Cardiovascular system

• Atria are thin-walled chambers that receive blood from veins
• The heart has four chambers - two atria and two ventricles
• The heart is located between the lungs, behind the sternum (breastbone) and to the left side.
• Cardiovascular System


  The system responsible for circulating blood throughout the body
• Heart


  • Location in the thoracic medially, in the mediastinum
  • Apex formed by the tip of the left ventricle
  • Base opposite the apex
• Pericardium


  The membrane that surrounds and protects the heart and holds it in place
• Parts of the pericardium

  • Fibrous pericardium
  • Serous pericardium
• Fibrous pericardium


  Tough, inelastic, dense irregular connective tissue
• Serous pericardium


  Thinner, more delicate membrane that forms a double layer
• Parietal layer of serous pericardium

  Fused to the fibrous pericardium
• The order of the pericardium layers can be remembered using the acronym FART POLICE SMELL VILLAINS
• Layers of the heart wall

  • Epicardium
  • Myocardium
  • Endocardium
• Epicardium


  External layer composed of mesothelium and connective tissue
• Myocardium


  Middle layer consisting of cardiac muscle tissue, which constitutes the bulk of the heart
• Endocardium


  Inner layer, a thin layer of simple squamous epithelium that lines the inside of the myocardium and covers the valves and tendons
• Cardiac muscle fibres


  • Involuntary, striated, and branched
  • Arranged in interlacing bundles
  • Connected by intercalated discs with gap junctions
• Cardiac muscle fibres form two separate networks - one atrial and one ventricular
• The myometrium in the left ventricle is significantly thicker than that of the right ventricle
• Chambers of the heart

  • Right atrium
  • Left atrium
  • Right ventricle
  • Left ventricle
• Interatrial septum


  Thin partition between the right and left atria
• Fossa ovalis


  Prominent oval depression in the interatrial septum, normally closes after birth
• Interventricular septum


  Separates the right and left ventricles
• Great vessels of the heart

  • Superior vena cava
  • Inferior vena cava
  • Coronary sinus
  • Pulmonary trunk
  • Pulmonary arteries
  • Ascending aorta
• Arteries


  Blood vessels that carry blood away from the heart
• Pulmonary circulation


  Deoxygenated blood flows from the right ventricle to the lungs via the pulmonary arteries
• Systemic circulation


  Oxygenated blood flows from the left ventricle to the body via the ascending aorta
• Heart valves


  • Tricuspid valve
  • Bicuspid (mitral) valve
  • Pulmonary valve
  • Aortic valve
• Atrioventricular (AV) valves


  Lie between the atria and ventricles, open and close in response to pressure changes
• Tricuspid valve


  AV valve between the right atrium and right ventricle, has three cusps
• Bicuspid (mitral) valve


  AV valve between the left atrium and left ventricle, has two cusps
• Chordae tendinae


  Tendon-like cords that connect the AV valves to papillary muscles
• Semilunar valves


  Valves near the origin of the pulmonary trunk and aorta, prevent backflow
• Pulmonary valve


  Lies in the opening where the pulmonary trunk leaves the right ventricle
• Aortic valve


  Situated at the opening between the left ventricle and the aorta
• Each semilunar valve consists of three half-moon-shaped cusps that attach to the artery wall
• Coronary (cardiac) circulation


  Blood supply to the heart muscle via the left and right coronary arteries
• Components of the conduction system

  • Sinoatrial (SA) node
  • Atrioventricular (AV) node
  • Atrioventricular (AV) bundle
  • Bundle branches
  • Purkinje fibers
• Sinoatrial (SA) node


  Natural pacemaker of the heart, located in the right atrial wall
• Atrioventricular (AV) node


  Slows the action potential, allowing time for the atria to empty into the ventricles
• The conduction system generates and distributes action potentials to coordinate the contractions of the heart