Heart Chapter 22

• Heart


  • Center of the cardiovascular system
  • Generates blood pressure through alternate cycles of contraction and relaxation
• Arteries


  • Carry blood away from the heart
• Veins


  • Carry blood back to the heart
• Great vessels


  • Arteries and veins entering and leaving the heart
• Heart valves


  • Ensure blood flow is unidirectional
• Heart


  • Two side-by-side pumps that work at the same rate and pump the same volume of blood
  • One pump directs blood to the lungs
  • One pump directs blood to body tissues
• Pulmonary circulation


  1. Right side of heart pumping deoxygenated blood through pulmonary arteries to lungs

  2. Pulmonary veins carry blood to left side of heart after oxygen pickup and carbon dioxide release
• Systemic circulation


  1. Left side of the heart pumps oxygenated blood through systemic arteries to body's cells

  2. Nutrients, respiratory gases and wastes are exchanged, and systemic veins carry the blood back to the right side of the heart
• Position of the Heart

  • Slightly left of midline, deep to the sternum, in space called the mediastinum
  • Slightly rotated
  • Right border is located more anteriorly
  • Left border is located more posteriorly
  • Base of the heart: its posterosuperior surface, mainly the left atrium
  • Superior border of the heart is formed by the great arterial vessels and the superior vena cava
  • Apex is the inferior conical end
  • Inferior border is formed by the right ventricle
• Pericardium


  • Heart is enclosed within a tough sac called the pericardium
  • Restricts heart movements so that it moves only slightly within the thorax
  • Composed of fibrous pericardium (tough outer sac) and serous pericardium (parietal and visceral layers)
  • Pericardial cavity: thin space between layers of serous pericardium containing serous fluid
• Heart Wall Structure


  • Epicardium: Visceral layer of serous pericardium and areolar connective tissue
  • Myocardium: Cardiac muscle; thickest of the three layers
  • Endocardium: Internal surface of heart chambers; simple squamous epithelium and areolar connective tissue
• External Heart Anatomy


  • Composed of four hollow chambers: Two superior, smaller atria and two inferior, larger ventricles
  • Anterior part of each atrium forms an auricle
  • Right atrium feeds right ventricle, feeds pulmonary trunk, pulmonary circulation
  • Left atrium feeds left ventricle, feeds aorta, systemic circulation
  • Coronary sulcus: groove separating atria and ventricles
  • Anterior interventricular sulcus and posterior interventricular sulcus are located between the right and left ventricles
• Internal Heart Anatomy


  • Four hollow chambers: Right atrium, right ventricle, left atrium, left ventricle
  • Four valves: Two atrioventricular valves, Two semilunar valves at base of great arteries
  • Closure of atrioventricular valves causes first heart sound "lubb"
  • Closure of semilunar valves causes second heart sound "dupp"
• Fibrous Skeleton


  • Dense regular connective tissue between the atria and ventricles
  • Provides structural support and acts as an electrical insulator between atria and ventricles
• Right Atrium


  • Receives venous blood from heart and systemic circulation through superior vena cava, inferior vena cava, and coronary sinus
  • Interatrial septum: divides right atrium from left
  • Pectinate muscles: ridges on internal surface of atrial wall
  • Right atrioventricular valve (tricuspid valve): ensures one-way blood flow from right atrium to right ventricle through atrioventricular opening
• Right Ventricle


  • Receives deoxygenated blood from right atrium
  • Interventricular septum: thick wall between right and left ventricles
  • Trabeculae Carnae: irregular muscular ridges on inner wall
  • Papillary muscles: cone-shaped muscle projections anchoring chordae tendineae
  • Chordae tendineae: attach muscle to atrioventricular valve and prevent cusps from flipping into atrium when ventricle contracts
  • Conus arteriosus: smooth funnel shaped region at superior end of right ventricle leading to pulmonary semilunar valve
  • Semilunar valve ensures one-way flow from ventricle to pulmonary trunk
• Left Atrium


  • Oxygenated blood from the lungs travels through the pulmonary veins to the left atrium
  • Left atrioventricular valve: controls flow through opening between left atrium and ventricle
  • Also referred to as the bicuspid (two flap) or mitral valve
  • Valve is forced shut when the left ventricle contracts
• Left Ventricle


  • Pumps blood through entire systemic circulation
  • Generates very high pressure
  • Aortic semilunar valve: controls flow from left ventricle to aorta
  • Located at superior end of left ventricle
• Coronary Circulation


  1. Right coronary artery branches into right marginal artery and posterior interventricular artery

  2. Left coronary artery branches into anterior interventricular artery and circumflex artery

  3. Three major cardiac veins drain into the coronary sinus, which drains into the right atrium
• Cardiac muscle tissue differs from skeletal muscle tissue
• The Heart's Conducting System

  1. Electrical impulse begins at the Sinoatrial node

  2. Impulse travels via gap junctions to atrioventricular node

  3. Impulse leaves AV node, enters the atrioventricular bundles

  4. AV bundle divides into left and right bundles (bundle branches)

  5. Purkinje fibers spread the impulse superiorly from the apex to all of the ventricular myocardium
• Electrocardiogram: P wave (atrial depolarization), QRS complex (ventricular depolarization and atrial repolarization), T wave (ventricular repolarization)
• Innervation of the Heart

  • Heart is innervated by sympathetic and parasympathetic divisions of the autonomic nervous system
  • Autonomic innervation does not initiate a heartbeat, but it can increase or decrease the rate of the heartbeat
• Cardiac Cycle


  1. Contraction of a chamber is called Systole

  2. Relaxation of a chamber is called diastole

  3. One cycle consists of five phases: 1) Atrial contraction and ventricular filling, 2) Isovolumic contraction, 3) Ventricular ejection, 4) Isovolumic relaxation, 5) Atrial relaxation and ventricular filling