The Circulatory System

• What are the functions of the Circulatory System?

  1. Transport gases, nutrient molecules, and wastes.
  2. Regulates internal temperature and transports hormones (homeostasis).
  3. Protects against blood loss from injury and disease-causing microbes or toxic substances.
• What is meant by a closed system?

  Blood remains contained in the vessels. Nutrients exchange through the vessel walls.
• What are Capillaries?

  Tiny blood vessels that connect the arteries and veins.
• Where does Gas and Nutrient exchange occur?

  In the capillaries.
• What do Arteries have that keep blood moving in the correct direction?

  Elastic walls that can snap back.
• What are the three layers in Arteries?

  connective / elastic

  muscular / elastic

  smooth / one cell layer thick reducing friction
• What do Veins have that keep blood moving in the correct direction?

  One-way valve
• Which blood vessel are most cells of the body near?

  Capillaries
• What are precapillary sphincters?

  Rings of smooth muscle at the ends of arterioles that regulate blood flow into the capillaries.
• What would happen if all Precapillary Spincters were open?

  There would not be enough blood in the body to fully fill all the capillaries at once.
• What part of the body have arteries carry deoxygenated blood and have veins carry oxygenated blood? (opposite from the usual)

  The pulmonary circuit (lungs)
• What does the Heart do?


  Pumps blood, keeps oxygenated and deoxygenated blood separated, and ensures that blood flows in one direction in the body.
• Where do Atria receive blood?

  From the body (vena cavae) and lungs (pulmonary veins).
• Where do Veins receive blood?

  From the atria and pump blood to the body (aorta) and lungs (pulmonary trunk and arteries).
• What structure in the heart separates left side from right side?

  A muscular wall called the septum.
• What are the atrioventricular valves between the atria and ventricles?

  Bicuspid (mitral) valve on the left, tricuspid valve on the right.
• What is the role of heart valves?

  Ensure blood flow in proper direction.
• What is the Epicardium?


  Outside layer of heart; prevents it from adhering to surrounding structures.
• What is the Pericardium?


  Fibrous, protective saclike structure surrounding heart; a fluid between epicardium and pericardium allow for frictionless movement of heart in sac.
• What is the Myocardium?

  Middle cardiac muscle layer of the heart.
• What is the Endocardium?

  The inner lining of the heart.
• What are Papillary Muscles?

  Nipple shaped projections that extend from the floor of each ventricle.
• What are Chordae Tendinae?

  Thin, strong connective tissue threads connecting the edges of the valves to papillary muscles; prevents the AV valves from opening upwards into the atria.
• What is the Pulmonary pathway?

  Oxygen-poor blood pumped from heart to lungs, is oxygenated in the lungs, and returns to the heart.
• What is the Systemic pathway?

  Oxygen-rich blood pumped from the heart to body, is oxygenated, and returns to the heart.
• What is the Coronary pathway?

  Blood vessel pathway that provides blood to the tissues of the heart itself.
• Recall that proteins are transported to the liver by the bloodstream to be processed and distributed throughout the body
• What is the name of the bundle of nerve fibres that stimulate rhythmic contractions and relaxation of the heart?


  The sinoatrial (SA) node (pacemaker).
• What does the Atrioventricular (AV) node do?


  Transmits electrical signal through the bundle of His to two bundle branches to the Purkinje fibres.
• What do Purkinje fibres do?


  Initiate simultaneous contraction of the ventricles.
• What does an Electrocardiogram (ECG) do?


  Records electrical activity of the heart during contractions and relaxation of the atria and ventricles (voltage changes)
• What does a P wave signify?

  Impulse prior to atrial contraction
• What does a QRS wave signify?


  Impulse prior to ventricular contraction
• What does a T wave signify?

  Ventricle recovery
• What does the “lub” sound come from?


  From the simultaneous closing of the bicuspid and tricuspid atrioventricular valves as ventricular contraction occurs.
• What does the “dub” sound come from?


  From the simultaneous closing of the aortic and pulmonary semilunar valves as the ventricles relax.
• When ventricles contract

  Higher blood pressure
• When ventricles relax

  Lower blood pressure
• What is Systolic pressure?

  Max b.p. during ventricular contraction
• What is Diastolic pressure?

  Lowest b.p. before ventricular contraction