cardiovascular system

• Cardiovascular System


  Circulatory system, Lymphatic system, Heart, Blood vessels, Lymph nodes, Lymph vessels
• Heart


  • Chambered muscular organ
  • Pumps blood received from the veins into the arteries, thereby maintaining the flow of blood through the entire circulatory system
  • Lies in the mediastinum (between lungs)
  • Lies obliquely (little more to left than right)
  • Presents a base above and an apex below
  • Apex – 9 cm to left of midline at level of 5'th intercostal space
  • Base – extends to level of 2'nd rib
• Relations of the heart

  • Inferiorly – apex rests on central tendon of diaphragm
  • Superiorly – the great blood vessels i.e. aorta, SVC, pulmonary artery and pulmonary veins
  • Posteriorly – oesophagus, trachea, left and right bronchus, descending aorta, IVC and thoracic vertebrae
  • Laterally – the lungs – left lung overlapping the left side of the heart
  • Anteriorly – the sternum, ribs and intercostal muscles
• Pericardium


  • Fibroserous sac that encloses the heart and the roots of the great vessels
  • Lies within the middle mediastinum
• Functions of the pericardium


  • Restrict excessive movements of the heart as a whole
  • Serve as a lubricated container in which the different parts of the heart can contract
• Layers of the pericardium

  • Fibrous pericardium (superficial)
  • Serous pericardium (deep, two-layer)
  • Parietal layer (lines the internal surface of the fibrous pericardium)
  • Visceral layer or epicardium (lines the surface of the heart)
  • Pericardial cavity (fluid-filled space between the layers)
• Layers of the heart wall

  • Epicardium (visceral layer of the serous pericardium)
  • Myocardium (cardiac muscle layer forming the bulk of the heart)
  • Fibrous skeleton (crisscrossing, interlacing layer of connective tissue)
  • Endocardium (endothelial layer of the inner myocardial surface)
• Endocardium


  Deepest layer of the heart, smooth lining to reduce friction of bloodflow
• Myocardium


  Middle layer of the heart, location of muscle fibers responsible for pumping
• Pericardium


  Outer protective layer of the heart
• The heart


  • Hollow muscular organ that is somewhat pyramid shaped
  • Lies within the pericardium in the mediastinum
  • Connected at its base to the great blood vessels but otherwise lies free within the pericardium
• Surfaces of the heart

  • Anterior (sternocostal) surface
  • Inferior (diaphragmatic) surface
  • Posterior surface (base)
• Heart chambers


  • Two atria (Right and Left)
  • Two ventricles (Right and Left)
• Atria


  • Small, thin-walled chambers
  • Receiving chambers for blood returning to the heart from the circulation
  • Push the blood into the adjacent ventricles
• Blood received by the atria


  • Right side: Superior and Inferior Vena Cava, Coronary Sinus (draining the myocardium)
  • Left side: Pulmonary Veins
• Ventricles


  • Make up most of the mass of the heart
  • The walls of the left ventricle are 3X thicker than those of the right
  • Discharging chambers of the heart
  • Propel blood to Pulmonary Trunk (right ventricle), Aorta (left ventricle)
• Right Atrium


  • Receives deoxygenated blood from the inferior vena cava below and from the superior vena cava above
  • Receives the coronary sinus in its lower part
  • The upper end of the atrium projects to the left of the superior vena cava as the right auricle
• Right Atrium (internal)


  • The sulcus terminalis is a vertical groove on the outer surface, corresponding internally to the crista terminalis
  • Above the coronary sinus the interatrial septum forms the posterior wall, with the depression in the septum the fossa ovalis presenting the site of the foramen ovale
• Right Ventricle


  • Receives blood from the right atrium through the tricuspid valve
  • The edges of the valve cusps are attached to chordae tendineae which are, in turn, attached below to papillary muscles
  • The wall contains a mass of muscular bundles known as trabeculae carneae
  • The infundibulum is the smooth walled outflow tract
• Right Ventricle (outflow)


  • The pulmonary valve is situated at the top of the infundibulum
  • It is composed of three semilunar cusps
  • Blood flows through the valve and into the pulmonary arteries via the pulmonary trunk to be oxygenated in the lungs
• Left Atrium


  • Receives oxygenated blood from four pulmonary veins which drain posteriorly
  • The cavity is smooth walled except for the atrial appendage
  • On the septal surface a depression marks the fossa ovalis
• Mitral (bicuspid) valve


  Guards the passage of blood from the left atrium to the left ventricle
• Left Ventricle


  • The wall is thicker than the right ventricle but the structure is similar
  • The thick wall is necessary to pump oxygenated blood at high pressure through the systemic circulation
  • Trabeculae carneae project from the wall with papillary muscles attached to the mitral valve cusp edges by way of chordae tendineae
  • The vestibule is a smooth walled part located below the aortic valve
• Heart valves


  • Atrioventricular (AV) valves
  • Semilunar valves
• Atrioventricular (AV) valves


  • Lie between the atria and the ventricles
  • R-AV valve = tricuspid valve
  • L-AV valve = bicuspid or mitral valve
  • Prevent backflow of blood into the atria when ventricles contract
  • Chordae tendineae anchor AV valves to papillary muscles of ventricle wall to prevent prolapse
• Semilunar valves


  • Prevent backflow of blood into the ventricles
  • Have no chordae tendinae attachments
  • Aortic semilunar valve lies between the left ventricle and the aorta
  • Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk
  • Heart sounds ("lub-dup") due to valves closing - "Lub" is closing of AV valves, "Dup" is closing of semilunar valves
• Heart valves


  • Right AV (Tricuspid) valve
  • Left AV (Bicuspid) valve
  • Pulmonary valve
  • Aortic valve
• Heart valve components


  • Pulmonary semilunar valve
  • Aortic semilunar valve
  • Left AV (bicuspid) valve
  • Right AV (tricuspid) valve
  • Chordai tendineae
  • Papillary muscle
• Arterial supply of the heart

  Provided by the right and left coronary arteries, which arise from the ascending aorta immediately above the aortic valve
• Origins of the coronary arteries

  • Left coronary artery arises from the aortic sinus immediately above the left posterior cusp of the aortic valve
  • Right coronary artery arises from the aortic sinus immediately above the anterior cusp of the aortic valve
• Branches of the right coronary artery

  • Right marginal arteries (acute marginal artery)
  • Posterior interventricular artery (in posterior interventricular sulcus)
  • Sinoatrial nodal artery
  • Atrioventricular nodal artery
• Branches of the left coronary artery

  • Left anterior descending (LAD) or anterior interventricular artery (lies in anterior interventricular sulcus)
  • Septal branches
  • Diagonal branches
  • Left marginal artery (Obtuse marginal artery)
  • Left circumflex artery
• Venous drainage of the heart

  Most blood from the heart wall drains into the right atrium through the coronary sinus, which is a continuation of the great cardiac vein
• Nerve supply of the heart

  • Innervated by sympathetic and parasympathetic fibers of the autonomic nervous system via the cardiac plexuses situated below the arch of the aorta
  • Sympathetic supply arises from the cervical and upper thoracic portions of the sympathetic trunks
  • Parasympathetic supply comes from the vagus nerves