circulatory system

• Functions of the circulatory system

  • Transportation
  • Regulation
  • Protection
• Circulatory systems


  • Single circuit
  • Double circuit
• Cardiac cycle


  1. Ventricles relaxed and filling (diastole)

  2. Ventricles contracted and pumping (systole)
• Cardiac cycle sounds


  • Lub - AV valves closing
  • Dub - Closing of semilunar valves
• Heart


  • Contains "self-excitable" autorhythmic fibers
  • Sinoatrial (SA) node acts as pacemaker
  • Autonomic nervous system can modulate rate

  
• Electrophysiology of the heart

  1. Signals from SA node spread through atria

  2. Signals delayed at AV node

  3. Bundle branches pass signals to heart apex

  4. Signals spread throughout ventricles

  
• Blood vessels


  • Arteries - Conduct blood away from heart, layers of smooth muscle and connective tissue
  • Arterioles - Can dilate or constrict to control blood distribution
  • Capillaries - Site of gas and nutrient/waste exchange, single-celled layer of endothelium
  • Venules - Small, thin extensions of capillaries
  • Veins - Conduct blood back to heart, thinner and less muscular than arteries, need help returning blood

  
• Plasma


  Fluid matrix of blood
• Formed elements of blood

  • Leukocytes (white blood cells)
  • Erythrocytes (red blood cells)
  • Platelets
• Platelets


  Cell fragments that pinch off from larger cells in the bone marrow, function in the formation of blood clots
• Blood pressure increases with blood volume
• Hormones regulating blood volume

  • Antidiuretic hormone (ADH)
  • Aldosterone
  • Atrial natriuretic hormone