pumps of the heart
• The septum that divides the heart longitudinally is referred to as either the interventricular septum or the interatrial septum, depending on which chamber it separates
• The heart receives relatively oxygen-poor blood from the veins of the body through the large superior and inferior vena cava and pumps it through the pulmonary trunk
• The pulmonary trunk splits into the right and left pulmonary arteries, which carry blood to the lungs, where oxygen is picked up and carbon dioxide is unloaded
• Oxygen-rich blood drains from the lungs and is returned to the left side of the heart through the four pulmonary veins
• Blood returned to the left side of the heart is pumped out of the heart into the aorta, from which the systemic arteries branch to supply essentially all body tissues
• Atrioventricular or AV valves are located between the atrial and ventricular chambers on each side, and they prevent backflow into the atria when the ventricles contract
• The left AV valve, the bicuspid or mitral valve, consists of two flaps or cusps of endocardium, while the right AV valve, the tricuspid valve, has three flaps
• The semilunar valves guard the bases of the two large arteries leaving the ventricular chambers, the pulmonary and aortic semilunar valves
• The coronary arteries branch from the base of the aorta and encircle the heart in the coronary sulcus (atrioventricular groove) at the junction of the atria and ventricles, and these arteries are compressed when the ventricles are contracting and fill when the heart is relaxed
• The myocardium is drained by several cardiac veins, which empty into an enlarged vessel on the posterior of the heart called the coronary sinus
• As the heart beats, blood is propelled into large arteries leaving the heart, then moves into successively smaller and smaller arteries and arterioles, which feed the capillary beds in the tissues, which are then drained by venules and veins that finally empty into the great veins entering the heart