CIRC

• Mediastinum


  Cone shaped area where the heart is located in the middle of the thoracic cavity
• Apex


  Tip of the heart & points downward. Located above the diaphragm into the left
• Pericardial membrane


  • Outermost layer of the heart that looks like a loose sack
  • Made out of strong fibrous connective tissues
  • Extends inferior to the diaphragm but exterior to great vessels (ex. aorta)
• Serous pericardium


  • Folded membrance with parietal (inner) and visceral (outer) pericardium (a.k.a epicardium)
  • Contains serous fluid that prevents friction as our heart heats
• Layers of the Heart Wall

  • Epicardium / visceral pericardium
  • Myocardium
  • Endocardium
• Epicardium / visceral pericardium


  • Outer protective layer
  • Not really a muscle but a layer
• Myocardium


  • Middle layer & the thickest layer
  • Comprises of the walls & chambers of the heart
• Endocardium


  • Inner layer & the thinnest layer
  • Made of simple squamous epithelium
  • Lines the chambers and covers the valves of the heart into the vessels
  • Endothelium - term for endocardium once it reaches the vessels
  • Very smooth surface to prevent abnormal blood clotting
• Heart Chambers


  • Atria
  • Ventricles
• Atria


  • Upper layers (left & right)
  • Thinner layers because they push blood from one chamber to the other
• Inter-atrial septum


  Divides the left & right atria
• Ventricles


  • Lower layers (left & right)
  • Thicker layers because they push to blood to our body circulation
• Inter-ventricular septum


  Divides the left & right ventricle
• Parts of the Heart Chambers

  • Superior Vena Cava
  • Inferior Vena Cava
  • Tricuspid valve
  • Mitral / Bicuspid valve
  • Pulmonary Artery
  • Pulmonary Valve
  • Capillary Muscles
  • Chordae tendineae
  • Aortic Valve
• Tricuspid valve


  • Aka right atrioventricular valve
  • Has 3 flaps
  • Located between the right atrium and ventricle
  • Prevents backflow of blood to both chambers
• Mitral / Bicuspid valve


  • Aka atrioventricular valve
  • Has 2 flaps
  • Located between the left atrium and ventricle
  • Also prevents backflow
• Left atrium receives blood from the lungs, via the 4 pulmonary veins
• Parts of the Heart Chambers

  • 2 pulmonary veins
  • Pulmonary artery
  • Aorta
• Atrial Natriuretic Peptide (ANP)


  Hormone produced by the atria which decreases BP through reabsorption of sodium ions in kidneys (so that more sodium will be released during excretion)
• Aldosterone


  Inverse of ANP, increases BP
• Pulmonary Artery


  Carries deoxygenated blood into the lungs (so they can be oxygenized)
• Pulmonary Valve


  Door/junction between the pulmonary artery & right ventricle. Also prevents backflow
• Capillary Muscles


  Located at the lower right ventricle, composed of myocardium
• Chordae tendineae


  • Strands of fibrous connective tissue
  • Extends from capillary muscles to the tricuspid valve
  • Makes sure that the tricuspid valve does not reverse
• Aortic Valve


  • Another door (prevents backflow)
  • Aortic valve OPEN -> Mitral valve CLOSE and vice versa
  • Happens when left ventricle relaxes
• Fibrous Skeleton of the Heart


  • Seperates the myocardium of the atria and ventricles
  • Prevents the contraction of the atria from reaching the ventricles (unless there is a normal conduction pathway)
• From the aorta, arteries -> arterioles -> capillaries (gives oxygen to blood, important for myocardial contraction)
• Ischemia


  • Obstruction of coronary arteries due to blood clot
  • Area is deprived of oxygenated blood
• Infarction


  • Prolonged ischemia that causes the area w/o oxygen to die out
  • Aka the heart attack / myocardial infarction
• Cardiac Cycle and Heart Sounds

  • Cardiac Cycle
  • Heart Sounds
• Cardiac Cycle


  • Sequence of events in one heartbeat
  • Sound we hear is the simultaneous contraction of the 2 atria & 2 ventricles (after a fraction of a sec later)
  • 1st sound produced is caused by the ventricular systole and the closing of the AV valves
  • 2nd sound produced is caused by the closure of the aortic and pulmonary semilunar valves
• Heart murmur


  Extra sound produced by the heart caused by various factors (ex. arythmia / irregular heart beat)
• Systole


  Heart contraction
• Diastole


  Heart relaxation
• Cardiac Conduction Pathway

  • Sinoatrial (SA) Node
  • Atrioventricular (AV) Node
  • AV Bundle / His Bundle
• Sinoatrial (SA) Node


  • Natural pacemaker of the heart
  • Specialized group of cardiac muscle
  • Located in the right atrium wall just below the superior vena cava
  • Most rapid rate of contraction (depolarizes 60-80 times per min) as its cells are more permeable to sodium ions, which enables it to contract faster each heartbeat
• Atrioventricular (AV) Node


  • Impulse from contraction travels through here
  • Located in the lower interatrial septum
  • Atrial systole - transmission of impulses from SA to AV node through the rest of the atrial myocardium
• AV Bundle / His Bundle


  • Only pathway for electrical impulses from the atrium to the ventricle
  • Located in the upper interventricular septum & leads to the bundle branches
  • Impulse in the bundle branches leads to the Purkinje fibers, then to the ventricular muscles which brings ventricular systole
• Electrocardiagram / ECG


  Can detect the activity of the atria and ventricles
• Ventricular fibrillation


  Rapid & uncoordinated ventricular beat that is ineffective in blood pumping