The heart

• Which structure surrounds the heart?

  pericardium
• Describe the pericardium?

  + fibrous epicardium made of dense connective tissue

  + double walled, fluid-filled sac

  + anchors heart to surrounding structures

  + offers mechanical protection for heart

  + lubrication reduces friction between heart and surrounding structures
• What is the auricle?

  a muscular pouch extending from the atria (increases holding capacity when needed)
• What do the coronary arteries do?

  + supply oxygenated blood to cardiac muscle

  + can cause angina or even myocardial infarction (heart attack) when constricted
• Which tissues make up the internal layers of the heart?

  + myocardium - cardiac tissue ( does not tire)

  + endocardium - squamous epithelial tissue: smooth to reduce friction to blood flow
• What do tendinous chords do?

  prevent valves turning inside out
• What do the semi-lunar valves do?

  at the base of arteries to prevent blood flowing back into the ventricles
• Explain why the wall of the left ventricle is thicker than the wall of the left atrium.

  + more muscle to create more force

  + needs to create a higher pressure

  + pushes blood against greater resistance/ friction

  + pushes the blood further/ all parts of body
• What does cardiac muscle do?

  + contracts to create pressure in the blood

  + a higher pressure means blood is further pushed around the body
• What is the thickness of the left ventricle walls compared to the right ventricle?

  + 2-3X thicker than right ventricle walls

  + blood is pumped through aorta and needs sufficient pressure to overcome the resistance/ friction of the systemic circulation
• What is systemic circulation?

  carrying blood around the body
• What is the relative thickness of the right ventricle walls and why?

  + thicker than atria, to pump blood near the lungs

  + alveoli are also delicate and would be damaged by high pressure
• What is the path of deoxygenated blood?

  + deoxygenated blood enters RA at low pressure

  + pressure builds in RA and open tricuspid valve

  + RA and RV fill with blood

  + when full, RA contracts - filling RV with blood

  + RV stretched - increases pressure and RV contracts to close tricuspid valve closes

  + tendinous chords prevent valve from turning inside out from RV pressure

  + slightly thicker RV muscle contacts, semi-lunar valves open - blood to lungs overcoming resistance of pulmonary circulation
• What is the paths of oxygenated blood?

  + oxygenated blood enters LA at low pressure and pressure builds up in LA - opening bicuspid valve

  + LA and LV fill with oxygenated blood

  + when full, LA contacts, filling LV with oxygenated blood

  + LV stretched - increases pressure and LV contracts, bicuspid valve closing

  + tendinous chords prevent valve from turning inside out from LV pressure

  + thick LV muscle contracts, semi-lunar valves open so blood enters aorta to overcome resistance of aorta and arterial systems