Circulatory System

• Arteries

  Large blood vessels that carry oxygen-rich, or oxygenated, blood away from the heart
• Arteries

  • Made of three layers: an outer layer of connective tissue, a middle layer of smooth muscle, and an inner layer of endothelial tissue
  • The endothelial layer is thicker than that of other blood vessels because blood is under higher pressure when it is pumped from the heart
• Capillaries

  Microscopic blood vessels where the exchange of important substances and wastes occurs
• Capillaries

  • Red blood cells move single-file through them
  • Capillary walls are only one cell thick, allowing easy exchange of materials between the blood and body cells
• Veins

  The largest blood vessels that carry oxygen-poor, or deoxygenated, blood back to the heart
• Veins

  • The endothelial walls are thinner than those of arteries because the heart's original pushing force has lessened
  • Larger veins have flaps of tissue called valves that prevent blood from flowing backward
  • Breathing movements squeeze against veins in the chest, forcing blood back to the heart
• Heart


  A hollow, muscular organ that pumps blood throughout the body
• Heart


  • Located in the center of the chest
  • Performs two pumping functions at the same time: pumps oxygenated blood throughout the body, and pumps deoxygenated blood to the lungs
• Parts of the heart


  • Right atrium
  • Left atrium
  • Right ventricle
  • Left ventricle
• How the heart beats

  1. Atria fill with blood

  2. Atria contract, filling the ventricles with blood

  3. Ventricles contract to pump blood out of the heart and into the lungs and then to the body
• Pacemaker/Sinoatrial (SA) node

  Group of cells in the right atrium that send out signals to tell the heart muscle to contract
• Atrioventricular (AV) node

  Receives signals from the SA node, causing both ventricles to contract
• Running hard while playing soccer

  SA node will respond by adjusting the heart rate
• Pulse is the alternating expansion and relaxation of the artery wall, caused by the contraction of the left ventricle
• Blood pressure

  Measure of how much pressure the blood is applying against the vessel walls
• Systole

  Contraction of the heart, causing blood pressure to rise to its highest point
• Diastole

  Relaxation of the heart, causing blood pressure to drop to its lowest point
• Normal blood pressure reading for a healthy adult is about 120 (systolic pressure)/80 (diastolic pressure)
• When blood is returning from the body to the heart, it enters the right atrium first
• Blood flow through the body

  1. Blood travels from the heart to the lungs and back to the heart (first loop)

  2. Blood is pumped from the heart through the body and back to the heart (second loop)

  3. Right side of the heart pumps oxygen-poor blood to the lungs

  4. Left side of the heart pumps oxygen-rich blood through the body
• Circulatory system


  • Delivers oxygen and nutrients to the cells and removes waste products
  • Transports disease-fighting materials produced by the immune system
  • Distributes heat throughout the body to help control body temperature
• Blood components

  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• Plasma

  Clear, yellowish fluid part of blood that carries the products of digested food, vitamins, minerals, chemical signals, and waste products
• Red blood cells


  Carry oxygen to all body cells, made mostly of hemoglobin which binds with oxygen
• White blood cells

  The body's disease fighters, recognize and fight disease-causing organisms
• Platelets

  Cell fragments that play an important part in forming blood clots
• Carbon dioxide is a waste product, not a nutrient
• Plasma carries the products of digested food, vitamins, minerals, chemical signals, and waste products
• Hemoglobin


  Protein in red blood cells that binds with oxygen and carries it to the body's cells
• Blood types

  • A
  • B
  • AB
  • O
• Blood type markers

  Type A has A markers, Type B has B markers, Type AB has both A and B markers, Type O has neither A nor B markers
• Type O blood can be transfused into anyone
• Atherosclerosis


  Can lead to heart attack or stroke, two leading causes of death
• Blood vessels


  Circulate blood throughout the body, help to keep blood flowing to and from the heart
• Major types of blood vessels


  • Arteries
  • Capillaries
  • Veins
• Arteries


  • Carry oxygen-rich blood away from the heart
  • Made of three layers: outer layer of connective tissue, middle layer of smooth muscle, inner layer of endothelial tissue
  • Endothelial layer is thicker than other blood vessels because blood is under higher pressure when pumped from the heart
• Capillaries


  • Microscopic blood vessels where exchange of important substances and wastes occurs
  • Red blood cells move single-file through them
  • Capillary walls are only one cell thick, allowing easy exchange of materials
• Veins


  • Carry oxygen-poor blood back to the heart
  • Endothelial walls are thinner than arteries because heart's original pushing force has lessened
  • Larger veins have valves that prevent blood from flowing backward
  • Breathing movements squeeze against veins in the chest, forcing blood back to the heart
• Heart


  • Hollow, muscular organ that pumps blood throughout the body
  • Located in the center of the chest
  • Performs two pumping functions: pumps oxygenated blood throughout the body, and pumps deoxygenated blood to the lungs
• Parts of the heart


  • Right atrium
  • Left atrium
  • Right ventricle
  • Left ventricle